Hi all,

I went out last nigth to recheck my polar alignment. In the first attempt at
precise polar alignment I used my TOA-130 with a 12.5mm reticle EP. Everything
seemed very close with little drift if any.

Last night I decide to employ my Televue 5x powermate with the 12.5mm
reticle(now were talking magnification!) Well, with this magnification the star
drifted after about a minute or so. Small adjustments were made in azimuth and
then I pointed at a star in the east and hade to slightly adjust the altitude.
The star remained fixed in the DEC position! So the key is to use as much power
as possible. I rechecked the position of Polaris in my reticle of the polar
scope after I set the date and time and it was in the BOX!! Although the time
was my local daylight savings time and Polaris was near the 2020 date. If I turn
the dial to account for standard time, then Polaris is on the side of the box.

Since I'm not exactly 75 degrees but more like 75.14 perhaps I need to offset
just a tad from 0.

Anyway, this is working for me.

Just for your info, I watched the star in my reticle with the fore mentioned 5x
powermate and 12.5mm reticle EP, and I observed the star slowly trek to the
right just outside the retiicle center square for about 4 minutes and then it
slowly drifted left at the end of another 4 minutes until it went back to its
original starting position.

I guess this is the 7 arc second drift that is inherant in these mounts. So I
don't think that I will have to speef up or down the tracking rate that I
thought I might have to do.

I'm not sure if the 7 arc second drift would cause too much elongation of the
stars. I will have to image and see. If I have to I will continue to manually
guide or breakdown and get an autoguider.

Clearskies,
Don

--- In UncensoredTakGroup@yahoogroups.com, "John" <johnnyha@...> wrote:
>
> Don -   Roughly align your scope by sight. Power on. Loosen the bolt holding
the mount to the tripod a bit so the mount can move in AZ, and the clutch for
the LAT adjuster. If you are at 75 degrees then your offset is zero.  Adjust the
RA until you level the bubble and clamp it down.  Set the polar alignment dial
with your local time and align with the current date. Adjust the proper knobs to
bring the slot in alignment with Polaris at 2010 (make sure it is the Polaris
slot and not that Southern one ;)) Tighten down the clamps and the main bolt. 
This will probably cause Polaris to move out of the slot, so keep reclamping and
moving until you get Polaris in the slot with the clamps tightened (don't
overtighten!) Hope this helps? Good luck!
>
>
> --- In UncensoredTakGroup@yahoogroups.com, "Don" <chesssquare@> wrote:
> >
> > Thanks everyone for your input. If it clears tonight I may check the
alignment again and be sure the offset is correct and the bubble level is level.
> >
> > As far as elogated stars in unguided 2 minute + exposures, I will attempt to
slow or speed up the RA to see if the slow constant drift can be stablized.
> >
> > I will keep you all informed on my progress.
> >
> > Don
> >
> >
> >
> > --- In UncensoredTakGroup@yahoogroups.com, "Pawel T. Lancucki"
<pawel.lancucki@> wrote:
> > >
> > >
> > > Hi Don
> > >
> > > It could be the case that your bubble level is not properly calibrated.
> > >
> > > If you have set up the mount very well polar aligned using drift method,
> > > and you are still off looking at the polar finder, *but* could bring
> > > Polaris to the box by turning the RA, this is most probably the case.
> > >
> > > Keep your mount aligned using drift method, set your location offset
> > > correctly (this compensates for the difference between your central time
> > > zone and your local time), match date and time and than turn RA until the
> > > Polaris is in the box on 2010 mark. Now, there is a small (IIRC Allen) set
> > > screw which you need to loosen to get the bubble level turning. With RA
> > > switched off, turn the bubble level until it is - well - level - and
> > > tighten the screw to keep it in place. From now on, your polar finder
> > > should work. In my experience, it is very hard to knock the internal polar
> > > finder out of alignment.
> > >
> > > All the best.
> > >
> > > Pawel
> > >
> >
>

Don -   Roughly align your scope by sight. Power on. Loosen the bolt holding the
mount to the tripod a bit so the mount can move in AZ, and the clutch for the
LAT adjuster. If you are at 75 degrees then your offset is zero.  Adjust the RA
until you level the bubble and clamp it down.  Set the polar alignment dial with
your local time and align with the current date. Adjust the proper knobs to
bring the slot in alignment with Polaris at 2010 (make sure it is the Polaris
slot and not that Southern one ;)) Tighten down the clamps and the main bolt. 
This will probably cause Polaris to move out of the slot, so keep reclamping and
moving until you get Polaris in the slot with the clamps tightened (don't
overtighten!) Hope this helps? Good luck!


--- In UncensoredTakGroup@yahoogroups.com, "Don" <chesssquare@...> wrote:
>
> Thanks everyone for your input. If it clears tonight I may check the alignment
again and be sure the offset is correct and the bubble level is level.
>
> As far as elogated stars in unguided 2 minute + exposures, I will attempt to
slow or speed up the RA to see if the slow constant drift can be stablized.
>
> I will keep you all informed on my progress.
>
> Don
>
>
>
> --- In UncensoredTakGroup@yahoogroups.com, "Pawel T. Lancucki"
<pawel.lancucki@> wrote:
> >
> >
> > Hi Don
> >
> > It could be the case that your bubble level is not properly calibrated.
> >
> > If you have set up the mount very well polar aligned using drift method,
> > and you are still off looking at the polar finder, *but* could bring
> > Polaris to the box by turning the RA, this is most probably the case.
> >
> > Keep your mount aligned using drift method, set your location offset
> > correctly (this compensates for the difference between your central time
> > zone and your local time), match date and time and than turn RA until the
> > Polaris is in the box on 2010 mark. Now, there is a small (IIRC Allen) set
> > screw which you need to loosen to get the bubble level turning. With RA
> > switched off, turn the bubble level until it is - well - level - and
> > tighten the screw to keep it in place. From now on, your polar finder
> > should work. In my experience, it is very hard to knock the internal polar
> > finder out of alignment.
> >
> > All the best.
> >
> > Pawel
> >
>

Excellent pic there well done.
Tom.

--- On Thu, 12/11/09, filippociferri <filippo.ciferri@...> wrote:


From: filippociferri <filippo.ciferri@...>
Subject: [UncensoredTakGroup] NGC 6726 from Atacama with FSQ 85
To: UncensoredTakGroup@yahoogroups.com
Date: Thursday, 12 November, 2009, 23:31


 



Dears all,

Following the links to NGC 6726 taken from Atacama, during my last trip, with my
FSQ-85.

Medium Resolution:
http://farm3. static.flickr. com/2558/ 4098693879_ 1507ec43a4_ o.jpg

Core Nebula crop at full resolution:
http://farm3. static.flickr. com/2669/ 4098695333_ dcb7b75366_ o.jpg

Image data:
OTA: FSQ-85 f/5.3
Mount: Takahashi EM-200
CCD: SBIG STL-11000M
Filters: Baader
L: 20x15min bin1x1
RGB: 5x10 bin2x2 for each channel
Location: San Pedro de Atacama, Chile

Comments and suggestions are welcome

Thanks

Filippo Ciferri

www.chasingtheworld .com
www.flickr.com/ photos/filippoas tro











[Non-text portions of this message have been removed]

Dears all,

Following the links to NGC 6726 taken from Atacama, during my last trip, with my
FSQ-85.

Medium Resolution:
http://farm3.static.flickr.com/2558/4098693879_1507ec43a4_o.jpg

Core Nebula crop at full resolution:
http://farm3.static.flickr.com/2669/4098695333_dcb7b75366_o.jpg

Image data:
OTA: FSQ-85 f/5.3
Mount: Takahashi EM-200
CCD: SBIG STL-11000M
Filters: Baader
L: 20x15min bin1x1
RGB: 5x10 bin2x2 for each channel
Location: San Pedro de Atacama, Chile

Comments and suggestions are welcome

Thanks

Filippo Ciferri

www.chasingtheworld.com
www.flickr.com/photos/filippoastro

Thanks everyone for your input. If it clears tonight I may check the alignment
again and be sure the offset is correct and the bubble level is level.

As far as elogated stars in unguided 2 minute + exposures, I will attempt to
slow or speed up the RA to see if the slow constant drift can be stablized.

I will keep you all informed on my progress.

Don



--- In UncensoredTakGroup@yahoogroups.com, "Pawel T. Lancucki"
<pawel.lancucki@...> wrote:
>
>
> Hi Don
>
> It could be the case that your bubble level is not properly calibrated.
>
> If you have set up the mount very well polar aligned using drift method,
> and you are still off looking at the polar finder, *but* could bring
> Polaris to the box by turning the RA, this is most probably the case.
>
> Keep your mount aligned using drift method, set your location offset
> correctly (this compensates for the difference between your central time
> zone and your local time), match date and time and than turn RA until the
> Polaris is in the box on 2010 mark. Now, there is a small (IIRC Allen) set
> screw which you need to loosen to get the bubble level turning. With RA
> switched off, turn the bubble level until it is - well - level - and
> tighten the screw to keep it in place. From now on, your polar finder
> should work. In my experience, it is very hard to knock the internal polar
> finder out of alignment.
>
> All the best.
>
> Pawel
>

Hallo and thank you for welcoming in the group, we would like to share a few
thoughts, from our viewpoint of carbon fiber manufacturers.
Choosing a carbon fiber tube or Serrurier truss is certainly beneficial,
especially in astrographs.
In regards to carbon fiber performance, the points about fine-tuning the resin
amount are questionable. If ready-to-use carbon fabrics are used (pre-peg) they
are already impregnated and the amount of resin is determined and cannot be
changed: it is instead possible to choose the type of resin that impregnates the
weave. The only way to regulate the resin amount is the technique of soaking via
aspiration in a vacuum environment (at low rpm), however this technique never
achieves a lower percentage of resin than the pre-pegs do, and in any case it is
not possible to control with high confidence and reliability the amount of resin
that actually gets to be included in the weave. Other techniques, such as
termoformation, have no place in astronomy applications.
There are pre-pegs that can be shaped upon mould without working in vacuum
(autoclave), they make use of thermal curing only, in order to achieve
polimerization. My opinion is that this method is not ideal for maximum
performance of a telescope tube, and is interesting only for those parts that
must address weight reductions, but have no structural role and their mechanical
qualities are not important.
Thus, in a carbon fiber telescope tube, it is important to address:
a) the proper setting of the carbon skins in order to achieve maximal axial and
radial resistance with the smallest possible amount of fabric for these
performances;
b) choosing pre-pegs with the appropriate resin (polimerization at 80 C and 8
atm for 4-5 hours)
c) choosing a design that allows, for example with high-module carbon
insertions, to keep high axial resistances with a small amount of carbon fiber;
d) avoiding honeycomb in any instruments that can not rely on a very reliable
and accurate thermal control system.

Demanding high performances from homemade solutions is rarely advisable.

In regards to other remarks, it is true that the carbon fiber tube or truss
keeps under control thermal dilations, it is also true that the metallic parts
are subject to thermal variations, but it is also true that it's possible to
design thin mirrors (25-30mm up to 300mm diameter) that work together with
high-precision cells. A thin glass follows more easily the thermal curve of the
observational environment and keeps a better correction, closer to the
theoretical one in the cleanroom. Also, using very low expansion glasses does
not solve all problems, as the mirror will not have astigmatism induced by
differential expansion, but the boundary layer ruins the photographical
performances of any mirror which is not within 1C of the surrounding air, as it
was shown by Anthony Wesley among many others.
I have had occasion to design some intubations, monolithic and truss, and to
simulate many others, and it turns out that all details, both the metal parts
and the composite, must always be fine-tuned keeping in mind the performances of
the design as a whole. Using precision machined parts (no laser-cut or
water-cut) and choosing high-performance aluminum alloys (in order to allow for
thinner parts) allows a successful exploitation of geometrical strengthpoints of
a design, and as a result, to use a smaller amount of metal.

Hi Don

It could be the case that your bubble level is not properly calibrated.

If you have set up the mount very well polar aligned using drift method,
and you are still off looking at the polar finder, *but* could bring
Polaris to the box by turning the RA, this is most probably the case.

Keep your mount aligned using drift method, set your location offset
correctly (this compensates for the difference between your central time
zone and your local time), match date and time and than turn RA until the
Polaris is in the box on 2010 mark. Now, there is a small (IIRC Allen) set
screw which you need to loosen to get the bubble level turning. With RA
switched off, turn the bubble level until it is - well - level - and
tighten the screw to keep it in place. From now on, your polar finder
should work. In my experience, it is very hard to knock the internal polar
finder out of alignment.

All the best.

Pawel

Don,

the EM200/400 have perfect polar scopes and they do a lot for you but before you
start, the bubble must be leveled and the offset scale in a position according
your longitude offset from the meridian, from which you take the local time.
Now bring your local time and date to match and turn corrections in AZ and Alt
until you Have Polaris at the 2010 marker (we are very close to 2010).
All that has been discussed 2 years before in this forum. You can find some help
in my folder HVB.

Hartmut


--- In UncensoredTakGroup@yahoogroups.com, "Don" <chesssquare@...> wrote:
>
> Hi John,
>
> I'm in central NY. 45 degrees by 75 degrees give or take. I think the offset
is near zero or one at most.
>
> I did a drift method to rid of DEC drift. The bubble and polar alignment scope
didn't seem to help much in getting me close to polar alignment. So I just did
the drift method to get it precise. I then checked the illuminated reticle on
the polar alignment scope and the Polar rectangle wasn't even close when
applying the correct time and date? I'd used my local Eastern standard time and
it was off a lot. I even tried univeral time and it was a lot closer. I'm not
sure if I should be using EST or Univeral? I take it that if the correct offset
is applied on the bubble level that the mount is squared up and pointing in the
correct direction. I noticed that even the slightest rotation that the rectangle
moved in a circular motion in proportion to the direction the mount is moved.
>
> I thought in theory that by placing Polaris in the rectangle that Precise
polar alignment would be very close and to get it precise I would have to make
very fine adjustments in RA and Altitude.
>
> I even have my mount on a steel pier that is leveled.
>
> Maybe I was wrong in my assumption that the rectangal with Polaris correctly
positioned would get me close to precise alignment.
>
> For it to be way off, I must be doing something wrong or it isn't as accurate
as I thought and am relying too much on the polar alignment scope.
>
> Any incite would be appreciated.
>
> Thanks,
> Don
>
> --- In UncensoredTakGroup@yahoogroups.com, "John" <johnnyha@> wrote:
> >
> > Don - just for grins what is your longitude and what offset are you using? 
And, I've also had tracking problems when I had forgotten to level the bubble
before using the polar alignment scope, d'oh!
> >
> > --- In UncensoredTakGroup@yahoogroups.com, "Don" <chesssquare@> wrote:
> > >
> > > Hi all,
> > >
> > > Thanks for the responses. I am not using an autoguider. I manually guide.
I imaged last night and this is what I noticed.
> > >
> > > I took ten images ranging from 1-2.5 minutes. I did not guide at all while
my Canon 30D was taking the exposure.
> > > The first exposures under 90 seconds resulted in nice tight round nicely
guided stars but the longer 2-2.5 minute images showed some small star trails. I
read that during a cycle that there may be a drift of +/- 7 arc seconds perhaps
the mount tracks well for a while then moves a bit during a certain postion on
the gear cycle causing this drift?
> > >
> > > In the end of my imaging session I scrolled through the ten images on the
camera's LCD screen which resembles a short movie when scrolled quickly and the
stars tended to drift continuously downward? I my mount and scope are balanced
correctly and the drift on the mount is slight? Perhaps the tracking speed is
too fast or too slow? I'm not sure which. Is there a way to slow the tracking
speed up or down to cease the continuous drift? When I think of it, maybe this
is my problem rather than gear issue.
> > >
> > > Thanks for all your insight. I may have to break down and purchase a
autoguider at some point. I heard that thew Orion Starshooter is a good option.
> > >
> > > Don
> > >
> > > --- In UncensoredTakGroup@yahoogroups.com, "Don" <chesssquare@> wrote:
> > > >
> > > > Hi all,
> > > >
> > > > I've been imaging using my EM200 mount and have to manually guide.
> > > > I did the drift method and DEC drift had ceased but the RA needs to be
corrected. There is no PEC for this mount which is unfortunate. My friend
commented that I paid a lot of money for the mount and there is no PEC? I told
him that hopefully Takahashi hopefully will at some point incorporate it into
the future mounts. Not sure if there are any plans or if the newer mounts have
PEC now? If you can train out the errors you can take images for sveral minutes
without making corrections.Anyway is there anything out there such as third
party software?
> > > >
> > > > Thanks Don
> > > >
> > >
> >
>

Hi Don,
Have you tried PolarAlignMax? Its acccurate, takes the drudgery and guesswork
out of polar alignment, and above all it's free.
See http://users.bsdwebsolutions.com/~larryweber/

Dale




________________________________
From: Don <chesssquare@...>
To: UncensoredTakGroup@yahoogroups.com
Sent: Thu, November 12, 2009 1:41:47 AM
Subject: [UncensoredTakGroup] Re: EM200 Tracking Issues

 
Hi John,

I'm in central NY. 45 degrees by 75 degrees give or take. I think the offset is
near zero or one at most.

I did a drift method to rid of DEC drift. The bubble and polar alignment scope
didn't seem to help much in getting me close to polar alignment. So I just did
the drift method to get it precise. I then checked the illuminated reticle on
the polar alignment scope and the Polar rectangle wasn't even close when
applying the correct time and date? I'd used my local Eastern standard time and
it was off a lot. I even tried univeral time and it was a lot closer. I'm not
sure if I should be using EST or Univeral? I take it that if the correct offset
is applied on the bubble level that the mount is squared up and pointing in the
correct direction. I noticed that even the slightest rotation that the rectangle
moved in a circular motion in proportion to the direction the mount is moved.

I thought in theory that by placing Polaris in the rectangle that Precise polar
alignment would be very close and to get it precise I would have to make very
fine adjustments in RA and Altitude.

I even have my mount on a steel pier that is leveled.

Maybe I was wrong in my assumption that the rectangal with Polaris correctly
positioned would get me close to precise alignment.

For it to be way off, I must be doing something wrong or it isn't as accurate as
I thought and am relying too much on the polar alignment scope.

Any incite would be appreciated.

Thanks,
Don

--- In UncensoredTakGroup@ yahoogroups. com, "John" <johnnyha@.. .> wrote:
>
> Don - just for grins what is your longitude and what offset are you using?
And, I've also had tracking problems when I had forgotten to level the bubble
before using the polar alignment scope, d'oh!
>
> --- In UncensoredTakGroup@ yahoogroups. com, "Don" <chesssquare@ > wrote:
> >
> > Hi all,
> >
> > Thanks for the responses. I am not using an autoguider. I manually guide. I
imaged last night and this is what I noticed.
> >
> > I took ten images ranging from 1-2.5 minutes. I did not guide at all while
my Canon 30D was taking the exposure.
> > The first exposures under 90 seconds resulted in nice tight round nicely
guided stars but the longer 2-2.5 minute images showed some small star trails. I
read that during a cycle that there may be a drift of +/- 7 arc seconds perhaps
the mount tracks well for a while then moves a bit during a certain postion on
the gear cycle causing this drift?
> >
> > In the end of my imaging session I scrolled through the ten images on the
camera's LCD screen which resembles a short movie when scrolled quickly and the
stars tended to drift continuously downward? I my mount and scope are balanced
correctly and the drift on the mount is slight? Perhaps the tracking speed is
too fast or too slow? I'm not sure which. Is there a way to slow the tracking
speed up or down to cease the continuous drift? When I think of it, maybe this
is my problem rather than gear issue.
> >
> > Thanks for all your insight. I may have to break down and purchase a
autoguider at some point. I heard that thew Orion Starshooter is a good option.
> >
> > Don
> >
> > --- In UncensoredTakGroup@ yahoogroups. com, "Don" <chesssquare@ > wrote:
> > >
> > > Hi all,
> > >
> > > I've been imaging using my EM200 mount and have to manually guide.
> > > I did the drift method and DEC drift had ceased but the RA needs to be
corrected. There is no PEC for this mount which is unfortunate. My friend
commented that I paid a lot of money for the mount and there is no PEC? I told
him that hopefully Takahashi hopefully will at some point incorporate it into
the future mounts. Not sure if there are any plans or if the newer mounts have
PEC now? If you can train out the errors you can take images for sveral minutes
without making corrections. Anyway is there anything out there such as third
party software?
> > >
> > > Thanks Don
> > >
> >
>







[Non-text portions of this message have been removed]

Don,

Did you setup the sliding ring thing on the back of the mount that is supposed
to deal with offset from the middle of the "time zone"?   In my opinion, the
description of how to use that thing is confusing.  And it affects the position
of the box in the reticle.

And now we're not supposed to subtract one hour for DST.   Did you remember
that?

Perhaps you just have a bad reticle.   Mine seems to do an amazing job of
nailing the polar alignment.

Robert


--- In UncensoredTakGroup@yahoogroups.com, "Don" <chesssquare@...> wrote:
>
> Hi John,
>
> I'm in central NY. 45 degrees by 75 degrees give or take. I think the offset
is near zero or one at most.
>
> I did a drift method to rid of DEC drift. The bubble and polar alignment scope
didn't seem to help much in getting me close to polar alignment. So I just did
the drift method to get it precise. I then checked the illuminated reticle on
the polar alignment scope and the Polar rectangle wasn't even close when
applying the correct time and date? I'd used my local Eastern standard time and
it was off a lot. I even tried univeral time and it was a lot closer. I'm not
sure if I should be using EST or Univeral? I take it that if the correct offset
is applied on the bubble level that the mount is squared up and pointing in the
correct direction. I noticed that even the slightest rotation that the rectangle
moved in a circular motion in proportion to the direction the mount is moved.
>
> I thought in theory that by placing Polaris in the rectangle that Precise
polar alignment would be very close and to get it precise I would have to make
very fine adjustments in RA and Altitude.
>
> I even have my mount on a steel pier that is leveled.
>
> Maybe I was wrong in my assumption that the rectangal with Polaris correctly
positioned would get me close to precise alignment.
>
> For it to be way off, I must be doing something wrong or it isn't as accurate
as I thought and am relying too much on the polar alignment scope.
>
> Any incite would be appreciated.
>
> Thanks,
> Don
>
> --- In UncensoredTakGroup@yahoogroups.com, "John" <johnnyha@> wrote:
> >
> > Don - just for grins what is your longitude and what offset are you using? 
And, I've also had tracking problems when I had forgotten to level the bubble
before using the polar alignment scope, d'oh!
> >
> > --- In UncensoredTakGroup@yahoogroups.com, "Don" <chesssquare@> wrote:
> > >
> > > Hi all,
> > >
> > > Thanks for the responses. I am not using an autoguider. I manually guide.
I imaged last night and this is what I noticed.
> > >
> > > I took ten images ranging from 1-2.5 minutes. I did not guide at all while
my Canon 30D was taking the exposure.
> > > The first exposures under 90 seconds resulted in nice tight round nicely
guided stars but the longer 2-2.5 minute images showed some small star trails. I
read that during a cycle that there may be a drift of +/- 7 arc seconds perhaps
the mount tracks well for a while then moves a bit during a certain postion on
the gear cycle causing this drift?
> > >
> > > In the end of my imaging session I scrolled through the ten images on the
camera's LCD screen which resembles a short movie when scrolled quickly and the
stars tended to drift continuously downward? I my mount and scope are balanced
correctly and the drift on the mount is slight? Perhaps the tracking speed is
too fast or too slow? I'm not sure which. Is there a way to slow the tracking
speed up or down to cease the continuous drift? When I think of it, maybe this
is my problem rather than gear issue.
> > >
> > > Thanks for all your insight. I may have to break down and purchase a
autoguider at some point. I heard that thew Orion Starshooter is a good option.
> > >
> > > Don
> > >
> > > --- In UncensoredTakGroup@yahoogroups.com, "Don" <chesssquare@> wrote:
> > > >
> > > > Hi all,
> > > >
> > > > I've been imaging using my EM200 mount and have to manually guide.
> > > > I did the drift method and DEC drift had ceased but the RA needs to be
corrected. There is no PEC for this mount which is unfortunate. My friend
commented that I paid a lot of money for the mount and there is no PEC? I told
him that hopefully Takahashi hopefully will at some point incorporate it into
the future mounts. Not sure if there are any plans or if the newer mounts have
PEC now? If you can train out the errors you can take images for sveral minutes
without making corrections.Anyway is there anything out there such as third
party software?
> > > >
> > > > Thanks Don
> > > >
> > >
> >
>

Hi John,

I'm in central NY. 45 degrees by 75 degrees give or take. I think the offset is
near zero or one at most.

I did a drift method to rid of DEC drift. The bubble and polar alignment scope
didn't seem to help much in getting me close to polar alignment. So I just did
the drift method to get it precise. I then checked the illuminated reticle on
the polar alignment scope and the Polar rectangle wasn't even close when
applying the correct time and date? I'd used my local Eastern standard time and
it was off a lot. I even tried univeral time and it was a lot closer. I'm not
sure if I should be using EST or Univeral? I take it that if the correct offset
is applied on the bubble level that the mount is squared up and pointing in the
correct direction. I noticed that even the slightest rotation that the rectangle
moved in a circular motion in proportion to the direction the mount is moved.

I thought in theory that by placing Polaris in the rectangle that Precise polar
alignment would be very close and to get it precise I would have to make very
fine adjustments in RA and Altitude.

I even have my mount on a steel pier that is leveled.

Maybe I was wrong in my assumption that the rectangal with Polaris correctly
positioned would get me close to precise alignment.

For it to be way off, I must be doing something wrong or it isn't as accurate as
I thought and am relying too much on the polar alignment scope.

Any incite would be appreciated.

Thanks,
Don

--- In UncensoredTakGroup@yahoogroups.com, "John" <johnnyha@...> wrote:
>
> Don - just for grins what is your longitude and what offset are you using? 
And, I've also had tracking problems when I had forgotten to level the bubble
before using the polar alignment scope, d'oh!
>
> --- In UncensoredTakGroup@yahoogroups.com, "Don" <chesssquare@> wrote:
> >
> > Hi all,
> >
> > Thanks for the responses. I am not using an autoguider. I manually guide. I
imaged last night and this is what I noticed.
> >
> > I took ten images ranging from 1-2.5 minutes. I did not guide at all while
my Canon 30D was taking the exposure.
> > The first exposures under 90 seconds resulted in nice tight round nicely
guided stars but the longer 2-2.5 minute images showed some small star trails. I
read that during a cycle that there may be a drift of +/- 7 arc seconds perhaps
the mount tracks well for a while then moves a bit during a certain postion on
the gear cycle causing this drift?
> >
> > In the end of my imaging session I scrolled through the ten images on the
camera's LCD screen which resembles a short movie when scrolled quickly and the
stars tended to drift continuously downward? I my mount and scope are balanced
correctly and the drift on the mount is slight? Perhaps the tracking speed is
too fast or too slow? I'm not sure which. Is there a way to slow the tracking
speed up or down to cease the continuous drift? When I think of it, maybe this
is my problem rather than gear issue.
> >
> > Thanks for all your insight. I may have to break down and purchase a
autoguider at some point. I heard that thew Orion Starshooter is a good option.
> >
> > Don
> >
> > --- In UncensoredTakGroup@yahoogroups.com, "Don" <chesssquare@> wrote:
> > >
> > > Hi all,
> > >
> > > I've been imaging using my EM200 mount and have to manually guide.
> > > I did the drift method and DEC drift had ceased but the RA needs to be
corrected. There is no PEC for this mount which is unfortunate. My friend
commented that I paid a lot of money for the mount and there is no PEC? I told
him that hopefully Takahashi hopefully will at some point incorporate it into
the future mounts. Not sure if there are any plans or if the newer mounts have
PEC now? If you can train out the errors you can take images for sveral minutes
without making corrections.Anyway is there anything out there such as third
party software?
> > >
> > > Thanks Don
> > >
> >
>

Hello to all



Quite a long time I posted some images on this group, so let me present you
the latest one done with my brave Newton MT200.



Telescope  = MT200 (Newton, Fd6)

Camera  = ST2000 + Astrodon LRGB filters

Mount  = MK70



Location = North of France



Luminance = 17 exposures of 15 ‘ at -15°c  (1X1)

RGB = 16 exposures for each channel of 10 ‘ (2X2)



Process through Maxim 5 and Cs3



Average resolution is 2.8”



http://astrosurf.com/candrzej/cielprofond/galaxies/abell262.html



I hope you will like it



Christian



http://astrosurf.com/candrzej





Ps : some other NGC objects done with that OTA this year can be seen on my
site







[Non-text portions of this message have been removed]

We have a tube in stock. We can covert you telescope for you.

Art
   ----- Original Message -----
   From: tommack7882
   To: UncensoredTakGroup@yahoogroups.com
   Sent: Wednesday, November 11, 2009 12:30 PM
   Subject: Re: Fw: Fw: [UncensoredTakGroup] Mewlon & Carbon Fiber Tube





   --- In UncensoredTakGroup@yahoogroups.com, "Art Ciampi \(Texas Nautical
Repair\)" <artc@...> wrote:
   >
   > Here is Gary Walker's statement.
   >
   > Art
   > ----- Original Message -----
   > From: "Gary Walker" <bailyhill@...>
   > To: <artc@...>
   > Sent: Tuesday, November 10, 2009 8:29 PM
   > Subject: Re: Fw: [UncensoredTakGroup] Mewlon & Carbon Fiber Tube
   >
   >
   > Hello Tom--Art please forward to Tom
   >
   > It is true that the carbon tube will not compensate for any change in
   > focus causeed by the change in the mirror optics. However, in a
   > casagrain optical system, the focus change depends upon 2 factors--the
   > optics and the primary to secondary spacing--which happens to be the
   > dominant error source in the Mewlon system. The focus change is also a
   > function of the f ratio of the system. The longer the f ratio, the
   > more the change. As I remember, it goes as the square of the f ratio.
   >
   > So much for the theory. I have measured the focus before and after the
   > carbon tube modification. The difference is huge. I measured a factor
   > of 32 times smaller with the carbon tube. If you are a Mewlon 300
   > owner who images, you know that the change in focus is very noticeable.
   > With my carbon tube, I have a very hard time measuring it.
   >
   > I am sure that the optics expert is correct as far as the optics is
   > concerned, however, this is a system problem and there are other
   > issues. The optics may indeed change focus, but the system focus
   > change is greatly reduced.
   >
   > Let me know if you have any questions. BTW: I image all night, doing
   > time series that last several hours. The focus is rock solid. I do
   > not have to refocus during the night. You might want to look on the
   > Public Missiles web site, which talks about the focus change of sct's.
   > Perhaps if the Mewlon used zerodur it would be even better. It is true
   > that if the carbon is done wrong, then the expansion will not be small.
   > It seems that based on my tests, that the carbon tube in the Mewlon
   > 300 works very well.
   >
   >
   > Thanks
   >
   > Clear Skies
   > Gary Walker
   > Maria Mitchell Observatory
   > 4 Vestal Street
   > Nantucket, Mass 02554
   >
   >
   > Hi Gary,
   Thanks for your input. Your measurements are hard to contradict, even by a
master optician. Yes, I had looked at Public Missiles but was wary because their
tubes are designed for amateur Rocketeers where strength and weight are more of
a concern than expansion coefficients. It is nice to know their tubes can also
be used for astro purposes.

   Best,
   Tom Mack





[Non-text portions of this message have been removed]

--- In UncensoredTakGroup@yahoogroups.com, "Art Ciampi \(Texas Nautical
Repair\)" <artc@...> wrote:
>
> Here is Gary Walker's statement.
>
> Art
> ----- Original Message -----
> From: "Gary Walker" <bailyhill@...>
> To: <artc@...>
> Sent: Tuesday, November 10, 2009 8:29 PM
> Subject: Re: Fw: [UncensoredTakGroup] Mewlon & Carbon Fiber Tube
>
>
> Hello Tom--Art please forward to Tom
>
> It is true that the carbon tube will not compensate for any change in
> focus causeed by the change in the mirror optics.  However, in a
> casagrain optical system, the focus change depends upon 2 factors--the
> optics and the primary to secondary spacing--which happens to be the
> dominant error source in the Mewlon system.  The focus change is also a
> function of the f ratio of the system.  The longer the f ratio, the
> more the change. As I remember, it goes as the square of the f ratio.
>
> So much for the theory.  I have measured the focus before and after the
> carbon tube modification.  The difference is huge.  I measured a factor
> of 32 times smaller with the carbon tube.  If you are a Mewlon 300
> owner who images, you know that the change in focus is very noticeable.
>  With my carbon tube, I have a very hard time measuring it.
>
> I am sure that the optics expert is correct as far as the optics is
> concerned, however, this is a system problem and there are other
> issues.  The optics may indeed change focus, but the system focus
> change is greatly reduced.
>
> Let me know if you have any questions.  BTW:  I image all night, doing
> time series that last several hours.  The focus is rock solid.  I do
> not have to refocus during the night.  You might want to look on the
> Public Missiles web site, which talks about the focus change of sct's.
> Perhaps if the Mewlon used zerodur it would be even better.  It is true
> that if the carbon is done wrong, then the expansion will not be small.
>   It seems that based on my tests, that the carbon tube in the Mewlon
> 300 works very well.
>
>
> Thanks
>
> Clear Skies
> Gary Walker
> Maria Mitchell Observatory
> 4 Vestal Street
> Nantucket, Mass  02554
>
>
> Hi Gary,
Thanks for your input.  Your measurements are hard to contradict, even by a
master optician.  Yes, I had looked at Public Missiles but was wary because
their tubes are designed for amateur Rocketeers where strength and weight are
more of a concern than expansion coefficients.  It is nice to know their tubes
can also be used for astro purposes.

Best,
Tom Mack

Here is Gary Walker's statement.

Art
----- Original Message -----
From: "Gary Walker" <bailyhill@...>
To: <artc@...>
Sent: Tuesday, November 10, 2009 8:29 PM
Subject: Re: Fw: [UncensoredTakGroup] Mewlon & Carbon Fiber Tube


Hello Tom--Art please forward to Tom

It is true that the carbon tube will not compensate for any change in
focus causeed by the change in the mirror optics.  However, in a
casagrain optical system, the focus change depends upon 2 factors--the
optics and the primary to secondary spacing--which happens to be the
dominant error source in the Mewlon system.  The focus change is also a
function of the f ratio of the system.  The longer the f ratio, the
more the change. As I remember, it goes as the square of the f ratio.

So much for the theory.  I have measured the focus before and after the
carbon tube modification.  The difference is huge.  I measured a factor
of 32 times smaller with the carbon tube.  If you are a Mewlon 300
owner who images, you know that the change in focus is very noticeable.
  With my carbon tube, I have a very hard time measuring it.

I am sure that the optics expert is correct as far as the optics is
concerned, however, this is a system problem and there are other
issues.  The optics may indeed change focus, but the system focus
change is greatly reduced.

Let me know if you have any questions.  BTW:  I image all night, doing
time series that last several hours.  The focus is rock solid.  I do
not have to refocus during the night.  You might want to look on the
Public Missiles web site, which talks about the focus change of sct's.
Perhaps if the Mewlon used zerodur it would be even better.  It is true
that if the carbon is done wrong, then the expansion will not be small.
   It seems that based on my tests, that the carbon tube in the Mewlon
300 works very well.


Thanks

Clear Skies
Gary Walker
Maria Mitchell Observatory
4 Vestal Street
Nantucket, Mass  02554


-----Original Message-----
From: Art Ciampi (Texas Nautical Repair) <artc@...>
To: Gary Walker <bailyhill@...>
Sent: Tue, Nov 10, 2009 5:29 pm
Subject: Fw: [UncensoredTakGroup] Mewlon & Carbon Fiber Tube

Gary:
Â
This conclusion flies in the face of what you
measured.
Â
Art
----- Original Message -----
From: tommack7882

To: UncensoredTakGroup@yahoogroups.com

Sent: Tuesday, November 10, 2009 4:22 PM
Subject: [UncensoredTakGroup] Mewlon & Carbon Fiber
Tube

Â




Being an owner of a Mewlon 300, I was close to buying a carbon fiber
tube
upgrade for image stability. At the recent AIC conference, one very
well known
optical designer said that not all carbon fiber tubes are made equally
and some
have significant expansion and contraction properties. Another well
know
optician said that carbon fiber only benefits a optical system that
uses zero
expansion mirrors (ie Quartz, Zerodor, Cervit.) When asked if carbon
fiber would
benefit a mirrored system using Pyrex (Mewlons) the response was that
the only
benefit would be a slightly lighter tube.
Food for
thought.

Best,
Tom Mack

The telescope in question is owned by Gary Walker of the Maria MItchell
Observatory.

It was he who measured the focus change.

Art
   ----- Original Message -----
   From: rlnielsen1960
   To: UncensoredTakGroup@yahoogroups.com
   Sent: Wednesday, November 11, 2009 7:52 AM
   Subject: [UncensoredTakGroup] Re: Mewlon & Carbon Fiber Tube



   Everyone,

   I seem to remember that Art said the carbon tube modification for the Mewlon
300 reduced the "effects" of temperature change by a factor of 32X. So someone
(likely at Tak HQ) did some measurements. Perhaps he can ask the folks back in
Japan for more specific data.

   Robert

   --- In UncensoredTakGroup@yahoogroups.com, "tommack7882" <tommack7@...> wrote:
   >
   >
   >
   >
   >
   > >
   > > > Another well know optician said that carbon fiber only benefits a
optical
   > > system that uses zero expansion mirrors
   > >
   > > IMO this statement is not correct.
   > >
   > > Gene
   > >
   > Hi Gene,
   > Appreciate your thoughts on this. The logic behind not using carbon fiber
with pyrex is that the primary to secondary distance remains constant with
carbon fiber; however, with pyrex the primary mirror focal length (mirror radius
shrinks) will change with dropping temperatures resulting in a change in back
focus. Aluminum tubing to some extent compensates for this but carbon fiber will
not. This is also why some claim carbon fiber tubes in refractors do more harm
than good.
   > Sure would like to see some valid research done on this to verify the
veracity of the claim.
   >
   > Tom Mack
   >





[Non-text portions of this message have been removed]

Well, coeficient of Pyrex is 32.5 x10e-7/degre C.

Carbon tubes are generally around 10x10e-7/degre C.

Even if you put a carbon tube, some length of the optical path (focuser
etc...) will still be Aluminum which is
220x10e-7/degre C

So, with the aprox numbers, if maybe 5% of the length of the optical path is
Aluminum tube, Pyrex + Carbon will be very very close from fixed focus with
temperature changes.





-- benoit

On Wed, Nov 11, 2009 at 4:13 AM, tommack7882 <tommack7@...> wrote:

>
>
>
>
> >
> > > Another well know optician said that carbon fiber only benefits a
> optical
> > system that uses zero expansion mirrors
> >
> > IMO this statement is not correct.
> >
> > Gene
> >
> Hi Gene,
> Appreciate your thoughts on this. The logic behind not using carbon fiber
> with pyrex is that the primary to secondary distance remains constant with
> carbon fiber; however, with pyrex the primary mirror focal length (mirror
> radius shrinks) will change with dropping temperatures resulting in a change
> in back focus. Aluminum tubing to some extent compensates for this but
> carbon fiber will not. This is also why some claim carbon fiber tubes in
> refractors do more harm than good.
> Sure would like to see some valid research done on this to verify the
> veracity of the claim.
>
> Tom Mack
>
>
>


[Non-text portions of this message have been removed]

Everyone,

I seem to remember that Art said the carbon tube modification for the Mewlon 300
reduced the "effects" of temperature change by a factor of 32X.   So someone
(likely at Tak HQ) did some measurements.   Perhaps he can ask the folks back in
Japan for more specific data.

Robert

--- In UncensoredTakGroup@yahoogroups.com, "tommack7882" <tommack7@...> wrote:
>
>
>
>
>
> >
> > > Another well know optician said that carbon fiber only benefits a optical
> > system that uses zero expansion mirrors
> >
> > IMO this statement is not correct.
> >
> > Gene
> >
> Hi Gene,
> Appreciate your thoughts on this.  The logic behind not using carbon fiber
with pyrex is that the primary to secondary distance remains constant with
carbon fiber; however, with pyrex the primary mirror focal length (mirror radius
shrinks) will change with dropping temperatures resulting in a change in back
focus.  Aluminum tubing to some extent compensates for this but carbon fiber
will not. This is also why some claim carbon fiber tubes in refractors do more
harm than good.
> Sure would like to see some valid research done on this to verify the veracity
of the claim.
>
> Tom Mack
>

>
> > Another well know optician said that carbon fiber only benefits a optical
> system that uses zero expansion mirrors
>
> IMO this statement is not correct.
>
> Gene
>
Hi Gene,
Appreciate your thoughts on this.  The logic behind not using carbon fiber with
pyrex is that the primary to secondary distance remains constant with carbon
fiber; however, with pyrex the primary mirror focal length (mirror radius
shrinks) will change with dropping temperatures resulting in a change in back
focus.  Aluminum tubing to some extent compensates for this but carbon fiber
will not. This is also why some claim carbon fiber tubes in refractors do more
harm than good.
Sure would like to see some valid research done on this to verify the veracity
of the claim.

Tom Mack

You're not properly polar aligned, hence star trails.

--- In UncensoredTakGroup@yahoogroups.com, "John" <johnnyha@...> wrote:
>
> Don - just for grins what is your longitude and what offset are you using? 
And, I've also had tracking problems when I had forgotten to level the bubble
before using the polar alignment scope, d'oh!
>
> --- In UncensoredTakGroup@yahoogroups.com, "Don" <chesssquare@> wrote:
> >
> > Hi all,
> >
> > Thanks for the responses. I am not using an autoguider. I manually guide. I
imaged last night and this is what I noticed.
> >
> > I took ten images ranging from 1-2.5 minutes. I did not guide at all while
my Canon 30D was taking the exposure.
> > The first exposures under 90 seconds resulted in nice tight round nicely
guided stars but the longer 2-2.5 minute images showed some small star trails. I
read that during a cycle that there may be a drift of +/- 7 arc seconds perhaps
the mount tracks well for a while then moves a bit during a certain postion on
the gear cycle causing this drift?
> >
> > In the end of my imaging session I scrolled through the ten images on the
camera's LCD screen which resembles a short movie when scrolled quickly and the
stars tended to drift continuously downward? I my mount and scope are balanced
correctly and the drift on the mount is slight? Perhaps the tracking speed is
too fast or too slow? I'm not sure which. Is there a way to slow the tracking
speed up or down to cease the continuous drift? When I think of it, maybe this
is my problem rather than gear issue.
> >
> > Thanks for all your insight. I may have to break down and purchase a
autoguider at some point. I heard that thew Orion Starshooter is a good option.
> >
> > Don
> >
> > --- In UncensoredTakGroup@yahoogroups.com, "Don" <chesssquare@> wrote:
> > >
> > > Hi all,
> > >
> > > I've been imaging using my EM200 mount and have to manually guide.
> > > I did the drift method and DEC drift had ceased but the RA needs to be
corrected. There is no PEC for this mount which is unfortunate. My friend
commented that I paid a lot of money for the mount and there is no PEC? I told
him that hopefully Takahashi hopefully will at some point incorporate it into
the future mounts. Not sure if there are any plans or if the newer mounts have
PEC now? If you can train out the errors you can take images for sveral minutes
without making corrections.Anyway is there anything out there such as third
party software?
> > >
> > > Thanks Don
> > >
> >
>

John,

The mount is in a permanent observatory and runs on AC.

Gordon.

--- In UncensoredTakGroup@yahoogroups.com, "John" <johnnyha@...> wrote:
>
> Did you try with a different battery?  Could just be low voltage?
>
> --- In UncensoredTakGroup@yahoogroups.com, "GordonM" <gmandell@> wrote:
> >
> > Hi Friends.
> >
> > I thought that I had solved the problem of my NJP mount stalling in RA but
unfortunately I have not.  The weird thing is that the mount still
intermittently stalls  but only when the mount is in a certain position, when
the counterweight shaft (Dec axis) and telescope are parallel to the ground with
the counterweights on the West side of the mount.  This is the position that I
use when "parking" the mount.
> >
> > The mount is well balanced and not overly loaded.  At first I thought that
the problem was related to the RA gear cover rubbing the reducing gear but even
with the cover off, the mount still stalled.  Next I cleaned the motor and
reducing gears and applied fresh lithium grease.  As Art suggested, I used a
folded piece of cigarette paper to space the gears but the mount still stalled. 
Finally I re-adjusted the worm block.  It seems to be even with minimal play in
the RA axis and no noticable wobble in the reducing gear.  It didn't stall
despite putting the mount in the "parked" position multiple times, however 2
nights ago at the end of the night it stalled again.
> >
> > Is there anything else I can do?  I'm hoping one of the mount gurus in the
group will point me in the right direction.
> >
> > Thanks in advance.
> >
> > Gordon
> >
>

> At the recent AIC conference, one very well known optical designer said
that not all carbon fiber tubes are made equally and some have significant
expansion and contraction properties.

Very true.  Carbon fiber itself has good properties.  The resins that hold
it all together, though, is pretty bad.  IIRC proper manufacturing for low
CoE involves high pressure and suction to remove as much excess resin as
possible and is not a common nor cheap process.

> Another well know optician said that carbon fiber only benefits a optical
system that uses zero expansion mirrors

IMO this statement is not correct.

Gene

Being an owner of a Mewlon 300, I was close to buying a carbon fiber tube
upgrade for image stability.  At the recent AIC conference, one very well known
optical designer said that not all carbon fiber tubes are made equally and some
have significant expansion and contraction properties.  Another well know
optician said that carbon fiber only benefits  a optical system that uses zero
expansion mirrors (ie Quartz, Zerodor, Cervit.)  When asked if carbon fiber
would benefit  a mirrored system using Pyrex (Mewlons) the response was that the
only benefit would be a slightly lighter tube.
Food for thought.

Best,
Tom Mack

Don - just for grins what is your longitude and what offset are you using?  And,
I've also had tracking problems when I had forgotten to level the bubble before
using the polar alignment scope, d'oh!

--- In UncensoredTakGroup@yahoogroups.com, "Don" <chesssquare@...> wrote:
>
> Hi all,
>
> Thanks for the responses. I am not using an autoguider. I manually guide. I
imaged last night and this is what I noticed.
>
> I took ten images ranging from 1-2.5 minutes. I did not guide at all while my
Canon 30D was taking the exposure.
> The first exposures under 90 seconds resulted in nice tight round nicely
guided stars but the longer 2-2.5 minute images showed some small star trails. I
read that during a cycle that there may be a drift of +/- 7 arc seconds perhaps
the mount tracks well for a while then moves a bit during a certain postion on
the gear cycle causing this drift?
>
> In the end of my imaging session I scrolled through the ten images on the
camera's LCD screen which resembles a short movie when scrolled quickly and the
stars tended to drift continuously downward? I my mount and scope are balanced
correctly and the drift on the mount is slight? Perhaps the tracking speed is
too fast or too slow? I'm not sure which. Is there a way to slow the tracking
speed up or down to cease the continuous drift? When I think of it, maybe this
is my problem rather than gear issue.
>
> Thanks for all your insight. I may have to break down and purchase a
autoguider at some point. I heard that thew Orion Starshooter is a good option.
>
> Don
>
> --- In UncensoredTakGroup@yahoogroups.com, "Don" <chesssquare@> wrote:
> >
> > Hi all,
> >
> > I've been imaging using my EM200 mount and have to manually guide.
> > I did the drift method and DEC drift had ceased but the RA needs to be
corrected. There is no PEC for this mount which is unfortunate. My friend
commented that I paid a lot of money for the mount and there is no PEC? I told
him that hopefully Takahashi hopefully will at some point incorporate it into
the future mounts. Not sure if there are any plans or if the newer mounts have
PEC now? If you can train out the errors you can take images for sveral minutes
without making corrections.Anyway is there anything out there such as third
party software?
> >
> > Thanks Don
> >
>

Did you try with a different battery?  Could just be low voltage?

--- In UncensoredTakGroup@yahoogroups.com, "GordonM" <gmandell@...> wrote:
>
> Hi Friends.
>
> I thought that I had solved the problem of my NJP mount stalling in RA but
unfortunately I have not.  The weird thing is that the mount still
intermittently stalls  but only when the mount is in a certain position, when
the counterweight shaft (Dec axis) and telescope are parallel to the ground with
the counterweights on the West side of the mount.  This is the position that I
use when "parking" the mount.
>
> The mount is well balanced and not overly loaded.  At first I thought that the
problem was related to the RA gear cover rubbing the reducing gear but even with
the cover off, the mount still stalled.  Next I cleaned the motor and reducing
gears and applied fresh lithium grease.  As Art suggested, I used a folded piece
of cigarette paper to space the gears but the mount still stalled.  Finally I
re-adjusted the worm block.  It seems to be even with minimal play in the RA
axis and no noticable wobble in the reducing gear.  It didn't stall despite
putting the mount in the "parked" position multiple times, however 2 nights ago
at the end of the night it stalled again.
>
> Is there anything else I can do?  I'm hoping one of the mount gurus in the
group will point me in the right direction.
>
> Thanks in advance.
>
> Gordon
>

The metal back distance is the distance between the rearmost metal surface of
the reducer or flattener that the next part comes into contact with,  to the
focal plane or best focus point. The metal back distance is a function of the
design of the particular device.

Art
   ----- Original Message -----
   From: Pawel T. Lancucki
   To: UncensoredTakGroup@yahoogroups.com
   Sent: Tuesday, November 10, 2009 5:56 AM
   Subject: [UncensoredTakGroup] Re: TOA-150 Reducer Connection?




   > Hi Art - There seems to be serious confusion here.
   >
   > Assuming the metal back distance refers to the distance between the
   lens-side corner
   > of the TOA130R and the focal plane, this suggests that the unvignetted
   circle has a diameter
   > of 31 mm (TOA130) and 29 mm (TOA150).
   >
   > Could you put this to rest once and for always - what does "metal back
   distance" mean?
   >
   > Clearest
   > Bruce, Toronto

   Hi Bruce

   While clearly myself not being Art ;-), I hope to be able to bring some
   light.

   In the past, I did a lot of experimenting with a couple of Takahashi
   telescopes / reducers / flatteners (FS102, TOA130, SKY90). The "metal
   back" is sort of technical term, meaning the distance between the rear
   flange of the reducer / corrector (or, in case of FSQ106, racked-in
   focuser) to image plane. It is used to allow users to build their image
   train starting from reducer to equal this distance. In essence, knowing the
   location of the detector in your camera and using calipers, you could check
   the metal back distance yourself after unscrewing the adapters from
   reducer / flattener. For instance, with SKY90 and reducer having ca 72mm
   backfocus, when you add CA35, Takahashi wide-T ring and DSLR, you end up at
   that distance.

   What does this "Xmm image circle" mean in optical terms? At the design
   (metal back) distance, you get flat field with minimum of off-axis
   aberrations. I do not remember details but *I think* for new telescopes
   like TOA that means calculated spot images up to the specified radius of
   less than 10um for wavelengths between near-IR to V or UV - in practice
   "nice round stars to the corner". The calculated spot images for various
   wavelengths used to be available on Takahashi Japan pages.

   What you do not get is an even illumination of that image circle.
   Interestingly, even the old FSQ106 did not have even illumination
   (specified image circle of 88mm) - there was a "hot spot" in the center.

   Personally, if the vigneting is not severe (like 50% light drop-out), I
   definitely prefer to have good star images to the corner and get rid of
   vigneting using flat fielding. Off course, it is better to start with more
   even illumination, as flat fielding always increases noise in the darker
   portions of the image.

   One more point - depending on the camera, vigneting may be introduced less
   by the reducer and more by the baffling effects in the light path - I do
   not own STL11k but my friends noticed that vigneting in fast configurations
   could be minimized using wider input than standard T or 2" push-fit.
   Personally, while analyzing or designing my optical configurations, I do
   use simplified ray tracing to verify the fully illuminated field.

   Best regards

   Pawel





[Non-text portions of this message have been removed]

Hi Friends.

I thought that I had solved the problem of my NJP mount stalling in RA but
unfortunately I have not.  The weird thing is that the mount still
intermittently stalls  but only when the mount is in a certain position, when
the counterweight shaft (Dec axis) and telescope are parallel to the ground with
the counterweights on the West side of the mount.  This is the position that I
use when "parking" the mount.

The mount is well balanced and not overly loaded.  At first I thought that the
problem was related to the RA gear cover rubbing the reducing gear but even with
the cover off, the mount still stalled.  Next I cleaned the motor and reducing
gears and applied fresh lithium grease.  As Art suggested, I used a folded piece
of cigarette paper to space the gears but the mount still stalled.  Finally I
re-adjusted the worm block.  It seems to be even with minimal play in the RA
axis and no noticable wobble in the reducing gear.  It didn't stall despite
putting the mount in the "parked" position multiple times, however 2 nights ago
at the end of the night it stalled again.

Is there anything else I can do?  I'm hoping one of the mount gurus in the group
will point me in the right direction.

Thanks in advance.

Gordon

> Hi Art - There seems to be serious confusion here.
>
> Assuming the metal back distance refers to the distance between the
lens-side corner
> of the TOA130R and the focal plane, this suggests that the unvignetted
circle has a diameter
> of 31 mm (TOA130) and 29 mm (TOA150).
>
> Could you put this to rest once and for always - what does "metal back
distance" mean?
>
> Clearest
> Bruce, Toronto

Hi Bruce

While clearly myself not being Art ;-), I hope to be able to bring some
light.

In the past, I did a lot of experimenting with a couple of Takahashi
telescopes / reducers / flatteners (FS102, TOA130, SKY90).  The "metal
back" is sort of technical term, meaning the distance between the rear
flange of the reducer / corrector (or, in case of FSQ106, racked-in
focuser) to image plane. It is used to allow users to build their image
train starting from reducer to equal this distance. In essence, knowing the
location of the detector in your camera and using calipers, you could check
the metal back distance yourself after unscrewing the adapters from
reducer / flattener. For instance, with SKY90 and reducer having ca 72mm
backfocus, when you add CA35, Takahashi wide-T ring and DSLR, you end up at
that distance.

What does this "Xmm image circle" mean in optical terms? At the design
(metal back) distance, you get flat field with minimum of off-axis
aberrations. I do not remember details but *I think* for new telescopes
like TOA that means calculated spot images up to the specified radius of
less than 10um for wavelengths between near-IR to V or UV - in practice
"nice round stars to the corner". The calculated spot images for various
wavelengths used to be available on Takahashi Japan pages.

What you do not get is an even illumination of that image circle.
Interestingly, even the old FSQ106 did not have even illumination
(specified image circle of 88mm) - there was a "hot spot" in the center.

Personally, if the vigneting is not severe (like 50% light drop-out), I
definitely prefer to have good star images to the corner and get rid of
vigneting using flat fielding. Off course, it is better to start with more
even illumination, as flat fielding always increases noise in the darker
portions of the image.

One more point - depending on the camera, vigneting may be introduced less
by the reducer and more by the baffling effects in the light path - I do
not own STL11k but my friends noticed that vigneting in fast configurations
could be minimized using wider input than standard T or 2" push-fit.
Personally, while analyzing or designing my optical configurations, I do
use simplified ray tracing to verify the fully illuminated field.

Best regards

Pawel

Hi all

Just in case it is of value to someone, I mounted the diagonal for a FSQ106N
directly onto the CAA of my TOA-150.

This combination allows me to achieve focus with my Denk binoviewers / 30LE's
_without_ using a Barlow. There is still about 8 or 9 mm in focus available,
suggesting that most common bv eyepieces will come to focus.

The true field of view with a pair of 24 Pans is about 1.5 degrees, which is
about as good as it can get with this scope. The 30LE's produce a slightly
smaller field.

Clearest
Bruce, Toronto

Posted this last night.  HaLRGB, total time 2 hrs.
http://www.lalunasky.com/images/IC434_color-III-edit_label.jpg

Jeff
www.lalunasky.com