That was my point... it's why I specified equal aperture _area_, not equal
aperture. It's likely the difference between the two scopes in this case.

Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


----- Original Message -----
From: "Rod Mollise" <rmollise@...>
To: <sct-user@yahoogroups.com>
Sent: Saturday, November 21, 2009 6:30 AM
Subject: RE: [sct-user] Dimmer views of Moon/Jupiter between 6" f10 SCT
compared to 6" f8 Newt Why?


> Actually, an equal aperture scope of fast f/r will present a slightly
> DIMMER
> image than a slower one, usually, since it is likely to have a larger
> central obstruction. ;-)

I noticed in Chris's response that he specified aperture _area_, not plain
linear aperture.  There's only one reason he would have made that distinction.

-John




----- Original Message ----
> From: Rod Mollise <rmollise@...>
>
> Actually, an equal aperture scope of fast f/r will present a slightly DIMMER
> image than a slower one, usually, since it is likely to have a larger
> central obstruction. ;-)
>
>
> Peace,
> Rod Mollise
> Rod's new book:
> _Choosing and Using a New CAT_
> Available Now!
>
>
>
>
>
> -----Original Message-----
> From: sct-user@yahoogroups.com [mailto:sct-user@yahoogroups.com] On Behalf
> Of Chris Peterson
> Sent: Friday, November 20, 2009 5:54 PM
> To: sct-user@yahoogroups.com
> Subject: Re: [sct-user] Dimmer views of Moon/Jupiter between 6" f10 SCT
> compared to 6" f8 Newt Why?
>
> > Negative. 100x is 100x and the Moon, a planet _or anything else_ is just
> > as
> > bright at 100x in an f/4 telescope as it is at 100x in an f/10 telescope
> > AND
> > VICE VERSA. ;-)
>
> Assuming equal aperture area, and that the aperture isn't limited by the
> exit pupil.
>
> Chris
>
> *****************************************
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
>
>
> ----- Original Message -----
> From: "Rod Mollise"
> To:
> Sent: Friday, November 20, 2009 3:42 PM
> Subject: RE: [sct-user] Dimmer views of Moon/Jupiter between 6" f10 SCT
> compared to 6" f8 Newt Why?
>
>
> > Negative. 100x is 100x and the Moon, a planet _or anything else_ is just
> > as
> > bright at 100x in an f/4 telescope as it is at 100x in an f/10 telescope
> > AND
> > VICE VERSA. ;-)
> >
> >
> > Peace,
> > Rod Mollise
>
>
>
> ------------------------------------
>
> Visit the sct-user home page at:
>
>
>
> http://skywatch.brainiac.com/SCThpYahoo! Groups Links
>
>
>
>
>
> ------------------------------------
>
> Visit the sct-user home page at:
>
>
>
> http://skywatch.brainiac.com/SCThpYahoo! Groups Links
>
>
>

That and the additional diagonal likely used in an SCT (as Doug mentioned), and
a few % lost at the air/glass corrector surfaces, depending on the AR coatings
used.

-John




----- Original Message ----
> From: Chris Peterson <cpeterson@...>
>
> That was my point... it's why I specified equal aperture _area_, not equal
> aperture. It's likely the difference between the two scopes in this case.
>
> Chris
>
>
>
> ----- Original Message -----
> From: "Rod Mollise"
> To:
> Sent: Saturday, November 21, 2009 6:30 AM
> Subject: RE: [sct-user] Dimmer views of Moon/Jupiter between 6" f10 SCT
> compared to 6" f8 Newt Why?
>
>
> > Actually, an equal aperture scope of fast f/r will present a slightly
> > DIMMER
> > image than a slower one, usually, since it is likely to have a larger
> > central obstruction. ;-)
>

And only 131 nights.

What is the earliest date one can take an image and enter it in the 2010
contest?

Drew S.

Yes, and I'd be surprised if the 6-inch were actually brighter, anyway.


Peace,
Rod Mollise
Rod's new book:
_Choosing and Using a New CAT_
Available Now!

<http://skywatch.brainiac.com/astroland>




-----Original Message-----
From: sct-user@yahoogroups.com [mailto:sct-user@yahoogroups.com] On Behalf
Of Chris Peterson
Sent: Saturday, November 21, 2009 9:04 AM
To: sct-user@yahoogroups.com
Subject: Re: [sct-user] Dimmer views of Moon/Jupiter between 6" f10 SCT
compared to 6" f8 Newt Why?

That was my point... it's why I specified equal aperture _area_, not equal
aperture. It's likely the difference between the two scopes in this case.

Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


----- Original Message -----
From: "Rod Mollise" <rmollise@...>
To: <sct-user@yahoogroups.com>
Sent: Saturday, November 21, 2009 6:30 AM
Subject: RE: [sct-user] Dimmer views of Moon/Jupiter between 6" f10 SCT
compared to 6" f8 Newt Why?


> Actually, an equal aperture scope of fast f/r will present a slightly
> DIMMER
> image than a slower one, usually, since it is likely to have a larger
> central obstruction. ;-)



------------------------------------

Visit the sct-user home page at:



http://skywatch.brainiac.com/SCThpYahoo! Groups Links

Both scopes in this case were 6".  Which one are you referring to?


-John



----- Original Message ----
> From: Rod Mollise <rmollise@...>
>
> Yes, and I'd be surprised if the 6-inch were actually brighter, anyway.
>
>
> Peace,
> Rod Mollise

>
>
> -----Original Message-----
> From:  Chris Peterson
>
> That was my point... it's why I specified equal aperture _area_, not equal
> aperture. It's likely the difference between the two scopes in this case.
>
> Chris
>

>
>
> ----- Original Message -----
> From: "Rod Mollise"

>
> > Actually, an equal aperture scope of fast f/r will present a slightly
> > DIMMER
> > image than a slower one, usually, since it is likely to have a larger
> > central obstruction. ;-)

brightstarcomputers wrote:
> When I match up my mags as close as I can between both telescopes, say a 18mm
(85x) in my 6" f10, and a 15mm (81x) in my 6" f8, the images of both Jupiter and
the moon appear darker in the 6" f10 SCT.

85x on a 6" produces an exit pupil of 1.8 mm.  81x produces an exit
pupil of 1.9 mm.  This might make a difference.  The SCT may have lower
light throughput due to larger secondary obstruction blocking light, and
light lost from reflection from the corrector plate.  There's light loss
in the star diagonal if you are using one.  Because we don't have specs
on the coatings on the corrector plate and mirrors on both telescopes it
is hard to guess.  The eyepieces also might have different light throughput.

Bud

Quoting Rod's recent message on the contest:
"images produced since the end of the last contest period will be eligible".
You'll have to check last year's contest page to find when the last deadline
was.

This issue was raised during the last contest.  The idea is that the contest
itself should cover a one-year period (of imaging).  The actual period for
submitting entries will be more limited, of course, for the obvious reason of
wanting to get one contest wrapped up, with some time off, before the next one
starts.

-John



----- Original Message ----
> From: ancient.sull <ancient.sull@...>
> To: sct-user@yahoogroups.com
> Sent: Sat, November 21, 2009 2:10:45 PM
> Subject: [sct-user] Only 131 shopping days left 'til April Fool's day
>
> And only 131 nights.
>
> What is the earliest date one can take an image and enter it in the 2010
> contest?
>
> Drew S.
>
>
>
> ------------------------------------
>
> Visit the sct-user home page at:
>
>
>
> http://skywatch.brainiac.com/SCThpYahoo! Groups Links
>
>
>

http://uncle-rods.blogspot.com/


Peace,
Rod Mollise
Rod's new book:
_Choosing and Using a New CAT_
Available Now!

<http://skywatch.brainiac.com/astroland>

I have a large Mak Cass with which is prone to tube currents on nights when the
temperature changes rapidly. It has been recommended that I wrap the OTA body in
some sort of insulation to reduce the rate of change of temperature.

What would people recommend I get at Home Depot/whereever for this purpose?

Thanks in advance

Drew Sullivan

ancient.sull wrote:
> I have a large Mak Cass with which is prone to tube currents on nights when
the temperature changes rapidly. It has been recommended that I wrap the OTA
body in some sort of insulation to reduce the rate of change of temperature.
>
> What would people recommend I get at Home Depot/whereever for this purpose?
I don't know whether it would work or whether The Home Depot has it.
There is a building insulation that is flexible, closed cell plastic,
aluminized on one side.  It looks about like aluminized bubble wrap.  I
can't think of a name.  It isn't hard to cut and you can tape it
together with aluminized mylar tape.

Slow cooling is kind of characteristic of large maksutovs.

Bud

That insulation you refered to is call REFLECTIX.
Works very well to insulate tubes and I use it to trap my dew heater  heat on
the tube.  Extend it out a few inches and it makes a dew shield.
I found mine at Lowe's.
LouChurch

--- In sct-user@yahoogroups.com, William Hamblen <wrhamblen@...> wrote:
>
> ancient.sull wrote:
> > I have a large Mak Cass with which is prone to tube currents on nights when
the temperature changes rapidly. It has been recommended that I wrap the OTA
body in some sort of insulation to reduce the rate of change of temperature.
> >
> > What would people recommend I get at Home Depot/whereever for this purpose?
> I don't know whether it would work or whether The Home Depot has it.
> There is a building insulation that is flexible, closed cell plastic,
> aluminized on one side.  It looks about like aluminized bubble wrap.  I
> can't think of a name.  It isn't hard to cut and you can tape it
> together with aluminized mylar tape.
>
> Slow cooling is kind of characteristic of large maksutovs.
>
> Bud
>

--- In sct-user@yahoogroups.com, "ancient.sull" <ancient.sull@...> wrote:
>
> I have a large Mak Cass with which is prone to tube currents on nights
> when the temperature changes rapidly. It has been recommended that I
> wrap the OTA body in some sort of insulation to reduce the rate of
> change of temperature.

That's VERY odd. Normally one wishes to INCREASE the rate to match the
outside air temp in order to reach thermal equilibrium as quickly as
possible or practical (to help reduce a dewing problem).

That's why a number of people use OTA cooling fans and other cooling
solutions, such as the Lymax CAT Cooler <http://www.lymax.com/sct/>.

> What would people recommend I get at Home Depot/whereever for this
> purpose?

If you really want to insulate your OTA, probably the best material is
Reflectix, available at any decent home improvement store and
well-equipped hardware store (OSH, Home Depot, etc.).

Manufacturer web page: <http://www.reflectixinc.com/>

Example of its thermos-bottle-like construction:

<http://thadlabs.com/PIX/Reflectix_split.jpg>

and the tape for joining pieces together:

<http://thadlabs.com/PIX/Reflectix_tape.jpg>

Stuff comes in rolls both 2' and 4' wide, up to 50' or 100' long,
though many/most home improvement stores will cut it to your spec.

An outside storage cover I made for my 14" LX200GPS in 2004 (and still
working fine) can be seen here:

<http://thadlabs.com/PIX/14_LX200GPS_storage.jpg>

----- Original Message ----

> From: ancient.sull <ancient.sull@...>
>
> I have a large Mak Cass with which is prone to tube currents on nights when
the
> temperature changes rapidly. It has been recommended that I wrap the OTA body
in
> some sort of insulation to reduce the rate of change of temperature.

That makes little or no sense.  Tube currents aren't just within the OTA, but
also in front of the corrector.  Insulating the scope will keep it warmer as the
air cools, so you'll have a stronger difference between scope temp and air temp,
which will increase thermally-induced turbulence just in front of the corrector.

At best, insulating the tube might keep the tube external wall from cooling, so
it will be closer to the mirror temp (the mirror would normally cool more slowly
than the tube wall), so you might reduce tube currents _inside_ the tube.  But
then you'd increase turbulence just in front of the scope.

-John

----- Original Message ----

> From: thad_floryan <thad@...>
>
> --- In sct-user@yahoogroups.com, "ancient.sull" wrote:
> >
> > I have a large Mak Cass with which is prone to tube currents on nights
> > when the temperature changes rapidly. It has been recommended that I
> > wrap the OTA body in some sort of insulation to reduce the rate of
> > change of temperature.
>
> That's VERY odd. Normally one wishes to INCREASE the rate to match the
> outside air temp in order to reach thermal equilibrium as quickly as
> possible or practical (to help reduce a dewing problem).

No, to avoid turbulence.  _Slowing_ the scope cooling would reduce the chance of
dew.

-John


> That's why a number of people use OTA cooling fans and other cooling
> solutions, such as the Lymax CAT Cooler .
>
> > What would people recommend I get at Home Depot/whereever for this
> > purpose?
>
> If you really want to insulate your OTA, probably the best material is
> Reflectix, available at any decent home improvement store and
> well-equipped hardware store (OSH, Home Depot, etc.).
>
> Manufacturer web page:
>
> Example of its thermos-bottle-like construction:
>
>
>
> and the tape for joining pieces together:
>
>
>
> Stuff comes in rolls both 2' and 4' wide, up to 50' or 100' long,
> though many/most home improvement stores will cut it to your spec.
>
> An outside storage cover I made for my 14" LX200GPS in 2004 (and still
> working fine) can be seen here:
>
>
>
>
>
>
> ------------------------------------
>
> Visit the sct-user home page at:
>
>
>
> http://skywatch.brainiac.com/SCThpYahoo! Groups Links
>
>
>

The insulation was suggested for nights when the temperature isn't stable but is
steadily dropping faster than the equilibration time of the scope so the scope
never can reach equilibrium.

I gather the problem is that the rate of change creates tube currents, that a
fast rate of change is worse than slow, and that a fast rate of change
overwhelms the scopes internal fans if you are in a situation where you will
never reach equilibrium.

The other choice, obviously, is to regard this scope as a "steady night time
temperature only" scope.

Drew S.

--- In sct-user@yahoogroups.com, "thad_floryan" <thad@...> wrote:

> That's VERY odd. Normally one wishes to INCREASE the rate to match the
> outside air temp in order to reach thermal equilibrium as quickly as
> possible

(Boy, a larger subject than I realized!)

The particular problem is internal tube currents.

If I am using a dew heater doesn't that make the front meniscus warmer than the
air anyway? (I also use a dew shield which I would think would reduce currents
right in front of the meniscus but then what about at the end of the dew shield?

Drew S.

--- In sct-user@yahoogroups.com, John Mahony <jmmahony@...> wrote:

> At best, insulating the tube might keep the tube external wall from cooling,
so it will be closer to the mirror temp (the mirror would normally cool more
slowly than the tube wall), so you might reduce tube currents _inside_ the tube.
But then you'd increase turbulence just in front of the scope.

Yes.

I use an insulated sleeve over my C14, and I find it does reduce internal
tube currents, it slso helps prevent the OTA 'over cooling' below ambient
air temperature. A bonus is that you need less power on the dew heaters, but
they are still required most nights here in the UK, which indicates to me
that the corrector is not taht much warmer than it would be without the
insulation.

I keep my OTA in an observatory so it is pretty cool to begin with, however
if you bring your OTA out from indoors then I would suggest letting it cool
without insulation initally to prevent trapping all that heat.

I use a rolled up aluminised camping mat, butt glued together at the joint.
The insulation extends beyond the OTA to form the dew shield as well. A thin
glass fibre rod coiled in the end of the dew shield section keeps it in
shape.

Regards
Mark
2009/11/23 ancient.sull <ancient.sull@...>

>
>
> (Boy, a larger subject than I realized!)
>
> The particular problem is internal tube currents.
>
> If I am using a dew heater doesn't that make the front meniscus warmer than
> the air anyway? (I also use a dew shield which I would think would reduce
> currents right in front of the meniscus but then what about at the end of
> the dew shield?
>
> Drew S.
>
>
> --- In sct-user@yahoogroups.com <sct-user%40yahoogroups.com>, John Mahony
> <jmmahony@...> wrote:
>
> > At best, insulating the tube might keep the tube external wall from
> cooling, so it will be closer to the mirror temp (the mirror would normally
> cool more slowly than the tube wall), so you might reduce tube currents
> _inside_ the tube. But then you'd increase turbulence just in front of the
> scope.
>
>
>


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

Hi all,
I've got an Optec 0.5X focal reducer for my C14 with an ST8XME and all works
well.
However, it comes with a minus violet filter and when I asked about using it
with my C14, Optec said it was necessary because of the corrector lens. Is this
possible? I thought it was for refractors and camera lenses. Also, how much does
this filter add to the exposure times?
Thanks for any input!
bob

Robert wrote:
> I've got an Optec 0.5X focal reducer for my C14 with an ST8XME and all works
well.
> However, it comes with a minus violet filter and when I asked about using it
with my C14, Optec said it was necessary because of the corrector lens. Is this
possible? I thought it was for refractors and camera lenses. Also, how much does
this filter add to the exposure times?
A corrector lens is as much a lens as the lens in a refractor or a
camera.  Some chromatic aberration apparently is introduced by the focal
reducer.  Optec may be able to provide a filter factor.  Otherwise you
could just make some test exposures.

Bud

----- Original Message ----

> From: ancient.sull <ancient.sull@...>
>
> (Boy, a larger subject than I realized!)

Thermodynamics is usually like that.  I never did like the subject much back in
school.

> The particular problem is internal tube currents.

You see the currents running around the baffle tube, or accumulating at the
"top"?

> If I am using a dew heater doesn't that make the front meniscus warmer than
the
> air anyway?

Not necessarily.  An unheated object at night will eventually drop to _below_
ambient temp by radiating to the cold black vacuum of space.  Dew happens when
the temp of the object drops below the dew point, which is below ambient (unless
rel. hum. is 100%, in which case it's foggy).  So a dew heater only has to keep
an object warmer than the dew point, not necessarily warmer than ambient
(although thermally-induced turbulence is minimized if everything is kept as
close to ambient as possible).

> (I also use a dew shield which I would think would reduce currents
> right in front of the meniscus but then what about at the end of the dew
shield?

Like you said, it's complicated.

CATs represent an inherent internal struggle where you want the mirror to cool,
but don't want the corrector to cool to much.  The best solution I've seen is at
<http://groups.yahoo.com/group/sct-user/photos/album/1116687651/pic/list>
where a C8 owner rigged a couple external tubes with fans connected to holes in
the sides of the OTA, to circulate air between the front and back of the scope. 
So the mirror cools faster, but the warmth from the mirror keeps the corrector
from colling too mcu, and it's all done without blowing new dusty air into the
OTA.

-John


>
> --- In sct-user@yahoogroups.com, John Mahony wrote:
>
> > At best, insulating the tube might keep the tube external wall from cooling,
> so it will be closer to the mirror temp (the mirror would normally cool more
> slowly than the tube wall), so you might reduce tube currents _inside_ the
> tube.  But then you'd increase turbulence just in front of the scope.
>
>
>
>
> ------------------------------------
>
> Visit the sct-user home page at:
>
>
>
> http://skywatch.brainiac.com/SCThpYahoo! Groups Links
>
>
>

Chris,

Thanks for easing my fears about the "noisy" mount. Even if the controller was
working, I would have been afraid to use it for fear of damaging the mount
(unnecessarily so). Now if I can just get the handbox working. I've tried it in
two of the ports, I guess I will try it in the third when I get home (I'm out of
town for Thanksgiving in the dark Texas Hill Country with only a StarBlast to
keep me comapny at night... its doing yeoman duty out here though). The male end
of the cord looked fine, but I'll try cleaning it. I do not have another
controller to test with, but I may be able to get one. Is it possible something
came loose inside the controller? Is there anything I can check inside it? Also,
can anyone recommend a Nexstar-specific discussion group, yahoo or otherwise?

Thanks!

--Robert Harris

--- In sct-user@yahoogroups.com, "Chris" <chris_group_mail@...> wrote:
>
> The NS11 is a good cure for aperture fever :-)
>
> 1. Try cleaning the connectors on the HC or sockets.  Do the arrow buttons
work? Can you try a different HC?
>
> 2. That's pretty normal, the Azimuth has three small bearings running on a
track. If the movement is lumpy then it might be worth taking the covers off and
cleaning the track and the outside of the bearings.
>
> 3. That's good!  It's the level switch operating.
>
> Chris
>
> --- In sct-user@yahoogroups.com, "robertnharris1972" <rharris@> wrote:
> >
> > Greetings! After suffering chronic aperture fever for the past few years, I
finally got off the fence and picked up a used Nexstar 11 GPS off of Astromart.
What a magnificent beast! I've got it all assembled, but I have one problem and
a couple of questions:
> >
> > 1. When I power it up, the handbox lights up, but does nothing else. No text
displays. I left it turned on for several minutes to see if it would come up. I
tried two different battery packs just to make sure it wasn't my power supply. I
tried with the handbox plugged into the fork arm cavity, and one of the aux
ports, but no change. I used only the power cord that came with it. Halp.
> >
> > 2. When I move it in azimuth with the clutch fully disengaged, it makes a
mild but noticeable grinding noise. It sounds like dragging a wooden cutting
board across a formica counter top. Is that normal for this scope?
> >
> > 3. When I move the OTA in altitude with the clutch fully disengaged, it goes
"click click" as it moves through the level position. Is that normal for this
scope?
> >
> > Any help is greatly appreciated.
> >
> > Thanks!!
> >
> > --Robert Harris
> >
>

Yes it could be something in the HC that stops the display working. Try the
arrow buttons, if the scope moves then internally it is working and it's a
display problem. I'm not sure how easy it is to fix.

If you have a Windows Laptop and a suitable serial interface cable then you can
try NexRemote. You can download a 30 day evaluation from the Celestron web site.

The Nexstar people hang out on the Nexstar and NexStarGPS yahoo groups.
http://tech.groups.yahoo.com/group/nexstar/
http://tech.groups.yahoo.com/group/NexStarGPS/

Also find and bookmark Mike Swanson's Nexstar site. It's full of useful
information.

No time to be more explicit, searches should find all these pretty easily.

Chris

--- In sct-user@yahoogroups.com, "robertnharris1972" <rharris@...> wrote:
>
> Chris,
>
> Thanks for easing my fears about the "noisy" mount. Even if the controller was
working, I would have been afraid to use it for fear of damaging the mount
(unnecessarily so). Now if I can just get the handbox working. I've tried it in
two of the ports, I guess I will try it in the third when I get home (I'm out of
town for Thanksgiving in the dark Texas Hill Country with only a StarBlast to
keep me comapny at night... its doing yeoman duty out here though). The male end
of the cord looked fine, but I'll try cleaning it. I do not have another
controller to test with, but I may be able to get one. Is it possible something
came loose inside the controller? Is there anything I can check inside it? Also,
can anyone recommend a Nexstar-specific discussion group, yahoo or otherwise?
>
> Thanks!
>
> --Robert Harris
>
> --- In sct-user@yahoogroups.com, "Chris" <chris_group_mail@> wrote:
> >
> > The NS11 is a good cure for aperture fever :-)
> >
> > 1. Try cleaning the connectors on the HC or sockets.  Do the arrow buttons
work? Can you try a different HC?
> >
> > 2. That's pretty normal, the Azimuth has three small bearings running on a
track. If the movement is lumpy then it might be worth taking the covers off and
cleaning the track and the outside of the bearings.
> >
> > 3. That's good!  It's the level switch operating.
> >
> > Chris
> >
> > --- In sct-user@yahoogroups.com, "robertnharris1972" <rharris@> wrote:
> > >
> > > Greetings! After suffering chronic aperture fever for the past few years,
I finally got off the fence and picked up a used Nexstar 11 GPS off of
Astromart. What a magnificent beast! I've got it all assembled, but I have one
problem and a couple of questions:
> > >
> > > 1. When I power it up, the handbox lights up, but does nothing else. No
text displays. I left it turned on for several minutes to see if it would come
up. I tried two different battery packs just to make sure it wasn't my power
supply. I tried with the handbox plugged into the fork arm cavity, and one of
the aux ports, but no change. I used only the power cord that came with it.
Halp.
> > >
> > > 2. When I move it in azimuth with the clutch fully disengaged, it makes a
mild but noticeable grinding noise. It sounds like dragging a wooden cutting
board across a formica counter top. Is that normal for this scope?
> > >
> > > 3. When I move the OTA in altitude with the clutch fully disengaged, it
goes "click click" as it moves through the level position. Is that normal for
this scope?
> > >
> > > Any help is greatly appreciated.
> > >
> > > Thanks!!
> > >
> > > --Robert Harris
> > >
> >
>

Hi Bud,
I did some test exposures and I came up with about a 10% increase in exposure
would be needed.
Thanks,
Bob

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

For Sale

MEADE ETX 125PE 5"
Maksutove-Cassegrain
GOTO

Photos are in Alan's ETX 125PE 5" for sale album

New only used a few times

$650.00
Pickup Only

Comes with Autostar Computer controller
AC Power adapter
ONE Super Eyepiece

Meade Heavy Duty Field Tripod / with carry bag
Tripod has built in wedge.

Also includes Piggyback Camera Adapter
Software & manual

Contact:

Alan D. Otterson

Three Rivers, MI
(30 Minuets from MI, In state line)

E-Mail
alancath@ earthlink.net





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

I've had many SCTs in the past, but mainly used visually.  I bought it to
supplement my current refractor for doing some minor deep sky imaging and plenty
of planetary stuff as I have pushed my refractor as far as it can go.

On the deep sky side.  Using my ST7XME (mostly photometry is planned), what is
the method for the flattest field possible.  Is it a .63 R/C or MPCC or what? 
If a .63, what is supposed to be the imaging train from the back of the
corrector to the chip.  Obviously the presense of my CFW8 makes a big
difference.  Does it matter what visual adapter you use on the back of the SCT. 
The options I am looking at are the TV 2" it comes with, an AP to go on the
bigger threads or perhaps a aftermarket focuser.  But with each of those, your
chip would end up at different distances from the corrector.

Thanks for any feedback,
Kevin

It matters. The _Celestron_ 6.3 r/c will give the best results.

Peace,

Rod Mollise

Author of _Choosing and Using a

Schmidt Cassegrain Telescope_







Like SCTs and MCTs?

Check-out sct-user, the mailing

list for CAT fanciers:





--- On Thu, 11/26/09, kevinbm13 <_kevin1231@...> wrote:


From: kevinbm13 <_kevin1231@...>
Subject: [sct-user] C11 on way- have questions
To: sct-user@yahoogroups.com
Date: Thursday, November 26, 2009, 6:10 PM


I've had many SCTs in the past, but mainly used visually.  I bought it to
supplement my current refractor for doing some minor deep sky imaging and plenty
of planetary stuff as I have pushed my refractor as far as it can go.. 

On the deep sky side.  Using my ST7XME (mostly photometry is planned), what is
the method for the flattest field possible.  Is it a .63 R/C or MPCC or what? 
If a .63, what is supposed to be the imaging train from the back of the
corrector to the chip.  Obviously the presense of my CFW8 makes a big
difference.  Does it matter what visual adapter you use on the back of the SCT. 
The options I am looking at are the TV 2" it comes with, an AP to go on the
bigger threads or perhaps a aftermarket focuser.  But with each of those, your
chip would end up at different distances from the corrector. 

Thanks for any feedback,
Kevin



------------------------------------

Visit the sct-user home page at:



http://skywatch.brainiac.com/SCThpYahoo! Groups Links





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

Hi all. This appears to be another case of a pawn-shop-type seller listing a
scope on ebay that they know nothing about:


http://cgi.ebay.com/Celestron-C8-SCT-Telescope-Optical-Tube-Assembly-UHTC_W0QQit\
emZ170412065600QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item27ad59c340

The photos show an older orange C8 with a sand-cast fork mount (w/holes) but the
ad describes it as an "OTA only" with UTHC. Further down the ad, the page states
that it is Fastar-compatible, has XLT coatings, and a whole bunch of other
gobbledy-gook that makes no sense at all.
(WOW, some early orange C8s were way ahead of their time!).

If anyone here is bidding on it, I would be a little concerned as to what you'll
actually get!

Best, Bob Piekiel

Hey Bob,
Funny you bring that one up because I noticed it earlier today. Got quite a
needed hearty laugh out of it myself. None of it really fits does it? Good one.

Jim



On Nov 26, 2009, at 5:59 PM, Robert Piekiel <piekielrl@...> wrote:

Hi all. This appears to be another case of a pawn-shop-type seller listing a
scope on ebay that they know nothing about:

http://cgi.ebay.com/Celestron-C8-SCT-Telescope-Optical-Tube-Assembly-UHTC_W0QQit\
emZ170412065600QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item27ad59c340

The photos show an older orange C8 with a sand-cast fork mount (w/holes) but the
ad describes it as an "OTA only" with UTHC. Further down the ad, the page states
that it is Fastar-compatible, has XLT coatings, and a whole bunch of other
gobbledy-gook that makes no sense at all.
(WOW, some early orange C8s were way ahead of their time!).

If anyone here is bidding on it, I would be a little concerned as to what you'll
actually get!

Best, Bob Piekiel




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

kevinbm13 wrote:

>  On the deep sky side.  Using my ST7XME (mostly photometry is
>  planned), what is the method for the flattest field possible.  Is it
>  a .63 R/C or MPCC or what?  If a .63, what is supposed to be the
>  imaging train from the back of the corrector to the chip.  Obviously
>  the presense of my CFW8 makes a big difference.  Does it matter what
>  visual adapter you use on the back of the SCT.  The options I am
>  looking at are the TV 2" it comes with, an AP to go on the bigger
>  threads or perhaps a aftermarket focuser.  But with each of those,
>  your chip would end up at different distances from the corrector.

The Celestron 0.63x focal reducer/corrector was designed to be used with
Celestron SCTs and a camera with a focal plane located 105 mm from the
rear face of the focal reducer.  The focal reducer screws onto the rear
port of the SCT.

Bud