My first reaction upon discovering the disparity between the quality of the SSAG
images seen through the autoguider port, versus those obtained via the guide
scope, was similar to your thought; but I found out that people using the
QSI-583wsg with other scopes (e.g. Takahashi FSQ-106) are getting much better
results than I.  It seems likely to me that the pickoff prism of the 583wsg is
too far off at the periphery of the light cone coming through the field
flattener.  That is what the folks at QSI have suggested.  Although I have
arranged to borrow a Starlight Express Lodestar next time out from the
aforementioned Takahashi owner to see whether a better autoguider will improve
the view, I'm inclined to think it won't help much and that I'll be stuck with
using the autoguider with the guide scope.  Anyway, thanks to the people who
responded to my post; best regards and clear skies to everyone.

--- In William-Optics@yahoogroups.com, "Astro Huyps" <astro@...> wrote:
>
> Perhaps the explanation is simply that an off-axis guider only picks-up a
fraction of the total light via the intercepting prism; the rest of the light is
going to the main camera; In case you have a dedicated guide scope,  all the
light of the guide scope is going to the autoguider. The focal length (and the
focal ratio) of the guide scope versus the main scope is I think only a
secondary effect.
>
> regs
> Ronald
>
>
>
>   ----- Original Message -----
>   From: mackey
>   To: William-Optics@yahoogroups.com
>   Sent: Monday, February 22, 2010 12:03 PM
>   Subject: [William Optics] Re: Is anyone using an FLT-132 with a QSI-583wsg
camera and Orion SSAG Autoguider?
>
>
>
>
>
>   --- In William-Optics@yahoogroups.com, "Bazarov" <jlfloyd@> wrote:
>   >
>   > This is because only the brightest stars show up in the autoguider
>   > when it is mounted in the guide port; others are too faint to be
>   >recognized as guide stars or are not visible at all. However, when I
>   >remove the Orion SSAG from the QSI guide port and install it in a
>   >guide scope mounted on top of the FLT-132, star images are much
>   >brighter and more distinct, more stars show up, the SSAG has no
>   >trouble acquiring guide stars and calibration is generally successful.
>
>   I *assume* that the focal length of your guide scope is shorter
>   than that of FLT-132 which has a focal length of 921mm.
>
>   921mm is quite long and it *distributes* the star image over
>   a larger area than the guide scope does. It means that each pixel
>   of Orion SSAG gets less light. Also a long focal length scope
>   simply gives your guide chip *smaller* field of view, which
>   usually means less bright stars.
>
>   Orion SSAG is not a very sensitive guiding CCD, the same as
>   QHY5. I'd suggest you try a more sensitive guiding camera, like
>   Fishcamp Starfish. It is *much* more sensitive than QHY5.
>
>   Hojong Lin
>

Hello, My Zenithstar 80mm suffered an unfortunate acciDENT! (Big one).
I sent an email to WO about getting parts for repair, but haven't gotten a
reply. Does any one know how to contact them directly, and are parts (tube and
baffles) are available to buy?
Thanks, Paul

Hi Folks

I am the only non-WO employee who volunteers to help moderate this FREE Yahoo
group.

When someone posts a message that is obviously worthless SPAM I immediately BAN
the member permanently, and then delete the message.

If you post a reply to the SPAM message through emailing the group, it
resurrects the already deleted message and really serves no purpose other than
to make more work for me to now delete your message.

Thanks and clear skies

Timm

 

Hi Folks

I am the only non-WO employee who volunteers to help moderate this FREE Yahoo group.

When someone posts a message that is obviously worthless SPAM I immediately BAN the member permanently, and then delete the message.

If you post a reply to the SPAM message through emailing the group, it resurrects the already deleted message and really serves no purpose other than to make more work for me to now delete your message.

Thanks and clear skies

Timm

Thanks - not a big deal really but it's been a long time since we had spammer
problems, but they still sneak in from time to time by pretending to be WO users
when they join.

So I haven't had to remind people in a long time to just ignore any SPAM posts -
usually either one of the WO folks or me deletes them and bans them right away.

Thanks everyone! - I rarely have to do anything to moderate this group any more
- seems like there are very few off topic posts or arguments these days - guess
that's a good thing

Now if only Winter in Chicago would end!

Timm

--- In William-Optics@yahoogroups.com, William Neboyskey <hibibby@...> wrote:
>
> Sorry, Timm. I won't do it again!
>
>
> Timm B wrote:
> >
> >
> > Hi Folks
> >
> > I am the only non-WO employee who volunteers to help moderate this
> > FREE Yahoo group.
> >
> > When someone posts a message that is obviously worthless SPAM I
> > immediately BAN the member permanently, and then delete the message.
> >
> > If you post a reply to the SPAM message through emailing the group, it
> > resurrects the already deleted message and really serves no purpose
> > other than to make more work for me to now delete your message.
> >
> > Thanks and clear skies
> >
> > Timm
> >
> >
>

Hi Tim... In regards to the above RMA... Looking for informatiom on status of
repair to M110 front element- No response to e-mails..
Please advise?...
Thanks Tim
Dave

Very useful indeed,

Thanks
Tasos

--- In William-Optics@yahoogroups.com, "williammoderator07"
<williammoderator07@...> wrote:
>
> Dear WO FLATIV users,
> You may find the link below useful for finding the best position for your set
up with FlatIV:
> http://www.williamoptics.com/accessories/images/FLAT4_Layout.jpg
>
> Regards,
> WO
>

Just wondering if anyone had tested the  Avian Starseeker 100mm  against the
williams Megrez90?

Hi, I have a 2" STC Crayford focuser dual speed 1:10 unit.  I believe it is a
mark 2 model.

I have had a few problems with the tension being too slack.
The unit has two sets of screw (one an allen key one a slot head) positioned at
2 o'clock and 10 o'clock (with the focus shaft at the bottom of the unit). 
Tightening the allen keys certainly improves the tension but what do the slot
head screws do?

Does anyone know the correct method for adusting tension please?

A small set of instructions in the box would have been nice!
TIA

Hi,

Can you post a picture showing the screws you are referring to?  I have the
newer model, the Linear Power focuser, but I think you might have the model
prior to this.  Either way, with a picture, I think someone will be able to
help.

Thanks,

Timm

--- In William-Optics@yahoogroups.com, "allanberzins" <allan.berzins@...> wrote:
>
> Hi, I have a 2" STC Crayford focuser dual speed 1:10 unit.  I believe it is a
mark 2 model.
>
> I have had a few problems with the tension being too slack.
> The unit has two sets of screw (one an allen key one a slot head) positioned
at 2 o'clock and 10 o'clock (with the focus shaft at the bottom of the unit). 
Tightening the allen keys certainly improves the tension but what do the slot
head screws do?
>
> Does anyone know the correct method for adusting tension please?
>
> A small set of instructions in the box would have been nice!
> TIA
>

Hi Timm,
Have posted a picture.
It's in the SCT Cryford directory.
I've marked it with what I beleive to be the adjustments.  The two I've maked
tension ?? are duplicated on the other side of the ring and as I say not sure
about the what exactly to do with either of them.

Thanks

Allan.

--- In William-Optics@yahoogroups.com, "Timm B" <t.bottoni@...> wrote:
>
> Hi,
>
> Can you post a picture showing the screws you are referring to?  I have the
newer model, the Linear Power focuser, but I think you might have the model
prior to this.  Either way, with a picture, I think someone will be able to
help.
>
> Thanks,
>
> Timm
>
> --- In William-Optics@yahoogroups.com, "allanberzins" <allan.berzins@> wrote:
> >
> > Hi, I have a 2" STC Crayford focuser dual speed 1:10 unit.  I believe it is
a mark 2 model.
> >
> > I have had a few problems with the tension being too slack.
> > The unit has two sets of screw (one an allen key one a slot head) positioned
at 2 o'clock and 10 o'clock (with the focus shaft at the bottom of the unit). 
Tightening the allen keys certainly improves the tension but what do the slot
head screws do?
> >
> > Does anyone know the correct method for adusting tension please?
> >
> > A small set of instructions in the box would have been nice!
> > TIA
> >
>

Hi - I see the pic in the Files section of the group.  I think the small black
one might be a hole designed to accept the WO Finder Bracket - it looks similar
to the one in this http://www.williamoptics.com/support/download/synta.pdf

If anyone else out there owns one of these and can say for sure please let us
know.

And you are correct on the other ones you identified, from what I know.

Timm

--- In William-Optics@yahoogroups.com, "allanberzins" <allan.berzins@...> wrote:
>
> Hi Timm,
> Have posted a picture.
> It's in the SCT Cryford directory.
> I've marked it with what I beleive to be the adjustments.  The two I've maked
tension ?? are duplicated on the other side of the ring and as I say not sure
about the what exactly to do with either of them.
>
> Thanks
>
> Allan.
>
> --- In William-Optics@yahoogroups.com, "Timm B" <t.bottoni@> wrote:
> >
> > Hi,
> >
> > Can you post a picture showing the screws you are referring to?  I have the
newer model, the Linear Power focuser, but I think you might have the model
prior to this.  Either way, with a picture, I think someone will be able to
help.
> >
> > Thanks,
> >
> > Timm
> >
> > --- In William-Optics@yahoogroups.com, "allanberzins" <allan.berzins@>
wrote:
> > >
> > > Hi, I have a 2" STC Crayford focuser dual speed 1:10 unit.  I believe it
is a mark 2 model.
> > >
> > > I have had a few problems with the tension being too slack.
> > > The unit has two sets of screw (one an allen key one a slot head)
positioned at 2 o'clock and 10 o'clock (with the focus shaft at the bottom of
the unit).  Tightening the allen keys certainly improves the tension but what do
the slot head screws do?
> > >
> > > Does anyone know the correct method for adusting tension please?
> > >
> > > A small set of instructions in the box would have been nice!
> > > TIA
> > >
> >
>

Hello All... Its decision time.. I have an SD66 Orange and a Black 66mm
Petzval... I have to sell one... but here's the crutch I want to have a scope
for guiding as well as wide field astro photography with my Canon 20D...Question
is which one should I keep.. One is 388mm and the other 400mm (Petzval)
I am quite smitten with the Orange SD but the Petzval is better for Astro??...
Any thoughts would be welcome..
Thanks
Dave

Here is a new photo of the Rosette Nebula taken Friday night.  1.5 hours,
Modified Canon 350, through a W/O FLT 110 APO, more details are with the photo.

http://tinyurl.com/ylowk5s

or

http://www.pbase.com/tom_arrington/image/122514526

as always comments are welcome

Tom

Hello all
I am new to this group and I would introduce myself. I practice astronomy since
the return of Comet Halley in 1986. I just bought a FLT-110 with an TEC optic(an
used one). It complements my two Celestron C8 (one of them is an orange tube) I
live in eastern France about 65 km northeast of Lyon.
So, soon on this group.

Claude

I own 2 WO telescopes - FLT110 and ZS80.
Actually 3, with the 83mm spotting scope.
Plus a collection of 1.25" and 2" EPs from 4mm to 40mm.

I wanted to check that the following are correct:
(Please bear with me if some of this is painfully obvious).

1   EPs take the image created by the telescope and make it visible.
2   The higher the power, the smaller the % of the light cone that is used.

  From this I conclude:

Low-powered EPs utilise all the light collected by the telescope.
There would seem to be an 'optimum' EP for any scope providing
the maximum magnification possible and brightest image.

High powered EPs 'waste' light leading to fainter images.

Is this true? Comments?

What is the result of using a low powered EP that is 'too big'
for the light cone emanating from the telescope.

eg if I like looking thru a 40mm EP on the Zenithstar 80, does this
affect the visual image in any way? Will I achieve a wider real field
of view than using say a 32mm EP?

All comments and explanations welcome!

David K
Melbourne.au

----- Original Message -----

From: Subs

To: William-Optics@yahoogroups.com

Sent: Sunday, March 07, 2010 9:29 AM

Subject: [William Optics] Clarifying my understanding how EPs work.

 

I own 2 WO telescopes - FLT110 and ZS80.
Actually 3, with the 83mm spotting scope.
Plus a collection of 1.25" and 2" EPs from 4mm to 40mm.

I wanted to check that the following are correct:
(Please bear with me if some of this is painfully obvious).

1 EPs take the image created by the telescope and make it visible.
2 The higher the power, the smaller the % of the light cone that is used.

From this I conclude:

Low-powered EPs utilise all the light collected by the telescope.
There would seem to be an 'optimum' EP for any scope providing
the maximum magnification possible and brightest image.

High powered EPs 'waste' light leading to fainter images.

Is this true? Comments?

What is the result of using a low powered EP that is 'too big'
for the light cone emanating from the telescope.

eg if I like looking thru a 40mm EP on the Zenithstar 80, does this
affect the visual image in any way? Will I achieve a wider real field
of view than using say a 32mm EP?

All comments and explanations welcome!

David K
Melbourne.au

 



Hi David,

 

the situation is different and more complicated;

 

A good start is the Eyepiece calculator:

 

http://www.davidpaulgreen.com/tec.html 

 

and similar from televue:

 

http://www.televue.com/engine/page.asp?ID=107

 

and ofcourse our trusted source of information, Wikipedia:

 

http://en.wikipedia.org/wiki/Eyepiece 

 

Perhaps others can find some more illustrative drawings because above references focus more on the formula's.

 

regards

Ronald

 

 

www.huyps.com

 

 

 

 

----- Original Message -----

From: Subs

To: William-Optics@yahoogroups.com

Sent: Sunday, March 07, 2010 9:29 AM

Subject: [William Optics] Clarifying my understanding how EPs work.

 

I own 2 WO telescopes - FLT110 and ZS80.
Actually 3, with the 83mm spotting scope.
Plus a collection of 1.25" and 2" EPs from 4mm to 40mm.

I wanted to check that the following are correct:
(Please bear with me if some of this is painfully obvious).

1 EPs take the image created by the telescope and make it visible.
2 The higher the power, the smaller the % of the light cone that is used.

From this I conclude:

Low-powered EPs utilise all the light collected by the telescope.
There would seem to be an 'optimum' EP for any scope providing
the maximum magnification possible and brightest image.

High powered EPs 'waste' light leading to fainter images.

Is this true? Comments?

What is the result of using a low powered EP that is 'too big'
for the light cone emanating from the telescope.

eg if I like looking thru a 40mm EP on the Zenithstar 80, does this
affect the visual image in any way? Will I achieve a wider real field
of view than using say a 32mm EP?

All comments and explanations welcome!

David K
Melbourne.au

Hi,

Don't need to overthink eyepieces, light cones, etc - just use your eyes.  What
you see depends on things more than what you are trying to analyze including:
Your eye's ability to resolve details - best at about 2mm exit pupil
The scope's optical quality
The sky conditions
The type of object you are looking at
How well your eye is dark adapted
The eyepiece quality, field of view, sharpness, clarity, etc
And other personal preferences that can't be quantified

Pick the eyepiece that shows you the most detail, with your scope, under your
sky conditions, for the object you are looking at, with your eyes.

Basically ignore all the theory and trial end error wins because every person is
different (oh, and it changes as you age but don't even worry about that)

Timm

--- In William-Optics@yahoogroups.com, Subs <subs@...> wrote:
>
> hi ronald - thanks for responding.
>
> I'm pretty OK with calculating magnification, exit pupil, real/apparent
> FOV etc.
>
> My interest lies in how the EP uses the light collected by the telescope.
>
> This topic does not seem to be addressed in the places I've looked (many!)
>
> My thinking was that there must be benefits to using as much of the
> collected light as possible, for brightness, sharpness etc.
>
> It seems to me that high-powered EPs must simply discard some or most of
> the gathered light. We pay megabucks for aperture especially for refractors.
>
> It's rather similar to DSLRs with smaller sensors which use only part of
> the light collected by lenses, thereby magnifying the image relative
> to a camera with a full size sensor. With cameras I fully understand all
> the implications and chose my equipment accordingly.
>
> I'm not at all sure I 'get it' re telescopes and eyepieces.
>
>
>
> Astro Huyps wrote:
> >
> >
> > 
> >
> > Hi David,
> >
> > the situation is different and more complicated;
> >
> > A good start is the Eyepiece calculator:
> >
> > http://www.davidpaulgreen.com/tec.html
> > <http://www.davidpaulgreen.com/tec.html>
> >
> > and similar from televue:
> >
> > http://www.televue.com/engine/page.asp?ID=107
> > <http://www.televue.com/engine/page.asp?ID=107>
> >
> > and ofcourse our trusted source of information, Wikipedia:
> >
> > http://en.wikipedia.org/wiki/Eyepiece
> > <http://en.wikipedia.org/wiki/Eyepiece>
> >
> > Perhaps others can find some more illustrative drawings because above
> > references focus more on the formula's.
> >
> > regards
> > Ronald
> >
> >
> > www.huyps.com <http://www.huyps.com>
> >
> >
> >
> >
> >
> >     ----- Original Message -----
> >     *From:* Subs <mailto:subs@...>
> >     *To:* William-Optics@yahoogroups.com
> >     <mailto:William-Optics@yahoogroups.com>
> >     *Sent:* Sunday, March 07, 2010 9:29 AM
> >     *Subject:* [William Optics] Clarifying my understanding how EPs work.
> >
> >
> >
> >     I own 2 WO telescopes - FLT110 and ZS80.
> >     Actually 3, with the 83mm spotting scope.
> >     Plus a collection of 1.25" and 2" EPs from 4mm to 40mm.
> >
> >     I wanted to check that the following are correct:
> >     (Please bear with me if some of this is painfully obvious).
> >
> >     1 EPs take the image created by the telescope and make it visible.
> >     2 The higher the power, the smaller the % of the light cone that
> >     is used.
> >
> >     From this I conclude:
> >
> >     Low-powered EPs utilise all the light collected by the telescope.
> >     There would seem to be an 'optimum' EP for any scope providing
> >     the maximum magnification possible and brightest image.
> >
> >     High powered EPs 'waste' light leading to fainter images.
> >
> >     Is this true? Comments?
> >
> >     What is the result of using a low powered EP that is 'too big'
> >     for the light cone emanating from the telescope.
> >
> >     eg if I like looking thru a 40mm EP on the Zenithstar 80, does this
> >     affect the visual image in any way? Will I achieve a wider real field
> >     of view than using say a 32mm EP?
> >
> >     All comments and explanations welcome!
> >
> >     David K
> >     Melbourne.au
> >
> >
>

Pierluigi,

Thanks for looking.  Glad you like the photos.

I uploaded another version processed to retain more detail in the nebula.  Here
is the link.

http://tinyurl.com/yzg7s4p

Tom

--- In William-Optics@yahoogroups.com, pierluigi criscuoli <pierluigibiker@...>
wrote:
>
> Hello Tom, what can I say ...... they are both very beautiful I was thinking 
to put it as my desktop background!
> Pierluigi
>
> --- Sab 6/3/10, notgnirramot <notgnirra@...> ha scritto:
>
> Da: notgnirramot <notgnirra@...>
> Oggetto: [William Optics] New Photo - Rosstte Nebula
> A: William-Optics@yahoogroups.com
> Data: Sabato 6 marzo 2010, 19:12
>
>
>
>
>
>
>
>  
>
>
>
>
>
>
>
>
>
>       Here is a new photo of the Rosette Nebula taken Friday night.  1.5
hours, Modified Canon 350, through a W/O FLT 110 APO, more details are with the
photo.
>
>
>
> http://tinyurl. com/ylowk5s
>
>
>
> or
>
>
>
> http://www.pbase. com/tom_arringto n/image/12251452 6
>
>
>
> as always comments are welcome
>
>
>
> Tom
>

IMHO opinion the 66SD is the better of the two, it certianlly has less CA then
Petzval, but you will need a FF/FR to get a flat field for AP.

Clear Skies, Chris S

--- In William-Optics@yahoogroups.com, "Dave" <daveyates80@...> wrote:
>
> Hello All... Its decision time.. I have an SD66 Orange and a Black 66mm
Petzval... I have to sell one... but here's the crutch I want to have a scope
for guiding as well as wide field astro photography with my Canon 20D...Question
is which one should I keep.. One is 388mm and the other 400mm (Petzval)
> I am quite smitten with the Orange SD but the Petzval is better for Astro??...
> Any thoughts would be welcome..
> Thanks
> Dave
>

Hello David,

The magnification is the focal length of the objective (FL_Obj) divided by the focal length of the eyepiece (FL_EP), or m = FL_Obj/ FL_EP, as you know.  The magnification is also the apparent field (AFOV) divided by the true field of vie (FOV), or m = AFOV/FOV.  If the eyepiece has an apparent field of 50-degrees, and m = 100x, then you are looking at a 0.5-degree FOV.  We can write FOV = AFOV/m.

So far, so good, but the limiting FOV is set by the focal length of the objective and the entrance pupil (field stop or FS) of the eyepiece.  Call this the limit FOV or LFOV.  This angle is—to a very good approximation with small angles—LFOV = (360 degrees)*FS/(2*pi*FL_OBJ).  (Strictly tan(LFOV/2) = FS/(2*FL_Obj), but for small angles we don’t need to worry about trig.)

Here is what you were getting at in your question, if the FOV we calculate from the eyepiece exceeds the limiting FOV (LFOV), you are wasting light.  Since FOV = AFOV/m, this happens when the magnification is too low, not too high.  In this case you also don’t illuminate the entire apparent field of the eyepiece.  You can find a really good discussion in the Observing Handbook of the Royal Canadian Astronomical Society, pages 54-62 in the 2010 edition.