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AT92- A Fast Widefield Imaging Scope

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#51 georgian82

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Posted 12 May 2020 - 10:32 PM

Here is the Aberration Inspector of this sub:

AA.JPG

.

Stars look great! Glad that FF worked.
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#52 ChrisWhite

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Posted 12 May 2020 - 10:36 PM

.

Stars look great! Glad that FF worked.


Yes, it was a great suggestion! Thanks for that.

#53 georgian82

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Posted 12 May 2020 - 10:51 PM

Yes, it was a great suggestion! Thanks for that.

Now I want to get that combo! 😉

Was this test done using the 183MM or 1600MM?

Edited by georgian82, 12 May 2020 - 11:15 PM.

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#54 ChrisWhite

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Posted 13 May 2020 - 10:10 AM

Here is a very rough process of 2.5 hours of M106 from last night.  This is with the QSI6120+Esprit Flattener on the AT92.

 

Color correction is not too bad.  There is a little fringing with color correction, but it's not bad and with more careful processing I could minimize it.  I literally spent 10 min in PI combining the channels and giving it a little more saturation.  No noise reduction, decon or drizzle was applied.  Nothing fancy here other than STF stretches and combination.

 

Tonight I will be testing this with my QSI 683.  Will see if the Esprit FF performs as well with the larger 4/3 chip. 

 

M106_AT92.JPG

 

M106_AA_At92.JPG


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#55 ChrisWhite

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Posted 13 May 2020 - 10:19 AM

PSA 2:  I'd also like to point out something else that I learned with this scope.  When you loosen the thumbscrew to rotate the focuser you will notice that there is a lot of slop in the focuser to OTA connection.  This is significant and easily manifests itself in images as a very strong source of tilt.  

 

I noticed that if I loosen the thumbscrew and rotate on my target, then tighten... sometimes there is a little bit of tilt still present.  The moral of the story is, you need to make sure that there is no tilt from your imaging train present when you tighten that screw, or it might not mate the focuser perfectly square. 

 

The solution.  Point towards the zenith when rotating your focuser and tighten the thumbscrew while gravity is pulling your imaging train straight down from the scope.  This will allow the mating to be square and you will be sure to not experience any tilt.  Alternatively (if you dont want to point to the zenith), you could gently support the imaging train with one hand while tightening the thumbscrew with the other. 


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#56 ChrisWhite

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Posted 13 May 2020 - 10:23 PM

Tonight I was able to test out the Esprit Field Flattener with my larger chip QSI 683 with 4/3 size KAF8300.  I have to say, I'm really impressed with this field flattener.  It's a great match for this scope.  Stars look great to the corners, and guidestar is nice and tight and round. 

 

At this point I would absolutely recommend this flattener for this scope. 

 

I hope that those of you who are also imaging with this are able to confirm results with other flatteners that you are trying.  I have not tried the ATFF or the smaller of the TSflats.  I don't intend to at this point but would still love to see results. 

 

Below is a 10 minute sub:

 

683_EFF.JPG


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#57 ChrisWhite

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Posted 13 May 2020 - 10:24 PM

Here is the AA of that sub:

 

683_EFF_AA.JPG


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#58 elmiko

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Posted 13 May 2020 - 10:48 PM

Looking great Chris!



#59 ChrisWhite

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Posted 14 May 2020 - 08:29 AM

Looking great Chris!

 

Thanks Mike!  Yes, this is VERY encouraging.  At least for up to a 4/3 size sensor the Esprit 100ED Field Flattener produces excellent results on this scope.  The goal of having a flat field fast imaging refractor for well under $2,000 is achievable.

 

Here is the same M106 scene but with the larger sensor.  Again, a hack processing just to show off the integration with a little color.  I have several clear nights forecasted and will collect more data so I can produce a proper first light. 

 

Next week I hope to test the Starizona 0.65x Flattener.  Dependent on the efficiency of the United States Postal Service.  foreheadslap.gif

 

M106_FF.JPG

 

M106_FF_AA.JPG


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#60 ChrisWhite

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Posted 14 May 2020 - 07:27 PM

Here is the CCDI Analysis of the sub I shared in Post 56.  There is a tiny bit of tilt in the system, which is able to be seen when you view the stars at 100%, but it's insignificant as far as I'm concerned.  There is a little bit of curvature as well, but again... extremely small.  I'm not sure it's even worth fooling around with spacing to try and dial it in.  I do have a bunch of 48mm shims in various sizes thanks to CN member Terry (telfish).  He printed me a grab bag of spacers, and they are top notch.  Easy to get over the threads, unlike some I have tried and I have a variety of thicknesses.  With a fast refractor, shims are your best friend as a mm or less can make a difference. 

 

Curvature and 3D Plot below:

 

CCDI_Curve.JPG

 

CCDI-3D.JPG


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#61 Hilbily

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Posted 14 May 2020 - 08:58 PM

Very nice results, I hope you go for curvature perfection!

Is it the Apex 5-Element?



#62 ChrisWhite

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Posted 15 May 2020 - 05:14 AM

Very nice results, I hope you go for curvature perfection!
Is it the Apex 5-Element?


You had to challenge me...


The above is the esprit 100 flattener, and next week I'll be testing the apex 5-element.
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#63 rockstarbill

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Posted 17 May 2020 - 02:25 AM

Looks like that's coming along nicely.
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#64 RajG

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Posted 18 May 2020 - 06:43 PM

Hi

I've been a lurker for a long time, this is my first post. I recently purchased an AT92 based on user reviews in CN, very satisfied so far. Considering a flattener for imaging - the SkyWatcher Esprit 100 version looks very good.

 

Chris, are you planning on using the long or short version of the Starizona Apex? I guess both should work for the AT92 since it's 506mm focal length?

 

Has anyone tried the Borg 7872 flattener/reducer which is designed for the 90FL (same focal length & focal ratio as the AT92)? It's 0.72X, which will convert the scope to f/4.0. It's supposed to give full frame coverage, unlike the Apex which I think would only work up to APS-C. Very expensive at $555, though. 

 

Rajesh


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#65 ChrisWhite

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Posted 18 May 2020 - 06:58 PM

Hi

I've been a lurker for a long time, this is my first post. I recently purchased an AT92 based on user reviews in CN, very satisfied so far. Considering a flattener for imaging - the SkyWatcher Esprit 100 version looks very good.

 

Chris, are you planning on using the long or short version of the Starizona Apex? I guess both should work for the AT92 since it's 506mm focal length?

 

Has anyone tried the Borg 7872 flattener/reducer which is designed for the 90FL (same focal length & focal ratio as the AT92)? It's 0.72X, which will convert the scope to f/4.0. It's supposed to give full frame coverage, unlike the Apex which I think would only work up to APS-C. Very expensive at $555, though. 

 

Rajesh

Welcome to CN Rajesh,

 

I went with the short version.  I'd like to say it's because I did a bunch of math and determined it would be a better fit, but in reality the Long wont be available for a couple of months and the short was in stock.  Starizona did say that the short would probably be a better fit for this scope... so I went with short.

 

I wouldnt be surprised if the Borg flattener/reducer was a good fit considering the Borg is very similar spec as the AT92.  I think you should try it!
 

I will say, that I would be very surprised if you could get good enough performance with ANY reducer (or flattener for that matter) to correct a field large enough for a full frame sensor.  I don't think this scope could handle it.  I've not tested anything larger than an 8300 chip, so can't say for sure... but I'd be surprised.  Would be nice to see some data from some larger sensors out there with a flattener or reducer. 



#66 RajG

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Posted 19 May 2020 - 10:24 AM

Welcome to CN Rajesh,

 

I went with the short version.  I'd like to say it's because I did a bunch of math and determined it would be a better fit, but in reality the Long wont be available for a couple of months and the short was in stock.  Starizona did say that the short would probably be a better fit for this scope... so I went with short.

 

I wouldnt be surprised if the Borg flattener/reducer was a good fit considering the Borg is very similar spec as the AT92.  I think you should try it!
 

I will say, that I would be very surprised if you could get good enough performance with ANY reducer (or flattener for that matter) to correct a field large enough for a full frame sensor.  I don't think this scope could handle it.  I've not tested anything larger than an 8300 chip, so can't say for sure... but I'd be surprised.  Would be nice to see some data from some larger sensors out there with a flattener or reducer. 

Thanks! I suspect you are right about (the lack of) full frame coverage. Anyway it will be a long time before the CFO approves the purchase of the Borg flattener. I will probably have to start with something cheaper like the SW flattener.


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#67 tdickenson110

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Posted 19 May 2020 - 12:39 PM

Just a quick note to:

(a) Express my appreciation for people's efforts to find a good flattener/reducer for the AT92 bow.gif 

(b) ask Does anyone know the thread size of the focuser end of the AT92 onto which the flattener/reducer goes?


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#68 ChrisWhite

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Posted 19 May 2020 - 12:54 PM

Thanks! I suspect you are right about (the lack of) full frame coverage. Anyway it will be a long time before the CFO approves the purchase of the Borg flattener. I will probably have to start with something cheaper like the SW flattener.

I think you'll be happy with the Esprit 100 Field Flattener. I'm a pixel peeper, and more critical than most ,and I am quite satisfied. 

 

Just a quick note to:

(a) Express my appreciation for people's efforts to find a good flattener/reducer for the AT92 bow.gif

(b) ask Does anyone know the thread size of the focuser end of the AT92 onto which the flattener/reducer goes?

 

Of course! This is an interesting setup.  It's tough to find a fast widefield imaging scope that can perform like this... at this kind of price point.  The thread size on the drawtube is m68x1.  Same as moonlite, which is convenient because moonlite makes a ton of m68x1 adapters to whatever you are interested in hooking up.  Keep in mind though, that the m68x1 threads are not super deep, so you should also get at minimum a 1/2" m68 drawtube extension to ensure that your adapter can thread in.  (There is a funny shoulder about 8mm inside the AT92 drawtube that can prevent some adapters from inserting). 

 

I also recommend getting drawtube extenders anyway, as the focuser has sag when the drawtube is extended too far.  If you can keep this inserted more and extend with threaded extenders there is zero sag and everything is rick solid. 


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#69 rockstarbill

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Posted 19 May 2020 - 03:56 PM

Thanks! I suspect you are right about (the lack of) full frame coverage. Anyway it will be a long time before the CFO approves the purchase of the Borg flattener. I will probably have to start with something cheaper like the SW flattener.

For the flattener I would suspect it would get very very close though with the right amount of spacing work. Maybe hit 40mm well corrected and have to crop the remainder. Not a bad tradeoff for the price. 


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#70 ChrisWhite

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Posted 20 May 2020 - 05:31 AM

OK.  I was able to test out the Starizona APEX 0.65x reducer last night.  I am using the "S" Version.  Starizona advised that it would be a better fit for the AT92, however if I planned to get a longer scope in the future  I should buy the "L" version.  Since I do not plan to go longer, AND the "S" was in stock now (with pandemic delays on the "L") I went with the "S".  Initial tests are very encouraging.  As you can see the stars are not perfect in all corners. I think this is something that I can dial in though.  I literally just slapped it on the scope with 59.5mm of backspacing and started imaging. I would have tried to work on it last night but I spent a couple of hours debugging something totally unrelated and by the time things were running smoothly, I didnt have the will power to spend more time working on spacing.  I have another clear night forecast tonight and I will try 60mm of spacing, which is what the spec calls for for this reducer at ~500mm focal length.  (Well it calls for 59mm but gotta add an additional mm for filters).

 

I also have a tiny bit of tilt in my camera that I need to dial in.  This was also evident with the Esprit flattener so could be lending a hand with the result I got here.  Fortunately the design of the QSI makes it pretty easy to shim for minor tilt.  That will be dealt with later.  I also am seeing more vignetting than before.  I have 1.25" mounted filters, which I will be switching out for 31mm unmounted... so that will hopefully take care of most of that. 

 

This reducer takes an already fast imaging scope and makes it really fast. It turns it into a 330mm focal length scope at f3.6.  With my KAF8300 chip that gives a really wide field of view of 3.12 x 2.35 degrees.  I'm pretty undersampled at 3.38"/px, but for widefield imaging this setup will be pretty tough to beat.  The reducer is expensive, but man this thing is a little photon vacuum!  Apologies if I am taking more than my fair share.   smile.gif

 

Results from initial test below:

 

M106.JPG

 

M106_ReducedAA.JPG


Edited by ChrisWhite, 20 May 2020 - 06:59 AM.

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#71 chongo228

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Posted 20 May 2020 - 06:52 AM

OK.  I was able to test out the Starizona APEX 0.65x reducer last night.  Initial tests are very encouraging.  As you can see the stars are not perfect in all corners. I think this is something that I can dial in though.  I literally just slapped it on the scope with 59.5mm of backspacing and started imaging. I would have tried to work on it last night but I spent a couple of hours debugging something totally unrelated and by the time things were running smoothly, I didnt have the will power to spend more time working on spacing.  I have another clear night forecast tonight and I will try 60mm of spacing, which is what the spec calls for for this reducer at ~500mm focal length.  (Well it calls for 59mm but gotta add an additional mm for filters).

 

I also have a tiny bit of tilt in my camera that I need to dial in.  This was also evident with the Esprit flattener so could be lending a hand with the result I got here.  Fortunately the design of the QSI makes it pretty easy to shim for minor tilt.  That will be dealt with later.  I also am seeing more vignetting than before.  I have 1.25" mounted filters, which I will be switching out for 31mm unmounted... so that will hopefully take care of most of that. 

 

This reducer takes an already fast imaging scope and makes it really fast. It turns it into a 330mm focal length scope at f3.6.  With my KAF8300 chip that gives a really wide field of view of 3.12 x 2.35 degrees.  I'm pretty undersampled at 3.38"/px, but for widefield imaging this setup will be pretty tough to beat.  The reducer is expensive, but man this thing is a little photon vacuum!  Apologies if I am taking more than my fair share.   smile.gif

 

Results from initial test below:

 

attachicon.gifM106.JPG

 

attachicon.gifM106_ReducedAA.JPG

Is that reducer the S or L model? The 92 is right on the 500mm line between the two.


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#72 ChrisWhite

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Posted 20 May 2020 - 07:00 AM

Is that reducer the S or L model? The 92 is right on the 500mm line between the two.

This is the "S" version.  I modified my previous post to include details on this. 



#73 rockstarbill

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Posted 20 May 2020 - 09:30 AM

Looking good. How much is that reducer?

 

EDIT: $450, not bad at all. 


Edited by rockstarbill, 20 May 2020 - 09:56 AM.

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#74 Lead_Weight

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Posted 20 May 2020 - 09:55 AM

Is it the KAF that's making the stars have points? Or is that the reducer?


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#75 rockstarbill

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Posted 20 May 2020 - 10:00 AM

Is it the KAF that's making the stars have points? Or is that the reducer?

Its the KAF-8300. It will do the + sign thing on bright stars, that is the worst you will see with 8300 cameras that use the AR coated sensor SKU. Cameras with this SKU will not do what the 1600 does. The KAF-16200 does it as well, and there are no SKUs without AR coating, so will also not do what the 1600 does on bright stars, regardless. 


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