Is this tilt in the image train?


Tom Blahovici
 
Edited

Hi
Now that I have my new AP1100, I am seeing the starts in their true shapes.  Gone are the guiding issues and so on with the new APPM models.
So, this is the first image taken as a test unguided at 5 minutes.  I took the same image with the autoguider running and it made no corrections.

Does this looks like tilt?  In your experience is it? CCDInspector shows a tilt in the direction from lower left to upper right.
It appears to come from before the focuser since the image changes with a 180 degree shift in the camera rotation.

I have tilt adapters both before the focuser (Moonlight nightcrawler) and after.
The telescope is that notorious FSQ106, the telescope plagued with this type of issue.



Thanks, Tom


Dean Jacobsen
 

What camera was used?
--
Dean Jacobsen
Astrobin Image Gallery - https://www.astrobin.com/users/deanjacobsen/


Bill Long
 

If no reducer is being used, that's a scope that needs to go back to Takahashi for collimation adjustments IMO.  While they're could be some tilt, it would need to be insanely large to cause that much error in the field.


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Tom Blahovici <tom.va2fsq@...>
Sent: Monday, September 27, 2021 12:20 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: [ap-gto] Is this tilt in the image train?
 

[Edited Message Follows]

Hi
Now that I have my new AP1100, I am seeing the starts in their true shapes.  Gone are the guiding issues and so on with the new APPM models.
So, this is the first image taken as a test unguided at 5 minutes.  I took the same image with the autoguider running and it made no corrections.

Does this looks like tilt?  In your experience is it? CCDInspector shows a tilt in the direction from lower left to upper right.
It appears to come from before the focuser since the image changes with a 180 degree shift in the camera rotation.

I have tilt adapters both before the focuser (Moonlight nightcrawler) and after.
The telescope is that notorious FSQ106, the telescope plagued with this type of issue.



Thanks, Tom


Tom Blahovici
 

The camera is a full frame ASI6200.
As to going back to Takahashi, that's always a pain from up here in Canada.  From what I have heard it could be a few weeks or months if it has to go to Japan.


Bill Long
 

You can certainly check to make sure everything is rigid and square on the system. Some of the ASI 6200 cameras are known to have tilted sensors, but nothing like it would need to be to cause that level of problems.

What do you see on out of focus stars?


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Tom Blahovici <tom.va2fsq@...>
Sent: Monday, September 27, 2021 12:57 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Is this tilt in the image train?
 
The camera is a full frame ASI6200.
As to going back to Takahashi, that's always a pain from up here in Canada.  From what I have heard it could be a few weeks or months if it has to go to Japan.


Tom Blahovici
 

Hi
The image may be somewhat misleading.  The horizontal zoom, results in an image of 85" wide.  So it is extremely zoomed in. CCD inspector shows a tilt of 3-4 arc seconds.
Interestingly, I look through lots of past images and the tilt seems to change depending on where in the sky I am pointing.
Sound like flex, however I have gone through 3 image trains.  All do the same. It's as if something is lose in a cell somewhere in the telescope. 
Currently I am using a Moonlight nightcrawler with all screw in adapters.


Bill Long
 

I highly doubt it's the focuser. I hang an 11lb camera system off the back of the NC with no flex, sag, etc. The ASI camera package with wheel and OAG weigh less than the filter wheel I have in use.

I suspect the telescope. I have owned an FSQ in the past and had to send it in for collimation as well. Mine did not have to go to Japan, but others in the same boat had to. 




From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Tom Blahovici <tom.va2fsq@...>
Sent: Monday, September 27, 2021 1:21 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Is this tilt in the image train?
 
Hi
The image may be somewhat misleading.  The horizontal zoom, results in an image of 85" wide.  So it is extremely zoomed in. CCD inspector shows a tilt of 3-4 arc seconds.
Interestingly, I look through lots of past images and the tilt seems to change depending on where in the sky I am pointing.
Sound like flex, however I have gone through 3 image trains.  All do the same. It's as if something is lose in a cell somewhere in the telescope. 
Currently I am using a Moonlight nightcrawler with all screw in adapters.


Eric Weiner
 

Have you tried reinstalling the OEM focuser and giving it a quick test? Have you performed any collimation tests?

Eric


Luca Marinelli
 

Tom,

 

While most likely there are optical aberrations contribute to what you are seeing, there is a simple test that you can run to see how much tilt is affecting your image. Run a set of exposures from outside of focus to inside of focus. With the Nitecrawler on this OTA and camera, I would recommend starting about 1,000 steps outside of focus and moving in 250 steps at a time. If there is tilt in your system, there has to be a line with stars in focus that moves through your images with each frame. This will allow you to look at the shape of stars inside and outside of focus both on and off axis. If there are aberrations (coma, astigmatism, and curvature are prime culprits) due to misalignment of the four lenses, it will be very obvious.

 

I just went through this with the same OTA and camera this past Spring. I had been using my OTA with smaller sensors (ASI1600, Atik 383L+) and then a bigger sensor but with large pixels (FLI ML16200), which gave good results without any obvious star shape problems. When I put the ASI6200MM on the OTA in the Winter it was a mess. Using the Sidewinder I was able to get it to be somewhat acceptable but definitely not great. I sent the OTA to Houston in May and received it back in late August. It’s very much improved and after some minor adjustment for sensor tilt is now giving a tight star field all over the field of view.

 

Luca

 

From: main@ap-gto.groups.io <main@ap-gto.groups.io> On Behalf Of Tom Blahovici via groups.io
Sent: Monday, September 27, 2021 3:58 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Is this tilt in the image train?

 

The camera is a full frame ASI6200.
As to going back to Takahashi, that's always a pain from up here in Canada.  From what I have heard it could be a few weeks or months if it has to go to Japan.


Tom Blahovici
 

Hi
Sounds like a plan. Did you remove the nightcrawler and put back the stock focuser when you shipped it to tak?
I would hope they don't rely on a take focuser that could be out of alignment also.
Tom


 

Is the FSQ even capable of supporting a true full frame 35mm like the 6200?

I would be surprised if the image circle was that good. 

When we went to stellarvue for the SVX80T and the 6200, they had to hand-pick the telescope and flattener, and even then it's very very sensitive to any tilts or backfocus distances

On Mon, Sep 27, 2021 at 12:57 PM Tom Blahovici <tom.va2fsq@...> wrote:
The camera is a full frame ASI6200.
As to going back to Takahashi, that's always a pain from up here in Canada.  From what I have heard it could be a few weeks or months if it has to go to Japan.



--
Brian 



Brian Valente


Bill Long
 

The FSQ106 has an 88mm imaging circle.


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Brian Valente <bvalente@...>
Sent: Monday, September 27, 2021 2:08 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Is this tilt in the image train?
 
Is the FSQ even capable of supporting a true full frame 35mm like the 6200?

I would be surprised if the image circle was that good. 

When we went to stellarvue for the SVX80T and the 6200, they had to hand-pick the telescope and flattener, and even then it's very very sensitive to any tilts or backfocus distances

On Mon, Sep 27, 2021 at 12:57 PM Tom Blahovici <tom.va2fsq@...> wrote:
The camera is a full frame ASI6200.
As to going back to Takahashi, that's always a pain from up here in Canada.  From what I have heard it could be a few weeks or months if it has to go to Japan.



--
Brian 



Brian Valente


Luca Marinelli
 

This is what mine looks like after its trip to Houston. It still needs a slight tweak of one of the corners and I think I can bring the entire frame to eccentricity <0.45.

 

Tom: Tak USA requested that I install the original focuser back on before sending the telescope in. They test on the bench with an eyepiece at high magnification and under the stars with a full frame DSLR (not as punishing as the ASI6200MM).

 

Luca

 

From: main@ap-gto.groups.io <main@ap-gto.groups.io> On Behalf Of Bill Long via groups.io
Sent: Monday, September 27, 2021 5:16 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Is this tilt in the image train?

 

The FSQ106 has an 88mm imaging circle.

 


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Brian Valente <bvalente@...>
Sent: Monday, September 27, 2021 2:08 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Is this tilt in the image train?

 

Is the FSQ even capable of supporting a true full frame 35mm like the 6200?

 

I would be surprised if the image circle was that good. 

 

When we went to stellarvue for the SVX80T and the 6200, they had to hand-pick the telescope and flattener, and even then it's very very sensitive to any tilts or backfocus distances

 

On Mon, Sep 27, 2021 at 12:57 PM Tom Blahovici <tom.va2fsq@...> wrote:

The camera is a full frame ASI6200.
As to going back to Takahashi, that's always a pain from up here in Canada.  From what I have heard it could be a few weeks or months if it has to go to Japan.


 

--

Brian 

 

 

 

Brian Valente


Luca Marinelli
 

Better frame with more stars (widefield Sh2-155, the Cave Nebula).

 

Luca

 

 

 

From: main@ap-gto.groups.io <main@ap-gto.groups.io> On Behalf Of Luca Marinelli via groups.io
Sent: Monday, September 27, 2021 5:21 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Is this tilt in the image train?

 

This is what mine looks like after its trip to Houston. It still needs a slight tweak of one of the corners and I think I can bring the entire frame to eccentricity <0.45.

 

Tom: Tak USA requested that I install the original focuser back on before sending the telescope in. They test on the bench with an eyepiece at high magnification and under the stars with a full frame DSLR (not as punishing as the ASI6200MM).

 

Luca

 

From: main@ap-gto.groups.io <main@ap-gto.groups.io> On Behalf Of Bill Long via groups.io
Sent: Monday, September 27, 2021 5:16 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Is this tilt in the image train?

 

The FSQ106 has an 88mm imaging circle.

 


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Brian Valente <bvalente@...>
Sent: Monday, September 27, 2021 2:08 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Is this tilt in the image train?

 

Is the FSQ even capable of supporting a true full frame 35mm like the 6200?

 

I would be surprised if the image circle was that good. 

 

When we went to stellarvue for the SVX80T and the 6200, they had to hand-pick the telescope and flattener, and even then it's very very sensitive to any tilts or backfocus distances

 

On Mon, Sep 27, 2021 at 12:57 PM Tom Blahovici <tom.va2fsq@...> wrote:

The camera is a full frame ASI6200.
As to going back to Takahashi, that's always a pain from up here in Canada.  From what I have heard it could be a few weeks or months if it has to go to Japan.


 

--

Brian 

 

 

 

Brian Valente


Tom Blahovici
 

Ok, that's how it should be.  Was never like that for me, from day 1.
Did they send it to Japan?
Seems like the normal situation is 4 months without Japan!!


Luca Marinelli
 

No, the collimation for my FSQ106 was performed in Houston. It didn’t have to go to Japan.

Luca

On Sep 27, 2021, at 5:40 PM, Tom Blahovici via groups.io <tom.va2fsq@...> wrote:

Ok, that's how it should be.  Was never like that for me, from day 1.
Did they send it to Japan?
Seems like the normal situation is 4 months without Japan!!


Joseph Beyer
 
Edited

Tom,  

I have a 2016-2017 vintage FSQ-106, the model where they changed the color from white to a bluish white.  I’ve used a full frame Nikon D800 for several years and it will produce pinpoint stars across the entire sensor.  I’ve not had a problem with my current scope as long as I’ve owned it. 

I recently purchased an ASI6200 and am dealing with the same problem you are.  Given my prior camera experience I know it’s the new camera causing problems. Initially I connected my filter wheel to the camera with the stock tilt adjuster sandwiched in between.  Images were terrible with elongation of stars nearly across the frame.  I removed the tilt adjuster and immediately got better stars but not great yet. Here is the first test image with 30 X 90 second exposures (45 min) https://www.astrobin.com/wgfes0/0/ . The image is completely full frame with no cropping and was calibrated with only darks and bias as I was interested in seeing what degree of vignetting I was going to get with m48 connectors.  I’ve since purchased a Gerd Neumann CTU but haven’t gotten it set up due to the terrible conditions we’ve had out here in CA. 


My first guess is tilt for your system.  


Joe


Bill Long
 

Mine was fixed in Houston as well. AndySea on CN had to have his sent back to Japan.


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Luca Marinelli <photo@...>
Sent: Monday, September 27, 2021 2:45 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Is this tilt in the image train?
 
No, the collimation for my FSQ106 was performed in Houston. It didn’t have to go to Japan.

Luca

On Sep 27, 2021, at 5:40 PM, Tom Blahovici via groups.io <tom.va2fsq@...> wrote:

Ok, that's how it should be.  Was never like that for me, from day 1.
Did they send it to Japan?
Seems like the normal situation is 4 months without Japan!!


Tom Blahovici
 

Joe,
That image is close to perfect.  You would never see any funny stars even with a 4 foot wide print.
So my next outing will be to tighten everything up.  That includes the adapters and the screws on the flanges for the nightcrawler.
Then I will start looking.
1) Take images at different points in the sky to see if things shift.
2) If not then attempt to adjust the tilt.
I guess I should attempt this before returning the scope.  If I do send the scope, then it will wait until March when I switch scopes to my galaxy scope.
Thanks all.


Joseph Beyer
 

The individual sub images are more telling of the remaining problem.  Stacking the subs seemed to “fix” the remaining elongation more than I expected. I agree with you though, it sure looks reasonable.  I’ll post a link to one of the subs later.  Good luck! 


Joe