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Orion 8" f/8 RC Astrograph - disappointing results

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#1 nikivan

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Posted 12 June 2019 - 06:39 PM

I recently bought a brand new Orion 8" RC astrograph and I've been struggling to get any good images out if it. The scope was collimated by a very experienced person, so this is not the issue. The problem is that the stars look quite bloated. When carefully adjusting the focus it looks like the stars are about to get into focus, but then they turn into blobs again. Here is a snapshot taken directly from PixInsight work window with scale 1:1. This shows absolutely the best focus I am able to achieve. I am using ZWO ASI071MC Pro. There is also quite a variation from the center of the filed to the corners (will upload samples in the next posts). Is this is normal, or I've got a lemon? Please share your thoughts.

 

Orion RC 8 frame snapshot.jpg

 



#2 nikivan

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Posted 12 June 2019 - 06:59 PM

Orion RC 8 frame snapshots - top right.jpg



#3 nikivan

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Posted 12 June 2019 - 07:02 PM

Orion RC 8 frame snapshots - bottom right.jpg



#4 nikivan

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Posted 12 June 2019 - 07:04 PM

Orion RC 8 frame snapshots - bottom left.jpg



#5 nikivan

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Posted 12 June 2019 - 07:05 PM

Orion RC 8 frame snapshots - top left.jpg



#6 TinySpeck

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Posted 12 June 2019 - 07:15 PM

Do you have any telecompressor or other devices in your optical chain?



#7 Jim Waters

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Posted 12 June 2019 - 07:39 PM

Are you using a FF?



#8 nikivan

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Posted 12 June 2019 - 07:41 PM

Do you have any telecompressor or other devices in your optical chain?

No, I don't. I have the telescope, two extension rings, the stock focuser and the camera train.



#9 Jim Waters

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Posted 12 June 2019 - 07:45 PM

Does Orion make a FF?

 

I would call Orion Tech Support about the focus issues.  The center should be in focus.


Edited by Jim Waters, 12 June 2019 - 07:46 PM.


#10 starhunter50

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Posted 12 June 2019 - 07:46 PM

There is coma there for sure but im more concerned about the focus being way out.

are you using your Mask? (Bahtinov)



#11 starhunter50

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Posted 12 June 2019 - 07:51 PM

Next time out , slew to Vega defocus in both direction and grab a shot of the star at center both in/out racked in/out .

defocus quite a bit. then post here.


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#12 Jim Waters

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Posted 12 June 2019 - 08:10 PM

Next time out , slew to Vega defocus in both direction and grab a shot of the star at center both in/out racked in/out .

defocus quite a bit. then post here.

Excellent recommendation.

 

nikivan - Is there a UV/IR Block filter on the ASI071MC Pro?  If not try to get one and test 'with' and 'without' the filter.  This may be some of the problem causing the star bloat.  It will not fix the coma in the corners.


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#13 TinySpeck

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Posted 12 June 2019 - 08:41 PM

It looks to me like the mirror adjustment isn't right somehow, since the appearance in each corner is so different.  Collimating RC scopes can be very tricky I hear (even though I haven't had to on mine).  You need to adjust mirror tilt, spacing, and co-axiality, and the adjustments interact.

 

Can you tell us a little more about the procedure?  Has the guy done RCs before?  What kind of equipment did he use?


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#14 futuneral

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Posted 12 June 2019 - 09:35 PM

http://www.deepskyin...ure_Ver_1.0.pdf

 

Read staring at around page 11. Looks very much like what you're seeing.


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#15 Bowlerhat

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Posted 13 June 2019 - 08:37 AM

Isn't if it's focused properly you won't be able to see any donuts shape? since that's just an OOF shape.



#16 starhunter50

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Posted 13 June 2019 - 12:12 PM

Isn't if it's focused properly you won't be able to see any donuts shape? since that's just an OOF shape.

Which is why  i mentioned the Bahtinov mask at the outset. 


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#17 starhunter50

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Posted 13 June 2019 - 12:15 PM

I recently bought a brand new Orion 8" RC astrograph and I've been struggling to get any good images out if it. The scope was collimated by a very experienced person, so this is not the issue. The problem is that the stars look quite bloated. When carefully adjusting the focus it looks like the stars are about to get into focus, but then they turn into blobs again. Here is a snapshot taken directly from PixInsight work window with scale 1:1. This shows absolutely the best focus I am able to achieve. I am using ZWO ASI071MC Pro. There is also quite a variation from the center of the filed to the corners (will upload samples in the next posts). Is this is normal, or I've got a lemon? Please share your thoughts.

 

attachicon.gif Orion RC 8 frame snapshot.jpg

please send me an Email in order for me to send you an  RC collimation instruction that make sense..

 

rcfmitch at gmail dot com 


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#18 nikivan

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Posted 13 June 2019 - 01:01 PM

Lyra_out_of_focus_1.jpg

 

Next time out , slew to Vega defocus in both direction and grab a shot of the star at center both in/out racked in/out .

defocus quite a bit. then post here.

Here is the first snapshot. The 500KB size restriction does not allow me to post the entire field.

 

 

Excellent recommendation.

 

nikivan - Is there a UV/IR Block filter on the ASI071MC Pro?  If not try to get one and test 'with' and 'without' the filter.  This may be some of the problem causing the star bloat.  It will not fix the coma in the corners.

Yes, I have UV/IR filter. It is 2" Baader UV/IR-Cut/L. Are you suggesting the issues may be related to it?

 

 

It looks to me like the mirror adjustment isn't right somehow, since the appearance in each corner is so different.  Collimating RC scopes can be very tricky I hear (even though I haven't had to on mine).  You need to adjust mirror tilt, spacing, and co-axiality, and the adjustments interact.

 

Can you tell us a little more about the procedure?  Has the guy done RCs before?  What kind of equipment did he use?

The collimation was done during the day, on an artificial star. I was shown the out of focus rings not being symmetrical before the procedure, and quite symmetrical after it. Only the secondary mirror was adjusted. I am not sure if adjusting the primary is even possible on this scope. 

 

 



#19 nikivan

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Posted 13 June 2019 - 01:10 PM

Out.

Lyra_out_of_focus_2.jpg



#20 Jim Waters

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Posted 13 June 2019 - 01:55 PM

Yes, I have UV/IR filter. It is 2" Baader UV/IR-Cut/L. Are you suggesting the issues may be related to it?

No, but without you will likely get bloating.  

 

Could the ASI017MC Pro be tilted?



#21 nikivan

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Posted 13 June 2019 - 02:40 PM

No, but without you will likely get bloating.  

 

Could the ASI017MC Pro be tilted?

I can't tell if the camera is tilted. The extension rings are tightened very well and there is absolutely no play in the camera train. But even if it was a little bit of camera tilt, that will not explain the reason for inability to achieve sharp focus in the middle of the field.


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#22 starhunter50

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Posted 13 June 2019 - 02:41 PM

Nikivan, i need you to defocus Vega Even more ....and lower the exposure. let me show you.

if you can use Sharpcap 3.2 

 

the bottom image is what you want.  yes the primary can be adjusted. 

 

https://drive.google...iew?usp=sharing

Attached Thumbnails

  • Single__2019-04-12_23-14-16_23-14-16_M51_G1000_Bin1x1_3s.jpg
  • Single__2019-04-12_23-13-49_23-13-49_M51_G1000_Bin1x1_3s.jpg
  • Single__2019-04-12_23-13-01_23-13-01_M51_G100_Bin1x1_3s.jpg
  • RC6 collimated.jpg


#23 Jim Waters

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Posted 13 June 2019 - 03:21 PM

I can't tell if the camera is tilted. The extension rings are tightened very well and there is absolutely no play in the camera train. But even if it was a little bit of camera tilt, that will not explain the reason for inability to achieve sharp focus in the middle of the field.

You are correct about the focus problem.  You may have more than 1 issue.  The ASI071MC Pro has tilt adjustment screws. I was referring to that.  


Edited by Jim Waters, 13 June 2019 - 03:22 PM.


#24 starhunter50

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Posted 13 June 2019 - 03:57 PM

Collimating RC s is NOT for the faint at heart...

 

Here is what it looks like , looking down a Cheshire EP after perfect collimation.

All the circles are concentric and the spider vanes line up.

took 4-5 hours but was worth it. 

 

Attached Thumbnails

  • Perfect colimation RC6.JPG

Edited by starhunter50, 13 June 2019 - 04:03 PM.


#25 Stephen Kennedy

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Posted 14 June 2019 - 07:53 AM

Here is a 30" unguided defocused image of Vega taken with my TPO RC6 on a Vixen Super Polaris GEM with the OTA   right out of the box with no collimation done by me.

 

IMG_2885 (4).jpg

 

 

All of these RCs and CCs whether sold by Orion, TPO or AT are all made by GSO at their factory in Taiwan,

 

 

 




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