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Help, spacing with a tilter.

Anthony RS

By Anthony RS
in Imaging - Discussion

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Anthony RS

Anthony RS

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Hello,

 

I'm having some tilt issues with my gear, probably from the camera's sensor. I'm using an 8 inch newtonian with a dslr and the skywatcher f4 aplanatic 2 inch coma corrector.

 

My question is if I buy a tilter like this one https://www.teleskop-express.de/shop/product_info.php?products_id=4744#cs, how will I be able to achieve the right spacing between the DSLR and the CC? 

 

The required spacing for this CC is 55 mm which I already get by using just the m48 t-ring adapter (11mm + 44m dslrbackfocus). Won't the tilter increase the spacing by another 11mm?

 

Unless I completely misunderstood how the tilter mechanism works, please let me know if there's any way I can make it work without changing the spacing between the DSLR and the CC.

 

Thanks,

 

Anthony

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Craney

Craney

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Can't you keep the CC to  Dslr  distance as is, but put the tilt adapter before the CC in the optical train ?   

Might need an adapter of sorts and a short 2" section to connect into the focuser, but this will be before the correction and hopefully not upset the focus point.

Just a guess.  Good luck.

Sean.

 

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nightster

nightster

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Do you have proof the tilt is in the sensor? Could it be the focuser? I've been down that rabbit hole and it can get frustrating. I only ask because you said 'probably.' 

If you use a Tilt Adjuster (TA) that attaches to the removable part of the imaging package, you will need to verify you have reinstalled everything in its exact position if you every separate the gear. I would suggest using some kind of index marks on each part to ensure its assembled in correct position. If the tilt is coming from the focuser once you get the image plane flat on the sensor with the TA I don't think you will be able to rotate the focuser/sensor for framing. 

If you have verified the tilt in the sensor forgive me and disregard the rest of my post. But if not, maybe use the CCDInspector to show tilt % and direction. Also are you using Compression fittings for your imaging package? I would suggest all threaded connections if possible. And finally are you using a high quality focuser?  I went through this list in my quest for round stars. Good luck.

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Anthony RS

Anthony RS

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36 minutes ago, Craney said:

Can't you keep the CC to  Dslr  distance as is, but put the tilt adapter before the CC in the optical train ?   

Might need an adapter of sorts and a short 2" section to connect into the focuser, but this will be before the correction and hopefully not upset the focus point.

Just a guess.  Good luck.

Sean.

 

that's what I'm trying to find out ?

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Anthony RS

Anthony RS

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6 minutes ago, nightster said:

Do you have proof the tilt is in the sensor? Could it be the focuser? I've been down that rabbit hole and it can get frustrating. I only ask because you said 'probably.' 

If you use a Tilt Adjuster (TA) that attaches to the removable part of the imaging package, you will need to verify you have reinstalled everything in its exact position if you every separate the gear. I would suggest using some kind of index marks on each part to ensure its assembled in correct position. If the tilt is coming from the focuser once you get the image plane flat on the sensor with the TA I don't think you will be able to rotate the focuser/sensor for framing. 

If you have verified the tilt in the sensor forgive me and disregard the rest of my post. But if not, maybe use the CCDInspector to show tilt % and direction. Also are you using Compression fittings for your imaging package? I would suggest all threaded connections if possible. And finally are you using a high quality focuser?  I went through this list in my quest for round stars. Good luck.

Ouf! You can't imagine how many threads I've opened regarding this issue. I've been trying to solve my problem for 2 years now. Recently I've replaced my GSO CC with the aplanatic one hoping the GSO was defected ( a sign of that is huge and totally unacceptable chromatic aberration. A star would literally appear as 3 stars each with a different color. Tried all possible spacings from 55 to 85 in 1mm increments...). I'm still waiting for the new CC to test it. If it doesn't work, i would use the tilter to try and remove the tilt. If that doesn't work either, i'll upgrade the focuser. I know there are some tests I could do to determine whether the tilt is from the sensor or the focuser, but so far i couldn't really do them from reasons i don't want to bore you with. Plus after some tinkering done on the focuser to make it sturdier, i took a CCDInspector analysis and came with the results in the image below. It showed only 5% tilt (my friend using the same scope has 27% tilt and has perfect stars with his Baader CC). The worrying part is the curvature which is huge, which made me consider the CC was either defective or terrible.

Curvature 1.jpg

Curvature.jpg

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Anthony RS

Anthony RS

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16 minutes ago, nightster said:

Do you have proof the tilt is in the sensor? Could it be the focuser? I've been down that rabbit hole and it can get frustrating. I only ask because you said 'probably.' 

If you use a Tilt Adjuster (TA) that attaches to the removable part of the imaging package, you will need to verify you have reinstalled everything in its exact position if you every separate the gear. I would suggest using some kind of index marks on each part to ensure its assembled in correct position. If the tilt is coming from the focuser once you get the image plane flat on the sensor with the TA I don't think you will be able to rotate the focuser/sensor for framing. 

If you have verified the tilt in the sensor forgive me and disregard the rest of my post. But if not, maybe use the CCDInspector to show tilt % and direction. Also are you using Compression fittings for your imaging package? I would suggest all threaded connections if possible. And finally are you using a high quality focuser?  I went through this list in my quest for round stars. Good luck.

and yes I did try an all threaded imaging train. the result is the RAW image i attached. It was actually slightly better than with the unthreaded configuration but still the result was unacceptable. The problem with an all-threaded configuration is that as yuou said I won't be able to frame my images. As for the focuser, it is the worse you can get, the stock rack and pinion shitty focuser :) But as you can see in the CC Inspector analysis above, tilt is minimal but could still be the problem which is why I might invest in a TA if it works with my setup. IF you have any other ideas regarding my issue I would be really grateful. I've been fighting this for 2 years now. THe main problem is one side of my images always has terrible coma, and the whole image suffers from terrible CA. 

CC Test.jpg

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