9 replies to this topic

[nebulaperson9]

Hi everyone. Last night I was using my skywatcher 10” goto dobsonian to do some short exposure on test images. I got this image with only 3 minute integration. I was using short exposures. The problem is the stars are elongated in one corner. If anyone knows what may be causing this please let me know. My telescope was collimated so I don’t know what the problem is.

[KTAZ]

Hi everyone. Last night I was using my skywatcher 10” goto dobsonian to do some short exposure on test images. I got this image with only 3 minute integration. I was using short exposures. The problem is the stars are elongated in one corner. If anyone knows what may be causing this please let me know. My telescope was collimated so I don’t know what the problem is.

No image is attached.

 

An image train may introduce some abberation based on whatever effect the sum of the components introduces to the image plain (usually tilt or backspacing related). This may not be related to colimation at all.

[nebulaperson9]

No image is attached.

 

An image train may introduce some abberation based on whatever effect the sum of the components introduces to the image plain (usually tilt or backspacing related). This may not be related to colimation at all.

[Quadstronomer]

This is likely a relative sensor tilt. It only takes microns of difference in distance. The lower right side of your sensor is too close to your terminal optical surface(where you measure your back spacing from). 

 

And fast optics and long focal lengths don't make it any easier either lol..

Edited by Quadstronomer, 08 May 2024 - 05:48 PM.

[nebulaperson9]

This is likely a relative sensor tilt. It only takes microns of difference in distance. The lower right side of your sensor is too close to your terminal optical surface(where you measure your back spacing from).

Will I need to buy something or can I just easily fix it myself

[hyiger]

Will I need to buy something or can I just easily fix it myself

Depends. Sometimes tilt can be caused by focuser sag. So could possibly make adjustments there. Some of the larger cameras come with a tilt plate. You'll need some interactive tool like ASTAP (which is what I use) to measure tilt in near real-time as you are making adjustments or you will pull your hair out in frustration. 

Edited by hyiger, 08 May 2024 - 06:36 PM.

[KTAZ]

Will I need to buy something or can I just easily fix it myself

Correcting tilt in an imaging train can be challenging. And as @hyiger stated, it gets harder with faster optics.

 

Both my DSO cameras have a tilt plate, but those have pretty coarse screw adjustments. I added Gerd-Neumann CTU's to both my rigs and they have made things much easier with the assistance of ASTAP and Hocus Focus in NINA.

[Spaceman 56]

Will I need to buy something or can I just easily fix it myself

you can load an unprocessed sub into ASTAP, and the software can show you where the tilt is orientated and how bad it is.

 

it gives you an indication if Tilt is the actual problem or not. 

 

possibly a good thing to do before you try adjusting the optics and sensor.

[Oort Cloud]

This is likely a relative sensor tilt. It only takes microns of difference in distance. The lower right side of your sensor is too close to your terminal optical surface(where you measure your back spacing from).

And fast optics and long focal lengths don't make it any easier either lol..

Focal length is not a factor here, only ratio.

[Oort Cloud]

Also, try removing any el-cheapo extensions; they often introduce tilt. Stick with brands that have thick walls (more likely to be squared at the end) and a nice matte finish on the inner threads, otherwise the can cause reflections.

Once you see a well made extension, it becomes clear how cheaply the rest are made. ZWO's recent extensions shipping with their cameras are a good example, the older ones had thick walls, but no matte finish; the new ones have both.