Misshapen stars only on one side of image

[chris_g]

Hello all,

I've been going through my data since I discovered the issue with back focus being off on my flattener. The last time I knew it was correct was back in April when I imaged NGC 7000. In that image, the stars are round a lot farther out the edge on the right side than they are on the left. It this caused by tilt?

Clear Skies,
Chris

[AstroBee]

It sure sounds like tilt if it's not even on both sides. If the tilt is perfect and it was a back focus issue it would be fairly equal all around. Here's a good chart to help you remember about back focus and which way you need to adjust if the corners are even.
https://cdn.shopify.com/s/files/1/1594/ ... 1606528627

[chris_g]

Camera sensor too far away left side, right side very close but still off. Thank you, I remember seeing that visual aide when I first started out. Now, it makes sense, more stuff to the image train! At least they're not that expensive...

[AstroBee]

I'm not sure if you use NINA but if you do, and you have an easy way of adjusting your tilt, this video will come in VERY handy.

[chris_g]

I use APT but am familiar with NINA. I've used one of it's plugins, TPPA. I'll load it up and check out Hocus Focus. I like that ASTAP will show you with one key press

Thank you for the info, very good!!!

Clear Skies,
Chris

[AstroBee]

Yeah, ASTAP shows you the problem but NINA will tell you what you need to do to fix it.

[chris_g]

i checked out the images with the C8 tonight. I love that graphic aide, I had the sensor too far out and since i had used variable extension tubes, I was able to adjust it down to almost flat across the sensor, very little tilt with C8. Talk about a pain in the backside though, pulling camera off and what not, the prism for the OAG ended up inside the camera! And the micrometer almost ended up i my foot. Glad it fell in and not out. All in all, It was worth the exercise. I got more round stars. Need to look into some good quality extension tubes to replae the ones I'm using now. They can be sloppy.

Thanks for the tools showing how to resolve this particular issue.

[Juno16]

I'm not sure if you use NINA but if you do, and you have an easy way of adjusting your tilt, this video will come in VERY handy.

Excellent information Greg. I don't have a tilt issue right now, but I am a N.I.N.A. user and will pack this Youtube link away for future reference. Much appreciated!