QHY 268M non uniform back focus

[Taraobservatory]

Hello,


I have some issues with my QHY 268. The back focus seems to not be uniform. I get elongated stars in 3 corners which they are pin sharp in another. This leads me to believe that the sensor not uniform with the optics. I have also tested with another telescope and the same issues occur so its definitely a sensor misalignment in the camera. I understand that I can adjust this at the front if the camera but I wonder if there are some tips on how to do this successfully ? As my attempts to tackle this has so far failed. Is there some kind of software or an easy way to get this done ? 

 

Kind regards

Roger 

[Adam J]

1 hour ago, Taraobservatory said:

Hello,


I have some issues with my QHY 268. The back focus seems to not be uniform. I get elongated stars in 3 corners which they are pin sharp in another. This leads me to believe that the sensor not uniform with the optics. I have also tested with another telescope and the same issues occur so its definitely a sensor misalignment in the camera. I understand that I can adjust this at the front if the camera but I wonder if there are some tips on how to do this successfully ? As my attempts to tackle this has so far failed. Is there some kind of software or an easy way to get this done ? 

 

Kind regards

Roger 

Really you need to post an image. 

Adam 

[Taraobservatory]

4 hours ago, Adam J said:

Really you need to post an image. 

Adam 

Hi Adam,

 

Ill post next time as I didn't save any of my tests and now the clouds are rolling in. 

 

Kind regards

Roger

[Richard_]

If you use NINA, there is a plug in called "Hocus Focus". It has a built in auto focus routine which calculates if you have any sensor tilt issues with your camera. 

If you don't use NINA, you can use image inspector in ASTAP which will tell you the same thing. 

Before you go and play with tilt setting, I'd highly recommend double checking your focus tubes for sagging any anything else which could simulate tilt. Someone else suggested I do this with my QHY268M and I found my refractor focus tube sagged a little bit, and my William Optics adjustable flattener needed to be square when setting the lock ring. 

Below are some screenshot of both tools I talked about above. As you can see, both analyses indicated tilt with my sensor, but after tightening up my focus tube and setting my flattener correctly, I was able to achieve a flatter sensor without touching the tilt adjuster. I don't have any "after" pictures sorry! 

ASTAP

 

NINA - Hocus Focus