Collimation or Something else?

[astrosathya 138]

Hello Everyone,

I have a GSO 6" f/4 Astrograph, and there's always been this issue with elongated stars on one edge. I've checked collimation and it is perfect, but for the elongation on one corner. Could someone please throw some light on what's happening

[Jkulin 816]

It could be tilt, have you got a tilt plate adapter? Recheck the seating of your filter wheel and camera.

Are you using a dew heater on either mirror, I had some very odd shapes on my stars due to the dew heater warping the mirror from the heaters being to hot?

CCD Inspector seems to suggest that there is something amiss with your optics: -

Quite how you are going to fix this will need some thinking about.

 

[Peter Drew 8,925]

How tight is your primary in its cell? Manufacturers tend to have them too tight when assembled at the factory. The mirror should be reasonably free moving. 

[astrosathya 138]

On 26/01/2019 at 16:48, Jkulin said:

It could be tilt, have you got a tilt plate adapter? Recheck the seating of your filter wheel and camera.

Are you using a dew heater on either mirror, I had some very odd shapes on my stars due to the dew heater warping the mirror from the heaters being to hot?

CCD Inspector seems to suggest that there is something amiss with your optics: -

Quite how you are going to fix this will need some thinking about.

 

Hi John, I don't use dew heaters on either mirror. The mirror clamps aren't tight either. I am suspecting that the focuser isn't square to the tube. The Filter wheel and CCD are fine because I use them with my 80ED and haven't noticed any odd stars.

[astrosathya 138]

22 hours ago, Peter Drew said:

How tight is your primary in its cell? Manufacturers tend to have them too tight when assembled at the factory. The mirror should be reasonably free moving. 

not tight at all. I made sure of that when I removed and replaced it. Its not pinched.

[Peter Drew 8,925]

That's good to know, tightness is so often the cause of such issues.