Weird shaped stars

[Blackrose]

Dear Astrofriends,

 

 

I have a relatively old EQ5goto, a TSQ 65 telescope, a D800 standard imaging camera and an ASI120MM mini guidecamera with Orion 50mm guidescope controlled via ASIAIR. Stars in every photo I take with this setup, turn out to be elongated in the same general direction. Since I'm using ASIair there aren't any log files I can provide, but the curve is relatively smooth and reproducible. It generally resides under 2 arc-second total and RA Error is normally around 0.8 arc-seconds. I know that guiding curve is not everything, but I don't think my stars should look like as bad as this at the end of the day. I have a very good balance and neither dec nor RA axis fall, when clutches are released. I even tried being a little east heavy to no avail. I kinda ran out of options to figure out the problem. Since I'm an electrical engineer I have the necessary skills to open the mount and tune it and grease it, if you guys think that would solve my problem. The photo looks as attached. Would appreciate any kind of insight. Thanks in advance,

 

 

Clear skies,

 

Kamyar

[newbie alert]

Try refocusing on a bright star and see what you get, I've got a hunch you have pinched optics, not unusual for a TS65 and a easy fix..

[michael8554]

Are they elongated in the RA direction ?

For round stars the RA and Dec RMS figures need to be similar, but often RA is larger.

Michael

[Adam J]

I would say that this is more like bad colimation to my eye.

Adam

[Blackrose]

1 hour ago, newbie alert said:

Try refocusing on a bright star and see what you get, I've got a hunch you have pinched optics, not unusual for a TS65 and a easy fix..

I think you might be right. I looked the topic up and saw some promising stuff and as you said an easy fix. I'll do it and wait for the first CS to see if it's working. There was a reason that previous owner kinda gave away this telescope rather cheaper than usual to me. I should have known

https://www.cloudynights.com/topic/569527-is-this-pinched-optics/

[Blackrose]

1 hour ago, michael8554 said:

Are they elongated in the RA direction ?

For round stars the RA and Dec RMS figures need to be similar, but often RA is larger.

Michael

Yes its the case. 0.8 for RA and 0.4-0.5 DEC. But again judging by numbers of my optical terrain, it should translate to an error of 1 or maximum 2 pixels in my final image. What we are seeing here is more than that. and there is also a very bad color fringing biased to one side, which should not be the case with triplet design. Full res ->

https://ibb.co/r4yxzTT

[Blackrose]

58 minutes ago, Adam J said:

I would say that this is more like bad colimation to my eye.

Adam

I think you might be right, I have to see if this fix works and I'll get back to you. 

https://www.cloudynights.com/topic/569527-is-this-pinched-optics/