Weird shaped stars in some light photos

[Blackrose]

Hello,

 

I just recently bought a used ZEQ 25 mount and there is a problem, which I don't understand the reason. Pictures below were an attempt on Andromeda galaxy. As you can see one is tack sharp but the other one has this weird shape. If the problem was set-up, mount, PA or whatever, I should not have gotten a sharp image at all. I figured it might be an RA issue. I found the youtube videos of Paul Chasse and tuned my mount. Right now there is no movement or looseness in RA axis. Have you had the same problem or you can guess what the problem might be? I would be very thankful for your help.

 

CS

Kamyar

[kendg]

I had a very similar problem with my AZ-EQ6, 

It turned out to be mainly an issue of proper balance (and a slight bit of backlash).

 

[Blackrose]

14 minutes ago, kendg said:

I had a very similar problem with my AZ-EQ6, 

It turned out to be mainly an issue of proper balance (and a slight bit of backlash).

 

My mount has Anti-backlash option. I have to give a certain number of steps, in which each step is 0.14 arcsecond. How do I know how many steps I should use?

 

As a side question, since I'm new to the hobby I just wanted to know the shape I'm getting is related to RA or both RA and dec?

[kendg]

I'm not familiar with your mount so can't answer your question.

All I can suggest it to make sure everything is in balance.

 

[michael8554]

Movement appears to be N-S rather than E-W.

Assuming you're set up as a EQ mount rather than an AZ, then Dec is deviating, not RA. so possible due to high Dec backlash.

You haven't said if you're guiding ?

Michael

[Blackrose]

31 minutes ago, michael8554 said:

Movement appears to be N-S rather than E-W.

Assuming you're set up as a EQ mount rather than an AZ, then Dec is deviating, not RA. so possible due to high Dec backlash.

You haven't said if you're guiding ?

Michael

No, I'm not guiding. I'm new to the hobby and wanted to buy least possible equipments. So I have a CEM (chineese eq mount) and no guiding with ED80 ES.