Star tails?

[StuW]

Hi all

Been out tonight for my first proper attempt at imaging and have a few queries....

About 80% of my images have little tails. Strangely my M13 didn't have any, but my M27, M57 always have them and my M81/82 has 90% of the time...

Any Ideas?

Equipment was SW 200p DS on HEQ5 and Samsung GX-20

TIA

Stu

[JohnnyD333]

There can be a number of reasons why this happens. Your polar alignment could be off. You may not be autoguiding (I dont know if you are). Periodic error can cause this. Your scope being unbalanced on the mount could cause trails, especially if its when imaging certain DSOs as opposed to others (the shift in weight puts strain on the motors). Its hard to pinpoint exactly why but there are many reasons. I go through this at least a few times a month so dont worry its part of the fun;)

[StuW]

Thanks for that Johnny, I think it's a combination of collimation and balance as I didn't balance the scope with the camera attached and looking back through some early attempts at focussing with the camera on I found what you see in the attached picture. It seems there's a large amount of clipping on the secondary but it's only a couple of mm from the spider mount, any ideas?

Stu