Star elongation

Good evening.

The past few nights I've been trying to image M13. However, I've noticed I'm getting a fairly uniform elongation on the stars. I think it's roughly aligned with the RA axis.

This is the first time I've noticed the issue and I'm wondering if anyone has any idea what could be happening?

Any advice folks have would be great.

Hi,

I can see in your latest image the elongated stars in one axis. There could be several reasons as you mentioned.
Do you see this in every frame or only in some ? If in some then reason could be wind gusts or seeing deviations during the session(s) or intermittent guiding errors

Uri

Hi Uri,

It's in every frame unfortunately. I'm planning on doing some unguided exposures to see if the issue is the guiding.

Thanks

Hi Dominic,

Your image has the same north-south elongation as some of my (posted and unpostefd) images have and I am also trying to figure out what the cause is.
This week I also shot M13 with elongated stars. So for a second I thought the stars of M13 just changed their shape :-).

Was your guiding worse that night then normally? Even if I have decent guiding (0.6 - 0.7 total RMS) i have elongation, albeit that my stars look more like eggs.

If your image suffers from flexure, using an OAG can be the solution. I am now corresponding with other Astrobin member, he says you can check if its flexure by using PixelMath process in Pixinsight (dont know if you use that program). Haven't tried it yet.

Shooting very short exposure (max 5 sec) can tell if there is a problem with the optics. You can also do this guided. If the stars are not round, there can be an optical problem (both in telescope or in camera). If you have 2 telescopes and/or 2 camera's you can rule this out (or confirm of course).

Since I'm having this problem too, please update me on your findings.

CS,
Douwe

Hi Douwe,

Thanks for the info. I'll definitely post my findings once I've had a chance to experiment a little.

Hi Dominic,
I've been going through a similar problem which turned out to be vibrations from the camera's fan. Try taking 1 second exposures and see if the problem is there, and try with/without the 12V connected to the ASI.

I hope you get to the bottom of this soon, good luck!

Could be your filter causing abberation

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