Whats happening here? First attempt issues

[AshleyCUK]

This was my first attempt at astro photography.  I have a Stellalyra 8" f5 newtonian and have put my Fuji x-t2 on it and was trying for the Orion nebula last night.

 

This was shot at 1/4 sec iso1600 and is one of an interval run of 200 images, the fuji was in electronic shutter mode to minimise shake.  Is this wobble, collimation, bad focus, star trails, mirror pinching?  I dont think i can focus it any sharper on the zoomed in fuji screen.  Any thoughts on what is causing this arrow head look to the stars? This is a crop from a zoomed in frame.

DSCF0556.tif

Edited January 18 by AshleyCUK

[Stu]

Hi Ashley,

It looks on the face of it to be a collimation type error BUT, could be a number of things. First thing, how does the collimation look visually? Does a defocused star in the centre of the field of view have concentric rings or are they offset? Before doing anything else, let us know this as it helps to rule things in or out.

[alacant]

43 minutes ago, AshleyCUK said:

This is a crop from a zoomed in frame.

Hi
To help us, maybe post: 
- an uncropped frame
- a frame of a bright out of focus star in the centre of the frame
- a view in daylight -with the imaging camera removed- into the focuser
- a view of the camera assembly fitted into the focuser
- details of the optical train e.g. is there a coma corrector or filter

Cheers

[malc-c]

What mount is the 8" scope sitting on...??

To me it looks like a collimation error

[AshleyCUK]

its an EQ5 non motored.  I'll double check the cllimation tonight. It looks ok in daylight but i'll do it with the defocused stars as well.

[Elp]

Might help to show the whole frame. As asked previously are you using a coma corrector? They're essential for a full flat field across the FOV with a Newtonian.

[AshleyCUK]

added the whole frame as a tiff for reference, no coma corrector last night but I did get one delivered today so will give that a go as well

Edited January 18 by AshleyCUK

[Elp]

Id say its the lack of CC, there might be some tilt too as it's more pronounced at one side. Your stars look a little bloated so check the backspacing distance, it might just look like that in the image due to the focal length of the scope, longer focal length the larger the stars.