Elongated star on one side of the image.

[Petar b]

I'm getting elongated stars on only one side of an image it is always on the right. I don't know what the problem is I don't think that it is collimation but I think that the problem is either with focuser sag or FF. The telescope I'm using is Explore Scientific ED80 essential series and the ff is Hotesch SCA

Star test:

 

[Petar b]

Raw images:

[alacant]

Hi. Camera sensor: I'd say it's too close at the right and too far at the left; the camera is tilted. Try re-seating/threading the ff/camera/focuser so it's square. HTH.

[sloz1664]

Upload a raw file and I will run it through CCD Inspector to check your alignment.

Steve

[Petar b]

 

Here is what I got after running stacked M45 in Pixinsight:

IMG_0319.CR2

[Petar b]

Other two files

IMG_0361.CR2

IMG_9737.CR2

[RayD]

I have a Hotech SCA and find it very very touchy for alignment, really critical.  I found that I had to sit the scope end down, let the FF settle on its collar, and then tighten slowly whilst putting slight pressure on it.  In the end I actually ended up unscrewing the SCA bit and using it as a screwed connection which solved the problem completely.

[RayD]

Below is my SCA now on my TS80.  I think it is a great idea for centring, but it seems if you have a reasonably heavy CCD and filter wheels, the rubber which holds it in place flexes a bit and causes tilt.  The SCA adaptor unscrews from the lens cell, and once fitted like this the issue went.

[Petar b]

I forgot to mention that I am using a DSLR and the distance between the FF and the sensor is as specified 55mm. When it gets clear here in Croatia I'm going to try all of your suggestions.

[RayD]

I would say start with facing downwards and pressing lightly whilst rotating the ring.  Then, as counter productive as it sounds, use your compression fittings as normal to tighten it in place, it stops the tipping caused by the rubber rings.  This should be sufficient with a DSLR.

[Petar b]

I tried to unscrew the SCA part but I couldn't.

[Sunshine]

i know next to nothing about AP but i did see you posted a CR2 file which is perfect for me to play with in lightroom so i zoomed in on a few stars and enhanced, maybe you can draw a conclusion from this image.

im not sure how long the exposure was but it was all pink for some reason, and the stars are pretty much pinpoints with the exception of some blue appendage's coming off to lower left, i don't know enough to comment but here is the image i drew

from the CR2 for you experts.

[Petar b]

You were looking at the wrong side of the image, you should have looked at the right side of the image. All of exposures were 30 sec long.

[alacant]

9 hours ago, Sunshine said:

you can draw a conclusion from this image

+1. Wrong side or not, stuff like this is easily corrected by modern software algorithms. As well as LightRoom, StarTools' excellent 'lens' module which corrects field curvature comes to mind.

Worth a try? HTH and clear skies.

[Petar b]

Last night I shot the same star in all corners. I think that the focuser is sagging.

1. How I normally take pictures

2. I rotated the camera 90°

3. I tried to put a new t-ring

4. I rotated the camera with the new t-ring 90°