Ugly stars - What could be the problem?

[mcbras]

Hi,

I don't know why but I'm getting the most ugly stars I ever seen. I do guided subs and PHD2 doesn't report big error, and I'm actually assuming that this can be due to anything, but would like to hear from you what are the most probable causes for this.

My rig is a 8'' newton with an RCC I baader coma corrector, apogee FW and CCD on top of a NEQ-6. My guiding telescope is Skywatcher Evoguide 50ED.

Below you can see one sub that I just saved as TIFF from FITS Liberator.

I appreciate if anyone can guide me to possible solutions, what to look for, any tools to help , anything, because I never seen any of this on other users reports, here or in other forums.

Thanks

MB

2020-06-20_300sec_1x1_lum_-15C_0300_fpos_20131_0002.tif

[MarkAR]

At a guess it might be image tilt or collimation.

[michael8554]

Hi MB

It could be image tilt, collimation, coma, poor guiding, pinched optics - but very hard to tell on this image.

To eliminate guiding submit a 10 to 15 second exposure at high ISO or gain, stretched if necessary, but not with burnt-out stars like your image.

Michael