out of collimation refractor?

[Joeistotalycool]

im not sure, but are these rings caused because the scope is out of collimation or is it that i need a field flatterer? (im using a skywatcher evostar ed80 ds-pro). the rings are most prominent on the dimmer stars. You need to zoom in to see them. 

[sloz1664]

It's not a collimation issue it's unfortunately your focusing. It is not as sharp as it should be hence the "doughnuts" on the smaller stars. If you haven't got a bahtinov mask for your ED80 I would invest in one asap. They are not too expensive.

Steve

[Joeistotalycool]

1 minute ago, sloz1664 said:

It's not a collimation issue it's your unfortunately your focusing is not as sharp as it should be hence the "doughnuts" on the smaller stars. If you haven't got a bahtinov mask for your ED80 I would invest in one asap. They are not too expensive.

Steve

yes, I do have one and use it every time. I have done some research since I posted, and it turns out my hot pixel removal on DSS was to strong. Thanks anyway =)

[RT65CB-SWL]

34 minutes ago, sloz1664 said:

It's not a collimation issue it's unfortunately your focusing. It is not as sharp as it should be hence the "doughnuts" on the smaller stars. If you haven't got a bahtinov mask for your ED80 I would invest in one asap. They are not too expensive.

Steve

"Yes! - that was my first thoughts too, and I am not into astro-photograhy... yet.

29 minutes ago, Joeistotalycool said:

yes, I do have one and use it every time. I have done some research since I posted, and it turns out my hot pixel removal on DSS was to strong. Thanks anyway =)

I am glad you have found the answer for question.

As M45 is 'middle aged' (estimated to be between +/- 60 to 80 million years) that it is a great capture. Well done. 

[Joeistotalycool]

9 minutes ago, Philip R said:

"Yes! - that was my first thoughts too, and I am not into astro-photograhy... yet.

I am glad you have found the answer for question.

As M45 is 'middle aged' (estimated to be between +/- 60 to 80 million years) that it is a great capture. Well done. 

thanks. i spent a whole night on the subject. I was going to image Orion, so i set up in a different place to usual so I got a good view to the south, but i decided to image this for the whole night. And then i forgot I moved my telescope, so half of my data (about 3 hours!) was completely useless. I did use a couple of frames, so that is what the defraction spikes are caused by (light hitting the branches). 

[Ben the Ignorant]

Hello, Joe.

This is defocusing. Your stars look exactly like the extrafocal pattern of defocus: a tiny dot (purplish because the scope is a semi-apo doublet; in a full apo it's white) surrounded by a ring. This is the smallest pattern one can see outside of focus, when you defocus more the rings become more numerous. I see these patterns all the time when I use my achromat doublet. When defocused on the other side (intrafocal) the pattern is a bit different in the spread of colors but it's also a dot with rings that multiply when you defocus more.

By the way, the minuscule pattern reveals poor alignment very, very strongly, and you just accidentally proved your doublet is absolutely perfectly aligned. Larger defocus makes the pattern much less accurate as a misalignment revelator. The field seems quite flat, too, the patterns in the corners are not shockingly larger or more oblong than those in the center.

Aside from that very small defocus, your picture is excellent.