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Need some help, egg shape/elongate stars?

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14 replies to this topic

#1 loveimac2

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Posted 22 February 2018 - 06:30 PM

I have asked this somewhere some other thread else but got no answer.

 

Please take a look attached cropped subs. One is @ 10 seconds exposure, the other was 60 seconds. What could be the problem to your eyes?

 

Equipment used are the one listed in my signature. I don't see such a problem when I have my C9HD, now with C11HD and new FR, I am unable to get it right. I know focusing is off, this is because I am still waiting a better autofocuser coming.

 

Thank you for your inputs.

 

10Sec sub:

 

 10Sec.jpg



#2 loveimac2

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Posted 22 February 2018 - 06:31 PM

This is 60 Sec sub

 

60Sec.png



#3 baron555

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Posted 22 February 2018 - 06:34 PM

Focus is way off, so the guide star is most likely also.   A C-11 on that mount may be pushing past its limits.



#4 pedxing

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Posted 22 February 2018 - 06:35 PM

What part of the frame is this from, the corner?

 

The 10s sub indicates that your FR isn't the right distance from the camera.

 

Hard to tell with the 60s sub, looks like focus problems as well.

 

It would be helpful to see the full frames.


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#5 leveye

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Posted 22 February 2018 - 06:35 PM

Is this center or corners? Looks like you'll need to play with spacing. The first image looks like bad guiding just IMHO. Might have to back off exposure length or do a finer polar alignment to the mount.



#6 loveimac2

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Posted 22 February 2018 - 07:03 PM

I attached full frame following. PA is quite good (I have no north view, so it was verified by drifting method in PHD2, the drift is less than 1", runs 5 minutes and more, reported by PHD2). And guiding was also good (OK I guess?), rms at about 0.8 total showed on PHD2 and those plot are quite stable...

 

 

Edited: Oh, and back ficus distance was good too, 146mm from end of FR to CMOS chip. Only focus was way off, my old eyes can't make it good enough so I need wait the moonlite focuser to arrive soon... but I think even if the focus is bad, the star shape should still be roundish, no?

 

10 Sec full :

 

10sec full.jpg

 

 

60 sec full:

 

60sec full.jpg


Edited by loveimac2, 22 February 2018 - 07:07 PM.


#7 pedxing

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Posted 22 February 2018 - 07:24 PM

Looks like your problem is in Dec:

 

Capture.JPG

 

so that rules out spacing as your immediate issue.

 

 



#8 loveimac2

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Posted 22 February 2018 - 07:44 PM

Hmm, this is exactly what was showing in Stellarium when I framing, about -50 degrees rotation. So you indicate it's the mount or tracking problem?

 

 

Edit: BTW, my OAG guiding is ASI 174, bin2, so the total pixel scale is 1.23"/pix vs the ASI071 at 0.503"/pix. This is based on FL of 1960mm. So 1 pix tracking error converted to more than 2 pix imaging error. Would this be a guiding problem source? But the "tail" of these stars are clearly much more than 2 pixels...


Edited by loveimac2, 22 February 2018 - 08:11 PM.


#9 loveimac2

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Posted 23 February 2018 - 01:52 AM

OK, I am searching my older testing frame, and found this, also 120 sec exp., this one looks perfect (OK, well, at least much better). And this one, as I remember, was I trying MetaGuide. And that is like 1-2 weeks ago, so, nothing was changed within this 1-2 weeks. So, maybe my PHD2 settings had problem?

 

What do you guys think? Thank you very much.

 

 

120sec better one.jpg

 

 

 



#10 pedxing

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Posted 23 February 2018 - 10:40 AM

Maybe you were guiding in RA only with PHD?



#11 elmiko

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Posted 23 February 2018 - 02:55 PM

Looks like your collimation is off to me



#12 Alex McConahay

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Posted 23 February 2018 - 03:07 PM

When asking a question like this it helps if you can include a screenshot of your corners and center. Your signature indicates you have Pixinsight. So:

 

Start Pixinsight, load your image file, give it a temporary stretch if necessary, and 

 

Script/Image Analysis/Abberation Inspector

Make sure your file designator is set to the image file in question, and take the defaults

Tell it OK

 

You will get an image that looks like this.

 

Call up the "Snipping Tool" (if you are not familiar, type "Snipping tool" in the Windows search box, start the Snip Tool. Tell it "New," and draw a box around your Pixinsight Abberation Window Mosaic. Save it in the snip tool.)

 

Then post it here as you would any other image file. 

 

This way we can tell a whole lot more about any optical or other problems than we can with just one clip.

 

(But, it looks like you are out of focus to start with.) 

 

Alex

 

Attached Thumbnails

  • temp abberration inspector.PNG


#13 PhysicsStudent

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Posted 23 February 2018 - 03:59 PM

https://www.adorama....ASABEgLogPD_BwE

 

If you don't already have one, you should definitely get one of these. They will make your life so much easier, for not very much money!



#14 loveimac2

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Posted 23 February 2018 - 08:47 PM

Today, I did another test and kind confirmed it PHD2 problem, but I don't know if it's getting or something else. I tried metaguide and took some subs, those are good enough, so for now switching to metaguide, but this need some time to digest than PHD I guess.

 

I also suspect collimation is off, but I have no experience and don't have too much time now, waiting my focuser to arrive, then I will spend some time learning more about it.

 

Next time if I attach image, I will try Pixinsight script Alex mentioned.

 

Thank you all!



#15 loveimac2

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Posted 09 March 2018 - 09:26 PM

Help still wanted...After the focuser has installed, focus is much better. This is mosaic from original stacked frames.

I think all corners  as well as centre, have the same shape like raindrops.

 

Please advise, to your eyes, what's the root problem? Thank you.

Attached Thumbnails

  • light_FILTER_Ha_BINNING_1_integration1_mosaic.jpg

Edited by loveimac2, 09 March 2018 - 09:28 PM.



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