Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Mak 180 astrophoto - question

  • Please log in to reply
7 replies to this topic

#1 planedriver

planedriver

    Sputnik

  • -----
  • topic starter
  • Posts: 34
  • Joined: 16 Aug 2020

Posted 20 June 2021 - 02:42 AM

Hi all,

 

We enjoy the Skymax 180 a lot when it comes to astrophotography however time to time our stars are gettin strange - one of their sides get flat. 

 

This does not happen all the time, so far these two cases were prominent - any suggestion ?

 

Thanks,

A

Attached Thumbnails

  • 2021-06-20_09-27-09.jpg
  • IMG_20210620_093101.jpg
  • 2021-06-20_09-28-34.jpg
  • Screenshot_20210620_093005.jpg


#2 luxo II

luxo II

    Skylab

  • -----
  • Posts: 4,011
  • Joined: 13 Jan 2017
  • Loc: Sydney, Australia

Posted 20 June 2021 - 02:50 AM

In the third one all the stars are slightly elongated in the same direction which suggests a tracking error, or possibly flexure.

#3 Tapio

Tapio

    Skylab

  • -----
  • Posts: 4,450
  • Joined: 24 Sep 2006
  • Loc: Tampere, Finland

Posted 20 June 2021 - 02:58 AM

Could be number of things - collimation, guiding etc.
Your scope has a lot of focal length.
How is your guiding?
Does it show in short exposure?
Have you checked collimation?

#4 planedriver

planedriver

    Sputnik

  • -----
  • topic starter
  • Posts: 34
  • Joined: 16 Aug 2020

Posted 20 June 2021 - 03:15 AM

In the third one all the stars are slightly elongated in the same direction which suggests a tracking error, or possibly flexure.

This is a good point - need to try OAG

 

Could be number of things - collimation, guiding etc.
Your scope has a lot of focal length.
How is your guiding?
Does it show in short exposure?
Have you checked collimation?

Collimation - star test is concentric although I'm far from expert in this area so try not to spend too much time with it. Also other in cases stars are round , definitely no sign of the described - see attached pics - same setup, guiding, exposure equipment

 

Will check short exposure - another good point.

Attached Thumbnails

  • 2021-06-20_10-07-35.jpg
  • IMG_20210620_100848.jpg
  • 2021-06-20_10-07-51.jpg


#5 PETER DREW

PETER DREW

    Surveyor 1

  • *****
  • Posts: 1,648
  • Joined: 31 May 2017

Posted 20 June 2021 - 06:31 AM

I would suspect a tilted plane somewhere in the imaging train.



#6 Rasfahan

Rasfahan

    Viking 1

  • -----
  • Posts: 723
  • Joined: 12 May 2020
  • Loc: Hessen, Germany

Posted 21 June 2021 - 06:52 AM

It‘s a bit difficult to tell with the stacked images. Stretched single frames from dense starfields will be easier. But I do not see even distortions in the field, which points to miscollimation instead of tracking/flex issue. In the last image the stars are far larger than in the first two - this can be focus or seeing, masking the issue. If it really is intermittent, it could be a stressed mirror or corrector, due to temperature. To rule out tracking/flex take some very short and some longer exposures and see if the elongation gets worse with more exposures time.

 

If your parameters for guiding are correct (FL, pixel size), this is very good - what mount are you using?



#7 planedriver

planedriver

    Sputnik

  • -----
  • topic starter
  • Posts: 34
  • Joined: 16 Aug 2020

Posted 21 June 2021 - 09:31 AM

I would suspect a tilted plane somewhere in the imaging train.

This is something I need to look at.

 

It‘s a bit difficult to tell with the stacked images. Stretched single frames from dense starfields will be easier. But I do not see even distortions in the field, which points to miscollimation instead of tracking/flex issue. In the last image the stars are far larger than in the first two - this can be focus or seeing, masking the issue. If it really is intermittent, it could be a stressed mirror or corrector, due to temperature. To rule out tracking/flex take some very short and some longer exposures and see if the elongation gets worse with more exposures time.

 

If your parameters for guiding are correct (FL, pixel size), this is very good - what mount are you using?

Thanks for the feedback - the ones posted are cropped a bit. I have attached two single frames instead of the stacked image.

 

This is a belt driven HEQ-5.

Attached Thumbnails

  • 2021-06-21_04-23-50.jpg
  • 2021-06-21_04-23-59.jpg


#8 lakeorion

lakeorion

    Surveyor 1

  • -----
  • Posts: 1,740
  • Joined: 03 Aug 2010
  • Loc: Lake Orion MI

Posted 23 June 2021 - 12:40 PM

Another possibility is mirror flop?  Are you focusing the mirror in the same direction all the time?

 

Great examples though with this long focal length / high f-ratio.  I have a 180 and I haven't considered trying deep sky AP.  Someday I'll give lunar / planetary a try but I don't have the patience for f15 deep sky...




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics