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

ZWO ASI1600MM Pro Bright Star Issue

art astrophotography CMOS imaging optics
  • Please log in to reply
14 replies to this topic

#1 IvgnfshngAstro

IvgnfshngAstro

    Lift Off

  • -----
  • topic starter
  • Posts: 2
  • Joined: 26 Jul 2018
  • Loc: Pacolet, SC USA

Posted 15 January 2019 - 11:03 AM

 

Hello, my name is James and I am experiencing significant halo art of some sort when imaging bright stars (see attachment).  The camera is the ZWO ASI1600MM Pro using a ZWO filter wheel with ZWO filters (31mm).  The scope is an ES 127mm FCD100.  I think this is an issue that has been discussed in the past but I couldn't find where anyone maybe came up with a solution or workaround.  Any help would be appreciated since the money is spent, my rig is set up, and there are plenty of bright stars up there to photograph!!

 

Thanks, James

Attached Thumbnails

  • ZWO Bright Star Issue.jpg

  • rwstanley and 1stan like this

#2 Mark326

Mark326

    Messenger

  • -----
  • Posts: 438
  • Joined: 26 Jul 2017
  • Loc: Florida

Posted 15 January 2019 - 11:20 AM

Microlensing is what you’re seeing I believe. Many threads on this issue with that camera. I do not own but am considering purchase. Alnitak (star) makes OSC difficult in that region too, hard to captiure dynamic range of Nebula without over exposing (blowing out) the bright star.

Edited by Mark326, 15 January 2019 - 12:58 PM.

  • mumbles likes this

#3 jerahian

jerahian

    Surveyor 1

  • *****
  • Moderators
  • Posts: 1,500
  • Joined: 02 Aug 2018
  • Loc: Maine

Posted 15 January 2019 - 11:26 AM

You can try Dave Ault's approach to remove the halo and the internal reflection artifact.  It's lengthy for one halo, but the Curse of Alnitak has struck your otherwise lovely image in a major way.

 

Dave's tutorial:  http://trappedphotons.com/blog/?p=616

 

The process is derived from this post on CN:  https://www.cloudyni...tak-i-hate-you/

 

If you decide to do it, please let us know how it turns out!



#4 FlankerOneTwo

FlankerOneTwo

    Viking 1

  • *****
  • Posts: 984
  • Joined: 30 Aug 2017
  • Loc: Vegas, baby!

Posted 15 January 2019 - 12:27 PM

You have classic ASI1600 microlens reflections (the little blotchy brights spots). The halo could be from the filter, the edge does appear to me more distinct than in some other microlens reflection examples that I've seen, not sure which one you are using in this image. In LRGB I get a smooth flare but not a distinct halo with Astrodon filters, I've heard reports that they are the best in this regard. I have not personally imaged this target with the Optolong LRGB I had before, though. The Optolong H-alpha I'm currently using does produce a (smaller) distinct halo, someday I'll pony up for an Astrodon and see if it's better.



#5 Der_Pit

Der_Pit

    Vanguard

  • *****
  • Posts: 2,326
  • Joined: 07 Jul 2018
  • Loc: La Palma

Posted 15 January 2019 - 03:01 PM



Microlensing is what you’re seeing I believe. Many threads on this issue with that camera. I do not own but am considering purchase. Alnitak (star) makes OSC difficult in that region too, hard to captiure dynamic range of Nebula without over exposing (blowing out) the bright star.

Just for the record, this is not Microlensing.  That is the name for small intensity fluctuations in star brightness caused by (often invisible) foreground objects, see Wikipedia

What you see there is diffraction patterns caused from reflections on the non-AR coated microlenses of the camera sensor.  And unfortunately there's nothing you can do about that (other than getting a camera with a different sensor).  Check this thread, especially the theoretical moddeling by sharkmelley.


  • Mark326 likes this

#6 PhotonHunter1

PhotonHunter1

    Viking 1

  • *****
  • Posts: 952
  • Joined: 19 Mar 2015
  • Loc: Northwest Suburbs of Chicago

Posted 17 January 2019 - 08:09 PM

A common issue with the ASI1600 cameras. I just imaged this object with my ASI1600MM-C and experienced the same distortion and halo effect. Here’s another thread that covers this same object/topic. https://www.cloudyni...ease/?p=9075189



#7 rottielover

rottielover

    Vostok 1

  • -----
  • Posts: 167
  • Joined: 11 Jun 2017
  • Loc: St. Louis MO

Posted 17 January 2019 - 08:15 PM

I'm sure you can find the threads but most of us have ditched the ZWO filters in favor of Astrodon's or Baader filters. 


Edited by rottielover, 17 January 2019 - 08:16 PM.

  • tcchittyjr likes this

#8 Seanem44

Seanem44

    Vanguard

  • *****
  • Posts: 2,285
  • Joined: 22 Sep 2011
  • Loc: Stafford, VA

Posted 17 January 2019 - 08:47 PM

It’s all about the filter. Astrodon are expensive but work perfect. I see motiveless difference between my AD Ha and Baader Oiii

#9 AdamJ

AdamJ

    Vostok 1

  • -----
  • Posts: 179
  • Joined: 23 Mar 2018

Posted 18 January 2019 - 08:31 AM

 

 

Hello, my name is James and I am experiencing significant halo art of some sort when imaging bright stars (see attachment).  The camera is the ZWO ASI1600MM Pro using a ZWO filter wheel with ZWO filters (31mm).  The scope is an ES 127mm FCD100.  I think this is an issue that has been discussed in the past but I couldn't find where anyone maybe came up with a solution or workaround.  Any help would be appreciated since the money is spent, my rig is set up, and there are plenty of bright stars up there to photograph!!

 

Thanks, James

 

As others have said this is two things. 

 

1) The microlense diffraction pattern is inherent to the camera (its the smaller spots closer to the star).

2) The large circular halo something else. Assuming the filter wheel is screwed directly to the cameras male connector then its too big to be a filter reflection between the sensor and the filter. That leaves three possibilities you have the older ZWO unmounted filter and its edge is not blackened. Or you have the filter in backwards (as is possible with 31mm). Or the anti-reflection coating on your reducer / flatter is poor and its causing reflections from the sensor to the reducer and its not related to the filter all all. 

 

The cure is to try reversing the filter in the holder to try and fix the large halo. If that does not work try masking off the edge of the filter, if that does not work then try imaging without the flattner / reducer to see of the halo vanishes. 

 

As for the micro lense diffraction effect, the only real way to reduce that is with a more expensive narrower filter such as the 3nm Astrodon that will greatly attenuate the star brightness. 

 

Good luck

 

Adam 


  • Shiraz and cfosterstars like this

#10 cfosterstars

cfosterstars

    Mercury-Atlas

  • *****
  • Posts: 2,876
  • Joined: 05 Sep 2014
  • Loc: Austin, Texas

Posted 18 January 2019 - 11:04 AM

As others have said this is two things. 

 

1) The microlense diffraction pattern is inherent to the camera (its the smaller spots closer to the star).

2) The large circular halo something else. Assuming the filter wheel is screwed directly to the cameras male connector then its too big to be a filter reflection between the sensor and the filter. That leaves three possibilities you have the older ZWO unmounted filter and its edge is not blackened. Or you have the filter in backwards (as is possible with 31mm). Or the anti-reflection coating on your reducer / flatter is poor and its causing reflections from the sensor to the reducer and its not related to the filter all all. 

 

The cure is to try reversing the filter in the holder to try and fix the large halo. If that does not work try masking off the edge of the filter, if that does not work then try imaging without the flattner / reducer to see of the halo vanishes. 

 

As for the micro lense diffraction effect, the only real way to reduce that is with a more expensive narrower filter such as the 3nm Astrodon that will greatly attenuate the star brightness. 

 

Good luck

 

Adam 

I agree with Adam. this is two issues and not one. I have the same camera with Astrodon filters. I see the same microlensing diffraction pattern from the sensor cover glass. However, the large bright halo is likely from the filers. Do you have the new ZWO filters or the OLD original ZWO filters? The old filters have serious halos for the Nb filters. The new ZWO filters are much better. However, the micro lens issue will still be there with even 5nm Astrodon filters.



#11 IvgnfshngAstro

IvgnfshngAstro

    Lift Off

  • -----
  • topic starter
  • Posts: 2
  • Joined: 26 Jul 2018
  • Loc: Pacolet, SC USA

Posted 18 January 2019 - 11:53 AM

Thanks guys for your responses.   Sad that it's not fixable but I guess I can't be too upset since the camera does pretty good with most targets, just not the brighter stars. The filter used was the Ha, sold as part of the package deal from OptCorp (camera, EFW, and lrgb + nb filters), but as to whether or not they are the new or old, I don't know. The purchase was about 3 months ago so hopefully they're the new version.  The camera is mounted directly to the filter wheel which I believe is preferable.  As far as flipping the filter I guess I can try that at some point along with the masking idea, to see if it helps with the halo. But the bigger defect is the micro lens diffraction pattern, so I'll just have to avoid the brighter stars with this camera anyways.

 

And thanks for the link to the tutorial.  I'll give it a shot and post any favorable outcome. As far as trying a camera with with different sensor, I've yet to purchase a cooled OSC, so any recommendations as to cameras with sensors without the micro lens problem I'd certainly like to hear what they are.

 

Thanks, James



#12 cfosterstars

cfosterstars

    Mercury-Atlas

  • *****
  • Posts: 2,876
  • Joined: 05 Sep 2014
  • Loc: Austin, Texas

Posted 18 January 2019 - 05:42 PM

If you look on the ZWO web site and look at the narrow band filters, it will show you how to tell the difference between the new and old filters. It is actually quite easy and clear which you have by looking a them.



#13 Seanem44

Seanem44

    Vanguard

  • *****
  • Posts: 2,285
  • Joined: 22 Sep 2011
  • Loc: Stafford, VA

Posted 18 January 2019 - 08:42 PM

Man... it must be a quality control issue. I’ve never had microlensing in my 1600. Maybe it has to do with the OTA as well.

#14 Stonius

Stonius

    Vostok 1

  • *****
  • Posts: 118
  • Joined: 28 May 2016

Posted 19 January 2019 - 12:05 AM

If you want to nail down exactly how far away from the sensor the reflection is, there is a handy calculator here http://www.wilmslowa...lae.htm#REFLECT

 

Cheers

 

Markus



#15 bigjy989

bigjy989

    Vostok 1

  • -----
  • Posts: 134
  • Joined: 23 Nov 2010
  • Loc: Saline, MI

Posted 19 January 2019 - 07:17 AM

The only work around with the ASI1600 is to stretch less or remove the stars and recombine the stars again at the end.  I have a similar setup with the ASI1600 but with a 140mm refractor and Astrodon filters (Recently got the same large halo/filter reflection and the same microlense reflections on the same target about 2 weeks ago.).  I gave up trying to correct it and just removed the stars completely in Startools 'heal function - an hour of tweaking the mask, max settings but detail radius 140pixels).  Removing the stars is not too complicated after you find a process.  The good news it is really only affects very few targets.

 

 

Starless Horsehead

Edited by bigjy989, 19 January 2019 - 07:18 AM.

  • TheZ3roCool likes this


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





Also tagged with one or more of these keywords: art, astrophotography, CMOS, imaging, optics



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics