183C live stacking issue

Discussion of features and issues relating to Altair Astro Cameras
Post Reply
Lokifish
Posts: 3
Joined: Tue May 07, 2019 6:30 pm

183C live stacking issue

Post by Lokifish » Tue May 07, 2019 7:13 pm

I've been banging my head against this for some time now. My 183C shows a magenta to green color cast gradient in every long exposure live stack I do. Doesn't matter if I use darks or not, and flats or not. I've tried RGB24 and RAW color space, all deBayer patterns, as well as the ASCOM and SharpCap's Altair drivers. Altair says is a software issue but I want to see what you guys think.

Examples
https://photos.app.goo.gl/98ZS1zmzura4TVpy6

User avatar
admin
Site Admin
Posts: 2597
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

Re: 183C live stacking issue

Post by admin » Wed May 08, 2019 6:53 am

Hi,

Firstly be good to hear what other equipment you are using (scope, filters, flatteners, etc.)

Another thought that comes to mind is to rotate the camera on the back of the telescope but leave everything else in the same orientation – if the pattern changes from left/right to up/down then you can conclude that something is coming from the optical components in front of the camera. If the pattern stays in the same orientation then we can exclude the optical stuff from consideration.

Overall, I suspect that there is a minor colour cast shift across the frame coming from somewhere that is being enhanced by the sort of stretching we apply to the image when we are doing deep sky astrophotography. Looking at an individual dark or flat frame without stretching would not show the colour cast as it will be too subtle to see.

Cheers, Robin

Lokifish
Posts: 3
Joined: Tue May 07, 2019 6:30 pm

Re: 183C live stacking issue

Post by Lokifish » Wed May 08, 2019 2:02 pm

I've eliminated optics, sky glow and orientation as a cause. It's been used/tested on six different OTAs and lenses. a handful of different filters, different orientations, and different points in the sky. Stretched darks showing glow have be taken on OTAs, with a cap on the table, and in a dark box. Additionally, different cables, different computers, different OS, and different ambient temps has been tried.

You make a very good point about the typical deep sky stretching we tend to use vs unstretched. Unfortunately, with as many variables as I've removed, I find it hard to believe it's a light leak or software issue (as Altair is suggesting). Just want to make 100% certain that it's not a SharpCap issue and that the results I'm getting are atypical for the 183C.

User avatar
turfpit
Posts: 686
Joined: Mon Feb 13, 2017 8:13 pm
Location: UK
Contact:

Re: 183C live stacking issue

Post by turfpit » Wed May 08, 2019 3:48 pm

Russell?

Consider capturing some lights, darks, flats & bias - FITS would be a good choice. Make those available online along with the SharpCap Camera Settings files for the different types of frames. No Live Stack , no filters, no applying darks & flats on the fly - just scope & camera to obtain some RAW frames for conventional processing. I would have a look at those.

Dave

BlackWikkett
Posts: 162
Joined: Sat Jun 23, 2018 8:48 pm
Contact:

Re: 183C live stacking issue

Post by BlackWikkett » Wed May 08, 2019 5:01 pm

Your initial post you mention that Altair thinks this to be a software issue. Obviously in this case you're using SharpCap but have you tried Altair's own capture software? It would be interesting to see the results using AltairCapture http://cameras.altairastro.com/

If you get similar results this would rule out SharpCap and may point to the camera itself.

User avatar
admin
Site Admin
Posts: 2597
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

Re: 183C live stacking issue

Post by admin » Wed May 08, 2019 5:03 pm

Hi,

It's certainly not something I've seen before. Have you tried removing the optical window in front of the camera sensor as a test to see if the issue is related somehow to that window (which of course would be always in the same orientation relative to the sensor and taken with the camera from telescope to telescope).

Cheers, Robin

Lokifish
Posts: 3
Joined: Tue May 07, 2019 6:30 pm

Re: 183C live stacking issue

Post by Lokifish » Fri May 10, 2019 2:04 am

While windy weather is getting in the way of capturing and posting a new sequence, I've been digging. I actually read the diagnose output and noticed something. The firmware is very old compared to the production date, and info/feedback on v1 or v1.1 183C's is pretty much nonexistent.

Production Date 20170809
Revision 1
Hardware Version 1.0
Firmware Version 1.4.1.20170111
FPGA Version 1.1

I know folks here are not Altair tech support, but could this be a possible issue leading to what the results I've been seeing?

User avatar
admin
Site Admin
Posts: 2597
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

Re: 183C live stacking issue

Post by admin » Fri May 10, 2019 8:36 pm

Hi,

To be honest I would guess not – once the data has come off the actual imaging sensor everything else is just copying bits and bytes around from one part of the camera to another and then to the computer. This sort of procedure tends to either work perfectly or not work at all, it's very rare for there to be an issue in the camera firmware that leads to image quality degradation without smashing the image completely to bits. Certainly something that affects the image differently in different parts seems very unlikely.

Cheers, Robin

Post Reply

Who is online

Users browsing this forum: No registered users and 2 guests