#1  
Old 28-02-2019, 03:18 AM
Astro_Hoff
Registered User

Astro_Hoff is offline
 
Join Date: Jan 2019
Location: South Oz
Posts: 3
ASI224MC Stuck Pixels

I am new to astrophotography and have a question about my ASI camera. It seems it has about 5 stuck pixels. When using LIVE STACK on SharpCap they become very obvious and ruin the output picture by leaving a bright green trails. Is it normal to have this many stuck pixels? Or should i return it?


I know these can be erased with processing in DSS etc, but they are really annoying for live EAA.


Please help.
Thankyou


PS. It is attached to this
https://skywatcheraustralia.com.au/p...discovery-red/


EQ mount on the way and hopefully an APO to follow soon
Attached Thumbnails
Click for full-size image (Stack_135frames_675s_WithDisplayStretch.jpg)
22.7 KB48 views
Reply With Quote
  #2  
Old 28-02-2019, 05:36 PM
ChrisV's Avatar
ChrisV (Chris)
Registered User

ChrisV is offline
 
Join Date: Aug 2015
Location: Sydney
Posts: 1,129
I don't know how many hot pixels you might expect to see in a new camera. My asi224 is a few years old now and has a few hot pixels (but I haven't counted them). So not sure if it's bad enough to return. Maybe others can answer this??

But if you persist with it - When live stacking in sharpcap I always first collect darks and then ask sharpcap to subtract them (it's under preprocessing) while stacking. This will remove the hot pixels, and also the amp glow with this camera. I do this all the time when doing live stacking. It doesn't take long as I rarely use subs longer than 15sec. Doing 8x darks only takes a few minutes.

I sometimes also do some sky flats. But more so with larger sensor cameras.
Reply With Quote
  #3  
Old 28-02-2019, 06:07 PM
Mosc_007 (Charles)
Registered User

Mosc_007 is offline
 
Join Date: Apr 2014
Location: Sydney, Australia
Posts: 158
I would not call those Green lines Hot pixels. There are 3 area's in the image with exactly the same green trail.

I would suspect its more likely a reflection somewhere in the optics.
Reply With Quote
  #4  
Old 28-02-2019, 06:11 PM
The_bluester's Avatar
The_bluester (Paul)
Registered User

The_bluester is offline
 
Join Date: Feb 2011
Location: Kilmore, Australia
Posts: 1,908
Just trying to work out why they are trailing like that. Unless the scope is moving around quite a bit and the stacking is pinning stars down out of frames significantly offset from each other?


I have an ASI294 and it does not have any significant number of hot pixels that I would expect to stack like that.
Reply With Quote
  #5  
Old 28-02-2019, 07:17 PM
Astro_Hoff
Registered User

Astro_Hoff is offline
 
Join Date: Jan 2019
Location: South Oz
Posts: 3
Thanks for your answers.


I called them stuck pixels (not hot pixels) because they are there all the time, including taking dark frames. They trail due to the AZ mount trying to keep centered on an object.


I am only using the demo SharpCap atm so I can't use dark/flat subtraction. Once i get my new EQ mount sorted i will upgrade to the full version. This may sort out the problem as ChrisV mentioned.


Originally i could only see 2-3, but now there is 5 or 6 squiggles. This is a little concerning


Dark example


Click image for larger version

Name:	Dark.jpg
Views:	23
Size:	8.7 KB
ID:	241080
Reply With Quote
  #6  
Old 28-02-2019, 07:44 PM
ChrisV's Avatar
ChrisV (Chris)
Registered User

ChrisV is offline
 
Join Date: Aug 2015
Location: Sydney
Posts: 1,129
Definitely hot pixels. Exactly what I get, green, red or blue worms - made when sharpcap debayers the image. They move as you aren't guiding, and sharpcap aligns to the stars and stacks. You can kind of see how they have followed the edge of your image.

If you improve your polar alignment that will help keep the image in frame.
Reply With Quote
  #7  
Old 28-02-2019, 07:55 PM
multiweb's Avatar
multiweb (Marc)
ze frogginator

multiweb is offline
 
Join Date: Oct 2007
Location: Hinchinbrook
Posts: 17,997
If your capture program has a feature to stack a couple dark frames and apply the master to your live view then that will get rid of these.
Reply With Quote
  #8  
Old 28-02-2019, 08:20 PM
The_bluester's Avatar
The_bluester (Paul)
Registered User

The_bluester is offline
 
Join Date: Feb 2011
Location: Kilmore, Australia
Posts: 1,908
Having looked up the camera, being uncooled I would imagine it will show up more by way of hot pixels than a cooled cam. I don't think either way is bad but there is a difference between 0 degrees and -15 sensor temp with my 294. But I am not familiar with any other cameras to say how many hot pixels is normal for it. I just know that a dark frame from my old 350D looked like a very colorful star field.
Reply With Quote
  #9  
Old 28-02-2019, 09:16 PM
ChrisV's Avatar
ChrisV (Chris)
Registered User

ChrisV is offline
 
Join Date: Aug 2015
Location: Sydney
Posts: 1,129
Here's 2x live stacked images from mid-2016, both with the ASI224MC, no post-processing.

First is the Antenna Galx with no dark frame subtraction (20x 12sec subs gain 350). You can see the green worms. And amp glow on the right.
Second is NGC55 with dark frame subtraction for pre-processing (16x 15sec subs gain 350). No worms, much less amp glow
Attached Thumbnails
Click for full-size image (AntennaeG UHC_Stack_20.jpg)
193.4 KB33 views
Click for full-size image (NGC55 Optec0mm_UVIR_Stack_16.jpg)
125.5 KB32 views
Reply With Quote
  #10  
Old 28-02-2019, 09:21 PM
Astro_Hoff
Registered User

Astro_Hoff is offline
 
Join Date: Jan 2019
Location: South Oz
Posts: 3
OK, Thanks everyone for your input. I feel a lot more reassured now. It seems the main problem is using the free version of SharpCap. My new EQ mount arrived today (along with the complimentary clouds), so once i figure out how to use that and upgrade SharpCap i think i should be good to go.


Your help is much appreciated
Reply With Quote
  #11  
Old 03-03-2019, 12:02 AM
tvandoore (Tim)
Registered User

tvandoore is online now
 
Join Date: May 2016
Location: Buderim
Posts: 35
Sharpcap doesn't do it all but is useful enough to get some good images under your belt and is well worth the purchase price. Simple to use, too.
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 06:21 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Advertisement
Bintel
Advertisement
Meade Australia
Advertisement
Lunatico Astronomical
Advertisement
Celestron Australia
Advertisement
NexDome Observatories
Advertisement
OzScopes Authorised Dealer
Advertisement
SkyWatcher Australia
Advertisement
Astronomy and Electronics Centre
Advertisement