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

questions/musings about cmos calibration

  • Please log in to reply
33 replies to this topic

#26 entilza

entilza

    Soyuz

  • *****
  • Posts: 3750
  • Joined: 06 Oct 2014
  • Loc: Oakville, ON, Canada

Posted 16 July 2018 - 08:36 AM

I ordered a qhy183 osc.
I plan to pair it with either my 600mm f4 newt, 480mm f5.6 refractor or soon to be 400mm f4.2 refractor and of course the 135mm f2 and 50mm lens for wide fields. The small pixels should play nicely with these optics and if calibration works the way I want it to, a second 183 will be paired with the osc, probably a mono.
 
how many darks are people using after lets say a 4hr lrgb session with 30-60s subs?


Nice choice Wes!

For me, with 60" subs. I'd probably take an hour of darks for mylibrary. You can reuse it for a long time which is nice. (Assuming same gain/temperature)
  • calypsob likes this

#27 calypsob

calypsob

    Aurora

  • *****
  • topic starter
  • Posts: 4729
  • Joined: 20 Apr 2013

Posted 16 July 2018 - 09:45 AM

Nice choice Wes!

For me, with 60" subs. I'd probably take an hour of darks for mylibrary. You can reuse it for a long time which is nice. (Assuming same gain/temperature)

Ok good to know, thanks Martin. I typically take darks in the field at astronomical dawn so I usually have about an hour before the sky brightens up substantially.  Im hoping that this gets me pretty accurate darks.    


Edited by calypsob, 16 July 2018 - 09:46 AM.


#28 entilza

entilza

    Soyuz

  • *****
  • Posts: 3750
  • Joined: 06 Oct 2014
  • Loc: Oakville, ON, Canada

Posted 16 July 2018 - 10:06 AM

Ok good to know, thanks Martin. I typically take darks in the field at astronomical dawn so I usually have about an hour before the sky brightens up substantially.  Im hoping that this gets me pretty accurate darks.


Did you order the cooled camera or non cooled?

#29 Ken Sturrock

Ken Sturrock

    Cardinal Ximénez - NO ONE EXPECTS THE SPANISH INQUISITION!

  • *****
  • Administrators
  • Posts: 8002
  • Joined: 26 Sep 2009
  • Loc: Denver, CO

Posted 16 July 2018 - 10:49 AM

Sounds like a perfect combination!

 

My dark frame library for the ASI-183 currently (no pun intended) only has nine subframes of each duration combined into masters. I prefer to use more, but I was in a hurry when I did it last time because I had decided to change my gain last minute. I usually re-use my calibration library for a few months. In the case of the flats, I leave the imaging gear attached.


  • calypsob likes this

#30 calypsob

calypsob

    Aurora

  • *****
  • topic starter
  • Posts: 4729
  • Joined: 20 Apr 2013

Posted 16 July 2018 - 11:45 AM

Did you order the cooled camera or non cooled?

Cooled from Cyclops, along with the free blade adapter. Shipped out today apparently 


Edited by calypsob, 16 July 2018 - 11:46 AM.


#31 calypsob

calypsob

    Aurora

  • *****
  • topic starter
  • Posts: 4729
  • Joined: 20 Apr 2013

Posted 16 July 2018 - 11:50 AM

Sounds like a perfect combination!

 

My dark frame library for the ASI-183 currently (no pun intended) only has nine subframes of each duration combined into masters. I prefer to use more, but I was in a hurry when I did it last time because I had decided to change my gain last minute. I usually re-use my calibration library for a few months. In the case of the flats, I leave the imaging gear attached.

Yea I'm excited about the possibilities it is going to bring. Interesting about your dark library, this is something I want to experiment with especially if I combine different exposure lengths.   



#32 calypsob

calypsob

    Aurora

  • *****
  • topic starter
  • Posts: 4729
  • Joined: 20 Apr 2013

Posted 16 July 2018 - 11:52 AM

In order to remove ampglow from certain cmos bodies we have to do Darks, Flats, and Dark flats, bias are omitted. 

 

Im wondering though, why are bias frames skipped?  I read a thread a while back about sample variance issues with master bias frames in certain cmos models.  Could this be due to ampglow build up in the extraordinarily short bias exposure?  Would it make sense to attempt applying dark bias frames to a master bias?  I also wonder if these cameras are able to expose too fast to properly record a bias frame, could slowing the exposures slightly to .5 seconds improve bias results?  

 

Additionally, I found that after adding a pedestal to the output offset and applying large scale structure rejection to my flats, ampglow was severely attenuated if not completely removed.  Has anyone else experienced similar results?  Hopefully this will inspire some helpful discussion.  

- I should add that my initial experimentation has been with my non cooled asi290 which exhibits ampglow similar to the 183



#33 entilza

entilza

    Soyuz

  • *****
  • Posts: 3750
  • Joined: 06 Oct 2014
  • Loc: Oakville, ON, Canada

Posted 16 July 2018 - 12:42 PM

Cooled from Cyclops, along with the free blade adapter. Shipped out today apparently


Great, so since it's cooled you can do all your darks at home and build a nice library for the different gains and exposure times you may use.

I also used the cyclops adapter and is very good. I had a hard time figuring out where the insertion point is of the Samyang lens so just be careful.
  • calypsob likes this

#34 calypsob

calypsob

    Aurora

  • *****
  • topic starter
  • Posts: 4729
  • Joined: 20 Apr 2013

Posted 16 July 2018 - 01:31 PM

Great, so since it's cooled you can do all your darks at home and build a nice library for the different gains and exposure times you may use.

I also used the cyclops adapter and is very good. I had a hard time figuring out where the insertion point is of the Samyang lens so just be careful.

Ok good to know, I was not quite sure what to expect about the adapter.  I hope its alot better than the zwo ccd adapter.  




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