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

Which master dark file do you choose?

  • Please log in to reply
5 replies to this topic

#1 nimitz69

nimitz69

    Viking 1

  • *****
  • topic starter
  • Posts: 835
  • Joined: 21 Apr 2017
  • Loc: A barrier island 18 miles south of Cocoa Beach

Posted 19 February 2019 - 12:29 PM

Let’s assume my imaging session started out at 75 degs and by the end of the 5 hr session it was 65 degs.  I’m.  Using an uncooled  D5300 and I have master dark files of 65 degs, 70 degs and 75 degs.  Which one would you use?



#2 twidget

twidget

    Mariner 2

  • -----
  • Posts: 241
  • Joined: 12 Jul 2016
  • Loc: SW Missouri

Posted 19 February 2019 - 12:48 PM

When I've somehow forgotten to turn on the cam cooler, and had large temp swings during those few sessions, I've checked each sub, and applied the dark closest in temp to the each sub.


  • bobzeq25 and bmhjr like this

#3 nimitz69

nimitz69

    Viking 1

  • *****
  • topic starter
  • Posts: 835
  • Joined: 21 Apr 2017
  • Loc: A barrier island 18 miles south of Cocoa Beach

Posted 20 February 2019 - 01:12 PM

unfortunately Nikon does not record temp data on the EXIF file so I have no idea what the temp was at the time of each sub



#4 Stelios

Stelios

    Fly Me to the Moon

  • *****
  • Moderators
  • Posts: 6521
  • Joined: 04 Oct 2003
  • Loc: West Hills, CA

Posted 20 February 2019 - 01:17 PM

I'm surprised temp sensor data is not recorded, but if so, I would assume a gradual lowering and I would divide my frames in three groups, match the earliest with the 75 degree darks, the middle with the 70 degree darks and the latest with the 65 degree darks.

 

If you believe this assumption is unlikely based on your conditions, then perhaps you need to do something like 1/5th of subs at 75, 1/5th at 70, rest at 65. 

 

But you *must* try to guess and divide your subs. A 10-degree difference in temperature matching will significantly affect the performance of your darks.


  • twidget likes this

#5 twidget

twidget

    Mariner 2

  • -----
  • Posts: 241
  • Joined: 12 Jul 2016
  • Loc: SW Missouri

Posted 20 February 2019 - 03:34 PM

"Ouch" on the lack of recorded temps, I couldn't image with that restriction!

 

It seems a bit weird that the usual stock reply, "Try different ones and see which ones work the best", hasn't shown up in this thread yet. Myself, I would assume that you have already tried such an approach, and for whatever reason, you'd like to hear of a more definitive approach.



#6 nimitz69

nimitz69

    Viking 1

  • *****
  • topic starter
  • Posts: 835
  • Joined: 21 Apr 2017
  • Loc: A barrier island 18 miles south of Cocoa Beach

Posted 20 February 2019 - 09:09 PM

It’s mostly an academic question at this point because the temp has not varied very much during what few sessions I’ve done and in Jul it will be moot as I’ll be switching to a 294 MC Pro CMOS.  I guess if the temp were forecast to change that much I’d just have to monior and record it every hr and then use matching darlks from my master file ...


  • twidget 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






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics