Go Back   IceInSpace > Equipment > Astrophotography and Imaging Equipment and Discussions

Thread Tools Rate Thread
Old 13-10-2020, 03:56 PM
MarkInSpace (Mark)
Registered User

MarkInSpace is offline
Join Date: Jul 2020
Location: Melbourne
Posts: 86
I dont need to collect dark slides every time... do I?

I am using an ASI294MC Pro. If I standardise my subs at 120 seconds at -5Degrees, do i need to collect dark frames every time, or is once enough?
Reply With Quote
Old 13-10-2020, 04:24 PM
Merlin66's Avatar
Merlin66 (Ken)
Spectroscopy Wizard

Merlin66 is offline
Join Date: Oct 2005
Location: St Leonards, Vic
Posts: 8,143


The dark current is so low <0 deg I'd say you're pretty safe with reusing a master dark.
Reply With Quote
Old 13-10-2020, 06:06 PM
Nikolas's Avatar
Nikolas (Nik)
Dazed and confused

Nikolas is offline
Join Date: May 2012
Location: Melbourne
Posts: 2,014
No that's what a dark library is, so long as you shoot lights with those settings. If you change settings on your camera then do the same with your darks, they are then part of the darks library.
Reply With Quote
Old 14-10-2020, 02:44 PM
Robert_T's Avatar
aiming for 2nd Halley's

Robert_T is offline
Join Date: Oct 2005
Location: Australia
Posts: 2,885
i just got got a new camera and that is the first thing I do. Lock it in a darkened room and run through a sequence of all the typical exposure lengths, gains etc I plan to use and store in separate folders good to go. Should be good for some considerable time
Reply With Quote
Old 14-10-2020, 02:48 PM
ChrisV's Avatar
ChrisV (Chris)
Registered User

ChrisV is offline
Join Date: Aug 2015
Location: Sydney
Posts: 1,541
I redo darks for my asi071 every 6 months. Why? Answer = dunno, but you don't need to do it every session.

I'm paranoid about flats, so do them every session.
Reply With Quote
Old 14-10-2020, 04:50 PM
glend (Glen)
Registered User

glend is offline
Join Date: Jun 2013
Location: Lake Macquarie
Posts: 6,308
Dark libraries are a common tool imagers use, just as long as you have sets that match sub exposure duration and temperature setting. Bias is the same. Some cameras can actually get away without Darks, like the ASI1600MM-C, IF you are shooting subs of short duration (say 30 secs, up to 60 sec) where there is no detectable AMP glow, just use Bias in that case. It is up to you, look at the Bias and Dark histograms and see what you think.
Of course the ASI294 is a different sensor, and has different needs, and issues. From my research it seems to require Flats as well, given the uneven sensor cooling producing gradients (a product of the back lit architecture not allowing a full sized TEC).
Reply With Quote
Old 14-10-2020, 05:11 PM
LewisM's Avatar
Novichok test rabbit

LewisM is offline
Join Date: Aug 2012
Location: Somewhere in the cosmos...
Posts: 10,011
Darks? What are those? (I use Starlight Xpress CCD's)

With my SBIG's, yes, I keep a dark library.
Reply With Quote
Old 15-10-2020, 08:18 AM
gregbradley's Avatar
Registered User

gregbradley is offline
Join Date: Feb 2006
Location: Sydney
Posts: 16,818
Darks can work for a long time. CCDs generally slowly degrade over time so they may develop columns and extra bad pixels.

CMOS will too but at what rate I don't know but these same CMOS sensors in mirrorless cams redo the bad pixel map once a month. So the fact your digital camera may be clean is because it does this routinely.

I also don't see any CMOS camera suffering from those hot columns that a lot of the KAF series CCD sensors do. But I have used 3 year old darks very occassionally and they worked nicely.

But with CMOS you need multiple darks to match the various settings as that all needs to be exactly the same as your lights.

So I would:

1. Standardise a temperature that can be achieved all year round and the lowest you can reliably achieve.
2. Use only 2 settings for gain, one for regular imaging and one for narrowband.
3. If you are using QHY that would be the readout mode for each type of imaging.

The usual advice for CMOS (not sure about the 16bit sensors) is not to use bias frames and use flat darks when making flats.

Reply With Quote


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 01:18 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.
NexDome Observatories
Limpet Controller
Astronomy and Electronics Centre