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

Reply
 
Thread Tools Rate Thread
  #1  
Old 13-06-2009, 07:47 PM
tornado33
Registered User

tornado33 is offline
 
Join Date: Jan 2005
Location: Newcastle, NSW, Australia
Posts: 3,931
Marvellous what a difference temperature makes

Was looking at some past images Ive done, and decided to check darks I did in summer and compare to ones I did 2 nights back when it was very chilly.
Both are full res crops from same part of image.
One was at an ambient temp or around 20 degrees, the other at 8 degrees. Look at the difference in noise. Bert has the right idia, making a fridge to go round the camera. DSLR's dont need to be cooled to 30 below. If this dark is so dark at 8 degrees, at around zero thermal noise would be almost non existant.
Scott
Attached Thumbnails
Click for full-size image (20deg.jpg)
142.8 KB124 views
Click for full-size image (8deg.jpg)
96.2 KB122 views
Reply With Quote
  #2  
Old 13-06-2009, 09:04 PM
jjjnettie's Avatar
jjjnettie (Jeanette)
Registered User

jjjnettie is offline
 
Join Date: Feb 2005
Location: Far Far Away
Posts: 16,726
That's incredible!
Reply With Quote
  #3  
Old 13-06-2009, 09:43 PM
leon's Avatar
leon
Registered User

leon is offline
 
Join Date: Apr 2006
Location: ballarat
Posts: 10,888
Yea Scott that is right, I love it when it is about zero, and the frost is on the ground, best time for imaging, nice comparision.

Leon
Reply With Quote
  #4  
Old 14-06-2009, 04:37 PM
rat156's Avatar
rat156
Registered User

rat156 is offline
 
Join Date: Aug 2005
Location: Melbourne
Posts: 1,653
I think that you'll find if you stretch the cold one, most of the dark current is still there.

Cheers
Stuart
Reply With Quote
  #5  
Old 14-06-2009, 04:52 PM
Bassnut's Avatar
Bassnut (Fred)
Narrowfield rules!

Bassnut is offline
 
Join Date: Nov 2006
Location: Sydney
Posts: 4,772
Quote:
Originally Posted by rat156 View Post
I think that you'll find if you stretch the cold one, most of the dark current is still there.

Cheers
Stuart

Yeah, posting a dark comparison as an 8 bit JPEG? , nice try
Reply With Quote
  #6  
Old 15-06-2009, 12:54 AM
Tandum's Avatar
Tandum (Robin)
Registered User

Tandum is offline
 
Join Date: Apr 2008
Location: Carindale, Brisbane.
Posts: 4,117
I went back and checked a pair of mine, 12/08 and 7/09 ... same iso/same time..no difference I can see. They are a lot noisier than yours
Reply With Quote
  #7  
Old 15-06-2009, 07:14 AM
cfranks (Charles)
Registered User

cfranks is offline
 
Join Date: Feb 2008
Location: Tungkillo, South Australia
Posts: 599
I bought one of those Car Cooler thingies from Tandy. Peltier cooler for $16.00 and left my 40D in it all day. It got down to about 3deg but the Darks were just as noisy as the room temp ones so I ordered a QSI 540wsg!
Reply With Quote
  #8  
Old 15-06-2009, 07:34 AM
Lester's Avatar
Lester
Registered User

Lester is offline
 
Join Date: Jan 2006
Location: E.P. S.A.
Posts: 4,963
Nice comparison Scott. What was the exposure time for those darks?

Some of the Canon camera models produce more noise than others too.
Reply With Quote
  #9  
Old 16-06-2009, 01:54 PM
Geoff45's Avatar
Geoff45 (Geoff)
PI rules

Geoff45 is offline
 
Join Date: Jul 2006
Location: Sydney
Posts: 2,436
Quote:
Originally Posted by cfranks View Post
I bought one of those Car Cooler thingies from Tandy. Peltier cooler for $16.00 and left my 40D in it all day. It got down to about 3deg but the Darks were just as noisy as the room temp ones so I ordered a QSI 540wsg!
Good choice! Great camera.
Reply With Quote
  #10  
Old 16-06-2009, 01:57 PM
Geoff45's Avatar
Geoff45 (Geoff)
PI rules

Geoff45 is offline
 
Join Date: Jul 2006
Location: Sydney
Posts: 2,436
Here's the 8 deg dark with a bit of a stretch. A cooler one would show less dark current.
Geoff
Attached Thumbnails
Click for full-size image (8deg.jpg)
153.4 KB23 views
Reply With Quote
  #11  
Old 17-06-2009, 03:56 PM
bmitchell82's Avatar
bmitchell82 (Brendan)
Newtonian power! Love it!

bmitchell82 is offline
 
Join Date: Jul 2008
Location: Mandurah
Posts: 2,597
hehehe the CON of a dslr lucky we ues it for "dark subtraction only "
Reply With Quote
  #12  
Old 17-06-2009, 06:47 PM
tornado33
Registered User

tornado33 is offline
 
Join Date: Jan 2005
Location: Newcastle, NSW, Australia
Posts: 3,931
Both darks were 10 mins.
They say each 6 degree drop in temp is 1/2 the dark current I think? The darks werent stretched or adjusted in any way, just opened with canon's software abd turned to jpeg
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 06:14 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
Advertisement
Bintel
Advertisement
Celestron RASA
Advertisement
Testar
Advertisement
Star Adventurer
Advertisement
Astromechanics
Advertisement
Lunatico Astronomical
Advertisement
EQ8-R
Advertisement
Astronomy and Electronics Centre
Advertisement