gfxgfx
 
Please login or register.

Login with username, password and session length
logo
 
gfx gfx
gfxgfx
 
 
gfx gfx
29560 Posts in 3543 Topics by 312 Members - Latest Member: Bob Gillette April 23, 2017, 02:43:07 PM
* Home | Forum | Help | Search | Calendar | Media | Members | Login | Register |
gfx
East Coast Astro  |  The Imagers Lounge  |  Beginners Astrophotography  |  Collecting Calibration frames
gfx
gfxgfx
 

Author Topic: Collecting Calibration frames  (Read 688 times)

0 Members and 1 Guest are viewing this topic.

Offline frainiea

  • *
  • Join Date: Mar 2012
  • Posts: 5
    • View Profile
Collecting Calibration frames
« on: September 07, 2015, 09:18:45 AM »
I am making the switch from DLSR to a FLI8300 CCD.  Running Maxim DL and my scope is an TAC FSQ.  Had very little experience with the DLSR.

1) With the DLSR I made Bias at 1/4000 sec.  For CCD I have seen reference to "shoot at the fastest shutter you can" and also "use a zero shutter time.  I have not been able to find what the minimum shutter time is for my camera on the vendor page.  There is some information but I do not understand its meaning.  So the simple question is do you really set the time in Maxim DL to zero. 

2) I am also confused about dark's and temp.  Yes I know you have to have them for various temperatures and at the same time as the subs.  What I don't understand is how to take into account the cooler temperature.  First of all is the "cooler temp as displayed in Maxim an absolute number or is it a subtraction from ambient.  So if it is 30 C ambient and and the software is showing cooler temp to be -15 C what's the deal.  If in a month the ambient temp is 20 C and the cooler is again showing -15 C do you need new dark's or is the temperature that counts the same.

Probably obvious answers but any education will be appreciated.

Ed



Offline gquinzi

  • Official
  • *
  • Join Date: Jan 2009
  • Posts: 325
    • View Profile
Re: Collecting Calibration frames
« Reply #1 on: September 07, 2015, 11:32:35 AM »
Hi,

Regarding an easy approach to acquiring bias frames using maxim, open your camera control window and select the Expose tab.  Then at the right, choose the autosave feature.  Pick a slot and click on it to make it active, then where it says type just choose bias and it will pretty much take care of the exposure time (0 seconds) for you.  Before you start the sequence be sure to set your CCD cooler at the same temp value you ran your lights. 

As for the temp settings, I've been imaging on cool and warm nights and hadn't noticed much fluctuation in sensor temp.  I just run my chip at -20 C at all times to promote lower noise and subframe consistency.  To answer your question, as long as the chip or sensor temp shows the same temp (FITs header in maxim will give you the aveerage sensor temp per frame including the setpoint) then no you will not need to take a new set of darks. 

Example text from the fits header for a single SII subframe....

SIMPLE     = T                                                 
BITPIX     = 16 /8 unsigned int, 16 & 32 int, -32 & -64 real     
NAXIS      = 2 /number of axes                                 
NAXIS1     = 3326 /fastest changing axis                           
NAXIS2     = 2504 /next to fastest changing axis                   
BSCALE     = 1.0000000000000000 /physical = BZERO + BSCALE*array_value           
BZERO      = 32768.000000000000 /physical = BZERO + BSCALE*array_value           
DATE-OBS   = '2015-08-26T03:50:16' /YYYY-MM-DDThh:mm:ss observation start, UT     
EXPTIME    = 1200.0000000000000 /Exposure time in seconds                       
EXPOSURE   = 1200.0000000000000 /Exposure time in seconds                       
SET-TEMP   = -20.000000000000000 /CCD temperature setpoint in C                  
CCD-TEMP   = -19.700000762939453 /CCD temperature at start of exposure in C       
XPIXSZ     = 5.3984399999999999 /Pixel Width in microns (after binning)         
YPIXSZ     = 5.3984399999999999 /Pixel Height in microns (after binning)         
XBINNING   = 1 /Binning factor in width                         
YBINNING   = 1 /Binning factor in height                       
XORGSUBF   = 0 /Subframe X position in binned pixels           
YORGSUBF   = 0 /Subframe Y position in binned pixels           
FILTER     = 'SII     ' /          Filter used when taking image                   
IMAGETYP   = 'Light Frame' /       Type of image                                   
JD         = 2457260.6599074076 /Julian Date at start of exposure               


Hope that helps.

P.S. - With the weather improving, my schedule and the fact my kid is a tad older, I am now able to actually set up and get some excellent data spanning multiple nights from my driveway.  I will be posting my image once it's processed so stay tuned  :party0036:



« Last Edit: September 08, 2015, 03:42:10 PM by gquinzi »
Tak FSQ-85ED
.73X QE reducer
Starlight Xpress H18 Mono/FW/OAG
EXview guide head
AstroDon 5nm Ha, SII, OIII, LRGB gen II
G11 w/Ovision & Gemini I
Several pieces of Televue glass

Offline frainiea

  • *
  • Join Date: Mar 2012
  • Posts: 5
    • View Profile
Re: Collecting Calibration frames
« Reply #2 on: September 08, 2015, 10:19:59 PM »
Thanks, that was clear and helpful,

Ed

Offline gquinzi

  • Official
  • *
  • Join Date: Jan 2009
  • Posts: 325
    • View Profile
Re: Collecting Calibration frames
« Reply #3 on: September 08, 2015, 11:15:05 PM »
You're welcome Ed. Good luck with everything and hope the weather is in your favor.

Greg
Tak FSQ-85ED
.73X QE reducer
Starlight Xpress H18 Mono/FW/OAG
EXview guide head
AstroDon 5nm Ha, SII, OIII, LRGB gen II
G11 w/Ovision & Gemini I
Several pieces of Televue glass

East Coast Astro  |  The Imagers Lounge  |  Beginners Astrophotography  |  Collecting Calibration frames
 

gfxgfx
gfx gfx
Powered by MySQL Powered by PHP Valid XHTML 1.0! Valid CSS!