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Mark,
Yes, best dynamic range is ISO1600 (9.4) on the 70D
If imaging wide band RGB ( no filters ) during the new moon period ( now ) forget the CLS filter as your skies are quite dark at Bortle 5 ( I used a CLS filter for 3 months and stopped using it under Bortle 8 Sydney as it reduced detail and it was difficult to get the white balance right )
My recommendation would be 90 sec to 120 sec subs to keep the read noise down and capture at least 3 hours or more on the object ( the Tarantula is quite a bright object especially at the core )
Dither each sub , APT dither 1 to 2 ( Random dither in PHD2 )
Take your Conventional Darks ( end cap on scope ) after your lights whilst cameras temp is stable ( 30 to 40 darks ) Disable internal noise reduction Darks in camera.
See how that turns out
DSLR’s run so warm 25 to 35 deg C , that pushing longer subs just increase noise not signal , lucky imaging with shorter subs can work in your favour
I shot most objects between 60 sec and 180 sec depending on location
Sydney Bortle 8 was 60 sec to 90 sec subs ( 6” f6 newt )
South Coast Bortle 3 was 120 sec to 180 sec subs ( 6” f6 newt and 8” f5 newt )
Here’s my Canon settings I used for Astrophotography on the 600D
Canon EOS DSLR Astro settings with for prime focus with telescope ( Canon camera’s manufacture dated 2004 to 2014)
Exposure - set to Manual
Autofocus - off or Manual
Grid display - off
Aspect ratio - 3:2
Screen colour - 1 or preferred
ISO - sweet spot is 800
Aperture - aperture is fixed through telescope
Shutter speed - Bulb with remote shutter release
White Balance - set to auto white balance AWB ( if Camera has been Astro modded you have to set a “custom” white balance )
Drive - set to single shooting
Colour Space - set to RGB
Image file - set to Raw + JPEG
Image review - turn off
Metering mode - set to Evaluative
Exposure compensation - set to 0
LCD Auto off - set to disable
Live View Shoot Function - enable
Live View Exposure Sim - enable
Custom functions -
ISO expansion - set to off
Exposure level increments - set to 1/3 stop
Long Exposure Noise reduction - off if shooting darks
High ISO speed noise reduction - off if shooting darks
Highlight Tone Priority - disable
Auto Lighting Optimiser - disable
Auto focus assist beam firing - disable
Auto power off - set to 2 minutes
Auto rotate - off
Built in flash - turn off
Red eye reduction - turn off
Dust delete data - set to none or turn off
Picture Style -
Sharpness 0 or halfway on slider
Contrast 0 or halfway on slider
Saturation 0 or halfway on slider
Colour tone 0 or halfway on slider
Mirror lock up - disable
Note : some older Canon cameras may not have some of the above settings so ignore them
Hope the above helps in some way
Cheers
Martin
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