Is it essential to use filters and/or other specialised equipment (other than a camera, telescope and tripod) to get colours to show up in astrophotos? I've taken quite a few photos and in some photos colours show up (eg Orion nebula) and in others they don't (eg Rosette nebula).
I suspect the trick lies in post-processing, but like I said in some photos the colours don't show up even though I've done everything I can/know in post processing, so I assume I either needed more photos or better knowledge of post processing techniques.
Hi Granada- to get nice colour you will generally need lots of integration time taken with many individual shots stacked together. Note also that if you’re in a heavy light pollution suburb everything looks greyed out So filters are useful for isolating the signal from surrounding light pollution and increasing contrast.
Perhaps some details of your post processing steps might also help
Thanks Ronson and David,
To answer both your questions, I usually only take about 20 or so exposures (rarely more than 30 seconds each). Most of the time I also take some biases, darks and sometimes flats but that's about it.
My post processing basically consists of stacking the images and subtracting the darks/flats/biases if I've taken them, then playing around with light curves in GIMP.
To your point David, yes I do live in a light polluted area so that's definitely a factor to consider.
I've attached an example which I was happy with (Orion nebula) but with others like the Rosette nebula, if you can just imagine a bunch of whitish, bluish & reddish stars on a black background, that's pretty much what they all look like. No gases or other colours showing up.
I started AP back in 2017 with a Canon 600D unmodded , HEQ5 mount and 150mm f6 Bintel GSO Newt ( still use the same Newt now with my 2600MC )
Imaged from Bortle 7/8 heavy light polluted Sydney and Bortle 3 dark skies South Coast NSW
I never used any narrowband or light pollution filters so just imaged broadband using ISO 800 ( best setting for this camera ) on all targets
I also used my Canon with TV Powermates for planetary imaging using BYEOS which produced some excellent images considering basic equipment
Sydney Bortle 7/8 Skies
Galaxy imaging during new moon period ( dark ) 30 to 60 sec subs ( at least 150 to 250 subs )
Emission Nebula during new moon period ( dark ) 60 to 90 sec subs ( at least 80 + subs )
Globular clusters anytime 60 sec subs ( 60 to 80 subs )
I didn’t bother imaging Emission Nebula when the moon was greater than 50%
Dark Site Bortle 3
Galaxy imaging during new moon period ( dark ) 90 to 120 sec subs ( at least 100 subs )
Emission Nebula during new moon period ( dark ) 150 to 180 sec subs ( at least 80 subs )
Globular clusters anytime 60 to 90 sec subs ( 60 to 80 subs )
I only took Darks with the Canon 600D ( No flats or other calibration frames )
Stacking software Deep Sky Stacker ( still use it , free and reliable , no issues in 6 years )
Post processing, Startools ( still use it , it’s developed into a superb post processing software)
Planetary imaging
Capture BYEOS
Processing Autostakkert 3 and Registax 6
Most DSLR’s have a quantum efficiency of only around 40% to 50% so it’s really important to capture as much data as possible on an object to improve your SNR , reduce noise by stacking , expose more fine detail , expose more dynamic range and produce more depth in colour as well
Unfortunately the sensor electronics in most DSLR’s run very warm ( 18 to 35 deg C depending on climate ) which causes unwanted dark current or dark thermal noise. This can be mitigated to some degree with calibration frames , dithering and lots and lots of good data for stacking
Used this set up for 3 years before I upgraded to a dedicated cooled cmos OSC camera the 2600MC
Some of my old photos attached using the 6” newt and Canon 600D
A lot of it will depend on what you're imaging. Probably the biggest issue with an un-modded camera is it's inability to capture H-Alpha due to the IR filter they have. They can get the tiniest bit, but if you're on a target like the Rosette Nebula it takes many, many hours of data to get anything as it is mostly Ha. You would do much better looking for bright reflection nebulae or galaxies.
Orion works so well because, while having a large amount of Ha in the region, it also offers a lot of reflection from the bright stars.
I also used my Canon with TV Powermates for planetary imaging
Martin, may I ask how did you attach the TV Powermate to your rig between the scope and the camera? I assume a special adapter?
I have always wondered why my planets came out really tiny in photos compared to some others' and just assumed they used some kind of magnification lenses, but never looked into it further.
Planetary imaging requires a large focal ratio which is dependent upon seeing conditions
Here’s some of my notes from 2018 on planetary imaging …..
Focal Ratio for Lunar and Planetary Imaging
General rule of thumb to determine the “best focal ratio” of your image train for Lunar and Planetary imaging is -
Poor night of seeing 3.5 x pixel size of your camera
Average night of seeing 5 x pixel size of your camera
Good night of seeing 7 x pixel size of your camera
Canon 600D pixel size is 4.3 uM
Poor seeing 4.3 x 3.5 = 15
So focal ratio F15 required
Average seeing 4.3 x 5 = 21.5
So focal ratio F21.5 required
Good seeing 4.3 x 7 = 30.1
So focal ratio F30.1 required
My 6” f6 Bintel GSO scope ( 900mm focal length )use 4 x or 5 x powermate
My 8” f5 Bintel GSO scope ( 1000mm focal length ) use 4 x or 5 x powermate
End of notes
Backyard EOS ( BYEOS ) software specifically design for Canon cameras is an excellent software package for both deep sky and planetary imaging, very intuitive and reliable. It provides live view , framing , focus and capture plans all in one bundle plus extra tools like polar alignment etc….About $60 ( Canadian product ) I still use it today for planetary only
My main acquisition software for deep sky imaging is APT
For planetary imaging I use my TV Powermates ( full set ) with a 35mm extension adapter ( Bintel ) to achieve focus
Photos from back in 2018 attached showing TV Powermate , 35mm extender and Canon 600D into focuser of 6” Newt
Plus photos of BYEOS both planetary and deep sky imaging
