Dark frames will reduce the noise in your final stacked image, meaning you final image will look much cleaner as you’ll have a better signal-to-noise ratio. Dark frames are an important part of the astrophotography imaging process, and capturing them could not be easier.
How to Take Dark Frames Video
In this video, I explain why dark frames are so important for astrophotography, and how to take them with a DSLR.
How to Take Dark Frames
1. Place the dust cover back on your telescope or camera lens
2. Cover the viewfinder to prevent reflected light hitting the camera sensor
3. Take the images using the exact same settings and in the exact same conditions that you used for your light frames.
It’s important to capture these images under the same conditions as you shot your light frames. Shooting darks just after you finish your imaging session has completed, or when the clouds have rolled in is the ideal time to do it.
Shooting immediately after your session will ensure your camera has the same settings loaded, and the ambient temperature outside is still the same. This is very important are dark frames are pure noise, which your stacking (I use Deep Sky Stacker) will use to offset against the noise in your light frames.
There are a couple of different ways to shoot your dark frames. You can either leave your camera connected to your telescope and take images by placing the dust cover back on your telescope.
Or you can take your camera off your mount, pop the camera dust cover on and shoot them that way. Both methods have pros and cons.
Leaving your mount on the scope
Pros
· Everything is already set up
· Your rig is set up to take flats when the sun comes up in the morning
Cons
· If you’ve already taken your flats during the day then you can’t start packing away
Removing the camera
Pros
· You can dismantle your set up while your camera is taking dark frames
· You can leave the camera outside and warm up for a few minutes while feeling smug that you’ve packed away
Cons
· If you haven’t taken your flat frames you’ll need to set up your equipment again
Camera settings
Example settings that I have used from an imaging sessions:
· ISO 1600
· Exposure 120 seconds
· White balance Daylight
· Number of exposures 20 minimum
If you have the time I recommend taking at least 20 dark frames, which is the minimum recommended by Deep Sky Stacker. If you don’t have the time, and I often don’t, then I have had plenty of success with 10-15 frames.
Taking more than 20 frames is perfectly acceptable, but if you’re taking over 50 then you may not be seeing much value out of those extra frames. My best advice is to find what works best for you, taking 50 frames is great if you have the time and can see the benefit, if you don’t then I would recommend sticking with 20 frames.
