Astrophotography Flats And Darks — The Ultimate Guide
When getting into astrophotography there may be a lot of different terms that you simply don’t understand as it relates to the topic. A couple of these terms being, flats, and darks. This can really confuse people who are just getting started.
In this blog post, I will cover astrophotography flats and darks. This will be a guide for beginners on the technical subject that is flats and darks in astrophotography. By the end of this, you will be able to improve the quality of your work.
Understanding Calibration Frames
First, we must understand, what a calibration frame is and how they work. A calibration frame is certain pictures that you will take in a certain way in the given condition. These photo's sole purpose is to improve the quality of your light frames.
When doing this part of the process, you are calibrating the light frames. You are removing certain aspects from the images you are targeting. What are you removing from them?
- Background Noise
- Dust Particles
- Anything else affecting image quality
The reason you do this is to clean up the images before you go to stack them, stacking the images allows you to gather the final image.
Flat and Dark Frames
We will discuss three of the 4 calibration frames in this post right here. Flats, darks, and also dark flats. Each of these calibration frames has their owned specific job that they do, they are all important to the final product.
Out of all the calibrations that you will be doing, dark dark frames are generally more tricky and take a little bit longer to get the hang of.
When taking dark frames, it takes longer, since you have to match the same exposure that you used to capture your light frames. So for instance, capture your target at two minutes, then each dark frame must be two minutes long.
Calibrating may be trickier as well since this is completely dependent on the temperature. Dark frames record the thermal noise of the sensor. Since you need to take your dark frames at the same temperature, or at least very close to it. You may want to have a camera that is cooled for astrophotography.
Cooled cameras give you the ability to control your sensor’s temperature. Cooled cameras will make your life easier.
In order to capture your dark frames, you will want to place the cap over the lens when you take them.
Your flat frames should be shot at the same ISO that your light frames were taken at. Flat frames do not get rid of the digital noise, it is for this reason that they do not depend on the temperature at all.
For a good flat, you will need proper exposure. Now you will have your histograms peak from the left edge about halfway.
I can not tell you a certain length of exposure to use for your flats as this varies. To find this, you will need to go to your histogram. You will tune it by changing the brightness. of your light source. Another way is to add an extra T-shirt if you feel like trying that out it works well.
Shoot for variation of brightness in the image, do not worry about what colors you are getting in your image.
For this step you will want an even source of light, that will cover your lens. I typically just use a tablet with a white screen on it. But use whatever you have as long as it completely covers your lens evenly.
Depending on the size of your telescope, what you use as a light source may vary.
When you are flat framing nothing should change in your setup, you do not want to affect your light frames this way. You can do this step at home, but might as well just do it at the photography site right?
Dark Flat Frames
Dark flat frames are simple, dark frames that need to match the exposure time and temperature of your flat frames.
How much To Take
You will want to capture as many pictures as possible, the more the better. There may be a couple that gets taken that don’t turn out or are not quality images.
I would try for at least 40 to 50 images of each calibration. Eventually, when you understand your camera better for astrophotography you will know how many pictures you will need for each calibration.
If you want great quality astrophotography photos, you will want to take your time with flats and darks. You will be spending a good amount of time doing this, and you will eventually get the hang of it.
There is no correct or one way to do astrophotography flats and darks, if you find a way that works for you then use it and make something magical.
I hope you learned a lot of good and valuable information in this post. Be sure to show me your amazing captures.
Photos and article source comes from Night Spy Pix.
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Originally published at http://astrophototips.wordpress.com on February 3, 2021.