Do I Need To Take Dark Frames If My Camera Is Cooled

Dark Frames are, for me, ane of the 2 disquisitional calibration frames that you just have to take (the other being Apartment Frames). Dark Frames besides have the dubious honor of being the almost time consuming calibration frame to take, which often leads to people (including me once upon a fourth dimension) skipping them in the quest for more than sleep, or just as desperately, taking them at the incorrect time. In this post we're going to await at;

What a Dark Frame is
Why you need to take Dark Frames
Uncooled (incl DSLRs) vs Cooled cameras
How to take Dark Frames
Nighttime Libraries

Nighttime Frames assist remove the thermal noise created by heat in your camera's sensor

Images like these don't just happen. They accept endeavor to get all the pieces right – and Dark Frames really are a fundamental slice. But that effort is worth information technology. You volition kick yourself rather hard if you lot don't bother.

What is a Dark Frame?

Nighttime Frames are i of four calibration frames that you need to have to improve your images and make mail-processing that much easier. The other three are; Bias Frames, Flat Frames and Night Flat Frames.

Dark Frames incorporate all the information well-nigh the 'noise' that your camera creates. Programmes such as DeepSkyStacker then use this information to subtract that racket from your Calorie-free Frames and requite you much cleaner images.

Without them, all the noise that your surroundings has created ends upward in your images. You so stretch that data to pull out the details y'all really desire, but at the aforementioned time you are inadvertently pulling out all the noise, likewise.

When you take an epitome with the lens cap on, you probably think that it's pitch dark and therefore all the pixels will just be blackness. Well, if you have a Dark Frame and stretch it in Photoshop, this is what you get.

This stretched Dark File shows all the noise that has been created by heat, ISO setting and other things – all this demand to be subtracted out of your terminal prototype

Why practice you need to take Night Frames?

Every time you accept a long exposure, rut creates 'thermal noise' in your images. Your camera is unable to distinguish between a genuine photon of light in that pixel, and thermal dissonance, and then information technology counts both. Basically your photographic camera can't tell whether information technology has registered light or estrus, then to be safe, counts them both.

There are three things that volition affect the amount of dissonance in your image. The exposure length – the longer the image, the more noise. Temperature – the hotter the sensor, the more noise. ISO/Gain – the higher these are set up, the more noise.

The trouble for you equally an astrophotographer is that at least two of these are e'er present. Long exposures and higher ISO settings. In the spring, summer and autumn, external temperatures are too a big factor. So it can be a tripple whammy, total house, slam dunk of noise generation in your camera sensor.

Dark frames seek to but detect this thermal noise. Past stopping any light coming into the sensor, any remaining signal must therefore exist racket. If you know what your pattern of racket is, you can safely subtract that from your low-cal frames without removing 18-carat signal – hey presto, less noisy images.

During image processing, if not reduced through Dark Frames. that noise will come back to haunt y'all. When yous first start editing the paradigm through levels and curves adjustments, you lot don't really see it. Information technology's then faint as to be unnoticeable, but then as you go to the point where details are starting to come up through, when you're finally seeing all that faint betoken from the past you have worked so difficult to collect, – Blindside. So does all your noise and yous discover yourself wanting to cry at your keyboard.

The higher up images are roughly the same sized office of edited images. The ane on the left has no calibration files used at all, the one on the right has a good number of calibration frames of each blazon. Y'all tin see the difference information technology makes to the heaven – and nearly of that is because of Dark Frames.

They say a picture speaks a chiliad words, well I have 2 pictures there, and they explicate perfectly why you need to take Dark Frames!

Uncooled (incl DSLR) vs Cooled cameras

You can be a bit different for uncooled/DLSRs vs cooled cameras, so permit's take them 1 at a fourth dimension.

But before we beginning, ane gilded rule of Dark Frames is that everything must exist the same. Don't modify anything. Including the temperature.

DSLRs and uncooled cameras

Staying up all nighttime watching your camera catching photons of lite that have taken thousands of years to attain your sensor is awesome. Staying up fifty-fifty longer to take photos that only expect black is less awesome – I get that.

I'm the Everyday Astronomer, and then staying up like that isn't my thing. I similar my sleep too much. Then how exercise I make time for Dark Frames? I leave my gear running whilst I sleep.

Because Night Frames are temperature sensitive, there is no point waiting until I wake upward in the morning before taking them – information technology will have warmed upward considerably by then and drastically inverse my sensor temperature.

So instead, I set up an alarm for when my Light Frame sequence is due to finish, head outside, pop the lens cap on and then set the sequence for my dark frames and pop myself back in my nice warm bed. Job washed. The temperatures will non exist exact, that's impossible, but they volition at to the lowest degree be close.

Nosotros will comprehend exactly how to take them in a moment, just showtime lets expect at what difference having a dedicated cooled photographic camera makes.

Cooled cameras

Call back when I said that there is no point me waiting until morning before taking Dark Frames? Well, welcome to the joy of cooled cameras. I tin can take Dark Frames when I similar. Any time, day or night.

So at present my night's routine goes something like; do my imaging, NINA runs end of sequence programme (parks my mount and warms my camera). My alarm goes of, I bring everything indoors and I go back to bed three minutes later. Like shooting fish in a barrel as that.

Next morning time when I get upwards, I cool the photographic camera back to the aforementioned temperature as last night, then take my dark frames whilst enjoying the delights of a freshly brewed tea. If you are later a good tea recommendation, my particular favourite is Yunnan Gilded.

Cooled cameras are very Everyday and actually do brand your life so much easier.

How to take Nighttime frames

Dark frames are actually unproblematic to accept, though can be rather time consuming – they generally take longer than all the other scale frames combined.

In the most EverydayAstro style I can put it, a Dark Frame is just a Light Frame with the lens cap on. Everything should stay the same as your lite frames. So these are the basic rules for Nighttime Frames;

No light tin get to the sensor – lens cap on and no lite bleed (my reflector suffers terribly for this and so I now accept a thick black purse over the lesser which you tin can see here on Twitter)
All settings on your camera must be the same
- Same exposure length
- Same ISO/Proceeds setting
Temperature is important, dark frames need to exist equally close to the same temperature as your Light Frames as possible.
Uncooled cameras and DSLRs need Dark Frames taken at the aforementioned time as your Light Frames. Cooled cameras tin can be taken any time and then long as you remember the temperature of the Light Frames.

Depending on the length of the individual calorie-free frames, I have anywhere between 15 and 40 dark frames. This image, for example, had 55 Light Frames, 20 Nighttime Frames, 40 Apartment Frames, 40 Dark Apartment Frames and 100 Bias Frames.

NGC 1499 – The California Nebula. This images had 55 Light Frames at 300 seconds, 20 Dark Frames, twoscore Flat and Dark Apartment Frames and 100 Bias Frames

There are no hard and fast rules on the number to take, the only rule is you there is no such thing as too many. I aim for twenty – xl depending on exposure length of light frames. The longer the Light frame, the fewer Dark Frames I do, but e'er that minimum of 20.

Night Libraries

This is something that is very EverydayAstro and also fills the long cloudy nights. Dark libraries are just what they sound like, a storage centre of Dark Frames that y'all tin use for any image at whatsoever time – simply take them out of the library.

I near always used my cooled photographic camera at -15 degrees. So that ways on cloudy nights I tin can take 50 dark frames at xxx seconds each. So another 50 at 60 seconds each, then 90 seconds and and then on up to 600 seconds if you wish.

Once I have these, any time I utilise that camera, and the Lite Frames are for 1 of the times I accept in the library (let'due south say 90 seconds) and are taken at -15 degrees, I already have 50 Dark Frames so don't demand to accept whatsoever more. When I am stacking my epitome, I use my squeamish new Light Frames and so use the Dark Frames from my library.

You can also do this for different temperatures, so I could build a library at -5, -10, -15, -20 and -25 if I wanted to. The more cloudy nights and patience you have, the bigger your library can get and the more time you can salvage in the long run.

Libraries accept fourth dimension to build, they really exercise. It'due south quite a flake of effort up front, but that'southward okay – that initial endeavour ways much less effort later downwards the line. And that's a very EverydayAstro way of doing things.