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Hi, I have red in a book about CCD astrophotography (CCD Astronomie in 5 Schritten (CCD Astronomy in 5 steps)) that, when using a camera with controlled cooling, you could create the darks as well at home, even at day time, when cooling down the chip of the camera to the same temperature you choose when taking your lights. The author of the book proposes to create an archive of darks by cooling down the chip in 5°C steps and using common exposure times and then just use these darks and do not create new ones during your sessions! What do you think about this? Could this possibly work? Thank you, best regards, Achim |
1.81
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| Creating a 'dark library' as described is one of the benefits of using a cooled camera, and yes it works well. You need to match the gain, temperature and exposure time of the lights to the darks from your library. If you don't have a matching master dark then create a new one and add it to your library. |
11.07
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Yes this works well. With some cameras you may need to use the refrigerator as well  Bias frames can be done the same way.Check your subs to make sure you didn't have any light leaks though. And cover the camera with a dark jacket or something similar. But be sure it still has an airflow. |
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| Hi Scott and Kevin, thanks a lot for your answers and help! If it works also for Bias, I guess it also works for FlatDarks, right? Only the Flats need to be captured then during the night in addition to the Lights? |
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| Yes, it will work for flat darks. Having a dark library will save you a good bit of time in the field. |
11.09
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With the right tools and some tricks, someone can build a library even for his uncooled DSLR  |
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I once created a darks library with a DSLR in the fridge and different fridge settings when outside temperatures could have fitted but the temperature was usually too much of a miss and I adjusted the exposuretimes of the lights for a session anyway according to sky conditions so the library didn´t help in the end. What other tools and tricks apart from changing the fridge setting between min. and max. do you mean, Diva?A helpful little programm if darks and lights differ in temperature for a single target is Dark Master v1.15. It sorts the lights and darks into matching groups according to temperature and creates a file group list for DeepSkyStacker. The temperature tolerance can be adjusted manually, default setting is 4 °C (= +- 2 degrees). DSS then stacks the whole lot but subtracts the fitting darks from the according lights. The sensor temperature of a DSLR changes anyway quite a bit during a session, so if one takes the temp. issue seriously Dark Master could also be used for a normal DSLR session without an existing darks library (in theory, in reality some problems arise which can be taken care of partially lowering ease of handling; if there is interest it can be discussed further either here or via PN). Here is an example of temperaturechanges for a session of 78 x 70 s lights and 27 darks (usually I only take 15) created with exiftool. There were a few shorter and longer pauses in the lights session so the graph goes up and down a few times. |
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11.09
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What other tools and tricks apart from changing the fridge setting between min. and max. do you mean, Diva? I am using a fan (and Dark Master of course). Nothing fancy. Indoors, using a fan blowing towards the camera (heh!) helps on minimizing the temperature variations. Thankfully, in my case, the lights "temperature" as reported by Dark Master is not varying that much, except at the beginning of the session. After taking my lights, I note the median "temperature" using Dark Master and then I am playing with the fan speed and pause duration between darks to match the darks "temperature" with the lights median "temperature". I then sort my darks by temperature and in time I have enough darks to match my lights. |
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| ah, ok, a fan :-) |
