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Tommy B

Worth creating a dark frame library?

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Hi folks,

Just a quick question about dark frames that I'd like to throw out there. I hate taking them at the end of a session because I'm usually very tired and get frustrated waiting around for the exposures to finish. I'm right in thinking that as long as the temperature and exposure time is the same with all light kept from entering the camera it doesn't matter when I take my dark frames right? Is it then feasible to create a library of dark frames on cloudy nights at different common exposures and temperatures to use at a later date?

Thanks,

Tommy B.

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Yup, you can do that. Some even take darks with the camera in the fridge. :p

I've saved up a small dark library so far on my most common exposures, I also find taking darks to be quite a pain after already collecting lots of data & just wanting to get inside to process it, so I've found it's important to set some time aside for it so you don't get too frustrated.

It was recommended to me to recycle the dark library every couple of months though, I guess because you might get a hot pixel or two after more use or the signal for the darks changes slightly.

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Excellent! Many thanks for the reply Amra, love the fridge idea haha. Think I will get started on this tonight.

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I assume this is for your canon as there isn't really a need for darks with your Atik.

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Yes, I'd agree that a library will work as long as temps,lengths,iso's etc are the same as your subs. be sure to update regularly as changes such as dust on the chip will need to be recorded. My only problem with creating a darks library is...... I'm just soooo lazy :).

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Not sure dust on the chip will be an issue given these are darks so the dust won't be seen. An issue with flats though.

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I assume this is for your canon as there isn't really a need for darks with your Atik.

This is for my Atik 314L+ as I do get a bunch of hot pixels and some noise.

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Surprised you are getting noise from your Atik. Are you sure it is not from something other than the cam itself as I don't think other Atik users have an issue. I don't with mine.

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With the Sony chip I'd be inclined to try a bias used as a dark, plus (ideally) a bad pixel map. It depends on whether your stacking software supports them. Astro Art 5 is particularly effective with BPMs. The hot pixel filter also works a treat. A BPM or defect map is just a master dark with 2000ADU clipped off the black point. Certainly with my Atik 11000 this is the best calibration routine.

If you have significant noise then I'b be wondering if the cooler was working properly.

Olly

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The noise is only very very minor on the 314L+ and I do wonder if it even affects the final image at all but the hot pixels can be very aggressive and Dark frames are the only method I currently know that shifts them.

I use DSS for stacking but I don't think it has a BPM function. Astro Art is something I have considered getting for a while but lots of money has gone on equipment lately :(

Are there any standalone programs that can remove hot pixels?

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I know this thread is several weeks old but I thought it would be better to add to it.

Having just got a NEW Canon 1100D (Modded with extras from Juan of CheapAstrophotography) I am now setting about creating my darks library. In the past I put my 350D in the fridge and freeze but could not really get a steady and controlled temp enviorment.

This time round I am using my beer fermenting fridge, it's an old fridge I picked up for free and use it to ferment my Pilsner, larger it. Using an STC-1000 controller (loads on ebay for a few quid) it controller the fridge at any set temp I want it for, so to ferment my Pilsner I set it at 12deg C, then when the fermenting is done I then set the temp at 0.1deg to then lager (Lager means to store in German) it.

So as I have just finished my last 4 month lager period I popped the canon 1100D in there to acclimatise for an hour, then ran APT to start taking my darks as the Canon is reporting a sensor temp of 11-12deg during the 30s and 60s darks (at ISO 800 and ISO 1600). This afternoon when the canon battery is recharged I will start on the 120s (ISO 800 and ISO1600) followed by 240s (ISO 800 and ISO1600).

So if anyone fancies making lager/pilsner get an old fridge and buy an STC-1000 and you will then also have a temperature controller environment to do darks in and then make some beer!!. I will also do my Bias the same way for a Bias Library.

Edited by SniffTheGlove
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Huge numbers of beginners use DSS and very few experienced imagers do so - in my experience. (In truth I don't personally know any who do.) I don't intend to knock DSS because it is free and can be perfectly competent, but I don't know anything about how to regulate it.

AA5 is a dream of non-mumbo-jumbo simplicity until you read the manual, then you need a maths PHD. Fortunately you rarely need the manual (though at least it has one!) because the individual componets have their functions written on the tin, so to speak. So you have the option of a hot pixel filter and can vary its strength on a scale of percentages. From what I can tell you might as well set the percentage high because it seems to do no harm when you do.

AA5 supports Bad Pixel Maps and tells you how to make them (but PM me for a simpler explanation!!) and these are great in conjunction with a bias becase I find they are far less temperature-match dependent than classic darks, though AA5 deals with these as well.

Olly

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Thanks Olly, your praise of AA5 has given me the push I needed to finally give some other software a go. AA5 came in the post today and the features really sound fantastic, especially its ability to run more than one camera at once. I had terrible trouble getting Artemis capture to recognise two cameras without it getting confused. All I need now is a clear sky to get a feel for it...old England is being a real menace lately weather wise.

Tommy.

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