Darks library...

[Stuart1971]

Hello,

I am new here and have a question...
I have always done my darks on the same night as images, but I read so many people build a library of them at different lengths...
So when you set the temp on an imaging camera at say -10 that means 10 degrees below ambient, so if 10 degrees outside, the it would be zero....
But if taking them inside to build a library, then setting the camera at -10 with an inside temp of say 20 degrees will only give a camera temp of 10 degrees which would not match....
So assuming all that makes sense how are these dark libraries achieved ..? And how do people get matching temps with images and darks with all the above being said....?

Thanks

Stuart

[tooth_dr]

Hi Stuart

Some cameras have set point cooling so -10oC is just that, a set point at -10.  Doesn’t matter where your camera is, it cools itself to -10 degrees (provided it can reach -10).  Cameras generally have the ability to cool to 25-50 degrees below ambient.  So some cameras will struggle to reach -10 indoors.

Other cameras can’t control the temp they cool to and so their final temp will vary with ambient.
 

It’s easier to build at library of sub lengths at a fixed temp.

 

 

[TerryMcK]

Stuart I think you may be misinterpreting something here. I use APT, EKOS and NINA with my ASI cooled cameras. I set the cooling to -20C and it cools the camera sensor to -20C regardless if I started off at +20C, 0C or -8C

Edited February 24, 2020 by TerryMcK

[tooth_dr]

Hi Stuart

Some cameras have set point cooling so -10oC is just that, a set point at -10.  Doesn’t matter where your camera is, it cools itself to -10 degrees (provided it can reach -10).  Cameras generally have the ability to cool to 25-50 degrees below ambient.  So some cameras will struggle to reach -10 indoors.

Other cameras can’t control the temp they cool to and so their final temp will vary with ambient.
 

It’s easier to build at library of sub lengths at a fixed temp.

 

 

[Stuart1971]

27 minutes ago, TerryMcK said:

Stuart I think you may be misinterpreting something here. I use APT, EKOS and NINA with my ASI cooled cameras. I set the cooling to -20C and it cools the camera sensor to -20C regardless if I started off at +20C, 0C or -8C

So if it’s 25 degrees indoors and you can set to -20 that’s 45 below ambient, what camera will go that low...that’s a huge drop.... 😮, mine will do 30 below ambient, so if it’s 20 degrees inside mine will go to -10... 

So I guess it’s all to do with what the camera will go to below ambient..? Which should be in the camera specs.. correct..?

Edited February 24, 2020 by Stuart1971

[david_taurus83]

People take a darks library of various exposure lengths and various temperature so they dont have to do them each imaging session. You can use the same darks over and over again. It's best to take the camera off the scope for shooting darks with a metal dust cap to keep light out. If you only have a plastic cap you could line it with foil for the same effect. If your struggling to reach a desired temperature indoors you could always put the camera outside where it will get to lower temps. I had an ASI1600 and it would cool to around 40°C below ambient. I done all my imaging at -20°C with that camera.

[TerryMcK]

8 minutes ago, Stuart1971 said:

So if it’s 25 degrees indoors and you can set to -20 that’s 45 below ambient, what camera will go that low...that’s a huge drop.... 😮, mine will do 30 below ambient, so if it’s 20 degrees inside mine will go to -10... 

So I guess it’s all to do with what the camera will go to below ambient..? Which should be in the camera specs.. correct..?

Hi Stuart. Yes my ZWO ASI cameras are TEC cooled and can go 40 to 45C below ambient. If you decide on the absolute temperature you want to image at, say -20C, you can do your darks at any time. Just make sure the exposure length and gain are the same as your lights and you are away. 
I keep a library of different settings and do new ones every 4 months or so as the sensor ages.