Shooting darks

[StuartT]

When shooting darks with my ASI2600MC I just screw in the camera cap (which has an o-ring) and assume this is light tight. But some people put the camera in a black bag too. My only problem with that is that it would mess up the cooling fan (as I am shooting darks at -15 C).

So is it necessary to put the camera in a light tight bag?

[Stuart1971]

1 hour ago, StuartT said:

When shooting darks with my ASI2600MC I just screw in the camera cap (which has an o-ring) and assume this is light tight. But some people put the camera in a black bag too. My only problem with that is that it would mess up the cooling fan (as I am shooting darks at -15 C).

So is it necessary to put the camera in a light tight bag?

Well, I find that these cameras are so sensitive that I have to do mine with the camera on the scope in my obsy which is pretty dark even in the day, with scope cap on and with a cover over the whole lot too, or I get light leak….and it does spoil the darks….

[david_taurus83]

If the cap is metal then it shouldn't leak. Or if its a plastic or rubber cap, put tin foil around it. No need to put the camera in a bag.

[StuartT]

53 minutes ago, Stuart1971 said:

Well, I find that these cameras are so sensitive that I have to do mine with the camera on the scope in my obsy which is pretty dark even in the day, with scope cap on and with a cover over the whole lot too, or I get light leak….and it does spoil the darks….

So how does that not obstruct the cooling fans?

38 minutes ago, david_taurus83 said:

If the cap is metal then it shouldn't leak. Or if its a plastic or rubber cap, put tin foil around it. No need to put the camera in a bag.

That's what I thought. And there's no other place light can get in, right? I guess I'd always wondered about the open fins on the cooler mechanism. But that shouldn't need covering up surely?

 

[david_taurus83]

To check, put the cap on and connect camera to PC and run a series of looped exposures. Note the average ADU value in the histogram/statistics. Then shine a very bright torch on the camera where you think it may be leaking in light and check the ADU value. If it goes up, you have a leak. If it stays as it is, no leak.

[Stuart1971]

13 hours ago, StuartT said:

So how does that not obstruct the cooling fans?

That's what I thought. And there's no other place light can get in, right? I guess I'd always wondered about the open fins on the cooler mechanism. But that shouldn't need covering up surely?

 

Because I took my dark library in the middle of the winter when it was 0 degrees, outside, also the cover is large and covers the whole mount and scopes, so plenty of air and room under….

Edited May 6, 2022 by Stuart1971

[StuartT]

11 hours ago, david_taurus83 said:

To check, put the cap on and connect camera to PC and run a series of looped exposures. Note the average ADU value in the histogram/statistics. Then shine a very bright torch on the camera where you think it may be leaking in light and check the ADU value. If it goes up, you have a leak. If it stays as it is, no leak.

Now why didn't I think of this!! 🤦‍♂️

[Padraic M]

12 hours ago, david_taurus83 said:

To check, put the cap on and connect camera to PC and run a series of looped exposures. Note the average ADU value in the histogram/statistics. Then shine a very bright torch on the camera where you think it may be leaking in light and check the ADU value. If it goes up, you have a leak. If it stays as it is, no leak.

I did this with my 1600MM recently and found no leaks in the camera. Found plenty in my 150PDS newt 😞

@BrendanC has an interesting conversation ongoing at present elsewhere on SGL (can't remember the post link) and Vlaiv has suggested ways to analyse if you do indeed have a light leak in your darks. Current consensus seems to be that the camera is fine; the scope leaks; darks aren't materially impacted but flats are.

[BrendanC]

Wow, my first ever mention! I must be becoming popular.

Here's the link and yes, you're right - Vlaiv is the man with all the answers, and gives a very interesting analysis of my darks: