2600MC Pro Calibration

[smr]

Hi,

Just wondering what other people are doing for this Camera or Cameras with the same sensor insofar as calibrations frames are concerned.

Is it ok to take Lights, Darks, Flats and Dark Flats, skipping Bias frames ?

[Laurin Dave]

With my ASI2600mc I use matched Darks for my lights and Bias for my flats, works well as flat exposures are sub 1 second, may need flat darks if using a mono camera with narrowband filters requiring longer exposures.   Just measure a bias, flat dark and 10 minute dark and  you'll see that dark current is next to nothing although there are numerus hot pixels.  Be interesting to see what other do ..

[Thorney]

I haven’t had my camera long but I’ve used darks to match the lights then flats and flat darks. To me I think it’s just experiment  though and see what works best. 

[mackiedlm]

I use darks and dark flats but no bias. It's easy enough to grab the dark flats at s the same time as the flats and I just prefer the idea of matching the frames. I have read many times that you need either dark flats or bias but not both, that if there is amp glow, none on the 2600, it has to be dark flats and other than that it makes no difference, but I prefer what I prefer.🙂

[Scooot]

I also only take darks, flats and dark flats with my 2600mc pro.

The bias is in the Dark Flat that’s subtracted from the Flat. The bias is also in the main Dark that’s subtracted from the lights, hence no need for a separate bias. As they’re all perfectly matched by temperature this works perfectly. 
 

I take Sky flats the morning after and the flat darks at the same time, which is all quite easy. 

Edited November 6, 2021 by Scooot

[smr]

Thanks for the replies guys. 

I seem to have a problem with flats...

I'm using a cheap led panel from Amazon dimmed all the way down with a target ADU of 32757.

When running flats aid wizard the ADU can't be met unless I use a minimum exposure time of 0.2 seconds - 1/5th of a second! 

I have read on CN that the 2600 likes flats of around 3 seconds. 

I calibrated with the flats anyhow and theyve made the stacked image much worse in that it looks like the data has been clipped.

How do I achieve longer flat length if my led panel is dimmed as much as can be?

 

[Scooot]

6 minutes ago, smr said:

Thanks for the replies guys. 

I seem to have a problem with flats...

I'm using a cheap led panel from Amazon dimmed all the way down with a target ADU of 32757.

When running flats aid wizard the ADU can't be met unless I use a minimum exposure time of 0.2 seconds - 1/5th of a second! 

I have read on CN that the 2600 likes flats of around 3 seconds. 

I calibrated with the flats anyhow and theyve made the stacked image much worse in that it looks like the data has been clipped.

How do I achieve longer flat length if my led panel is dimmed as much as can be?

 

My Sky flats are usually between 190 and 290 ms on a bright clear morning, maybe only 50 to 80ms on a cloudy morning. These seem to work very well.

[Ouroboros]

Looks like I’m doing the same as others. 

Darks at the same temperature and duration as the lights.

Flats usually taken of the sky with various layer of  cloth over the telescope requiring exposures of at least 3 seconds. 

Dark flats of the same duration. 

In processing I use the dark flats as bias. 

From what @Scoot is saying, longer flats are not necessary whereas I’d read they are with this camera. It would certainly be easier if they could be shorter. 

[tomato]

Put some sheets of printer paper over the screen to dim it, I need a couple to get the histogram where it needs to be when using the NINA flats wizard with my QHY 268c with flat exposures around 1-2 seconds.
 

The only problem I have is I perch the panel on top of the dewshield on the RASA which cuts off fresh air circulation to the camera, so the sensor temperature rises very quickly.

[Scooot]

44 minutes ago, Ouroboros said:

Looks like I’m doing the same as others. 

Darks at the same temperature and duration as the lights.

Flats usually taken of the sky with various layer of  cloth over the telescope requiring exposures of at least 3 seconds. 

Dark flats of the same duration. 

In processing I use the dark flats as bias. 

From what @Scoot is saying, longer flats are not necessary whereas I’d read they are with this camera. It would certainly be easier if they could be shorter. 

This is a calibrated image (sub) I'm working on at the moment, just a screen stretch and resized to see it. It looks OK to me? The flat was 290ms but  a bit longer than normal because I accidentally took the 3 minute exposures at gain 24 (the same as the guidescope) instead of my intended 100.

and the master flat for info, I took 30.

Edited November 6, 2021 by Scooot

[Thorney]

I have just taken some flats with a light pad. .420ms. The preview looks ok to me but we’ll see once stacked. If these fail I’ll try with a white T-shirt or think of some other method   

[Ouroboros]

4 hours ago, Scooot said:

This is a calibrated image (sub) I'm working on at the moment, just a screen stretch and resized to see it. It looks OK to me? The flat was 290ms but  a bit longer than normal because I accidentally took the 3 minute exposures at gain 24 (the same as the guidescope) instead of my intended 100.

and the master flat for info, I took 30.

Yes, looks OK doesn’t it. I don’t know where I read that taking short exposures with the ASI2600 was inadvisable.  I use the auto routine with the ASIair for flats which automatically determines what exposure duration is right for flats before taking them.  I’ve found it tricky flaffing around with different layers of paper/cloth trying to get flat durations longer than 2 to 3 seconds and less than 10s which it also advises. 

[Scooot]

10 minutes ago, Ouroboros said:

Yes, looks OK doesn’t it. I don’t know where I read that taking short exposures with the ASI2600 was inadvisable.  I use the auto routine with the ASIair for flats which automatically determines what exposure duration is right for flats before taking them.  I’ve found it tricky flaffing around with different layers of paper/cloth trying to get flat durations longer than 2 to 3 seconds and less than 10s which it also advises. 

I think I read that somewhere as well once, cloudynights site I think.

Yes I use the auto on Asiair too, I use one my late Granny’s very old white cotton napkins, I have to fold it so I’m shooting through 4 layers. The brightest point of the histogram is always dead centre with a little spilling over to the right. 

Edited November 6, 2021 by Scooot

[ONIKKINEN]

Not a 2600MC, but the same sensor.

I recently started taking dark flats, and noticed flats being applied better. I had a bright spot in the middle, which i just assumed was high cloud/some other source, but this disappeared after a)flocking my OTA b) taking dark flats . On paper the difference between a bias frame and a 0.6s dark is almost the same but there must be a difference large enough to make a noticeable difference. Also tried higher gain where my light panel produces good flats with an exposure of 0.053s and these also calibrate well with dark flats. I think bias frames become a bit redundant with darks and darkflats, since the appropriate noise is already removed with both.

[teoria_del_big_bang]

58 minutes ago, Ouroboros said:

Yes, looks OK doesn’t it. I don’t know where I read that taking short exposures with the ASI2600 was inadvisable.  I use the auto routine with the ASIair for flats which automatically determines what exposure duration is right for flats before taking them.  I’ve found it tricky flaffing around with different layers of paper/cloth trying to get flat durations longer than 2 to 3 seconds and less than 10s which it also advises. 

I have read similar in various websites and also on tutorials that generally CMOS do not act very stable when using short exposures, which is one of the reasons using Bias frames are not recommended.
How true this is, which cameras are particularly susceptible to this and how short a short exposure actually is I have no idea (although on his tutorials I have heard Adam Block recommend using exposures of at least 3 seconds).
So with my ASI1600M and my newer QHY268M I have just stuck to flats and dark flats of at least 2 seconds and preferably 3.
But I agree without a dimmable flat field generator this is difficult to achieve easily for all filters, I am lucky having a flat field source that is dimmable enough to achieve this across all LRGB and NB filters and can be programmed to achieve these different intensities through EKOS scheduler so is all automated.

Steve 

[StarWomble]

Following with interest on this one as I've just got a 2600MC-Pro