Do you take calibration subs for every session?

Curious about different photographers’ preference here.

If you mean a session with a cooled cam I would say yes for Flats and Flatdarks. No need to do (timeconsuming) darks every session. Build up a dark library instead and make use of it. Same for Bias I guess, but I don't use them.

Best
Mike

Nope, benefits of a cooled camera, and semi-permanent rigs.

The cooled camera means I only really do darks every 6 months or so just to renew the library.

And my rigs are pretty "permanent", they can go a whole season without coming apart.
So I don't take flats often unless it comes apart or I experience issues;

Because Yes - strictly speaking "old" flats don't get rid of all little dust spots and such that might happen over time. Or when using a field rotator. - But I rarely have issues.. I've only had one big dust spot "issue" once. So I made some flats to cover that session (not to waste the session). Then cleaned the imaging tray/scope and retook the flats.
So, flats could happen anytime, mainly it just depends on issues.

I have to set up and breakdown my rig every session so flats are done all the time. Dark flats and darks are done "seasonally" or if I run into an issue where they no longer match.

I do flats nearly every time for the DSLR shots as experience thought me that not doing them means courting disaster (this happens because dust motes are or can be electrically charged and prone to move around each time the mirror goes up and down). The other rigs do not suffer the same risks and I keep doing flats every so often, sometimes with months between each set.

This poll can't be answered in the way you have set it up, as it depends on the type of calibration frames.

I always do flats after every session as they correct any issues in the optical train. So they must be done with the exact same focus, camera rotation etc.

But biases and darks are a function of the camera only and so do not depend on the night to night optical train setup. So those I keep in a library and just use the relevant gain and exposure time master as I need them

My exposure times/temp setings are pretty standard and I create a dark library. Your camera should not be developing new hot/dark pixels between each session. For years I imaged with Sony CCD chips that do not need darks, only bias substraction.

I have a permanent set-up and only redo flats when I change scopes. When I go to a dark site, I try to get flats, and maybe darks.

Lynn K.

As others have said - library of Darks, but I take Flats and Dark Flats every session, every filter.

I'll reuse flats if I'm shooting multiple nights in a row and don't move the image train. Otherwise, new flats every session with master dark and bias.

My last image was the first one recently when I didn't take flats. Because I was using the same exposure settings, cooled camera temperature settings and filters as my previous session and had not altered anything in my imaging train I decided I would give it a go. I was actually surprised that the old flats worked OK, but they may just have added a tiny bit of noise.

Only flats on almost every session so neither yes or no :-/ poll needs more options

Yes, because I have a field rotator.

Yes, bro, do your thing

Yes for flats… sometimes I change scopes, sometimes I can't be sure that everything is spotless. I do all my AP in the field and at different dark sites so the rig is set up de novo each time.

Ian

I too setup and takedown every session. Flats and Dark Flats are taken each session. I maintain a library of darks.

As many others have said, with a cooled camera I take darks twice a year when the outside temperature forces me to shoot at a higher (or lower) temp. Flats and flat darks for every session.

Always take new flats. The darks are in a library as are darks for the flats, one of the benefits of a variable flatpanel so I can keep flat exposures the same.
Redo dark library about every 4-5 months depending on if i notice a change in calibrated lights.

CS Sean

In my case yes for darks and flats. Tha’ts because I shoot with a non modified DSLR. I wish to upgrade the sooner as possible to a cooled dedicated camera (maybe an OSC, the ASI 533 MC Pro).

Whith a cooled one you can do a dark library at home (for each temperature) and reuse it for a long time and no spend time in your sessions. Flats are obliged.

I know there’re people who takes dark-flats. I don’t know if it’s your case.

I have a permanent setup, so I have a library of Darks that I update every six months or so, a library of Flats that I update every three months or so, and a SuperBias frame (PI), that I rarely update.

- - Steve

I used to re-use flats for an entire year, no matter if the camera was rotated or if focus changed between summer and winter.

This worked well in removing the general vignetting, but I always struggled with background noise, no matter how many subs I stacked.

So I figured the pixel-to-pixel variation to be the cause of this and purchased a flatfield box to take flats after every session.

After all, the latter was not that easy with the T-shirt method…

Still have to take my first flats with this box to see if this evens out the background of future photos.

Chris

Have a 2600 MC since then it's enough to do the flats (20-30) (over 3sec. single exposure) after every night.
I only calibrate with bias, which I make every 2-3 months.
The only important thing is that you dither, otherwise the combination would not work.
Dither with about 100-150 pixels more than sufficient…

I might be a bit more crazy, but I take my flats / Flat Darks after each image I complete. As my exposure times are not that great it is not as big of a problem as I thought it would be. It comforts me to know that each image has its own flats.

The only area where I do have it easy is with Darks and Bias frames, as I have a cooled camera, and I only use a handful of settings, it is easy to create a library, and refresh it every so often.

Christian Koll:
I used to re-use flats for an entire year, no matter if the camera was rotated or if focus changed between summer and winter.

This worked well in removing the general vignetting, but I always struggled with background noise, no matter how many subs I stacked.

So I figured the pixel-to-pixel variation to be the cause of this and purchased a flatfield box to take flats after every session.

After all, the latter was not that easy with the T-shirt method…

Still have to take my first flats with this box to see if this evens out the background of future photos.

Chris

You will find it makes a world of a difference. I did not buy a flatbox, as the price for them was high for what it is. I purchased one of them tracing tablets that has different light levels I can set. Works very well, and easy to use.

Reg Pratt:
I'll reuse flats if I'm shooting multiple nights in a row and don't move the image train. Otherwise, new flats every session with master dark and bias.

I wondered if this was ok to do, dust or other minor variations that I would not be able to account for lead me to do the exact opposite. I do Flats and Dark Flas for each image. 3 objects in a night each object gets its own set of flats.

Darks every 6 months. Flats about every 2-3 months. This is a permanently mounted setup and the FW to Camera connection seals very well.

With a previous set up the seal between the FW and the camera was poor and flats were needed nearly every night due to new dust on the chamber window. I only learned where the problem lie when I took the FW off the camera to sell it. The face plate between the two was just filthy with dust raining on the chamber window.

Do you take calibration subs for every session?

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