RGB acquisition strategy - Forums

Topic starter

Sep 8, 2022

That's it, four years after (re) starting astrophotography with an EOS 6D and camera lens, I finally bought a dedicated mono camera (ASI2600)

What are the pros and cons of the various possible ways to spread the RGB acquisitions over night: all Rs then all Gs then all Bs, alternate RGB every other N images, Nxr, NxG, NxB & repeat? I suppose I should not be taking the Gs & Bs too close to the horizon. Maybe also there's an advantage in not doing each channel in one block to even out sky conditions?

I don't have many clear nights so although I'll try to image a target over several nights, I'd like to secure at least one complete RGB set per night, so I'm excluding taking one filter per night.

I'll typically be taking 2 minute long subs. I'm currently thinking of looping through 1 hour runs in each band. Any suggestion?

CS

Frédéric

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andrea tasselli

Frequent contributor

Sep 8, 2022

Not that makes much of a difference but I'd collect the RGB frames in the most clear nights with the worst seeing one colour band after another in one go.

Ron

Sep 8, 2022

I started by changing the filters after each shot - the idea being if I only managed a short period of time, I would have all the colors to make an image. In doing so, I relied on the filters being parfocal, which they really aren't even though they are "supposed" to be. But I did get a "full color" picture when I went out.

Once I got an electronic focuser is when I found that filters aren't as parfocal as claimed and I began automatically refocusing every hour. By refocusing each filter, I find that my data is now much better than it had been. Now I shoot at least an hour in one color before changing to another. If needed, I capture other colors on additional nights.

Now if I could just improve my processing . . .

Ron

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starfield

Sep 8, 2022

A lot for me depends on the weather and time window. I typically will shoot all my R, G, B and L in one shot. I often will try and arrange my sequence so I'm shooting my Lum when the target is the highest in the sky. Sometimes I will split my RGB up into smaller sets of 10 frames each, just to collect a mix of data at different altitudes and also use this if there's a chance of clouds rolling in. I avoid shooting single frames just because my normal focus routine is to run an autofocus on each filter change and that would add a lot of overhead.

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Andy Wray

Sep 8, 2022

That's a great question and has got me thinking:

Up until now I have done 60 frames of Lum and 20 frames of each RGB filter in a loop with autofocus on filter change. I might get two loops in an evening typically.

Having seen these posts, I will move from LRGB order to RGBL.

Frédéric Auchère

Topic starter

Sep 8, 2022

Ron:
I started by changing the filters after each shot - the idea being if I only managed a short period of time, I would have all the colors to make an image. In doing so, I relied on the filters being parfocal, which they really aren't even though they are "supposed" to be. But I did get a "full color" picture when I went out.

That's exactly why I want to do not too long blocks in each filter in case bad weather or technical issues creep in.

Ron:
Once I got an electronic focuser is when I found that filters aren't as parfocal as claimed and I began automatically refocusing every hour. By refocusing each filter, I find that my data is now much better than it had been. Now I shoot at least an hour in one color before changing to another. If needed, I capture other colors on additional nights.

I don't have a focuser yet, so I figured I'll refocus at each filter change, like you every hour.

Ron:
Now if I could just improve my processing . . .

Nice gallery

Frédéric Auchère

Topic starter

Sep 8, 2022

Sometimes I will split my RGB up into smaller sets of 10 frames each, just to collect a mix of data at different altitudes

I thought that could make a difference. Do you see one?

Sean van Drogen

Sep 8, 2022

Tend to collect 3:1:1:1 LRGB, invested some time in getting good filter offsets in my system. This way with NINA I tend to do the following loop.
15x 60s Lum
5x180s R
5x180S G
5x180s B
and let it run from asto dark to astro dawn
Similarly trying as @starfield get subs at different altitude levels. Have not tested what difference it makes if any but instinctively feels like the right approach.

CS Sean

starfield

Sep 8, 2022

Frédéric Auchère:
Sometimes I will split my RGB up into smaller sets of 10 frames each, just to collect a mix of data at different altitudes

I thought that could make a difference. Do you see one?

I do to the extent that subs collected closer to the horizon have stronger gradients. Normalization probably takes care of most of this so not sure if I've seen a big impact.

Karl Theberge

Sep 8, 2022

In NINA I use Dark Archon plugging to calculate the offset of each filter then you can run the channel one after the other without refocussing.

Also, just do a focus run every X RGB cycle or time. I personaly use HFR difference for my focus run so it only refocus if there is a need to do so.

Karl

Leonardo Landi

Sep 8, 2022

I usually shoot RGB in the same sequence in order to optimize my dithering. My rgb sequence is
5x40s G
5x40s R
5x40s B
Dither
Loop until nautical dawn.
You need a software like Nina to do so and an electronic focuser with filter offset.
Local normalization will benefit of the frames taken at higher altitude.
I shoot L on different nights with perfect conditions.

Frédéric Auchère

Topic starter

Sep 9, 2022 · Edited: Sep 9, 2022

Thank you all for the feedback! A motorized focuser is definitely on my Christmas list

Now the hard part: a clear night at my countryside site

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