How do you capture your RGB subs?

Hi Michael, I'm pretty much a noob on this myself but will be interested to hear from this thread what others do…I hadn't really thought of the gradient issue.

I use NINA as well and what I do may be a bit of a compomise between doing each filter for a single block or cycling R,G,B (or in my case Ha, OIII, SII).

What I do is blocks of between an hour and two hours per filter (typically 300s subs) depending on sky time with most targets over 2 to 4 nights. I use the filter change to trigger re-focus in this approach as well which also helps keep up with temperature focus fluctuations. For full night imaging this usually means two blocks of images from each filter per night.

I feel this gives a good balance, and if I can only get a single night I have enough of each filter to get an image done up and maybe give me a clue whether I need to run more on one or other filter in subsequent nights.

No doubt there'll be better more technically rational approaches but this is mine :-)

Good to hear it's not just me with these questions! Thanks for sharing your approaches, i tend to shoot a couple of hours of each filter too but was reading some other techniques which peaked my interest. 

While i love astrophotography because nothing is ever straight forward and everything is a challnge, it's also a curse at the same time!

I've found it best to focus on filter changes, so I prefer to shoot in groups, otherwise you'd add a ton of focus time to the whole shoot losing possible exposure time.

Hi,

I recommend shooting each filter in a row. You will also make the experience that you might need to shoot over several nights to capture all the data.
Furthermore, you also don't have to shoot RGB in that very sequence. Depending on the situation, it could be worth a try to change the sequence (shoot B first then G and then R):
Case 1: target starts low in the sky, shoot B and G as this filters (city) light pollution which is strongest at low altitudes. Shoot the R when the traget is high.
Case 2: bright moon rising. When the moon is still below horizon, shoot B and G first. Moonlight behaves like sunlight and when the moon rises the light is scattered in the atmosphere, giving it its blue color. If you have capture B and G the effect is a bit less. Of course, angular distance to the moon matters a lot.
Case 3: Here, when it's summer, nights become pretty short. If a target is high but I haven't achieved astronomical darkness yet, I shoot the R. While the horizon still glows in faint red, the sky above mostly sends the blue light that is scattered. Hence, the R is filtering out most of the sunlight. When it's finally dark, I take the B and G filters.

I haven't discussed this with many other photographers but I've seen (or at least believe it) a difference in the subs.

Björn

In my experience : gradients are to be managed on a per master basis, so there is no obvious reason to shoot your subs sequentially. If you want a very nice image at the end, you will need to spend some time tweaking it in Pixinsight or Photoshop removing the gradient carefully anyway on each channel.

What would drive my choice is « flats » : if you are asking yourself what is best between shooting your filters by group or sequentially to get the best image or less troubles during post processing, just think about what would happen if there is a slight shift in your filter wheel each time it turns… dust (static dust, not the one that moves during the night) wouldn’t be at the same place on each of your subs of the same filter, and when you take your flats at the end of the night, they won’t correct every subs.

That happended to me the first time I tried to shoot sequentially (you have that option on the Asiair Pro : just a button and it execute your plan sequentially instead of grouping each subs per filter). I know that defeats the purpose of having a filter wheel, at least a « cheap » one, but I lost a night due to that problem… (well, I cheated by offseting the flat in Photoshop, but the results are not very good when eyeballing the alignement of dust donuts….

So if you go that way, maybe clean your filters well before the night (vignetting is less sensible to that if your sensor is small compared to filters).

Now what I do is at most 2 filters per night when going fully automated : I take the flats of the first filter before triggering the session, and takes the flats of the second filter in the morning. If I need to do more filters in the night, well, I wake up and take flats before turning the wheel :-)

And of course, you can always try to automatize taking the flats (flat panel on the side of the telescope and your mount automatically aim it before coming back to the target)

Or you buy a nice filter wheel…

Some really interesting thoughts from everyone , thanks for sharing. I currently don't have an AF (on my long list of buys) and probably won't be investing in one soon given i just bought a new cooled cam & filters so sounds like continuing to shoot in groups is my best bet. My post processing skills are average and i'm trialing using Gradient Xterminator to manage my gradients (i'm in bortle 5 but have a large light pollution glow to the north from a large town). 

Ruediger
I combine for my "one-Night-Projects" horizontal and vertical plans. That is a combination of shooting one filter all subs then move to next and shooting one sub per filter and loop that. By combining the the 2 approaches I equalize seeing effects during the night and also ensure that I have data from each filter in case clouds roll in and I loose some hours.

Please find below an example of a sequence. The clue is the loop condition for the imaging block. If you have question feel free to ask.

This is also super helpful, i don't use the nightly builds just the stable release version so didn't realise there was a loop condition option 

Björn Arnold:
Hi,

I recommend shooting each filter in a row. You will also make the experience that you might need to shoot over several nights to capture all the data.
Furthermore, you also don't have to shoot RGB in that very sequence. Depending on the situation, it could be worth a try to change the sequence (shoot B first then G and then R):

Björn

Also a very good point i haven't considered, i always just ran RGB (then L) in that order without considering where the target is and the conditions of the sky. 

I've obviously still got a million and one things to learn