How do you set up for NB flats?

I use a light panel for taking flat.
RGB flats are pretty straightforward, and the default settings work well
H is ok if I increase the default max exposure a bit.
O and S however I seem to struggle - quite often the process fails.
I think it has to do with the min / max setting but I have min at 1 and max at 50s and it still fails.
I suspect it is the light source?
How do you take your NB flats? What with and with what settings?

After lots of trials and errors, for my fast newt this works:
O 0.1s min, 10s max; S max = 50; and H max = 15.
It seems that my light source is very rich in O and very poor in S.
Is there a better panel to use?

Hello Henry … have you tried with the SkyFlat ?

When I use panels for flats, I set them to the maximum brightness for narrowband flats. Usually this is 255 on most panels.

If this does not work for you – you can take sky flats as Leo mentioned.

My experience with Sky Flats has been very positive. I have now used them for both LRGB and narrow band Ha, SII, OIII.

I did have to watch the first time and adjust a few parameters (primarily the allowed error%) but I’m getting very close to the mid histogram I want and they look fantastic. I did LRGB this morning and they completed just fine (i.e. before the sky got too bright).

It sounds like I should.
I managed to get a set of flat using my f/3 newt, but even at that speed it took 23 seconds to properly expose the S2, so I can’t imagine how long it will take for my slower f/7-8 scopes.
Do you need to put anything at the opening of the OTA for sky flat? Surely for RGB flats the exposure time would be very short.


For skyflat no … just use the right order for filters … for dawn first the more light gathering filters like luminance after narrow band, inverted for dusk.

I don’t put anything over the front of the scope at all when doing SkyFlats with Voyager. In my case I’m using Drag Script to kick them off. I have a wait command that waits until 30 minutes before Dawn. Then it kicks off the Flats Sequence.

As Leonardo says, order is important. The sky where you are pointing is somewhat blue so you want to get things like L first, then Blue, then Green, then Red. For narrowband you want OIII first, then Ha, then SII (depending on your bandpass values). Basically there is less Red in the sky so you want to get them last when the sky is brightest.

I have my Flats sequence set to go to Altitude 60, Azimuth 310. That points somewhat away from the Sun in the morning from here. The Altitude avoids a tree in that direction. The idea is you want to point away from where the sun is rising. Adjust those as needed.

Don’t change the coords if not needed or other advanced parameters … coming from a deep case study. Just choose setting are avalaible in the skyflat sequence configuration …

I will give it a go.

Do you find cloud a problem with sky flat? Where I live there is tendency for cloud or fog developing in the early morning after a clear night.

It hasn’t happened to me yet so I don’t know. My gut feeling is that it wouldn’t matter all that much unless the clouds are really patchy.

You also have the option of doing Sky Flats in the evening.

From my experience, you will probably want to watch the process the first time just to make sure nothing needs adjusting.

In my case, I found that there was trouble because of the tight criteria for whether ADU matched. I loosened it up a bit and then things worked great. As Leonardo says though, I would try it with the default parameters first and see if they work for you.