LRGB and calibration images

[stevewanstall]

NEw to using a monochrome camera plus filters. MY question is, should i take flats with each of the L, R G anf B filters? I guess yes but just want reassurance!

 

Thanks

[Laurin Dave]

As you expected the answer is yes - although if your system is clean then with LRGB you might get away with using just the Lum flat for all..  

[stevewanstall]

Thank you. I had a go with a 'blower' to shift the few dust specks that had somehow managed to get on the filters when screwing them into the wheel, so its not too bad. However, I shall do 'flas for all' from now on!

[Notty]

I’m in the same boat as you, still feeling my way, but having done a bit this week as well I really would advise you to do separate ones for each channel but most definitely for Red. The reason I say so is I used to flats aid tool in SGP to solve for the optimum exposure time to give roughly 20000adu and it generates quite different exposure times for each eg 3S for red, .88 for G , .5 for B and I can’t remember L but less than B I think. In other words by using just L you’ll be under exposing for the other 3 and they might not work so well. But as mentioned take this as advice from someone else new!

[stevewanstall]

Thank you. That looks like an explanation for the 'colour problem' I am having.  As I said, this is the first time I have tried using LRGB filters and  with my data, I am finding it very hard to produce an image with any colour in. When I use the same methods with other people data, the colour is there. So, as you suggest, I thin I need to look at how long the exposure are for the R, G and B lights. I dont have SGP (I use APT).  I wll have to see how I can find out the ADU readings and adjust my exposure times.

[Laurin Dave]

So long as the flats are exposed to 20-30000 ADU they'll be fine... the different exposure times required for LRG and B are due to the varying intensity of light across the spectrum from whatever flat panel you are using..  LED tracing panels for instance are very Blue so exposure times for Red and Green will be somewhat longer than for Blue and L..  

What camera scope combination are you using ?  are you sure that what you believe to be the Red/Green/Blue channel is through the Red/Green/Blue filter etc..  and do the R G and B stacks look different 

[stevewanstall]

My 'Flat panel' is a  white t shirt over the end of the scope pointing up at a clear blue sky ! 

Celestron 9.25 at F10 with ZWO ASI  1600mm and the ZWO filter whee/set. I have checked that the filter names and that they are being selected correctly. This afternoon I have finally got to grips with  processing the images to get some colour and, suing only uncalibrated LRGB (i.e. no flats, dark flats or darks, even on luminance), this is myfirst ever LRGB image (and bear in mind my rudimentary processing skills!): 

[Laurin Dave]

That's an excellent start well done...  In my experience Sky flats work best (although a nice evenly illuminated sky isn't always available when you need it)