Starting LRGB Imaging

[clive200550]

Hi all I have just bought a starlight Xpress CCD camera and a set of LRGB filters. Being new to LRGB imaging do I need to compensate and give less exposure for the L filter than for the RGB filters. Also do I need to take darks, bias and flats with each filter.

I have also bought a H alpha filter can I use it with a Herschel prism I have to show more solar graining and prominences.

Any help will be gratefully recieved

[MikeD]

Hi

 Do I need to compensate and give less exposure for the L filter than for the RGB filters.

The L filter is where you want to spent as much time as possible, Shoot as long an exposure as your sky conditions will allow ( a light pollution  filter way be of use here) and as many as you can I usually aim for around 50 sub exposures @ 600 seconds.

RGB you can take shorter exposures than the L and less of them,  try not to saturate the brightest stars in the image, I personally set the relative  RGB exposure lengths  buy using G2V calibration See here.

 Do I need to take darks, bias and flats with each filter.

You will need to take Flats for all filters but you can usually get away with using one set of  scaled Darks (same length as the L data).

One set of Bias frames  is all you will need.

I have also bought a H alpha filter can I use it with a Herschel prism I have to show more solar graining and prominenc

Unfortunately not but a Ha filter while shooting in White light can sometimes help with the seeing but  I would recommend using the red filter for this.

Hope that helps and enjoy.

Mike.

[ollypenrice]

Good advice from Mike. The only thing I'd add is that, if you shoot equal amounts in each filter including luminance, you may find it easier to process at first. With more experience it's possible to shoot considerably more luminance than colour but adding strong L to weaker RGB requires a few additional processing techniques to boost the colour saturation and provide enough colour to 'fill' the deep luminance.

I have also found, heretically, that my L flats will flatten all my filters happily enough but I doubt that this will apply to all setups. I think it just happens that I have no dust on my filters and that, on my rigs, I'm not using filters which are very close to the chip, making filter bunnies diffuse anyway. If in doubt, do it properly!  

Olly