SharpCap Forums

Hello All,

I am starting to play around with taking photographs using a monochrome camera with LRGB filters. My question is whether or not I should use the BRAIN in Sharpcap to measure the sky background brightness and suggested exposure values each time I change filters or just measure the sky background brightness once say using the L filter and use that one suggested exposure value for all of the other filters. Looking at the file generated by the Deep Sky Sequence Planner. it looks to me like the brightness measurement is done only once and the and the resulting exposure used for all filters. Is this the intended operation? I would have thought that different exposures should be used for each filter but perhaps I am mistaken. Any hints as to the proper way to go? Thanks.

Bill

Hi Bill,

yes, you should really make a measurement with each filter separately and then judge your exposures from those results - however, it's not really as simple as that...

* Do you want to take all filters at the same exposure (perhaps the longest recommended), or take them at different exposures? If different exposures then you may need to take more care stacking and take darks for each different exposure...
* Some targets may have very limited blue in the background (ie nebulae that are primarily red/green wavelengths) - in that case does it make sense to worry about optimizing the darker areas of the image in the blue channel?
* Pushing all filters to longer exposures because one filter is darker risks increasing the number of lost frames due to guiding problems/satellites/etc

I don't think there is a clear 'right' choice here that the sequence planner can take - too many options really, so I would expect most of them to require using the advanced sequence editor or some manual choices on exposure/gain. I guess there might be an advantage in letting you choose the filter or colour channel for the measurement in the sequence planner so that if you decided to go for the 'green filter' optimal settings you can specify that.

cheers,

Robin

Hi Robin,

Thank you for the insights. Very good to ponder over. I did learn something ... nothing is ever as simple as you might think.

Best, Bill