Long Exposures

Andy Wilson

Hi Bill,

They were actually not that long compared to some deep sky imagers. The 27th April spectrum was from a 1 hour exposure, made up of 6 x 10 minutes. For some targets I’ve gone out to 2 hours and I would have liked to have done that or more for chi Cyg but there is a limit to how late I can stay up until with work the next day.

I suspect chi Cyg is a little easier than some mag 13 stars, as that is a V filter magnitude. It is a very red star, and even more red at minumum, so there will be more light around H-alpha which is in the red part of the spectrum. Also, whenever there is an H-alpha emission line, then it is easier to get a good signal on a faint star, as a lot of light is concentrated in a narrow emission line.