Long Exposures

Forums Spectroscopy Spectra of chi Cygni near minimum 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.