spectro-aras.com

Tonight I am trying to get a better SNR on AZ Cas at wavelegths <4000A. (LHIRES with 600 grating) Everything runs out at the left edge of the field. (camera response, grating efficiency, focus) so it takes about 3-4 hours to get 50 SNR. (This is a single 20min exposure) There is also an internal reflection from somewhere at the right edge but fortunately it is the left half of the spectrum which is important.

Cheers
Robin

You do like to test yourself Richard, well done on getting this far. One thought that might help. Given that the LHIRES III just has a doublet it might be worth refocusing it on the slit using a violet light (a violet colour filter would do) but then again it would be off for H alpha etc.

Regards Andrew