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I think that if the camera is vignetting, then in effect you're not using light from the full width of the grating, so you lose resolution.

I don't know for sure, but I've just looked at the UVEX website, and the optical diagram shows that the first mirror is not fully illuminated by the beam from the slit, so presumably it's effectively working at something like f/6 or 8. It also shows that the second mirror is​ fully illuminated, so p...

Just to add briefly to the discussion on classification, Gray and Corbally is the current standard text on classification, though it tends to have a lot of focus on detailed analysis of lines in the blue (reflecting where classification studies have traditionally come from), which isn't always the m...

We used it for some of the blended line fits. The person I am working with had previously used IRAF for this, but once I introduced him to VSpec he decided that it was easier to use for some things.

Radial velocity measurements on a close binary system with young stars, with spectroscopic observations mostly from a professional observatory but supplemented with some data from my Lhires (when we didn't quite get the curve coverage we needed from our time allocation on the big telescope). This pr...

I have watched the Nova Per workshop clips on Youtube, and wanted to say thankyou to Francois T and Shelyak for presenting these really interesting sessions. I found them fascinating. I'm looking forward to the Python sessions in February.

Most interesting, thankyou Christian, as always! I think this confirms my view that a fast newtonian has a lot to recommend it. The AAVSO workshop has some really fascinating presentations, but the time of day is terrible for this side of the world (this isn't a complaint - I know you can't accommod...

Most interesting,

Dear Christian - these are all very interesting developments indeed. I look forward, yet again, to the results of your astonishing work! I had been wondering whether there was any point in using a simple image slicer, like the CAOS one, to try and squeeze some additional resolution out of an eShel. ...

Out of interest, the standard focal ratio advertised for the eShel guiding module is 6. But how low can you realistically go with this instrument? Is it possible to go down to f/4?