Hi Andy,
I hope you have a go sometime. The arrangement for meteor spectroscopy couldn’t really be any simpler. I use an empty filter holder of the appropriate size (so the square transmission gratings fits into the circular aperture) secure it with the mounting ring (sometimes a piece of black card and some tape are needed to make up a holder to ensure a secure fit) then screw the the thing onto the lens.
There are some schools of thought about tilting the grating, since we’re using transmission gratings, to optimise performance in a given order. I don’t think its really worth the extra mechanical akwardness. Mind you I’ve yet to see any spectra from a tilted grating system to do a comparison with, so maybe it is…. Achieving good focus across as wide a range of wavelengths as possible is difficult (this is where tilting the grating might make a difference as well) It’s definitely a trade off between utility and absolute performance. Optical aberations, quality of lens design and the way it’s been corrected come into play as well. Is it worth tilting the grating and all that entails to do it only to have the quality dimished by lens limitations? Defocus in the near UV/Blue is rapid and dramatic in most CCTV lenses as they’re not really designed for astronomical spectroscopy! If they were they’d be made of fused silica/quartz and cost a LOT! (however such lenses are available if you REALLY want to get into it….)
Yes, I’ve been looking at ISIS as well. Some of the results Christian gets are simply remarkable. I had a look at his page recently and theres stuff about detecting startspots. Who’d have thought that amateurs would ever have the tools to do that!
You’re right about the learning curve but I think that’s a consequence of whats he’s trying to do, process a lot of stellar spectra in as automated and efficient a manner as possible. Like most things once you figure it out, it all seems quite straighforward 😉
Personally I think it’s rather wonderful he makes his software available for free!
Anyway, I’m preparing to set off to the International Meteor Conference in Austria and looking forward to it immensely….
cheers,
Bill.