Chuck asked:

Kurt, what's the ruling on the Rainbow optics grating? I have a number of ruled gratings; perhaps one or more might be suitable for a home-brewed spectroscope.

It is a 200 lp mm blazed grizm. That's not alot by today's standards. The spectroscopy newsgroups told me that in practice you can get 40 to 60 angstrom low precision slitless spectrographs of stars with it. The blazing is nice for inline transmission gratings since it keeps the specturm traveling about 5-10 degrees down the optical center, instead of the 30-40 degs for unblazed standard gratings. In December, I ordered some parts with the idea of using the grating to make an alternative slit tranmission grating spectrograph, so I could use the grating on extended objects like the Sun, comets and clusters. I have a Surplus Shed D1570 adjustable slit and some tubing. Then I set the project aside for other things. Last night's post inspired me to order a couple of aco lens from Surplus Shed - the last parts that I needed. A reflection grating is beyond my construction skills. - Kurt