What We Can Do With A SA-200 Grating

This page gives examples of the capabilities of the Star Analyzer SA-200 grating we have mounted in the filter wheel for the Barber Observatory 20-inch Telescope.

See this link for a tutorial on how the spectra were extracted from these images and wavelength calibrated.

Notes on Our Setup

We like the SA-200 grating. The only issue we had with installing it was its size. Our filter wheel takes 50mm unmounted filters. The SA-200 is too small in diameter to mount directly. The manufacture sells a mounting kit that is effectively a polystyrene sheet you cut to your own filter wheel size. 

You can find polystyrene sheets and circular stencils in just about any craft store in the US so we declined to pay for the official mounting kit and instead built our own for roughly the same cost. However, when you do that be aware of the vertical clearance in your filter wheel assembly and don't make your DIY-mount too thick! We found that care, patience, and some good silicon adhesive were also necessary ingredients to get the grating mounted as we wanted it in our filter wheel.

Examples

300 second exposure on the Ring Nebula (M57). Most of the light comes out in the [O III] 500.7 nm and H-alpha lines so there are three separate images visible. The H-delta image is faintly visible below the [O III] image. The images below the zero order images are the symmetric first order images on the other side of the zero order image.

A 300 second exposure of planetary nebula NGC 6803.

A 120 second exposure of Be Star EE Cep.

A 300 second exposure of Seyfert Galaxy (AGN) PG 1351+64. Note the H-alpha emission line red shifted by 25,000 km/s due to the expansion of the universe.

A 600 second exposure of ASASSN-14dz in galaxy Mrk 842. When we ran this spectrum through the SNID supernova identification software it came back with a better than 80% match to an early Type Ia supernova. We were not yet confident in our method so we did not report it. But our classification was confirmed a day later by ATEL 6312. This serves as a proof of concept that filter wheel gratings can be used to do spectroscopic follow-up on extra-galactic transients.