I found myself with a bit of free time over the last few days and used it to catch up on several of the AAVSO’s recent webinars. I really enjoyed the ones on spectroscopy. I actually had no idea the AAVSO had a spectroscopy section until I saw those webinars. This looks like a fascinating branch of astronomy to explore.
But, I want to ask the straightforward question. I cannot afford a slit spectrograph. I can afford a Star Analyzer 100. It is unclear to me if data from a SA100 are appropriate for the AVSpec database.
Are spectra obtained though the very low resolution SA100 useful to the AAVSO? Are there enough appropriate targets for a systematic observing program? Or would my efforts be akin to me measuring the rate of growth of the grass in my backyard….science, yes, but no botanist would care. :)
(For context, my rig would be a C9.25 coupled with a ZWO ASI290MC, a color camera with a relatively small sensor meant for planetary imaging. I did a lot of DSLR/CCD imaging about 15 years ago, so I have some experience in the image acquisition realm.)
--Michael in Houston (RMW)
Pardon the late…
Michael,
Pardon the late response, there is not much activity on this forum, and I just found your post. I, too, am a newbie to spectroscopy. I have learned much playing with an SA100 grating and a few prisms over the last year.
In answer to your question, you can do a lot with a slitless grating setup. The major emission and absorption lines of various star types is easy to document. And, the approximate temperature of the photosphere can often be determined. Capturing and learning the basics of this special type of imaging and data reduction takes some practice. But, once you have a working routine and figure out the submission requirements, your data will be posted on AVSpec with thousands of others. The SA100 or SA200 provide a wide band, visual spectrum of the targets. These targets are variable over time, so it is the statistical change that is of interest. Amateur spectroscopy is not yet as popular as photometry or any type of astro imaging. There are less than 60 contributing members on the AVspec forum, so your entries actually matter.
There are many software packages, but the easiest way to get started is with the RSpec. They have a bunch of teaching videos to introduce many concepts. The SCT is perfect for this stuff. I use a Celestron C6 with f/6.3 reducer, and various cameras, both color and mono. Color is great for showing people the spectrum, outreach style. Mono is better for capturing and quality data reduction, but that is not a rule. More aperture allows for shorter subs and dimmer targets. With the C6 I have had no lack of targets, and subs short enough to not use guiding.
You might want to set up a guide or finder camera to run plate solving, since our targets are often in a busy field of stars, that are hard to distinguish. And you can't plate solve the spectral image. The slit spectrographs use an OAG unique to their setup for this purpose.
Hope this helps a bit.
Dave Decker
Most astrometry programs eg astrometry.net will happily plate solve images taken with a slitless grating, identifying the zero orders and ignoring the spectra
Robin
All current commercial astronomical slit spectrographs for the amateur use on axis guiding showing the target and the surrounding field, mostly using a slit in a mirror (though one uses a beam splitter)
Cheers
Robin