I am thinking of getting started in spectroscopy and the more I learn, the more interesting it is becoming. (Also really enjoyed Conrad’s presentation last night.)
I have a little bit of an imaging background (I was really into DSLR stuff in the mid 2000s) and I have kept most of my equipment, including some refractors, an SCT, and an iEQ45M. I don’t have a guider and most critically, I sold all of my cameras (oops).
The one question I really have is if I am careful and really work on obtaining high-quality data, how far can I go with an SA100 as far as producing data that are appropriate for AVSpec? (And is there a minimum threshold; that is, can the basic SA100 + modest ZWO camera + apo refractor setup produce useful/meaningful data, or is the resolution just too small?)
(Again, I am quite new to this, but in Conrad’s presentation it seems he used an SA100 for several years before making the jump to high-res. That seemed promising to me.)
Here is the best advice I can give to some who wants to get started.
A SA100 + modest ZWO camera + apo refractor is the best way to get
started.
Start with the converging beam setup. It’s the easiest.
Buy RSpec for processing your spectra. It has excellent tutorial videos and
is very easy to use.
Buy a monochrome camera. I’ve used ASI 174MM for years and love it.
When imaging, start with bright B, A, and F class stars. Finding the Balmer
lines will be easy for a beginner. You will learn lots. You’ll K and M class
stars much harder.
When you’re ready to move up in resolution, you can some spacers between the camera and the SA100.
Please post any questions. I’ll be glad to answer them.
Thank you so much for replying! That is good to know I am basically on the right track. I’ll keep my eyes out for a used mono ZWO camera (I am sure people are upgrading their cameras this Christmas).
My available scopes are a 388 mm f/5.9 apo, 900 mm f/10 apo, and a C9.25. It seems of those three, the 388 mm would be the one to start out with…and no surprise it was my primarily imaging scope twenty years ago.
Hi Michael. Your expectations are quite attainabbe. I’ve successfully submitted several spectra to AvSpec myself, using a DSLR and camera lens. I then upgraded to an 8" SCT but kept the camera. All job done with SA-100.
I’m in the same situation as you and have found the Groups.Io AstronomicalSpectroscopy also quite supportive and useful. They also have other sub groups for specific instruments, particularily the DIY kits out there from solar and stellar. Here’s a link astronomicalspectroscopy@groups.io | Topics
The file TransSpec : Log In gives you a good overview of what you can achieve with your setup. Quick run through the data you provided (388 fl, f 5.9) shows that with just the SA100 you would get a Resolving power of about R=159, accurate to about 4 nm. Plenty good for resolving a Be Haplpha line, Balmer lines in O,A,B stars, methane bands on Neptune and Wolf Rayet, P Cygni stars. Adding a 3.8 Prim (turns it into a GRISM) bumps it up to R=222 - your scope is still fast enough to create some resolution limiting spectral coma error that limits your resolution just a bit.
I do recommend finding a way to have your rig guided, it will open the door for much fainter targets (through stacking images, while remaining linear: lower exposure time of the individual frames). I could get to 12 Vmag with a 51mm aperture (f4.9) refractor and stacking an hours of 30 second exposures using Siril (see link to my youtube, or HAS talk).
After the grism, the resolution is limited by seeing conditions and Vmag somewhat by light pollution and the other stars in the field (but you will be amazed how well it holds up). If you go for the StarEX slit spectoscopes @Charles_Moher suggested, you will be able to get much better signal even with poor seeing and high light pollution (we saw examples of Paris downtown). These are open source kits that you can print and assemble yourself - an incredible value with modest complexity.
A great, and very user friendly, alternative to RSpec is Bass Project - many here started using it. Hopefully future AAVSO Spec sessions will be recorded so you can see a couple of walk throughs. I posted one on Youtube half a year ago.
Camera wise - be on the look for ASI533MM, avoid the ones with amp glow most of the astrophotographers offer for cheap today - it simplifies calibration a bit. New cameras also have a much higher quantum efficiency. A new contender is the QHY 585MM, currently only uncooled its a smaller sensor, but a fantastic dynamic range, high QE and low read noise - its just as wide as the ASI533MM but half the price.
In any case, starting with a SA100 will get you to see stars different than ever before - with data that is well suited for some of the AAVSO campaigns in the AAVSO Spec SIG.
As far as the DIY options for amateur astro-Spec , Ken Harrison, esteemed author on the subject and a fellow by the name of Minh have come up with a much more rigid setup CNC machined out of aluminum and blackened, I believe, with anodizing. This is quite a new thing, this year. There were many of us expressing concerns about 3D printed versions of the StarEx for amateurs and certainly just looking at the propensity for many of the plastics to absorb water, get nasty hot in the sun and deform, they were candidates for material refinements. Their thermal rate of expansion alone is really bad. It lead many to suggest that someone needs to make these out of aluminum. Ken and Minh stepped up to the challenge and are now selling these at about $250 USD a pop, as I recall. I do have Ken’s email, but he is a regular on those IO groups I mentioned and you can get in touch with Minh there also. You should find a link on the group for Minh’s aluminum chassis. Paul Gerlach also made a 3D printed “Lowspec” model and freely offers the gcode files, I think, on Thingiverse.
Unfortunately, some of the pricier cmponents of these projects are the slit , mirrors and lenses. I’m trying to make a kit myself, of my own design, using some cheaper lenses, but am far from having a complete instrument yet.
Ken invented a Slit Wheel with assorted slits and dot aperatures on what looks like a 1/3 sized cd like disk. That was for Pauls LowSpec, I believe, but they’re a real hassle to obtain from Ovio as that company is difficult to order from. They are based in France and language is not their strong suit. Ordering is frustrating. Ken had contracted their fabrication with them, but I suspect regrets it.
You can get individual slit blocks for the StarEx and Solex , a helioscope, I think, from Shelyak. Shelyak sells the optical kits for these and has a host of other products including pricier complete instruments. Here is their website : Sol’Ex & Star’EX: a new way to approach astronomy | Shelyak Instruments
Be sure to get on those IO Groups as it’s where all the leaders and innovators hang out. Christien Buil is considered to be kind of the GodFather of the home brew Amateur Spectroscopy instruments. Here’s his website : http://www.astrosurf.com/solex/sol-ex-stars-en.html. Most of the activity is based in France.