AAVSO/BAA Day 1: Chasing Rainbows (or Spectra)

One of the hardest things you can observationally do in astronomy is spectroscopy. You have to guide really well to keep the light on the slit. You have to calibrate the sensitivity across you chip (flat fielding like you do in imaging), the sensitivity as a function of wavelength (using a hot standard star as a continuum source), and how the wavelengths are spaced (diffracted) as a function of wavelength (this is done with a standard lamp). If any step is screwed up, you are hosed. For this reason many people consider spectroscopy far to hard for any but the profs.

They are wrong. Anyone with a penchant for details and a love of science can do spectroscopy with a telescope (12inch works, bigger is better). Currently I’m listening to a talk showing amatuer measurements of the Recurrent Novae RS Cyg (I think I got that right), Nova Cyg08 and other systems using a LHIRES III diffraction grating, and in the later case with a DSLR camera as a camera. They also have completely usable spectra of SN2004DJ (mag 12) and SN207AF (no mag given on overhead). It is very easy with these systems to be first one on field identifying the type of Nova and Supernova that has just gone off. It was even possible to see that yes, Var Cas 06 was a remarkably improbable microlensing event.

Beyond identifying things, they are also measuring the velocities of components in binary star systems (allowing masses to be measured). They are reproducing measurements within 3-8 km/s for objects with 219 km/s velocity differences.

Be Stars are also a prime target for these systems. To get a solid understanding of these annoyingly confusion objects, night after night of constant observations are required to sort out the complicated behaviors. No pro who doesn’t have a dedicated campus telescope is going to be able to get this type of time (I couldn’t do this work, for instance). An amateur, however, can partner with a pro, get all the data and collaborate on the analysis, allowing hard questions to be answered more readily. Not all of them are using the HIRISE grating mentioned above. All sorts of systems – some home built – are used across the field.

While spectroscopic work hasn’t taken off among amateurs in the US, there is a small and vibrant community of observers in England, France, and Germany. This is a brave new frontier of amateur equipment that is opening the last of the closed doors between what pros do with university equipment and what amateurs do in their backyards.

Interested in getting a spectroscope and trying a new type of science? Want some help? There are upcoming campaigns on WR140 (also see: this link, and on Eps Aur . Join in and the campaign teams will help you learn while giving your observations a scientific purpose.

If someone tells you that you need a PhD to observe anything from the ground. Smile and tell them they are wrong – the tech is coming and what can’t be done today (like high redshift studies), will probably be doable in some future tomorrow.


  1. Colin J April 11, 2008 at 2:06 pm #

    That’s very cool. I wish I knew more about spectra and data processing to be able to do this kind of project. I guess I better head back to class somewhere. Pam, do you know a good university? 🙂

  2. pamela April 11, 2008 at 4:55 pm #

    There are a lot of Uni’s, Colin! Email me and let’s chat 🙂

  3. Robin April 12, 2008 at 9:43 pm #

    Hi Pamela,

    I had quite few people ask me for more details after the presentation. If anyone wants to follow up the things I mentioned, the spectroscopy section of my website and the links there would give a starting point.


  4. Brian Roth June 8, 2008 at 9:39 pm #


    After years of visual and astrophotography, I am ready for a little science. I dabbled in some Variable star work (cataclysmics) using a simple Meade DSI pro camera but I have to say, I have always been interested in spectroscopy. Thank you for the links, I guess its time to get to work.

    BTW, been a fan since the Slacker Astronomy podcasts (still have my shirt too) Always wondered if you got the stargeezer mugs I sent.

    Take care,

Leave a Reply