Wednesday, July 18, 2012

What professional astronomers know about telescopes (often, not much!)

Professor Astronomy and the Kitt Peak telescopes.
Yours truly at Kitt Peak in 2002 (I think).
Most people assume that we astronomers know everything there is to know about telescopes.  After all, we use giant ones for much of our work!  So it shouldn't be surprising that one of the most common questions we get asked (after the black holes and aliens have been addressed) is something like: "I've been thinking about getting a telescope.  What should I get?"

Many of these people are then quite disappointed to find out that I cannot help them much.  Sure, I give them the standard (and excellent, IMHO) advice that they should avoid $49 specials at Walmart, start with binoculars and then, if still interested, progress to something like an Astroscan. (Full disclosure - I own an Astroscan and love it, but I don't get any compensation whatsoever to talk them up).

But if you ask me which is better: a Celestron NexStar or an Orion StarMax, and I will give you a blank star.  I have no clue.  Or if you ask me why your iOptron SmartStar Maksutov has this weird coma when you put a certain filter in but not with a different filter by the same manufacturer, and I'll only be able to blurt out the obvious "maybe there is something wrong with the filter?"

Most professional astronomers probably know less about telescopes and the nitty-gritty details about how they work than many amateur and semi-pro astronomers.  Certainly I understand optics, and I know the basics of telescope design and operation.  When I am observing, I can tell if something is wrong and have helped diagnose the problem through testing.  But if I'm using the Keck Telescope and determine that a metal plate in the spectrograph is blocking most of our image, I don't go out into the dome and start banging on things with a wrench.  In fact, I wouldn't even know where the metal plates in the spectrograph are.  I call the engineers who come and fix everything.
A picture of the sky with a metal plate blocking three-quarters of the view.
It doesn't take a rocket scientist to see that something is blocking this picture of the sky.  Fixing it is altogether different.  (Keck I Telescope, August 2001)
 There are exceptions to this ignorance.  For example, our planetarium director, Dr. Kent Montgomery, was building his own telescopes as a teenager.  He directed the construction of our A&M - Commerce observatory, and has overseen its operation since.  I would have struggled mightily with these tasks, but Dr. Montgomery and his staff have developed a nice system.

This week, Dr. Montgomery started a two week vacation.  We have two undergraduate students here as part of our Research Experience for Undergraduates program, and they are using our observatory almost nightly to study asteroids and extrasolar planets.  And weird things have started happening in their images - instead of nice round dots for stars, sometimes they are little trails.  That's not supposed to happen.

So, Monday night I went with our assistant planetarium director, her staff, and the students to troubleshoot.  We checked wire connections, telescope balance, camera connections, and everything we could think of.  Yet at certain parts of the sky, the images were still wonky (a scientific term).  I ran some tests that convinced me the problem was mechanical - something in our telescope was moving when it shouldn't - and I was even able to narrow it down to a list of three most likely things: the mirror was moving (but it seemed tight), our guide telescope was moving (but it seemed tight, too), or our camera was bending slightly (it seemed tight, but this was my personal guess).  But at this point, I didn't know what to do.

Since our summer students are here only 10 weeks, I didn't want to wait for Dr. Montgomery to return to fix the telescope, but I don't trust myself to go mucking about in the telescope's guts.  A quick Google search did not help, and my schedule doesn't have a lot of time for deep searches on Internet forums.

So I put out a call for help.  Rather than contacting my colleagues at other PhD institutions (most of whom would not know any better than I, and those with the requisite knowledge are busy working on 2 to 30 meter telescopes and probably not likely to know much about modern 0.4-meter commercial telescopes), I emailed some contacts at the AAVSO and at the Central Texas Astronomical Society.  Within a couple of hours, I had a very detailed and extraordinarily diagnosis and likely resolution from an expert citizen scientist named Tom Krajci.  I still don't trust myself with the repairs, but at least we know what is going on and have some ideas how to minimize the problem until Dr. Montgomery returns.

I am very grateful to Tom and Mike Simonsen at the AAVSO as well as Brad, Willie, and Dean at the Central Texas Astronomical Society for their help, quick responses, and kindness not to roll their eyes when a bumbling novice like me comes along with a question.

Now, hopefully, you see why I can't give you detailed answers to your questions on commercial telescopes.  If you need help, your best bet is to find a nearby amateur astronomy club and ask - you'll get a better and more accurate answer than I would be able to help you with!  Now if you ever need help diagnosing problems with your 10 meter telescope, I may be able to help...


  1. Yup. Same with me! And I operate an 8 meter telescope (Gemini north). Hat's off to the volunteers and staff at visitor's centers who make small telescopes available to the public nightly and weekly.

  2. Thanks for the info. I have always wanted to invest on some kind of telescope. I am no professional when it comes to these things and would just want to get a telescope to look at the stars freely. I always thought that when buying a telescope you would need to take into consideration many different specifications but now, thinking that I am just going to use them for recreational purposes, I’ll probably just go for the most affordable one.

  3. Which telescope should I get? :p

  4. Hi. I have the proof of why Einsteins theory of relativity is wrong. I have written a long theory about the infinity reaction chain. If you do not understand it then its fine to ignore but if you do understand it. Help to spread;

    Kindly Regards / Martin (do not reply)