Is there enough uncertainty out there for visual?
Posted 21 November 2012 - 12:42 PM
I am curious about observing variable stars. A while back while sweeping through the Milky Way in Cassiopeia, I happened to stumble upon this dark red star. Most stars upon first glance appear white to me, so this star looked like a small ruby in a sea of diamonds.
I did some research and discovered that this star, WZ Cas, is a carbon star and that carbon stars are variable stars. Moreover, I’ve learned that carbon stars can be quite challenging to do visual magnitude estimates on due to their deep red color and the purkinje effect.
I’ve always been curious about variable star and the AAVSO. Many observers, such as David Levy, are active observers and seem to really, really enjoy it.
I already know that one of the aspects of variable star observing I would really enjoy: the star hopping. I love finding those needles in haystacks.
Reading about variable stars, periodic variables have not captured my interest. It seems to me that such stars like Cepheids and Miras are well understood and the periodicity of their variability is well established. Please correct me if I am wrong on this.
The stars that seem to interest me are the unpredictable ones, the irregulars, if you will. Observing a star that might brighten or dim unpredictably is fascinating to me. Here, this seems much more fun that recording observations of a star that has had the same light curve for centuries. (Of course, I can clearly see how starting off with Cepheids or Miras is great practice due to their known and predictability.)
So my question is this: are there enough irregular or otherwise unpredictable stars within the range of a small refractor to form a decent visual observing program?
Posted 21 November 2012 - 08:24 PM
Visual estimates are valuable because many variables reach magnitudes that are too bright for CCD observation. Its not the CCD, its the fact that comparison stars may not be in the same FOV and most amateurs do differential rather than all-sky photometry. So during the minimums CCD rules while when they are bright visual rules. DSLRs with wide fields or CCDs using lenses are exceptions but you do have to worry about scintillation effects. There is room for all. Naturally you need training and practice and the Miras are perfect training stars. BTW, Miras can change their periods, so continuing observations are scientifically valuable.
Posted 21 November 2012 - 10:12 PM
Thanks for replying. I never thought of the small FOV of the CCD as being as issue, but it makes perfect sense.
I've picked two stars to estimate to see if I stick with this: Delta Cephei and Beta Persei. They seem to have short enough periods that I should be able to match up my observations with a light curve to see how far off I am from others' estimates.
Posted 21 November 2012 - 10:44 PM
Clear skies and good measures,
Posted 22 November 2012 - 01:16 AM
You can find a program for these stars at the cv section of the AAVSO.
Posted 22 November 2012 - 07:32 AM
Miras are well understood but there max and min can vary during each cycle. You can have a nice variable star program with binoculars.
I also enjoy semiregulars and irregulars.
Posted 22 November 2012 - 02:40 PM
I don't know if this will work for you, but here is how I started.
I learned how to use the AAVSO nightly planner. I looked at Miras to begin with and those with recent observations.
I learned how to look up the recent observations.
I then picked some stars within my magnitude range so that I could compare my results with both the recent observations and the trend. I then downloaded the appropriate AAVSO finder charts and tried my hand at estimating magnitude.
That way I could build confidence that my observations were in line with more experienced observers. I did not worry about particular stars at first, only whether my results were similar to reported results.
Once I gained some confidence I felt I could branch out.
Posted 24 November 2012 - 07:29 AM
Granted, there are a lot of Mira's and other predictable stars, but also some interesting one's too. Some would certainly suit your refractor.
Also, you could consider looking for a nova, or indeed revisit older novae of the pat that just may blow again. There are a lot of details here:
I hoe that this helps.
Posted 24 November 2012 - 12:16 PM
Ed - I going to use your suggestion to help me pick stars for which I can easily compare my estimates with others afterwards. This estimating is more challenging that it initially seems. David Levy in his variable star book has an exercise in which you take the stars of a constellation or asterism and sort them according to brightness. This is not as easy as it seems for stars that are relatively close in brightness.
Keith - yes, I stumbled upon the binocular program last night and this seems great. Here are stars that are relatively easy to find in an instrument that I can easily take out often. In fact, I'm considering using my binoculars more often as dealing with mirror-reversed charts drives me crazy.
Posted 24 November 2012 - 11:29 PM
Posted 14 December 2012 - 06:44 PM
Posted 18 December 2012 - 02:16 AM
There is a chronic shortage of observers and many variable stars are simply neglected and could have had major changes in their light curve that have gone completely undetected.
Most importantly you need to find the type of variable star you enjoy observing. Especially if that motivates you to get out and use your equipment. Any variable star observation is better than none
Posted 18 December 2012 - 09:11 AM
One thing that helps is that I've become very honest with my observing time and observing habits. The instrument with which I'm able to get out and observe with any frequency are my 7x50 binoculars. I've been doing some careful measurements with the Pleadies near the meridian and have determined that my limiting magnitude with that instrument is about 7 to 7.5. Not much, but one works with what one has.
So, I'm really starting to look at the AAVSO's binocular program. And, of course, as a tripod helps (is required for?) for accurate magnitude measurements, stepping up to a set of binoculars with a greater light grasp is a possibility.
Posted 18 December 2012 - 11:39 AM