AM Tuesday September 23, 2014 - Observing Notes Part 2

  I had very clear skies overhead when I pulled into the driveway around 3:00 in the morning after getting home from work, and by 4:00 AM I had the 10" f/4 telescope set up out on the patio with the dew cap on, plugged in, and ready to go. This was the first time I'd had it out in months, and the first time I'd used it for variable star observing in a year.

  Skies remained crystal clear throughout the session, and there was no moonlight interference since New Moon was only a day away. I figured my naked eye limit was about 5.1 magnitude while the telescope limit was maybe 13.1 magnitude or better. The temperature while I observed was 50°F; chilly enough that I had a sweatshirt on. The dew point was 44°F and the humidity was 80%. The wind was light and from the north at 3 mph and the pressure was high at 30.29".

  There was a lot of dew on the cap and the metal telescope tube by the time I was done. A few chilly-sounding crickets were chirping, and the only other noises were the usual rumble of traffic on I-65 a mile away (which picked up in intensity as morning rush hour kicked in), and a few neighborhood dogs barking. After 4:30 AM the usual steady procession of low-flying jet aircraft started roaring low over the neighborhood from west to east. These were mainly FedEx planes outbound from the Indianapolis International Airport.

  I was outside between 4:10 AM - 5:40 AM (8:10 - 9:40 UT September 23). My main goal was to take some long first looks at SAO 58521 (see the first part of tonight's entry) so I started with the telescope pointed at Beta Tauri and star-hopped to the cluster M-37 in Auriga from it. This was my first look at this cluster in my 10" scope ever (I'm not much of a deep sky observer!) and I'd have to call the view stunning! Under 78x power the cluster filled my whole field of view. It looked like lots of brighter stars against a background of glittering diamond dust! Interestingly, the star cluster sometimes seemed to be "rippling" faintly, and I think this was due to poor Seeing conditions (lots of turbulence in the atmosphere).

  It was fairly easy to pick out the star SAO 58521, since it was the brightest star near the center of the cluster and had a reddish tint. I also found the comparison stars labeled as 9.9 and 10.2 on the chart. Since this was my first observing session with this star I decided to just try to get impressions instead of trying to make actual magnitude estimates. I first used 102x power and concentrated on the brightness of SAO 58521 compared to these two chart stars. I tried to stay as unbiased as possible; treating each look through the eyepiece as a new estimate. Here were the notes I made when looking at it under 102x:

  4:39 AM (8:39 UT) - SAO 58521 slightly brighter than 9.9.
  4:41 AM (8:41 UT) - SAO 58521 slightly brighter than 9.9.
  4:44 AM (8:44 UT) - SAO 58521 between 9.9 and 10.2?

  I decided to change eyepieces after this and take a look at SAO 58521 along with the 9.9 and 10.2 stars using 203x power. This cut the field of view down to just ten arc minutes or so and made the small brightness differences in the stars easier to see. I also tried the old trick of bringing the field slightly out of focus so that the stars looked like small circles of light instead of points. This always helped to exaggerate brightness differences and make variables easier to estimate. Since SAO 58521 is a red giant star and at least one of the comparison stars looked whiter in color, I tried to not look directly at any of the starts to avoid the Purkinje Effect. Here were the notes I made while gazing at it off and on using 203x power, again trying my best to remain unbiased from one look to another:

  4:47 AM (8:47 UT) - SAO 58521 definitely brighter than 9.9.
  4:48 AM (8:48 UT) - SAO 58521 definitely brighter than 9.9.
  4:50 AM (8:50 UT) - SAO 58521 definitely brighter than 9.9.
  4:52 AM (8:52 UT) - SAO 58521 same as 9.9? Not definitely brighter this time.
  4:55 AM (8:55 UT) - SAO 58521 definitely brighter than 9.9.
  4:57 AM (8:57 UT) - SAO 58521 definitely brighter than 9.9.
  4:59 AM (8:59 UT) - SAO 58521 much brighter than 9.9.
  5:02 AM (9:02 UT) - SAO 58521 much brighter than 9.9.
  5:04 AM (9:04 UT) - SAO 58521 much brighter than 9.9.
  5:06 AM (9:06 UT) - SAO 58521 equal to or dimmer than 9.9?
  5:08 AM (9:08 UT) - SAO 58521 definitely brighter than 9.9.
  5:13 AM (9:13 UT) - SAO 58521 definitely brighter than 9.9.

  Though it seemed possible that SAO 58521 was varying in brightness as I watched, and might be changing rapidly, I don't think these observations are really conclusive. As I mentioned, the Seeing seemed poor tonight. Also, though I tried to stay unbiased and tried to not expect to see any changes like those described by Wilson, I have to admit that this was a lot easier said than done! Another issue was that while SAO 58521 lies right near the center of the star cluster and is viewed against a bright background, the two comparison stars that I used are off to the side of that cluster and viewed against a dark background. This leads to it being tougher than I thought to make estimates. Still, this was just a "first look" for me. The next time I do this I'll try to make actual estimates of the magnitude of this star every few minutes to see if it actually "behaves erratically."

  I did end up pointing the telescope to the southwest part of Orion before calling it a night, to make an estimate of my favorite YSO (Young Stellar Object). This estimate was worth reporting to the AAVSO:

  5:23 AM (9:23 UT Sept. 23) - I estimated UX Orionis as 9.6 magnitude. I used the 9.5 and 9.8 comparison stars on Chart 12584ZJ (D scale). I used 39x. UX Ori seemed between these two stars but closer to the 9.5 star, and in fact was just barely dimmer than (almost equal to) 9.5. I'm sure this estimate was within +/- 0.1 magnitude in error.