Tuesday, 6 September 2011

26.8.2011 - Stargazing in Death Valley

Date: 26./27.8.2011
Observing location: Mosaic Canyon, Death Valley, California, USA (285 meters / 935 feet)
NE Lim.mag: 7.7m (zenith)
SQM-L: 21.72 (zenith)
Background sky: 9 (excellent)
Seeing: 8 (excellent)
Transparency: 8 (excellent)
Weather: +39.1 - 32.2°C, humidity <10%, a breath of wind from the north, thunderstorm in the SE.

Sagittarius above Death Valley, CA
Being a hardened veteran of Anza-Borrego as well as Palm Springs I knew what was ahead when the sun set behind the mountains. Earlier in the evening, the temperature had reached +48°C (118°F) down in Badwater. For our hotel that promotes astronomy by "renting binoculars for stargazing" they sure had a funny way of showing the love. About a mile to every direction of Stovepipe Wells, the glaring lights of the "town" will blind any starting star watcher (or more experienced) for sure. There was little more to do than escape this mini Las Vegas for a darker place near by; Mosaic Canyon.

Two brightest parts of NGC 6559 complex
It would be a shame to say when observing from a site with no visible light pollution I would start by sketching open clusters and I was well aware of this fact. So, I started with NGC 6559, M20 and NGC 6526 from the Uranometria's (Volume 2) A17-page. All of these nebulae displayed complex structure and required a lot of time to figure out. I especially liked NGC 6559 (smaller one on the left) which displayed 4 separate parts of nebulae at the eyepiece. Other two, not visible in this higher magnification sketch were IC 1274 and IC 1275. Both of these were quite difficult to discern but the dark nebula next to it - B91 - was actually quite obvious as a dark round patch in the middle of rich starfield and nebulae.

NGC 6526 turned out to be a little bit troublesome. Uranometria clearly shows this as an irregular shaped nebulosity between M8 and M20 but NGC/IC project disagrees; they list the object simply as the "SE part of M8" along with NGCs 6533, 6530 and 6523. This seems typical of William Herschel; cataloguing separate parts of one nebula with their own numbers. But there is a nebula in Uranometria's position for "NGC 6526" - if it is not it what should it be called? Well, I'm going to call it just that. Visually, I notice some variations in background brightness in this area when using UHC filter. Had I known that this a very faint object and in the middle of a star cloud, I surely would have spent more time with it. So it remains uncertain if I actually logged any nebulosity or simply the patchiness of the background sky caused by hundreds of faint stars. The sketch was doomed from the start as I knew the scanner would not be able to pick up my faint renderings without much background noise. For practical reasons, the sketch is only marginally cleaned up.

After three extensive (and exhaustive) nebula "studies", I had nothing else to sketch than open clusters so the couple worth mentioning would be NGC 6568 and NGC 6645. Then, continued by M17, M16 and a set of dark nebulae so I had my hands full for several hours. Later on some scattered clouds arrived but luckily it didn't interfere with my observing. This was a beautiful place to observe and a higher altitude would have probably made it a whole lot better. I especially enjoyed the naked eye views of the summer Milky Way so I continued to stargaze without equipment logging Messiers and several NGC objects with the naked eye. I had already noticed that during the past 4 years my eyesight has deteriorated to a point where I probably loose 0.3 - 0.5 magnitude with current set of eyeglasses. No matter, I still could enjoy the beautiful views.