Saturday, September 27, 2014

A hydrogen star and a fading comet.


Last weekend saw the most pleasant weather for stargazing for weeks, with clear skies and much less humidity than usual. Indeed, I was wearing a battle dress uniform blouse because temperatures dropped enough for it to get cool outside. The sky's transparency was also very good, evident by the fact I saw the Milky Way clearly except for the region near the southern horizon. With the near limitless numbers of galaxies, nebulae and star clusters to choose from, I set up the 15-inch then connected the Sky Commanders to my Toshiba laptop before commencing observations. Through the use of Sky Tools3, I can now locate any sort of object anywhere in the sky, not just deep sky objects and the planets the Sky Commanders alone are designed to locate. I now have the means to locate comets and asteroids far more easily than before, with C/2014E2 Jacques being the first. I've also observed the main belt asteroids 1 Ceres and 4 Vesta from home using this setup. Novae Cygni 2014 was also found this way from the driveway. To protect the computer from dew and keep it warm and dry, I made a plywood enclosure with a clear plastic top. Slots allow the mouse and the data cable to be plugged and unplugged from the laptop's USB ports without removing the computer. to keep the screen from dazzling my eyes at night, I bought a red screen filter and also use the night vision mode Sky Tools has. When placed over the screen then in the enclosure, there is little stray light from the computer to bother others observing nearby.
Once it became completely dark, I set about observing several objects I was interested in. One of them was the comet C/2014E2 Jacques, which is fading but still well placed for observation. That night it was passing in front of the asterism Collinder 399, or the Coat Hanger as it's popularly known. While it faded from the last time I drew it, the inner core became more noticeable and the tail looked less fork shaped. The best view was at 298X, which alleviated the interference from the dense star fields behind the comet. This comet is already 1.2 A.U. away from us, and soon would be out of reach of all but large telescopes and users of CCD cameras. Fortunately, there's always other comets to take this one's place for amateur astronomers to observe and photograph.

Scorpius is soon to be lost in the Sun's glare, so I spent time observing several objects there. One of them was the curious open cluster Collinder 333. This is a fairly small and not very concentrated open cluster, but for a curious group of five stars shaped like a perfect pentagon. At the top of the pentagon was a bright orange red star. Many Collinder star clusters are not terribly conspicuous, but this one was easy to spot even at low power. The central core almost looks like it could be some sort of logo.

Although I always am looking for objects I've never seen before, some objects like M-57 I observe time and time again. Through small and large telescopes it always shows considerable structure under good skies. However, one feature has eluded repeated efforts to spot. Many planetary nebula's central stars are visible through my telescopes, even my 6-inch. However, that is not the case with M-57, the central "hole" is filled with very evident nebulosity that usually hides the central star when the seeing is poor or mediocre, or magnifications are not high enough. I have searched for it a number of times with my 10 and 15-inch telescopes at high magnifications without success. The seeing was just not good enough until last Saturday night, or I wasn't expecting the central star to barely shine above the nebulosity in the central hole. When a fellow observer remarked the central star was visible, I turned my 15-inch to M-57 then raised the magnification to 425X, then 572X. Sure enough after staring at the nebula for a minute or so, the central star flickered into view at 425X. The view softened at 572X so I returned to 425X. I started staring again and saw the central star appear and disappear repeatedly. The central star appeared to be fainter than 15th magnitude visually, even though it's listed magnitude is about 14 in most catalogs. Even in telescopes much larger than mine, the central star can be difficult to see. The central star is shining some 200 times brighter than the Sun with a surface temperature of 125,000 degrees Celsius. The central star has ejected the current nebula less than 2,000 years ago, but there is also an older much larger nebula around it that is about 3.5 years across. Aside from the central star, the darkening along the long ends of the nebula was also evident along with hints of other features seen in photos. The nebula's magnitude is 8.8, and lies 2,300 light years from Earth. The diameter of the visible nebulosity is about one light year, and it is expanding at a velocity between 20 and 30 kilometers per second. M-57 responds well to narrow band and O-III filters, as well as high magnifications. It is also observable from light polluted locations and under moonlit skies. M-57 is very easy to locate and has been one of my top favorites among the nebulae ever since I started observing deep sky objects.

Another planetary nebula I observed last weekend was Campbell's Hydrogen Star in Cygnus. Also known as PK064+5.1, this nebula is quite bright but much tinier than M-57. It gives itself away by the strong red color of the central star with a fuzziness around it. Raising the magnification to 425X revealed a tiny disk around a reddish star that is slightly brighter around the rim and next to the central star. Last night I searched for it again from my driveway and succeeded in locating it despite the streetlight across from my house. Other than the peculiar color and the slight brightening around the star and the outer rim, I did not see any other signs of structure in this planetary nebula.

Other objects observed that night included the proto-planetary nebula PK80-6.1, or the Cygnus Egg Nebula, the globular clusters M-15, M-22, M-62, M-9, M-19, M-13, M-92 and M-80. I also looked at all three sections of the Veil Nebula, the Crescent nebula and the North American nebula. I've also stopped to observe Saturn, Uranus and Neptune. My trip to the airstrip last weekend paid off in several hours of good observing with like minded folks. Soon the Deep South Regional Stargaze will be held near Norwood LA, and I am currently preparing to attend this year.

No comments: