by Bruce Jensen
Lately at Del Valle Reservoir, the East Bay TAC (TAC = The Astronomy Connection) people have been encountering less-than-optimal weather conditions for observing, typically a great deal of humidity in the lower atmosphere, which not only obscures the view but reflects back light from the Tri-Valley Area (Livermore, Pleasanton and Dublin), as well as the rest of the Bay Area to the west. Not so on the night of December 3, 1999, however, as the dry air from northeast California blew into the East Bay Hills and gave us one of the best observing nights at Del Valle in two years. Even the cirrus clouds, which early on plied the skies from horizon to horizon, made their exit and left us with fine clarity overhead. The seeing was mediocre for the most part, but sometimes it improved markedly and gave us tantalizing glimmers of details.
For these observations, the scope used was an 18" (0.457 meter) Starmaster with various wide-field eyepieces. For each object, the name, type and magnitude (source SkyMap Pro 6 unless otherwise noted) are given, along with the magnification and any filtration used. The list in roughly chronological order. It was generated using SkyMap Pro 6, a software that I am just beginning to understand but nonetheless love already (Thanks, Chris Marriott!).
| Object | Type | Magnitude | Magnification | Filtration | Description |
|---|---|---|---|---|---|
| M57 | Planetary Nebula | 9.00 | 225x | The Ring Nebula, always a joy. No central star tonight with the less-than-steady skies. | |
| NGC 7640 | Galaxy | 11.30 | 225x | A large, almost edge-on spiral galaxy, bright overall but low surface brightness, 10' x 2', mostly inside a nice triangle of three mag. 12 stars. Pretty! | |
| NGC 404 | Galaxy | 10.30 | 290x | This elliptical galaxy, very near Beta Andromedae, showed as a fine glow with sharp center and bright haze extending outward from center. | |
| NGC 7662 | Planetary nebula | 8.60 | 290x | The lovely Blue Snowball Nebula, showing off its interior detail (a 3/4 circumference bright curl and central darkening) at high power. It really is blue! | |
| NGC 7707 | Galaxy | 13.40 | 225x | A fine line-up of galaxies in the same vicinity as the Blue Snowball (Andromeda). The NGCs each presented itself as a small galaxy with a bright core, both very pretty. The two UGCs were faint hazy objects of low surface brightness, and in fact 12632, a dwarf system, was anything but a certain bag. I intend to try again for this one at a darker site. | |
| NGC 7618 | Galaxy | 13.00 | 225x | ||
| UGC 12632 | Galaxy | 12.10 | 225x | ||
| UGC 12588 | Galaxy | 13.20 | 225x | ||
| NGC 7379 | Galaxy | 13.40 | 225x | A small round galaxy, bright center. | |
| NGC 7446 | Galaxy | 15.70 | 225x | A neat little trio of galaxies in Andromeda near the Lacerta border; they were amazingly visible from this near-town site on this night. Forming a nice triangle of three faint discs, I was led to believe that, for at least two of these, the listed magnitudes are about one magnitude too dim. The Uranometria lists them as mid-14s, which seems more reasonable. In any case, a lovely bag for this site. | |
| NGC 7445 | Galaxy | 15.60 | 225x | ||
| NGC 7449 | Galaxy | 14.00 | 225x | ||
| Jupiter | Planet | -2.75 | 225x | Jupiter was interesting all evening long; between a shadow transit, several lovely festoons and the apparent disappearance of the S. Equatorial Belt, it was as fascinating as ever. | |
| NGC 891 | Galaxy | 9.90 | 145x | The bright edge-on showpiece galaxy in Andromeda, large and eye-popping with its prominent dust lane. | |
| NGC 925 | Galaxy | 10.10 | 225x | Another large interesting spiral galaxy, this time face-on, which on nights of great seeing has a fabulous crab-like appearance. Tonight, it was less detailed and showed a mottled irregular disc. | |
| M1 | SN remnant | 8.40 | 145x | Deep Sky Filter | The Crab Nebula gave a nice showing despite its low elevation at the time of the observation, revealing a gentle S-shape and some modest edge detail. |
| NGC 1931 | Bright nebula | 10.10 | 225x | Deep Sky Filter | These three nebulae all offer very different pictures. NGC 1931, first spotted last evening by Richard Navarrete, was a delightful small knot of nebulosity containing a pretty triple star. It needed no filter, but I used one anyway just to see what the effect would be, which was little in this case. NGC 1554, also known as Hind’s Variable Nebula, was practically impossible to distinguish using any filters; once or twice I felt that I had seen a fleeting glimpse of nebula next to the core star, but I cannot claim this for certain as a bag. NGC 1514 is a fairly nondescript planetary in Taurus, a single brilliant star surrounded by an even haze with out any features so far as I could detect. |
| NGC 1554 | Bright nebula | – | 145x | Deep Sky Filter, O-III, and Ultrablock | |
| NGC 1514 | Planetary nebula | 10.80 | 145x | Deep Sky Filter | |
| PK172+ 0.1 | Planetary nebula | -- | 145x | O-III filter | This is Abell 9, which lies on the edge of star cluster M38 in Auriga. I tried looking for this one before I discovered that its magnitude was somewhere around 18.5. Needless to say, I did not spot it! |
| M 42 | Bright nebula | 4.00 | 145x | Deep Sky Filter, Ultrablock | These two showpieces of the sky, one well-known (The Orion Nebula) and one not so commonly observed (The Tank Tracks or Flame Nebula), were beautifully detailed and lovely, especially as the evening grew later and Orion rose higher in the sky. NGC 2024 showed its dark dusty gap clearly and with fine detail both with and without the filter, although the Deep Sky added some nice contrast. |
| NGC 2024 | Bright nebula | -- | 145x | Deep Sky Filter | |
| PK197-14.1 | Planetary nebula | 12.70 | 225x | O-III filter | These objects are all Abell planetary nebulae (Nos. 10, 4, 2 and 12 respectively), and are either faint or for some other reason difficult to spot, especially in the case of Abell 12, which lies less than ½ arcminute off the bright star Mu Orionis. Of this group, it is actually the brightest member and fairly easy to see (I do not believe the magnitude given here, but something rather brighter, perhaps M 12 or so), and the O-III filter passes the prominent lines of doubly ionized oxygen while masking the star’s brilliant light. Of the remaining three, the first two listed also have suspect magnitudes - I believe both to be in the low to mid 14th magnitude range. The first three all were invisible without the O-III filter, and when filtered appeared as faintly visible compact even discs. I was able to hold each of them about 50% of the time with indirect vision, and fleetingly with direct vision. |
| PK144-15.1 | Planetary nebula | 16.70 | 145x | O-III filter | |
| PK122- 4.1 | Planetary nebula | 14.10 | 145x | O-III filter | |
| PK198- 6.1 | Planetary nebula | 13.90 | 290x | O-III filter |
That brought an end to an extremely satisfying evening at a near-town site that often is less than ideal, but that occasionally really shines for clarity and darkness when the wind is right. The company, however, is always peerless and this night was no exception. Thanks to Craig Lambert, Peter Rathmann and Richard Navarrete for their kind and happy presence (it was great to meet you Craig, and see your new toy!), and to the noisy flock of ducks that winged their way overhead to their southerly grounds in the darkness - they did for our ears what the stars did for our eyes. It was a lovely evening.