On Wednesday night, Robert Leyland and I headed over to Lake Sonoma during commute time for a short but sweet evening of observing under quite dark and fairly steady conditions. There was no breeze or dew to contend with and the road through the park was pretty quiet on a weekday.
As a continuing project, I've been revisiting PNe which I last observed over 10-15 years ago with a 13-inch or 17.5-inch. This evening I headed into Perseus and Cassiopeia to take a look at IC 289, BV 5-3 and HFG 1. HFG 1 is one of larger known PNe, checking in at a whopping 9' in diameter, but has a low enough surface brightness that it was missed by George Abell when he visually searched the Palomar Sky Survey plates in the 1950's for new large planetaries.
After tracking these down, I spend quite a bit of time ogling the giant California Nebula (quite prominent this evening), the Supernova remnant IC 443 in Gemini and the interesting HII region NGC 2174/75 in Orion.
BV 5-3 (Bohm-Vitense) = PK 131-5.1 = PN G131.4-05.4
01 53 02.5 +56 24 20
V = 15.0; Size 30"
17.5": best view at 140x and OIII filter. BV 5-3 appeared faint, small, round, 0.4' diameter, fairly crisp-edged. Not difficult, but no obvious structure is evident. Situated just 50" W of a mag 10.8 star. Also a mag 12.5 star is a similar distance NE. Viewed unfiltered at 220x as a round, low surface brightness glow. Estimate V = 14.5-15.
HFG 1 (Heckathorn-Fesen-Gull) = PK 136+5.1 = PN G136.3+05.5
03 03 49 +64 53.5
V = 12.0; Size 523"
17.5": This ancient, giant planetary was discovered in 1982. Using a 31 Nagler (64x) and OIII filter an extremely faint, huge glow was visible, perhaps 8' in diameter. Generally the hazy region was just an ill-defined "stain" on the sky, but at moments the view sharpened up into a fairly well-defined disc. Several stars are superimposed. Located 7' NE of mag 9.2 HD 18611. This star is at the NE end of a string of stars heading to the SW and roughly collinear with HFG 1.
IC 289 = PK 138+2.1 = PN G138.8+02.8 = Hb 1
03 10 19.2 +61 19 01
V = 13.5; Size 42"x28"
17.5": at 140x, IC 289 was seen as a fairly faint, 35-40" disc with a modest contrast gain using a UHC filter. Situated 2' N of a mag 10 star and near the tip of two curving strings of stars which head N and NW from IC 289. Excellent view at 380x - the planetary is slightly elongated and has a mottled appearance and a marginally brighter rim, particularly on the W or NW side, giving an impression of weak annularity. At moments, there was a brief sparkle at the center, possibly the central star. A mag 14 star is 45" NE of center and a mag 13 star lies 1.3' following.
NGC 1499 = California Nebula = LBN 756 = Sh 2-220
04 03 14 +36 22.1
17.5" (1/16/02): despite its reputation as a challenging target, this was an easy, fascinating object at 64x with a H-beta filter. The California Nebula is HUGE and extended a full two eyepiece fields even using a 31 Nagler for a total length of over 2.5 degrees and with a varying width of 15'-30', extended WNW-ESE. The E-W border is well-defined with a filter, particularly in the general vicinity of Xi Persei on the southern border and a long straight stretch on the northern edge. Along the northern edge, there is some filamentary, wispy structure similar to the view of the Veil nebula in a small scope!
The nebulosity is weaker and more disorganized, though, close to the preceding and following ends. The nebula tapers towards the eastern end where there are some additional brighter streaks and dark intrusions near a group of stars. Portions of the central region are clearly fainter with no evident structure. At the west end the structure is also chaotic with an irregular mix of weak nebulosity and darker voids. There is much to view here even at 64x, and I spent 30 minutes scanning the entire length for structure.
NGC 2174 = Ced 67a = LBN 854 = Sh 2-252
06 09 23.6 +20 39 34
17.5" (1/16/02): at 64x and OIII filter, this is a beautiful, detailed nebulosity surrounding a mag 8 star (SAO 78049), extending at least 20' diameter. The OIII filter gives a dramatic contrast gain. With averted vision and careful viewing, the outer borders extend to ~25'. Structure includes interior streaky dark lanes visible to the west of the star. The rim is slightly brighter or has a higher contrast to the western edge but slightly more nebulosity is visible on the following side of the star.
Without a filter at 64x, I immediately noticed a moderately bright 3' round glow, situated ~11' NNW of SAO 78049 near the NW edge of the main glow. Interestingly, this patch of nebulosity is more prominent than the main body without a filter and is probably the section of the HII complex visually discovered by Stephan! It seemed quite strange that this section had such a different filter response and dimmed significantly with the OIII (mainly reflection component?). A curving arc of stars is situated along the north side of the glow. The nebula is set among a scattered group of stars, which is often mistaken for N2175.
N2174 was discovered by Stephan. His description does not describe the entire nebulosity or a scattered cluster but rather a small patch of nebulosity: "excessive., excess., faible (a peine observable); a l'interieur d'un triangle forme par trois petites etoiles".
Stephan gave an 1878 position of 06 02 07.47 +20 40 54.4 which precesses to 06 09 24.0 +20 39 53 (2000) and falls on the NW side of the nebula. This knot of nebulosity is quite prominent on the DSS just following the middle of these three stars.
IC 443 = LBN 844 = Sh 2-248
06 16.9 +22 47
17.5" (1/16/02): at 64x and OIII filter, the most prominent section of this supernova remnant is a gently curving band of nebulosity oriented NW-SE, ~10'x3' with a well-defined edge along the eastern (bowed-out) boundary. A larger region of low surface brightness haze, ~20' in size, spreads out to the west of the northern end. At the SE end, the bright band seems to hook to the SW towards a small arrowhead of stars.
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