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RA: 16h 11m 44.544s
Dec: +12° 04′ 17.06″
Ch: MSA:1254, U2:200, SA:15
Type: planetary nebula
Mag: B=10.89, V=10.7
Terzian Y (1980) Q.J. R.astr.Soc vol 21, p82-92 [09.16.1] notes that the nebula has a faint outer giant halo.
Tom Lorenzin, in the electronic version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "11M; 12" diameter; 11M center star in blue haze; requires high-x and N-filter."
Houston notes that this planetary in Hercules/Serpens appears starlike at low powers. Although catalogued at 15x11 arcseconds, Houston notes that it seems smaller viewed in a 10-inch. He notes: "Although about as bright as an 11th mag star, this object is so tiny (0.2') that it is difficult to recognize by its appearance."
Hartung notes: "This is a small bluish disk about 10 arcsec across with prominent central star; a fairly bright star lies 5' np. It is clear with 10.5cm and appears as a star with 7.5cm."
IC 4593 faint, small, little elongated, stellar nucleus. Greenish at all powers, central star most obvious at 165X. This planetary "blinks", look at it, then use averted vision and the nebulosity will appear and disappear. Sun Valley Parkway Seeing 5/10, transparency 6/10, easy at 150X, but needs power. 220X Pretty faint, small, very little elongated 1.2 X 1 in PA 90, central star is obvious. This planetary has been called the "while-eyed pea" and I see why, the nebula is light green and the star is as white as Spica. Averted vision makes it grow about twice its size and there is some very faint outer nebulosity seen.
13-inch: 100X-just recognized as a disk, pretty faint, very small, round, stellar nucleus; averted vision makes the disk grow three times what it is with direct vision. 220X brings out the central star. 440X is the best view, round light green disk with white central star.
Observer: Yann POTHIER (France)
Your skill: advanced (many years)
Date and UT of observation: 20 February 1994
Location & latitude: La Clapiere Obs. (France, latN44 40 00, longE06 27 36)
Site classification: rural, alt.1650m (5500ft)
Limiting magnitude (visual in UMi): 6.31 with averted vision
Transparency (1 to 5 - best to worst): 1
Seeing (1 to 5 - best to worst): 3 (stellar stars until 180x)
Moon up (phase?): no
Instrument: Coulter 445mm/17.5" F/4.5
Filters used: OIII, prism
Description: at 74x, slightly nebulous star, blue; located at 80x with prism as a mag11 stellar dot superimposed on a faint continuous spectrum (due to central star?); more nebulous at 125x and OIII filter (estimated diameter of about 25"), more brighter in the center and well condensed.
Instrument: Meade SCT 8" (203mm), F/10
Filters used: prism, UHC
Description: at 80x with prism, located as a stellar dot to the S of a mag8 star, with a faint continuum; at 100x, slightly nebulous, fainter than the mag8 star but with UHC filter, it looks brighter; at 310x, nice, quite round although slightly irregular in shape.
Steve Coe, observing with a 13" f/5.6, notes: "Pretty faint, very small, round, Central star seen with direct vision. Some blinking effect, it grows with averted vision."
pair 5' NW = ADS 9959: V=8.5,9.7; 7".2; pa146.
6cm - vis only as *: starting from close 10" dbl (on AE), it is first * of two
15cm - br & non*ar @ 80x. 295x: 15" diam, seems sl elong SE-NW. f halo surrounds
more-or-less uniformly br core w/in which cen * seems clear, m13.5. BS,
4Jul1989, Anderson Mesa.
25cm - 240x/510x: 10" diam, circ. fades quickly at edges. sharply concen core
not sparkling. vbr neb.
30cm - 10"-15" diam. neb fades suddenly from br cen * but has `hairy' indef
edges. prism shows one image for neb w/f continuum and two other poss
emission lines for *.
Observing site: Little Tycho Observatory
[16h 11m 42s, 12° 4m 0s] A tiny, (~3") bright, blue planetary, looking brighter than its 11mv in Sinnott's NGC. Also listed as a Tycho and Hipparcos star.
The Messier objects
The Bennett objects
The Caldwell list
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