(IAAC) NGC 6781 - 17.5" F/4.5

Observer: Yann POTHIER (France)
Your skill: advanced (many years)
Object: NGC 6781 (PK 041-02.1; PN G041.8-02.9; ARO 32)
Category: planetary nebula
Constellation: AQL
Object data: Vmag=11.4; Bmag=11.8; >109"; type IIIB+III; central star of
Vmag=16.2; discovered by Herschel in 1830; ELCAT: [OIII, 496+501nm] = 13 x
[Hbeta, 486nm].
RA/DE: 19h18.44m, +0632.5' (2000.0)
Date and UT of observation: 06 July 1994, 01h00 UT
Location & latitude: La Clapiere Obs. (France, latN44 40 00, longE06 27 36)
Site classification: rural, alt.1650m (5500ft)
Limiting magnitude (visual in UMi): 6.0
Transparency (1 to 5 - best to worst): 1
Seeing (1 to 5 - best to worst): 4
Moon up (phase?): no
Instrument: Coulter 445mm/17.5" F/4.5
Magnification: 45-145x
Filters used: UHC, OIII
Description: at 125x, large PN, medium to bright, about 2.1' in diam.
(126"); SW border fuzzier and less annular than the others; W, NW, NE, E
and SE borders are well defined; the ring is 3/4 of the nebula's edges,
like a crescent, 38" wide at the maximum (on the N side); the nebula is
seen at 45x without filter, medium in brightness and large, homogeneous;
frankly annular at 74x without filter and at 45x with OIII (difficult); at
145x, annular nearly with direct vision; the UHC gives a good contrast gain
and OIII a very good one; at 145x and OIII, annular with direct vision;
mag15 star in the ring to the W (and a little S) and another just outside
to the ENE; a mag12 star is 4.8' to the WNW.
I can provide a scanned drawing of NGC 6781 to anyone who can read the
binhex encoding of Eudora (for Mac); just mail me to try
(yann.pothier@fnac.net), it works quite often with other configurations...
Yann Pothier
11 impasse Canart, 75012 PARIS, FRANCE
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