(IAAC) M 57 (NGC 6720) - 17.5" F/4.5

Observer: Yann POTHIER (France)
Your skill: advanced (many years)
Object: NGC 6720 (M 57; PK 063+13.1; PN G063.1+13.9; ARO 9, VV 214)
Category: planetary nebula
Constellation: LYR
Object data: Vmag=8.8; Bmag=9.7; 83"x59" (88"x63" in IDB, 160"x145" for
outer shell); type IV+III; central star of Vmag=14.7; discovered by
Darquier in 1779; ELCAT: [OIII, 496+501nm] = 18 x [Hbeta, 486nm].
RA/DE: 18h53.56m, +3301.8' (2000.0)
Date and UT of observation: 08 July 1994, 23h30 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: 45-620x
Filters used: OIII

Description: at 45x, already annular; homogeneous ring at 87x; slight
surface brightness decrease on the WSW and ENE sides of the ring; no
central star but mirrors poorly collimated and seeing not too good; very
bright PN, overexposed for the eye with OIII filter; the N part of the ring
is brighter with and without OIII; as on photographs (without the color);
estimated to be 1.2"x0.8" (72"x47") along a ENE-WSW axis.

I can provide a scanned drawing of M 57 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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