(IAAC) M 1-7 (PK 189+07.1, PN G189.8-07.7) - 17.5" F/4.5

Observer: Yann POTHIER (France)
Your skill: advanced (many years)
Date and UT of observation: 28 December 1997, about 22h00 UT
Location & latitude: La Clapiere Obs. (France, latN44 40 00, longE06 27 36)
Site classification: rural, alt.1650m (5500ft)
Limiting magnitude (visual in UMi): 6.2 with indirect vision 5% of the time
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 17.5" (445mm) F/4.5
Magnification: 400x
=46ilters used: OIII, UHC, Hbeta
Object: M 1-7 (PK 189+07.1, PK 189+07 1, PN G189.8-07.7)
Category: planetary nebula
Constellation: GEM
Object data: Vmag=3D13.0:; dim.29"x29" (37.8"x12.2" according to IDB); type
II ; central star of Vmag=3D?; discovered by Minkowski in 1946; ELCAT: [OIII=
496+501nm] =3D 18 x [Hbeta, 486nm].
RA/DE: 06h37.4m, +24=B000' (2000); Uranometria 137
Description: at 400x with OIII, very small PN, oval and faint (but still
high surface brightness), homogeneous with quite sharp edges; seen stellar
from 74x to 125x, even with filter; about 17"x9" (based on drawing) along a
NW-SE axis; a mag13 star is at 47"E and another of mag10 at 1'WNW; UHC has
a good contrast gain, the same as OIII (Hbeta has no gain at all).
I can provide a scanned drawing of M 1-7 to anyone who can read the binhex
encoding of Eudora (for Mac); just mail me to try
(ypothier@abi.snv.jussieu.fr), it works sometimes with other
Yann Pothier
11 impasse Canart, 75012 PARIS, FRANCE
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