(IAAC) Simeis 57 - Newtonian 17.5" (445mm) F/4.5

Yann POTHIER yann.pothier at tiscali.fr
Thu Nov 8 02:33:45 EST 2007


Observer: Yann POTHIER (France)
Your skill: advanced (many years)
Object: Simeis 57 (DWB11, DWB118, DWB119)
Category: diffuse nebula, HII region
Constellation: CYG
Object data: 23.3'x22.0'
RA/DE: 20h16m09.7s, +43°41'09" (2000.0)
Date and UT of observation: 12 august 2007, 00h50 UT
Location & latitude: La Clapiere Obs. (France, latN44 40 00, longE06 27 36)
Site classification: rural, alt.1650m (5500ft)
Limiting magnitude (visual in UMi): 6.31 (30% of the time)
Transparency (1 to 5 - best to worst): 1
Seeing (1 to 5 - best to worst): 2
Height above horizon: 65°
Moon up (phase?): no
Instrument: Coulter 445mm/17.5" F/4.5
Magnification: 80-125x
Filters used: UHC, Hbeta

Description: at 80 & 125x, with UHC & Hbeta 
filters, large nebula, extremely faint, seen 
between 10 & 25% of the observing time according 
to the part concerned; irregular shape and 
ill-defined edges, homogeneous (no inner details 
observed) and difficult to see; UHC gives a 
slight contrast gain, OIII gives none and Hbeta 
gives a good contrast boost ! (emissive type for 
sure) Its global shape is that of a distorted 
greek lambda letter of about 20'x10' elongated 
N-S.
The best seen part (DWB119) is centered on 
20h16m28s et +43°47'14", just to the S of a mag.9 
star. It is seen 25% of the observing time like a 
nebulous curved wisp of 9.3' elongated N-S 
(width= 1.7') with concavity facing W. Its S end 
(to the S of two faint stars of mag.12-13) is 
much fainter, seen about 1% of the observing time 
at 80x with Hbeta filter.
Another part (ranked second in ease of detection 
order) called DWB111 extends on the SSE side of a 
double star (9+9th mag.), centered on 20h15m46s 
et +43°35'36". It is seen 10% of the observing 
time at 80x + Hbeta filter with a still fainter 
NE extension detected about 1% of the observing 
time. This wisp is about 9.5' long (width= 1.7') 
with concavity facing E and its shape and stellar 
surrounding reminds me of NGC 6960 (Veil Nebula 
around 52 CYG).
A last part (ranked third in detection order) is 
the faintest (DWB118) seen 5% of the observing 
time, to the SW of a mag.8 star, centered on 
20h16m19s et +43°33'59". It is an elongated patch 
of about 4.8'x1.7' NW-SE.


-- 

Carpe noctem, Yann.

Yann Pothier
11 impasse Canart, 75012 PARIS, FRANCE
yann.pothier at fnac.net
http://www.astrosurf.com/cielextreme



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