(IAAC) Obj: NGC 1535 - Inst: 17.5" f/4.5 dob

Observer: Lew Gramer
Your skills: Intermediate (some years)
Date/time of observation: 9/10 Feb 1999  04:00 UT
Location of site: MIT Haystack Obs., Westford, MA, USA (Lat 43N, Elev 30m)
Site classification: Exurban
Sky darkness: 6.6 <Limiting magnitude>
Seeing: 4 <1-10 Seeing Scale (10 best)>
Moon presence: None - moon not in sky
Instrument: 17.5" f/4.5 dob reflector
Magnification: 55x, 225x
Filter(s): None, OIII
Object(s): NGC 1535
Object category: Planetary Nebula.
Object class: 4+2c
Constellation: Eri
Object data: mag 9.6 12.24m*  size 18"/44" round
Position: 041415.78-124421.6
After Steve Clougherty & I finished setting up the ATMs of Boston
17.5" Club scope, we had to wait out a brief threat of cloud-over.
As bands of cirrus and cirrocumulus obligingly dissolved or swept
off to the S, we began this evening's observing in earnest. First
target was the bright n1535 in Eri, easily found by sweeping ENE
of gamma Eri just about exactly 4o, stopping just a wide field E
of a beautiful equilateral trio of mag 9 late spectral-type stars.
At lowest power n1535 was distinctly non-stellar, with a yellowish
coloring. Jumping immediately to 9mm (225x), the bright, seemingly
smooth face of the nebula became more yellow-green, with a fairly
obvious irregularity to the N, either the edge of a lobe of nebu-
losity or perhaps a dark obstruction. Also, the face showed a non-
symmetric flattening on the W, probably indicating more structure.
The central star was neither strikingly obvious nor very difficult
once looked for. Surprisingly, even without any filter there was a
hint of a faint outer halo, or at least of much fainter nebulosity
surrounding the central disk. This "second tier" of the nebula (if
it was not in fact the actual halo) was only subtle, and was best
seen to the ESE of the center. Finally, with the idea of enhancing
this outer haze, we blinked the view at 225x with an OIII filter.
Strangely, the central star was neither more nor less visible than
it had been. But suddenly, the annular (ring-like) nature of n1535
became apparent, with just the suggestion of irregularities in the
inner darkened area to averted vision. As expected, the outer halo
could be clearly seen to SE, but now actually showed up as brighter
and more elongated W of the disc, reaching out to perhaps twice the
radius of the bright inner disk, roughly per cataloged sizes.
Object data thanks to dObjects: http://www.eaglequest.com/~bondono/dObjects

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