(IAAC) Obj: ngc1535 - Inst: Newt 20" f/5

Observer: Lew Gramer
Your skills: Intermediate
Date and UT of Observation: 1997-2-6/7, 03:00 UT
Location: ATMoB Clubhouse, Westford, MA, USA (43N)
Site classification: semirural
Limiting magnitude: 6.2
Seeing: 2 to 3 - medium good
Moon up: no
Instrument: Newt Reflector 20" f/5 (dob)
Magnification: 70x, 210x, 360x
Filters used: None, UHC, OIII
Object: ngc1535
Category: Planetary nebula
Constellation: Eri
Data: mag 9.6 (star 12.25), size 18" (halo 44" per catalog)
RA/DE: 4h14m  -12o34m
This striking planetary is somewhat off the beaten path for Yankee
observers like myself (:>), as it's fairly low, and is a somewhat
sparse star-hop from either of 39 or Gamma Eridani. However once
found, it is a rewarding view even at 70x with a UHC, jumping out
as a pale greenish-blue disc some 30" wide, with a fainter halo
apparent to averted vision. At 210x using an OIII filter, 1535
seemed to suddenly balloon into a much larger disc, with the halo
brightening to the point where its boundary with the core of the
nebula became indistinct. The PN was estimated as a disc of fairly
uniform brightness some 30" wide, surrounded by an outer area of
nebulosity also generally uniform, but falling off rapidly out at
about 2'. (This wide estimate may be an effect of poor seeing; or
could OIII emissions in 1535 truly be more extended than at other
visual wavelengths?) At the edge of the central 30" disc however,
a strong "streamer" or filament was noted, arcing off into the
halo to the West, with an overall length of perhaps 10". Use of
360x was hardly possible at this altitude on this night. Little
more was seen, except that a hint of mottling(?) was noted in the
central disc in instants of good seeing. At all magnifications,
the central star was prominent, and the core showed a distinctive
"lobe" or elongation SSW, perhaps adding 5" to the disc size.
Karen Simmons & Lew Gramer dedalus@alum.mit.edu http://www.tiac.net/users/lewkaren