Author Topic: Speaking of subtle...  (Read 514 times)

mccarthymark

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Speaking of subtle...
« on: July 26, 2017, 08:41:33 PM »
There were a couple of other observations the other night at Pinnacles which intrigued me.  I was observing “without a list” and just seeing what I could find on the chart, so I saw these without knowing what they were beforehand:

GN 18.32.5 = PNG 27.0 +1.5, 18 35 11.6 -04 29 06.  Using 333x, the nebula sprouts to the SW of a relatively bright star, but is only seen with averted vision and OIII.  It is a diffuse, extremely faint small cloud which brightens near the star and fades to a round diffuse edge.  Searching the internet, I find one other observation from a German observer using a 27-inch; his sketch shows the object much brighter than what I saw*.  Simbad calls it a reflection nebula but it is plotted as a PN. 

Sherwood 1, PN, = Sd 1 = K 3-77.  Plotted in Interstellarum at the eastern edge of LDN 889, which is is part of the Gamma Cygni nebula complex.  I had to star hop from Gamma around this blank space in the sky to get to Sherwood 1, as it was labeled.  At 333x and only with OIII, a very small, excessively faint round shell with diffuse edges swam into view, held 50% with averted vision.  Very low surface brightness and no central star.  Very close star just to the ESE.  After getting home and searching for the object online, I found the discovery paper by William A. Sherwood who, as a graduate student in 1969, was blinking photographic plates at the Royal Observatory in Edinburgh.  I precessed the 1950 discovery coordinates and searched the result in Aladin, which confirmed the observation for me as my sketch matched the star field.  Distance: 18000 ly.  17.2 mag, 7.0” size.  Today I received Kent Wallace’s excellent (or better yet, monumental) Visual Observations of Planetary Nebulae book, and I find his observation in a similarly sized telescope revealed a faint stellar object, though I was 100x higher in magnification.  I observed this during the “peak” seeing and transparency period during our time at Pinnacles, so I believe that helped.

J014709+463037 = Andromeda's Parachute.  This object was noted on Deep Sky Forum** earlier in the week, a gravitationally lensed quasar with an incredible red shift z=2.377.  I printed some AAVSO charts and gave it a try.  But, now it was 2am and the good seeing window had closed, and the sky began to haze.  I spent almost a half hour in the field searching.   Unfortunately my charts were confusing, and I could not very well match the star fields with the eyepiece view, though I was very certain my star hop was correct.  In any case, there are better charts available at DSF now, so I hope to try again at CalStar.

* http://www.deepsky-visuell.de/Zeichnungen/GN18_32_5.htm
** http://www.deepskyforum.com/showthread.php?1036-Newly-discovered-quadruple-quasar-candidate-in-Andromeda
« Last Edit: July 27, 2017, 12:07:32 PM by mccarthymark »
Mark

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Re: Speaking of subtle...
« Reply #1 on: July 26, 2017, 11:00:16 PM »
McCarthy, have you gone thru the TAC Eye Candy List? Compilation of the RASC, Saguaro and Caron lists, plus some extra goodies thrown in. The whole selection is eyepiece-based.

Might just be time for an intervention, buddy.
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mccarthymark

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Re: Speaking of subtle...
« Reply #2 on: July 27, 2017, 12:12:46 PM »
I guess I have gone off the "deep" end, haven't I...    ;)
Mark

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Re: Speaking of subtle...
« Reply #3 on: July 27, 2017, 01:41:06 PM »
Phoo, McCarthy et al, I didn't pass along the link for that list. It's still archived at
http://old.observers.org/observing/eyecandy/

One of the most fun observing lists around, on purpose! Made with the same philosophy as Steve's DeepMap - these better look good.
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sgottlieb

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Re: Speaking of subtle...
« Reply #4 on: July 27, 2017, 10:22:09 PM »
Great set of targets, Mark!!

As far as GN 18.32.5 = PNG 27.0 +1.5, it's definitely a planetary neb and not a reflection nebula -- SIMBAD is wrong, wrong, wrong.

Check out this page from the MASH catalogue:  http://vizier.cfa.harvard.edu/viz-bin/vizExec/.show?V/127A&G027.0%2b01.5.  Perhaps I mentioned this one to you before?

I made two observations 9 years back with my 18" ---  I noted the planetary wasn't symmetric around the central star (as you also commented).

18" (7/31/08 and 8/1/08): At 175x unfiltered a mag 13 star was visible and a small ill-defined halo was highly suspected surrounding the star knowing the exact location.  Adding an OIII filter, the halo brightened nicely and the edge sharpened to a 20" disc.  The involved star appeared offset to the north side.

For comparison, here are a few more observations ---

Alvin Huey (22" @184, 255 and 328x): Considerably faint round glow with defined edge with a very bright central star.   Estimated magnitude of the central star is about 11.5.  Not visible without filter.  Ultrablock brings it out pretty well and a similar response with O-III filter.  About 0.5' across.

Kent Wallace (20" @134X and 169X): could see the star superimposed on the northern side of the PN as shown in the SuperCOSMOS blue image. Using the O-III filter and averted vision, a blob forms on the southern side of the star. Good response to the O-III filter. Fair response to the UHC filter. No response to the H-Beta filter. The image is best at 169X. At 254X, the image isn't very good. Identified the field in the AP finder chart. This is a first known visual sighting.

Kent Blackwell (25"): Easy to find because of its involvement with an 11.4 magnitude star.   Even in bright moonlight I could still see it. Once I sighted the nebulosity with the filter I could see it without a filter. It responds so well to the OIII the nebula nearly outshines the involved 11.4 magnitude star.

-- Steve