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Cosmic Challenge: Abell 33

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#1 PhilH


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Posted 01 March 2023 - 07:17 AM

Several of the challenges I have profiled over the years have involved hunting down tiny planetary nebulae. Many planetaries appear very small as seen from Earth, which can make them difficult to tell apart from surrounding stars. This also works in our favor, however, since their small size focuses all of the available light into small discs with high surface brightnesses. Their existence is also accented nicely by using narrowband and oxygen-III filters, which help suppress light pollution. That's why planetary nebulae are far better targets for urban observers than some other types of deep-sky objects.

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#2 Dynan


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Posted 01 March 2023 - 08:45 AM

Is this even visible during March? Or am I missing something obvious...again.


(from Stellarium)


Abell 33.jpg

#3 Redbetter



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Posted 01 March 2023 - 09:10 AM

I observed this with the 20" back on 2/8/18.  At the time my old 90's vintage Lumicon O-III was rusted so I was stuck using a 1.25" Farpoint UHC and a 2" DGM NPB.  This put me at moderate exit pupil for the 16.  My notes say "Large filmy soap bubble, with bright ~7th mag star on its S side.  Several other stars within perimeter, mostly to west.  East side is fainter."  Used DGM NPB on 26 T5 to get better appreciation of the bubble shape.  Very nice view, made it brighter than anticipated."  I also estimated it as ~1/5 field of 16 T5.


I was probably seeing the CSPN based on my description although I didn't look for it specifically.  


For the nebula or CSPN some will benefit from occulting devices.  I find that I am less sensitive to the glare than the average observer, although it is still an issue.

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#4 Jon Isaacs

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Posted 03 March 2023 - 05:42 AM

Looking at my notes, I logged Abell 33 last year in early January with my 16 inch.  I used an O-3 filter. "just a faint fuzzy patch."


I'll be looking again.. 



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#5 nighthoek


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Posted 06 March 2023 - 03:17 PM

This is on my list to image!  Thank you for sharing this one!

#6 sgottlieb


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Posted 09 March 2023 - 07:24 PM

I've observed Abell 33 a number of times beginning in February 1985 using a 13.1-inch.  Always a striking target in good conditions and a large scope.


18-inch f/4.3 at 73x with an OIII filter.

The planetary was immediately visible with direct vision as a very large, well-defined 4' disc attached to a mag 7.2 star at the SW edge.  The rim was slightly brighter, noticeably along a 120° arc on western side to the north of the bright star, giving a mild annular or bubble appearance.  Removing the filter and upping the magnification to 280x, the planetary was still visible unfiltered (though fainter) and a 12" pair of stars was embedded at the NNW edge of the rim. At this magnification, the mag 15.5 central star was visible and collinear with the double star.


48-inch f/4.0 at 287x with an OIII filter.

Abell 33 was a huge and beautiful annular planetary extending nearly 4.5' across, with a fairly thick brighter rim giving a donut appearance.  A mag 7.2 star (HD 83535) is attached to the south-southwest edge with the donut or ring dangling from the star in the upside-down eyepiece view.  The annulus is slightly brighter and wider in a 90° arc along the northeast quadrant (opposite the bright star) and also brighter along the western side.  The central region appeared slightly darker in an irregular region elongated N-S. The mag 15.5 central star was easily seen, even with the OIII filter, as well as a mag 13/13.5 pair embedded in the northwest rim and a mag 14 star at the north edge.  Removing the filter, the central star was prominent and two additional mag 15.5 stars were visible on the west side [1.3' WNW and 1.6' WSW of center] with four of these stars (including one component of the pair) perfectly collinear.

#7 Bivanus


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Posted 19 March 2023 - 07:08 AM

Occulting piece - like this one I think: https://www.oreilly....04/ch04s09.html

#8 Sky King

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Posted 29 March 2023 - 02:36 PM

Last night between the clouds, I found it with a 8 EdgeHD, .7 Celestron reducer, ASI533MC Pro, and Optolong L'Extreme filter. 300s x 36. Thanks Phil for bringing us these challenges, the write-ups are always very interesting!






Edited by Sky King, 29 March 2023 - 09:16 PM.

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