Object of the Week, July 16, 2017 - Abell 43 planetary nebula

Planetary nebula
Ophiuchus
RA 17h 53m 32
DEC +10d 37m 25s
Magnitude 14.7 (p)
Size: 78” x 72”

Attachment 2608

I had my first look observation of the planetary nebula Abel 43 a couple weeks ago at the Golden State Star Party, and it was especially gratifying after being skunked by the apparently invisible Abel 42.

Abel 43 is a decent size and bright enough to show a little detail. It appeared perfectly round although photos show it to have a somewhat lumpy outer perimeter and a beautifully lacy inner region.

Nonetheless, I did see a distinctly brighter perimeter, especially along the northern border and three stars that were superimposed on the round nebula, one of which is presumably the central star. The NPB and OIII filters seemed to enhance the planetary about the same, but the NPB gave a more natural view that showed more filed stars. I could faintly see the planetary without a filter at 220x. The sky was a dark and transparent 21.72 SQM at the time of this observation.

Given what I saw with my 28 inch, my guess is that Abell 43 would be visible in a 16 inch under comparable conditions.

Attachment 2609 Attachment 2610

"GIVE IT A GO AND LET US KNOW"

Saw this last October with a 22", 337x & an Ultrablock filter. "Needed the filter to catch a glimpse with direct vision. This PN is small, faint and round situated half way between a pair of semi-close stars and 1 bright star."

Al

My notes from August 05, 2016, using my 20" read:

At 83x and 151x very faintly visible without a filter. OIII makes visible a nice disk. According to images it is a ring, but I don't see that. One star lies at the eastern rim of the nebula and it is about as bright as the central star. According to images there is another star to the southern rim but I don't see it.

I included Abell 43 in an article I wrote in the current July issue of Sky & Tel on the best summer Abell planetaries. My most recent observation was two years back with my 24" ---

"Abell 43 was picked up at 200x using a NPB filter as a fairly faint, moderately large, crisp disc, roughly 1.1'x0.9'. With careful examination, I noticed the rim was slightly brighter in a thin strip around the periphery, creating a very weak annular appearance. The interior was uniform in surface brightness, though contained three stars (two were seen with the filter, including the central star). Removing the filter, the planetary was still easily visible and 3 stars were clearly superimposed including a relatively bright mag 14.7 central star. The two additional stars are on the south edge of the slightly brighter rim, as well as the east-northeast edge of the rim."

As far as the minimum aperture, Kent Wallace (who attended GSSP) reported a positive observation in a C-8:

"At 62.5x, very faint, good-sized disk, requiring the OIII filter and averted vision. Fair reponse to the OIII filter. Poor response to the UHC. At 100x the image is poor requiring the OIII and averted vision. At 200x, nothing is visible."

By the way, Abell 43 has an unusual pulsating central star. See the 2005 paper by Quirion et al: "The Nature of the Driving Mechanism in the Pulsating Hybrid PG 1159 Star Abell 43"

Nice and unknown Abell PN Howard. Here my notes and sketch of this PN.

20", 155x, [OIII], fst 6m3
with [OIII] and 155x round glow, can hold it with averted vision; some difficult structure, could not hold it, 3 stars within the PN without filter
Attachment 2611

27", 293x, UHC, fst 6m0+
even with bad transparency conspicuous in the finder eyepiece without filter; 3 stars within the PN, CS brightest one, S star faintest; [OIII] filter brings only slightly improvement; UHC best solution; round glow with good defined edges; implied shell structure but no ring structure; brightest part NW; no inner structure

Howard, I just observed this here in the eastern panhandle of WV just over a week ago on 6-18-22. Exceptional transparency that night for this area this time of year. I saw 5 other Abell's including 39, 45, 46, 61 and 71.

All things being relative it was a rather bright but small Abell PN under my SQM 21.0 skies using my 22" f/4.2 at 122x and an OIII:

Rather bright and round. About 1 min in diameter. A pair of 11th mag stars centered 3 mins SE point to the nebula. A 9th mag star lies 5 mns NW. The central star pops in and out with good seeing. An annular disk is detected when the seeing is steady. Averted shows a more diffuse glow within the nebula. In a nice star field.