Object of the Week, January 3rd, 2016 - Abell 24 in Canis Minor
Object of the Week, January 3rd, 2016 - Abell 24 in Canis Minor
Abell 24 = PN G217.1+14.7, PK 217+14.1, ARO 134
R.A.: 07h51m37.6s
Dec.: +03°00'21" (2000)
Size: 6.0'
Mag: 13.60 photographic
Canis Minor (the smaller dog) is ranked as the 71st constellation, in terms of size. Of course, it features blazing Procyon as its brightest star, and Procyon is the 7th brightest star in the sky; it is a very challenging double star with a huge delta between the bright mag 0.37 primary and the mag 13 secondary, 4.1" distant.
Canis Minor has very few deep sky objects, relatively speaking. SkyTools tells me that there are only 248 galaxies here brighter than mag 16, only 13 with the NGC designation, only 3 IC's, and only 6 brighter than mag 14! Other than galaxies, there are 6 or 7 open cluster and 5 planetary nebulae, but only 2 of these are brighter than mag 16, those being the mag 15.4 Abell 22 and the mag 13.6 Abell 24, the subject of the first OOTW of 2016!
I observed Abell 24 just once, in a nice sky, from my regular spot in the local Anza-Borrego desert, altitude about 2500 feet, in the clear and cold winter sky, using my 25" f/5 Obsession. Without any filter, it was difficult to acquire until I tapped the telescope, and then it was detected only as a faint annular stain on the sky, without any details whatsoever, and with a diffuse edge... and not much more. Hey, this guy has an estimated surface brightness of 16.71 magnitudes per square arcminute! Of course it is difficult to see :>)
I added an NPB filter and the PN became more than just a glow, and I could see a slight brightening in 2 spots, on both the east and west sides, and I didn't note any brightening in the middle. I also didn't see the binary central star, listed at a mere mag 17.1.
During my hunt for photos of Abell 24, I ran across this web page, http://www.darklights.org/gallery/pn/ which has a unique feature; when you hover your mouse over an image you see a different image superimposed, where the imager used either an OIII filter or an Ha filter.
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