Object of the Week, November 1st, 2020 - IC 5148/50, PN G002.7-52.4, PK 002-52.1, ESO 344-5… in Grus
R.A.: 21h59m35.1 Dec.: -39°23'08" (2000)
Size: 2’
Magnitude: 11.00 Surface brightness 21.1 Mag/arcsec²
Magnitude of the central star: 16.5

I finally went observing for the first time in a long time for 3 nights during the last new-moon window in mid-October. Both the weather and the pandemic had kept me home for many months. I had no observing program planned, so I just whipped up a couple of observing lists using the Data Power Search Tool in SkyTools. One of these lists was for planetary nebulae, and my wife Debbie and I just cruised from one to the next to the next, having a great time in the local Anza-Borrego Desert, and our telescope that night was our 25” f/5 Obsession classic. In the back of my mind, I was looking for a good candidate for my upcoming OOTW post. I found a good one in IC 5148!

ESO PHOTO OF IC 5148.jpg

Since I observe from about +33° latitude, IC 5148/50 rises to about 18° above my southern horizon when it transits, which give me a pretty good look when conditions are good. On this particular night, conditions were more-or-less average, but Deb and I got a pretty good look anyhow. IC 5148 presented itself as an exquisite and nearly perfect and fairly thick ring, looking almost exactly like what they call it in Australia, a “Spare Tyre”. On this night there was not much detail to be seen, but I’m pretty sure that I could glimpse the central star, which leads me to think that perhaps the stated magnitude of 16.5 might be understated. The eastern half looked a little brighter to me, but not by much.

IC 5148.jpg

IC 5150 was discovered by Australian amateur astronomer Walter Gale (from Sydney) in 1894… but was subsequently re-discovered in 1897 by Lewis Swift as IC 1848. There is some confusion here regarding position, with Swift’s position differing by about 30” of arc. In any case, the IC 5148 designation is apparently the most accepted one, even if it was discovered 3 years later. I’ll bet that Steve G. can shed light on this issue and set us all straight.

IC 5148/50 is about 3000 light-years away and is a couple of light-years across. It is expanding at a rate of about 30 miles per second, one of the fastest expansion rates of all planetary nebulae.

This guy was the highlight of our observing that night, and for good reason!

As always, give it a go and let us know.