Longmore-Tritton 5, LoTr 5, PN G339.9+88.4
12 55 33
+25 53 30
Longmore-Tritton 5 has a diameter of about 9' and is therefore one of the very large PN. However, compared with most of the other members of that illustrious list, it is an "easy" object with OIII filter (it's only very faint instead of extremely faint :-)).
DSS images of LoTr 5 (color and blue inverted).
LoTr 5 was discovered by A.J. Longmore and S.B. Britton in 1980 by visual inspection of blue plates of the ESO/SRC Southern Sky Survey taken with the UK 1.2m Schmidt telescope. LoTr 5's galactic coordinates are 339° +88°, the PN is therefore at a (for a PN) very unusual position close to one of the galactic poles: A single PN amidst thousand of galaxies at the Coma/Virgo border. At the time of its discovery, it was the PN with the highest galactic latitude. Its central star IN Com is a binary formed by a relatively bright (8m7 vis) G5 star and an extremely hot (150 000 K) white dwarf. Further, a third M5 companion to the G5 star had been suggested.
LoTr 5 is a bipolar PN, even if it doesn't look like it at the eyepiece (http://adsabs.harvard.edu/abs/1980MNRAS.193..521L). Its bipolar axis deviates only 17° from our line of sight, such that we are viewing this PN "head-on". Good images of this PN were obtained by Stefan Binnewies and Josef Poepsel http://www.capella-observatory.com/I.../PNs/LoTr5.htm and by Stefane Zoll http://www.astrosurf.com/zoll/images...LORGB_1280.jpg. On these deep images, the bipolarity becomes evident and the PN appears as two slightly excentric rings.
I have observed this PN already several times under various conditions with both my 14" and 22" Dobs:
Under fair skies, it is difficult to separate the diffuse glow of this PN from stray light of its mag 8.7 central star, even with OIII filter.
Under excellent conditions, the PN reveals a faint disk with well defined edge towards S, coinciding with the weak star in between the central star and the bright star S of it. Under such conditions, it is also visible using the UHC filter, albeit with somewhat lower contrast. Due to the relatively bright CS, it is very difficult to nail down any internal structure.
So when you're hunting in the Virgo Cluster, don't forget to switch to your OIII filter and take a look at this unusual PN. Can you see evidence of the bipolarity and the two slightly excentric rings?
"GIVE IT A GO AND LET US KNOW"
GOOD LUCK AND GREAT VIEWING!