Bipolar Planetary Nebula Sanduleak 2-237 (PNG 11.1+7.0)

[Uwe Glahn]

After an idea of Matthias Kronberger we both could observe the spectacular bipolar PN Sa 2-237.

Observing conditions were nearly perfect, transparency was very good (Alpine place 2900m/9500ft) seeing good.

Already with searching eyepiece the PN was visible as a bipolar structure around the faint CS. With 27" and 586x to 837x the lobes of the PN were easily visible without filters. Filters brings out the lobes a little bit better but I tried to pass on any filter. The NE lobe seems to be a little bit brighter with a spot at the W edge. The SW lobe seems to be triangular with a brighter spot to the W edge and a better defined edge along the S. Both lobes were absolute symmetrical but seems to elongated E-W, that means not in the lobe-star line NE-SW.

Matthias could also see both lobes and the CS with 15". Perhaps he could tell us more detail.

For me it was one of the easiest and most conspicuous bipolar PN I ever seen, perhaps a goal for you.

Perhaps there are some observing reports. I would be interested in the minimum aperture for the bipolar structure and the structure of the lobes itself with big aperture.

Schwarz, Corradi and Montez (http://iopscience.iop.org/0004-637X/565/2/1084/pdf/54278.web.pdf) analyzed the PN and expected a binary star as the central object which forms the bipolar structure.

sketch with 27" (home (http://www.deepsky-visuell.de/Zeichnungen/Sa2-237.htm))
288

ESO NTT telescope (3,6m)
289

[mkronber]

Hi Uwe,

indeed, the two lobes and the CS of Sa 2-237 were visible in my 15" (same location + time as for Uwe's observation, magnification 420x). The view was obviously not as detailed as in Uwe's large reflector, but the centrally located pair of stars could be easily split and both lobes could be seen as roundish blobs and were separated clearly from the central star. The UHC filter dimmed the stars considerably, but brought out the lobes better; yet, even without filter they were easily detectable with averted vision.

As Uwe noted already, this is one of the easiest and most obvious highly collimated bipolar PNe for visual observers and definitely a highlight of this region of the sky. In fact, I found it to be amongst the most impressive PNe that I observed so far and recommendable even for observers with apertures down to 10".


CS,
Matthias

[reiner]

Hi Uwe and Matthias,

mid September is obviously no longer the right season for this object and it was already quite low yesterday as it got dark. Nevertheless, seeing and transparency were fine, so I gave it a try with my 22".

After having located the approximate field and switching to 200x, the PN stood out already without filter. Best view was with my 7 and 5, 350 and 500x, without filter, with both lobes well visible and the CS sandwiched inbetween. After switching to UHC there was an only slight advantage for the two lobes, but the CS was lost. Internal structures? Forget it at 20° above the horizon :-)

[hajuem]

Hi Uwe
Interesting object! I'll try, hopefully with very good conditions with 16 inches. The observation of Matthias with 15 inches, makes hope!

lg Hajü
www.astromerk.de