Observation of IRAS 17436+5003 / PN G0.77.1+30.8, a post-AGB (PPNe) object

[sudhashn]

Hello all,

In my recent visit to Hanle (a Bortle 1 location in Ladakh, North India), a cold dry dessert at an elevation of 4300m, (32°47'N 78°58'E ), I tried to observe this Proto Planetary Nebulae in the constellation Hercules (about 1.8° of Eltanin in Draco).

From my voice notes
Located it in the 17mm Baader Hyperion (~90x) eyepiece, looked like a bluish star. Flanked by 2 stars of similar brightness forming an almost equilateral triangle with the object. Needed to go much higher in magnification.
Properly observed with 6.5mm ES eyepiece + 2x Barlow (460x). Did try with 10mm Super Plossl (150x), 6.5mm EP (230x). 230x started showing some nebulosity.
A definite bigger halo, almost circular in shape, was observed. Compared to the halo of nearby two (pretty close to each other) stars, this halo was larger & definitive. Nearby dimmer stars resolved into pinpoint sources too.

As it was a manual scope (with no tracking), I had great difficulty in maintaining the object in the FoV. After 15-20min of struggle, could keep for 20-30s in the FoV to observe properly.

Two accompanying friends (visual observers) confirmed elongation between 1-7O clock positions (in the FoV). However I couldn't observe elongation consistently.

Equipment used : 12" Skywatcher Dobsonian 300mm Flextube Collapsible, manual.
Conditions: Bortle 1 (pristine conditions I have ever observed).
Observation on 30th Sept 2024, 8pm - 10pm.

Other designations: V814 Her, HD 161796 Simbad query here.

P.S. As I was browsing through Stellarium for objects, usual grid search of 1.5° x 1.5° in Stellarium, found this & noted it down for observation (months before). Interestingly enough, did remember to observe it on the trip too.

Would love to hear from the community on your observations on the same object. Upon research, understood that this is an unique class of object that I have gotten to observe & conditions/friends helped.

Regards
Sudhash

[Clear Skies]

Hi Sudhash,

I took a look at the information you sent and I can not identify an extended, non-stellar object at the position of V814 Herculis. I am quite confident you observed a halo brought upon your optics by that mag. 7.3 star.

Cheers,


Victor

[Steve Gottlieb]

Here's an HST image, which shows an irregular dust shell elongated N-S, though scattered light from the bright post-AGB star does seem reasonable.

The Torun catalogue of Galactic post-AGB and related objects has a page on this star here with photometric data and bibliography.

[Clear Skies]

The problem with this "observation" is unfamiliarity with angular size and the true field of view in an eyepiece. In (visual) astronomy this is as basic a thing as understanding right ascension & declination and cardinal directions.

As the Hubble images show, the object is a mere 4"x2" in size. In speak, that is four by two seconds of arc. We call planetaries of that size 'stellar'.

The image below is a POSS2 Blue DSS image, 1/4 degree = 15' in size (fifteen minuten of arc) = 900" (nine hundred seconds of arc).

15.jpg

The size of the object, per Hubble image, translated to the DSS image scale is therefor 4/900 x 2/900.

Please note the little red speck centered on V814 Herculis; I drew an ellipse but on an image scale of 900 pixels, a 4 x 2 pixel ellipse becomes a rectangle. Anyway: that's the angular size of the object "observed". Is that an object that can be observed with a mag. 7 star smack in the middle of it..?

Finally, please compare this image posted on Cloudy Nights. The arc drawn onto that image is > 1' = > 60" (greater than one minute of arc = greater than 60 seconds of arc) which is well over fifteen times the (long side's) size of the object imaged by Hubble.

Please, fellow stargazers, do not use Hubble images to plan observations and please, do take the effort to familiarize yourself with the very basics of celestial mechanics, star charts and the gear you use. 'Cause if you skip the basics, you will be forever stuck in them.

[wvreeven]

The Hubble image shows that there is a shell so there is a possibility that it can be observed visually. In that sense the Hubble pic can very well be used for planning observations.

A shell of 4" x 2" is tiny but not impossible. 4" is comparable to the size of the disk of Uranus. 2" is comparable to the size of the disk of Neptune. It is possible to discern the disks of Ganymede and other Jovian moons visually and those are even smaller.

Having said that, discerning a faint tiny disk surrounding a magnitude 7 star is challenging, to put it mildly. But given the right sky conditions and optical elements, I don't think it is impossible, especially if filters can be used that dim the star but not the disk.


Clear skies, Wouter

[Clear Skies]

.

The Hubble image shows that there is a shell so there is a possibility that it can be observed visually. In that sense the Hubble pic can very well be used for planning observations.

A shell of 4" x 2" is tiny but not impossible. 4" is comparable to the size of the disk of Uranus. 2" is comparable to the size of the disk of Neptune. It is possible to discern the disks of Ganymede and other Jovian moons visually and those are even smaller.

Having said that, discerning a faint tiny disk surrounding a magnitude 7 star is challenging, to put it mildly. But given the right sky conditions and optical elements, I don't think it is impossible, especially if filters can be used that dim the star but not the disk.


Clear skies, Wouter

Yeah, no.