MASH Planetaries for Hawkeyes

by Steve Gottlieb

Haven't heard of a MASH planetary? The acronym stands for the "Macquarie/AAO/Strasbourg H-Alpha" planetary nebulae (PNe) catalogue. This international effort recently discovered 900 true, likely and possible new galactic planetaries during an H-alpha survey of the southern galactic plane.

The discoveries were made using the Anglo-Australian Observatory UK Schmidt Telescope (AAO/UKST) H-alpha survey. This deep, high-resolution survey (http://www-wfau.roe.ac.uk/sss/halpha/) was completed in 2003 and used an H-alpha interference filter to cover 233 survey fields. By visually scanning these fields under a microscope, the MASH team netted a 60% gain in the total number of known galactic PNe and doubled the number known in the galactic bulge. Final results were published in November 2006 (Monthly Notices of the Royal Astronomical Society, 373, 79-94).

The galactic bulge discoveries tend to be faint but compact planetaries. Outside the galactic bulge, the discoveries generally involve large, older planetaries that were missed in previous surveys because of their low surface brightness or by being obscured.

Is it still possible to observe a planetary that was discovered just a few years ago? Unfortunately, the vast majority of these planetaries are too faint for amateur scopes, but there are a few "brighter" entries and with some preparation it's possible to track down some of the MASH objects. Personally, I find it an exciting challenge to glimpse at an object that was discovered so recently that you know you're one of the first few observers to have ever taken a look. As of August 2008, I'm aware of observations of 7 MASH discoveries (discussed below). If you can add to this list, let me know and I'll post your observations. For the entire MASH catalogue see http://vizier.cfa.harvard.edu/vizier/MASH/index.htx

Here are observations of three summer MASH planetaries I made with my 18-inch Starmaster. You'll need good finder charts as well as OIII or narrowband filters to track these down. The following H-Alpha images are from MASH Image Gallery (http://vizier.cfa.harvard.edu/vizier/MASH/gallery.htx) and span 4'x4' with north up.

PN G027.0+01.5 = PHR J1835-0429
18 35 11.6 -04 29 06
Size 32"x25"

At 175x unfiltered a mag 13 star was visible and a small ill-defined halo was highly suspected surrounding the star knowing the exact location. Adding an OIII filter, the halo brightened nicely and the edge sharpened to a 20" disc. The involved star appeared offset to the north side.

This object was originally listed in Neckel and Vehrenberg's "Atlas of Galactic Nebulae" as a "star with nebula" and then erroneously included in the 2003 "Merged Catalogue of Reflection Nebulae. The MASH catalogue is the first to identify this object as a planetary.

PN G014.8-08.4 = PHR J1849-1952
18 49 24.3 -19 52 16
Size 19"x17"

Picked up at 300x as a very small, faint glow ~5" diameter attached on the NW side of a mag 14.5 star with a fainter mag 15.5 star sometimes visible on the NW edge of the glow. Adding a DGM Optics NPB filter, the contrast increased significantly and the planetary was visible continuously with averted vision as a ~10" disc. Surrounded by a small, partial 2' ring of mag 13-15 stars.

PN G026.2-03.4 = PHR J1851-0732
18 51 31.3 -07 32 29
Size 45"x35"

As this planetary is a recent MASH discovery, I was pleasantly surprised to find a relatively bright, fairly small disc at 175x using a NPB filter just west of a mag 12 star (barely detached). A fainter star is just off the NW edge. The planetary had a slightly elongated halo, ~30"-35" in diameter, with a fairly crisp edge. Removing the filter, it was very difficult to identify the planetary as it resides in a rich field 75' south of M11 and the suspected haziness at the position was similar to the general Milky Way patchiness in the field.

The following four MASH planetaries were observed by Kent Wallace using a 20" f/5 Obsession. These are the first known visual observations of these objects.

PN G010.1+07.4 = PHR J1741-1624
17 41 04.0 -16 24 47
Size 12"

At 134x, 169x and 254x, faint, unsteady small disk, requiring the O-III filter and averted vision. Fair response to the O-III and UHC filters. No response to the H-Beta filter. This is a first known visual sighting.

PN G013.1+05.0 = PHR J1755-1502
17 55 46.4 -15 02 44
Size 8"

At 254X, very faint, very small disk, unsteady, requiring the UHC filter and averted vision. Fair response to the O-III and UHC filters. No response to the H-Beta filter. The image was best through the UHC filter.

PN G020.9-11.3 = PHR J1911-1546
19 11 04.4 -15 46 07
Size 153"

At 134X, very faint, good sized mottled disk, requiring the O-III filter and averted vision. Fair response to the O-III and UHC filters. No response to the H-Beta filter. Actually the UHC filter sems to be a bit better than the O-III filter. At 169X, the image was worse.

PN G012.1-11.2 = PPA J1855-2328 = CGMW 4-3783
18 55 04.9 -23 28 12
Size 20"x18"

At 134X, can see it as an elongated object, perhaps a double star with averted vision alone. Using the O-III filter with averted vision a nice small disk envelopes the elongated object. Good response to the O-III and UHC filters. No response to the H-Beta filter. At 169X and 254X, the elongated object is a close double star aligned roughly NE-SW with the brighter component to the SW. Again, the use of the O-III filter with averted vision envelopes the double.