Planetary Nebulae in Aquila

2 August 2018, 22:00 – 00:00 BST

Transparency improving week by week, but the seeing seems to be going the other way. Saturn only showed well for fleeting moments, not enough to justify attaching the camera and the laptop. From about 23:00 onwards the entire Sagittarius “teapot” asterism was visible, with Epsilon Sagittarii (Kaus Australis) being the most southerly star I could see at -34 deg 23’ declination. (Apparent mag. +1.85).

The ISS also made one of its regular appearances.

All observations at 133x (Nagler 9mm) unless otherwise stated.

M17 (Omega/Swan Nebula), nebula in Sagittarius
Very bright both with and without the Ultrablock (although the filter really helps improve the contrast in this light-polluted part of the sky). An extended bar of nebulosity with the brightest part forming the characteristic “2” or swan shape around a conspicuous dark patch. The main bar takes on an impressively mottled structure with the filter in place.

M22, globular cluster in Sagittarius
A large, sprawling ball of stars. Surprisingly well resolved despite its very low altitude and the murky light pollution.

Intrigued by all the planetary nebulae symbols marked on the PSA chart for Aquila, I decided to take a closer look...

NGC 6751, PN in Aquila
Small, featureless disc of light.

NGC 6781, PN in Aquila
Large, low surface-brightness nebula. Responded well to the Ultrablock filter. Not perfectly round; suggestion of an asymmetric dark core.

NGC 6804, PN in Aquila
Medium sized planetary nebula. Faint field stars in and around disc – could trick a casual observer into thinking they were looking at a partially resolved star cluster.

Also looked without success for NCG 6741 and 6803 – though I discovered later it was probably due to their very small apparent size. I did however notice a couple of conspicuously bright aquamarine “stars” through the Ultrablock filter, so it’s possible I did see them without realising it.

M71, globular cluster in Sagitta
Not completely resolved (unlike the comparably rich M11), confirming its status as a globular cluster, albeit a very loose one. Roughly triangular in shape, with chains of stars forming two swept-back “wings”.

Mars
Current altitude (approx. 12 degrees) is so low I was literally looking at it through my neighbours’ fence, so the image was severely hampered by diffraction as well as poor seeing. Suggestion of polar brightening, but no significant detail seen.


Nature Note
Saw one big frog in the pond, but no froglets. The heavy rain on Friday night seems to have been the cue for a mass exodus. In recent evenings I’ve also seen a couple of bats hunting low over the garden.