Nebulae in Sagittarius

22 – 23 July 2020, 23:00 – 1:00

Conditions: Breezy, partial cloud cover to begin with – clearing over the course of the session and then returning towards the end.

Seeing: Poor / average
Transparency: Average / poor

I know I’ve spent a lot of time exploring Sagittarius lately, but at the rate the neighbour’s trees are growing and the likelihood of local light pollution returning to its pre-lockdown levels, this might be the last best chance I get to study this object-rich part of the sky. With the nights growing longer again, the wonders of Cygnus and Cepheus will still be well-placed for the next two or three months; the same can’t be said for the southern Milky Way.

NGC 6440, globular cluster, Sagittarius
133x. Faint condensed blur in same field as NGC 6445, brightens with averted vision.

NGC 6445, planetary nebula, Sagittarius
133x (no filter) and 171x (OIII). Quite faint without the filter (one of the consequences of averted vision is that this nebula was easier to see when I was looking straight at 6440). With the filter in place, 6440 disappeared and 6445 became much more obvious. The higher magnification made the misshapen ring structure more apparent (it looked more like a buckled wheel than a box). Most prominent feature was a bright condensation on the northern rim.

M8, Lagoon Nebula, Sagittarius
171x + OIII filter. Obviously M8 loses a lot of its impact at this magnification, but the brightest part of the nebula is easier to study. Hourglass shape apparent, of which the southern component brighter. Smattering of embedded stars visible with averted vision.

M20, Trifid Nebula, Sagittarius
171x + OIII filter. M20 also loses some impact at higher magnification, but the central star system was easier to resolve (when the seeing allowed) as a line of three very close stars. Nebula and dark lanes best seen with averted vision.

M16, Eagle Nebula, Serpens
171x + OIII. Averted vision showed a dark patch at the centre of the nebula, but the contrast was still too low to make out any kind of shape or structure. Lower magnifications are better for this object.

M17, Swan Nebula, Sagittarius
171x + OIII. Nebula still very bright at 171x. This magnification doesn’t really add anything to this object although the dark lanes were a little easier to see, giving it a segmented appearance. The body section does appear remarkably straight, like it’s been “dragged” across the sky with a paintbrush.

NGC 6629, planetary nebula, Sagittarius
171x + OIII. Very small, bright little disc, north of M28. I may have seen the central star with averted vision, but it was tough to separate from the nebula.

I also looked for other Sagittarius planetaries 6537, 6567 and 6644 with this eyepiece/filter combination, but they eluded me on this occasion. Or to put it another way, nothing jumped out at me in the manner that 6445 and 6629 did.

M28, globular cluster, Sagittarius
133x. As per previous observations. Bright, condensed; grainy with averted vision.

M22, globular cluster, Sagittarius
133x. If this is my last look at Sagittarius for the year I had to finish with arguably its most spectacular object. Several dozen stars seen in direct vision. The low altitude can make this cluster look somewhat washed-out at first glance, but it's well worth investing the time to let the magnificent view build up on your retina like a developing photo.

As usual I closed the session with a look at Jupiter and Saturn. Jupiter was the stand-out tonight with the GRS on show and all four Galilean moons positioned on one side of the planet. However the seeing was too mushy to bother with an imaging run.