12-13 August 2021, 23:00 – 02:00 (BST)
Seeing: Good to poor (and back again; sometimes in the space of a couple of minutes)
Transparency: Good / Average
Conditions: Mild, with a light breeze. The temperature dropped noticeably after midnight, and there was a thin layer of condensation on the scope by the end of the session. The transparency was quite good for the time of year (both M31 and the Double Cluster were visible to the naked eye without too much trouble), although Jupiter was so bright you could almost regard it as a source of light pollution.
Tonight the Perseids took centre-stage and they didn’t disappoint, although the first two meteors I saw were both sporadics, including a bright one flashing from the zenith towards the west. I didn’t see any fireballs, but several of them were bright enough to leave trails. In between being distracted by meteors, I found time to revisit a few telescopic targets:
RS Ophiuchi, Recurrent Nova, Ophiuchus
133x. The nova had noticeably dimmed since Tuesday night (to about 6th magnitude), but was still obvious in the finder. Through the eyepiece it had a strong red hue which was quite striking. According to the Astronomer’s Telegram service, the nova has been monitored intensively at wavelengths right across the EM spectrum, so I look forward to finding out what new discoveries have been made about this intriguing object.
I then spent a few minutes looking at M11 and M57 (again). At around 23:40 a very bright Perseid flashed south of Pegasus, leaving a long trail glowing in its wake for a second or two. A couple of minutes it was followed by two more fast meteors which also left brief trails.
M52, open cluster, Cassiopeia
133x. Expanding on previous observations. Rich, delta-shaped cluster in a busy Milky Way star-field. This shape tends to be lost in photographs but it’s quite distinct though the eyepiece. Member stars have a range of magnitudes. Bright yellow-orange star at the apex of the delta on the southwest corner. Elongated clump of stars on the northeast side of the cluster (at the back of the delta).
At around midnight I took another short break for meteor-spotting, including a super-short Perseid coming straight from the radiant near the Double Cluster. I then pointed the telescope south to revisit some targets in Aquarius.
M72, globular cluster, Aquarius
133x. Large round glow, brighter towards the centre. Two bright field stars to the east. Two stars just southeast of the cluster and a fainter one to the northeast (presumably these are field stars too). At 171x the cluster was fainter, but did appear speckly with averted vision. The core seemed to have a triangular shape (reminiscent of M71), pointing west. The effect was enhanced by what appeared to be a dark lane (running north-south) just east of the core. At 240x I could just make out little pinpricks of light winking in and out of view, but this was right on the limit of what I could see. I certainly wouldn’t regard this cluster as anywhere near “resolved”. It’s not a bad object, but I can think of a few NGC globulars visible at this time of year that are at least as good, if not better, such as NGC 6712 in Scutum.
M73, asterism, Aquarius
171x. As noted previously, four stars in a Y-shaped asterism pointing west. I hadn’t noticed this before (because the magnification wasn’t high enough) but M72 points roughly towards a very tight 10th magnitude double star, with north-south components separated by only 2 or 3 arcseconds. 171x barely splits it, but it’s a little easier at 240x. Aladin Lite lists it as HD 199524.
NGC 7009, “the Saturn Nebula”, planetary nebula, Aquarius
171x. Bright blue-green ellipse aligned east-west; compared to M72 and M73 it really does jump out. I couldn’t see any structure in the nebula (or the central star), but there was just a hint of the projections (the ansae) with averted vision, particularly on the western side. I doubt I would have noticed anything if I hadn’t already known they were there. Similar impression at 240x; this nebula holds its brightness well at high magnifications even without a filter.
It only seemed appropriate to follow the Saturn Nebula with Saturn itself (at 240x). The seeing was initially very poor in this part of the sky, but after a few minutes it stabilised, allowing a brief but very sharp view of the ringed planet. In addition to Titan, three other moons were visible: Tethys west, Dione and Rhea east.
I then switched to Jupiter, just in time to catch Io’s shadow moving onto the disc followed closely by Io itself, which surprisingly remained visible even after it had passed beyond the darker part of the limb (appearing as a bright spot against the equatorial zone). The Great Red Spot was also on show, although its colour still seemed rather subdued compared to recent years (more of a coral pink compared to its previous brick red). I increased the magnification from 240x to 343x (7mm DeLite + 2x Barlow) and the seeing was good enough for me to resolve the moons as tiny discs, with Ganymede appearing noticeably larger than the other three. The view was so good it was an effort to tear myself away from the eyepiece, but fortunately I got the laptop and the camera ready in time to capture one decent set of images before the seeing deteriorated. (South at the top to match the eyepiece view.)
Here's an attempt at a sketch in pastel showing the beginning of the transit, but even with a bit of tweaking in Photoshop I still think the result looks less like the eyepiece view than the digital image. With hindsight, perhaps watercolour or coloured pencil would be a better choice of medium for planetary sketching.
Two more Perseids closed the show as I was packing up.
Also:
Tonight’s soundtrack came courtesy of frogs roaming in the garden, drunken revellers singing in the town, and police sirens (it was the penultimate night of Folk Week).
I also noticed several bright satellites (presumably Starlinks, although there haven’t been any launches recently) following near-identical paths from the west, disappearing into the Earth’s shadow somewhere north of the zenith. There were also a lot more planes in the sky – some travelling east, but the majority travelling west (i.e. into the country).
