A Moonshadow, and some deep-sky treats.


Had a good session on Saturday night with the 10” reflector on a dobsonian mount. One of the highlights was the unexpected Jovian shadow transit of Ganymede. From around 1am to 2am I watched the shadow of the moon travel across the disc from left to right, (left to right in eyepiece). I saw later the transit was discussed in the July Sky at Night magazine, but I missed reading it, so it was a nice surprise. There are more shadow transits later this month.
Deep sky stuff; I started off in Sagittarius with one of my favourites that never gets very high in the UK, M8 the Lagoon Nebula, which also has open cluster NGC 6530 in the same field of view. It took a few minutes for the nebulosity to ‘grow’, but I managed to make a sketch. This is one of the most distinctive deep sky objects.
A failure tonight was the globular cluster M4 in Scorpius. I’ve never seen it, and still haven’t, though I suspect I wasn’t looking in the right place. After checking my Glyn Jones Cambridge Messier book, I was looking too far to the left I think. I’m pretty sure the 10” mirror should have picked up this 6.4 mag cluster, despite its low altitude.
Back to Sagittarius, and near M8 are globular clusters M22 and M28, which were easily found, and both markedly different in size and contrast. M22 is smaller in the eyepiece, bright and compact, and M28 much larger and ghostly.
With Capricorn so high, I was able to make my first observation notes on Messier objects M72 and M73. M72 is a loose, quite open globular cluster, 62,000 LY away. Easy to find by star-hopping from Capricorn (though M72 and M73 are technically in Aquarius). M73 is a four star asterism, and a quirk of the Messier list, (like M40 in Ursa Major).
Because I was looking mostly towards the south, it was an evening for bright globular clusters. M13 (Hercules), M5 (Aquarius) , all really bright, contrasty and resolvable.
M11 – The Wild Duck cluster is one of the Summer’s jewels. When doing a 10×50 Opticrom bino tour of the Scutum area I noticed a bright patch below it, which I found was the cluster M26. Not often visited by me, and a little underwhelming in the scope. A better binocular object?
Galaxies are a challenge in nautical darkness, but I managed observations of M101 (the Pinwheel) and M94 in Canes Venatici, which was surprisingly bright.
Around 2.45 the Milky Way disappeared, almost within minutes! The Sun was making its way towards the horizon and I just managed some binocular observations of M31 and the rising Pleiades open cluster (M45) in an adjoining field, rising in the east.
Edit – I forgot the planetary nebulas M27 and M57. The latter (Dumbell) being very bright indeed.
And, Saturn, of course.