Double Stars (and Galaxies) in the Moonlight

2 December 2019, 18:15 – 20:30 GMT

Not quite as chilly as Friday – at least not to begin with, but my feet were seriously cold after two hours. Negligible wind. No clouds until 20:30, but some patches of haze from what I think were lingering vapour trails (they were visible at sunset and didn’t look like they were going anywhere fast - unlike the planes that created them).

Transparency: Slightly better than Friday but some interference from six-day old moon (improving as it sank towards the horizon). I was able to see M74 through the scope so it couldn’t have been that bad.
Seeing: Good

The session began with a long-overdue first look at the Moon through the 13mm Ethos (with the Baader ND filter) and it didn’t disappoint. Wonderful, field-filling view with crisp detail right across the lunar surface. The image rippled a little bit (because the moon was low in the sky and near the rooftops), but the field was so large I could easily switch my attention to an unaffected part of the disc without having to touch the scope. Shadows were deep and very black, and (perhaps most impressively) the Ethos controlled the light scatter better than any other eyepiece I’ve looked through. I’ll be interested to see if this observation holds up at fuller phases. Notable features included the Theophilus crater group, Posidonius and the Messier A and B crater pair. The earthshine stood out clearly against the black sky and I was even treated to a bonus occultation at 18:26 of the 7.4mag star HIP 107610 (HD 207208) in Capricornus.

With the sky still relatively bright I exchanged the Ethos for the 5mm Nagler and observed a few double stars, including Polaris, Gamma Arietis and Almach (Gamma Andromedae). Zeta Persei looked much the same as it did on Friday, but the higher magnification revealed a few more faint stars in the background.

Omicron Persei wasn’t split, but it did look elongated, with the companion roughly due east of the primary. I noticed a small cluster of stars a few arcminutes south of Omicron, corresponding with the star forming region IC 348.

NGC 404 (Mirach’s Ghost), galaxy, Andromeda
Faint, but obvious at 240x. Clear brightening towards the core, even with Mirach still in the field of view.

Uranus
Similar view as Friday – tiny little green-grey disc. Titania suspected at 133x, but not at 240x.

M77, Seyfert Galaxy, Cetus
Viewed at 133x – obvious despite moonlight. Very bright nucleus; size of galaxy swells with averted vision. Could easily be mistaken for comet by unwary observer. Bright field star to west. Holds brightness well at 240x but no real increase in detail other than an extended core region (distinct from the nucleus).

Alpha Piscium (Alrescha), double star, Pisces
Very close double (1.8” separation), but clean split at 240x. Bright companion due west. Some occasional colour fringing where the diffraction rings overlapped, but the stars themselves looked white to me.

M74, spiral galaxy, Pisces
Viewed at 133x. Very faint, but not what I would class as difficult (at least compared to some of the Caldwell objects). Given the moonlight and the condensation I was surprised I could see it at all. Brighter towards the core with averted vision. With prolonged observation there almost seemed to be an impression of spiral structure, but I think this was an illusion caused by the 3 field stars east of the core and another one to the west.

At this point a combination of cloud, condensation and cold drove me back indoors.