Anno Domini MMXIX
My conversion to Newtonian telescopes continues apace. Though I’ve had my wonderful 130mm f/5 Newtonian travel ‘scope for a few years now, it never ceases to impress me. And my observations on the freezing night of November 18 with the same instrument only served to consolidate those sentiments.
I set the telescope out on its trusty Vixen Porta II alt-azimuth mount about 10.30pm local time and tweaked its collimation before leaving it to cool down from an indoor temperature of 20C to an outside temperature of -5C. The optical tube is quite rigid and it holds accurate collimation very well, which is fine for general observing, but I always fine-tune the alignment of its two mirrors when going after the tightest double stars. I knew conditions would be good for such an activity by noting how little Vega was twinkling low down in the western sky, while bright stars like Capella and Mirfak located high overhead shone with a steady, planet-like gleam.
The tube is insulated with a thin layer of cork and overlaid by black flocking material. I have noted that this affords extra thermal stability to the telescope, especially as temperatures drop rapidly(as occurs during acclimation on these cold nights). I do not use any air-blowing fans to accelerate cooling of the primary mirror, but this has never really been an issue with this small Newtonian telescope.
After enjoying a lengthy binocular session using my 20 x 60 on a simple monopod, I began an hour of telescopic observations on a number of seasonal double stars, beginning about 11:20pm. Orion was quite well placed east of the merdian, so I inserted my Meade 5.5mm UWA yielding 118x on a fairly low lying Rigel, carefully focused and observed the stellar image. Wow! What an amazing apparition! I was greeted by an intensely bright image of this white supergiant star, with beautiful diffraction spikes radiating outwards from a calm Airy disk. And just a little to its southwest, its faint close-in companion was easily discerned. That was enough of a confirmation that seeing conditions were indeed very good, so from there I panned the telescope northward to the better placed belt stars of Orion, examining both Mintaka and Alnitak at the same power. The images of both stellar systems were lovely and calm, with beautiful hard Airy disks betraying their companions with ease.
From there, I moved up to a more challenging system, 32 Orionis, located just a few degrees east-southeast of Bellatrix. Coupling a 3x achromatic Barlow lens to the Meade 5.5mm yielding a power of 354x, I carefully focused the image, watching it as it raced across the field of view. Sure enough, its close-in companion(separation ~ 1.3″) proved easy pickings for this light-weight 5.1-inch telescope situated just off to the northeast of the primary. Before leaving the celestial Hunter, I had a quick look at Eta Orionis, another fine, high-resolution target, consisting of a magnitude +3.6 primary and a tight, magnitude +4.9 secondary. Both were nicely resolved at 354x, and roughly orientated east-to-west.
Pointing the telescope at majestic Auriga, now very high in the sky, I trained the instrument at Theta, an old friend, and backed the magnification down to 236x by swopping out my 3x Barlow for a 2x Orion Shorty. That was more than enough to resolve its ghostly companion in the still midnight air.
I spent the next quarter hour exploring some favourite doubles in Cassiopeia, notably the lovely colour contrast pair, Eta Cassiopeiae, admiring the textbook perfect images of its yellow primary and ruddy secondary at 118x. And from there I moved to Iota Cassiopeiae, beholding this beautiful triple system at 236x. These views inspired me to swing the instrument westward into Andromeda, where I quickly tracked down another binary superstar, Almach, where the telescope showed me a gorgeous, crisp image of the orange primary and widely separated blue secondary at 118x.
After a quick look at Castor A, B and C at 118x, I trained my eyes on Propus, the ‘orange nemesis,’ as I have come to call it, which by now was reasonably well placed but still a few hours from culminating in the south. This system requires very high powers, so I broke out my 4.8mm T1 Nagler and coupled it to my 3x Barlow lens, delivering a magnification of 405 diameters. Carefully focussing the star, I watched it cross the field of view several times, observing its behaviour at this ultra-high power. During some moments, the system swelled up to become a rather unsightly seeing disk owing to a combination of thermal stress and variations in seeing, but sure enough, there was always prolonged moments where the image came together, as it were, allowing me to carefully examine the stable Airy disk. And it wasn’t long before I began to see the little blue pimple of light from its tiny secondary touching the marmalde orange primary. Having examined this system quite a few times with the 130mm Newtonian over the last few years, I have learned that good seeing doesn’t always yield commensurately good results. This I attribute to the slightly variable nature of this post-main sequence star, which can often hide the companion. But tonight, my patience paid off!
I ended the vigil shortly before half past midnight local time, by moving the telescope from my back garden to the front of the house, where I was greeted by the light of a silvery last quarter Moon, hanging above the Fintry Hills to the east. Inserting the little 4.8mm Nagler delivering 135x, I enjoyed some wonderful, crisp images of the battered lunar regolith, particularly the majestic Apennine Mountains strewn across its mid-section, near the terminator, as well as the magnificent desolation of the heavily cratered southern lunar highlands.
Simple pleasures of a telescope.
It was good to get out. But it was equally nice to retire the telescope indoors and reflect on the experience, sat next to a warm coal fire.