A Planet Pair Viewed in a Scope Atop a Trash Container
by Craig Cortis
Yes, you read it correctly. I thought my long title would make for an engaging introduction to an anecdote about the recent close conjunction of Venus and Uranus. Back on the evening of Thursday, February 9, these two worlds were drawing ever closer in apparent separation to a projected gap of just 18 arc-minutes – less than one-third of an angular degree – at 8:00 p.m. Actually, it’s more accurate to say that Venus was “approaching” the position of Uranus on the sky as the brilliant, much nearer planet moved swiftly eastward along the ecliptic. As of 7:00 p.m. on that evening, the planets were a little over 2 degrees of angle to the east-northeast of the Vernal Equinox point. The sky was nicely clear and no wind arose when I went outside to have a look at about 6:15. Although they would set at 8:42 from my location in Oxford, Mass., the planets were sufficiently high for easy viewing.
Some of you might recall past articles I’ve written having references to my strong inclinations to casual, low-tech observing, particularly with respect to compact, easily managed “grab-n’-go” scopes that can be set up and made ready to use in 5 minutes or so. The Edmund Scientifics Astroscan telescope has long been my favorite in this regard, because it often takes just a minute to set up. All you need is a fairly stable, small surface on which to place the little base that accepts the spherical base end of the scope – just plunk the thing down and set the Astroscan down on it, and you’re ready to view. Nothing could be simpler, provided you don’t mind being limited to the low magnifications yielded in an instrument having a focal length of just 445 millimeters (17.5 inches) and aperture of 105 millimeters (4.125 inches), which might seem puny in this day and age of so many larger telescopes in common use. Also, the Astroscan’s “fast” focal ratio of 4.24 makes for obvious coma on star images seen near the edge of the field and necessitates a level of collimation that’s very tough to achieve if your particular scope has gotten “out of whack” for some reason. (Even if the collimation is nearly perfect you’ll still have to accept some coma, after all.) I’m not bothered by these various features, though.
Perhaps 12 or more years back, I bought an Astroscan from Bob Horton at a Skyscrapers function. Ladd Observatory has a few in its equipment inventory; I usually use one during Tuesday public nights out on the deck to show wide-field views of things that simply can’t be seen well in more restricted fields of view. The Pleiades are a perfect example of just how pleasing a view can be obtained on large angular size objects like this; nothing else compares, except a binocular. One thing an Astroscan is notorious for is the fact that nobody other than factory techs or those experienced in collimating their optics can actually do so, because, basically, there is no adjustment provision inherent in this scope that permits external adjusting of the primary or diagonal mirrors! It’s a completely enclosed optical system with a window set in the front end. Partial disassembly must be done to clean or tweak the optics, and the narrow tube diameter makes it difficult to manage this – the scope has a solid, unibody form.
My own Astroscan had been badly in need of both cleaning and recollimating for years, so I turned it over to my friend Tim Dube of East Douglas, Mass. a few months back so he could work his usual magic. Tim can collimate almost anything, and has done so many times over the years. The result was a scope in better condition than at any time since I’ve owned it, and I was eager to use it for such a special occasion. By now you’re wondering about the trash container, I expect. If you’re using a scope that doesn’t have a Dobsonian base or tripod arrangement for mounting, you obviously need some sort of stable, solid, horizontal surface on which to set its base. A small table, level car hood, etc. works fine, but what if you can’t easily manage such a setup in a given location on your observing site? Many years ago I came up with the notion of using our wheeled plastic trash bin as a portable platform of just the right height for supporting my Astroscan. These trash containers are fairly heavy and sufficiently stable once placed upon pavement or hard ground, even on grass. The Astroscan’s ultra-stable mounting design and very low magnification possibilities easily adapt it to such a support. I put the base down directly on top of the hinged cover of my bin and it works fine, or you could pivot the top down and just lay a couple of boards across the top edges to make a temporary table top to support a small scope base. You can wheel the bin to any desired location and have a support for a small scope that places it at an ideal height by which you can avoid stooping or crouching. Not stable enough for your liking? Just add weight at the bottom of the bin. If boards laying across the top are not steady, just use small wedges where needed to stabilize them evenly atop the rim.
On the night mentioned, I saw that I’d have to place my scope in a certain position so as to take advantage of an unobstructed sightline through a gap between trees. Wheeling the trash bin 50 feet from its usual spot put me in a good location for viewing Venus and Uranus together. A 26 millimeter Plossl eyepiece gave me a magnification of only 17x in the Astroscan, which is about perfect for much of the observing I do. As usual, no problems with vibration or unsteadiness were experienced. (Very low powers can be quite forgiving when you don’t have a rock-solid mounting, after all.) I knew how Uranus would appear with respect to a number of field stars, having studied its position on a chart in Uranometria, my favorite star atlas for detailed star-hopping. Uranus, at only 3.4” in apparent diameter, and seen at such low power, looked like a background star with no appreciable color to distinguish it, due in part to the washing-out effect that the glare from Venus imparted to the surrounding area in the image. At magnitude 5.9, Uranus happened to be brighter than any of the field stars I used to locate it, which was fortunate. After a couple of minutes, I was satisfied beyond question that I’d positively identified the planet and could then concentrate on appreciating how close it looked to Venus, which shone at magnitude -4.1 and therefore was 10 magnitudes brighter, or a ratio of 10,000 times brighter!
In apparent diameter, Venus was about 16” and 4.7 times bigger than the perceived size of Uranus. This was strange to consider, because Uranus is approximately 4.22 times the actual size of Venus, but was nearly 19.88 times further from Earth than was Venus on February 9. I wanted to make sure that I didn’t just see these two vastly different worlds – so far apart from each other in actual distance – as an attractive close pairing of note, something to quickly see as a “snapshot” just so I could say I’d seen them together. When you view things only in two dimensions and can have no visual impression of their true, greatly disparate distances and physical sizes, it’s all too easy to rack up an observation so you can say you’ve done it without making the mental effort to truly appreciate the significance of such a pairing. Our dazzling neighbor planet was just over one astronomical unit of distance from Earth, but the reflected sunlight coming from Uranus took 2.88 hours to reach my eyes. Did I succeed in my efforts along these lines? Maybe not quite fully, I must admit. Still, I’m glad I gave it a try.
