It was quite cold here last night, but I got a new eyepiece - an TeleVue Ethos 3.7 mm - and I was determined to use it. Unfortunately, the atmosphere was restless and the seeing poor to atrocious, so I was largely limited to low magnifications and wide field views. The TeleVue 85 was perfect for the task. Early in the night, the jewels of winter started rising over the horizon. I was on our illuminated observation deck with a three-inch telescope, and Orion was still climbing above the light-polluted murk of the eastern skyline, but still: I had a nice view of the Trapezium at around 66x. I even captured something of the view on my iPhone, though of course: much is lost in the translation. The Orion Nebula is something that never, ever gets old to me. The Pleiades, being higher in the night sky, looked spectacular, especially at very low magnifications (11x with my 55mm Plossl). Towards the end of my night, I finally used the Ethos on Rigel, and managed to clearly make out Rigel's companion, Rigel B (itself a double star, but that was beyond my telescope) at 162x. Not bad, considering the terrible seeing! The TV 85 is a masterpiece. As I've written before, I just don't understand how so much telescope fits in such a tiny package. At low or high magnifications, the view is consistently spectacular - and surprisingly bright.
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From the time I was a young kid growing up under the dark skies of rural Canada, I dreamed of owning an eight-inch Schmidt-Cassegrain telescope. Glossy advertisements in astronomy magazines promised me that a “C8” would give me the aperture I would need to peer deeply into the cosmos, the portability that would encourage me to peer often, and the robotic gizmos that would unfailingly point me in the right direction. It was an irresistible combination . . . except for the (fittingly) astronomical price. Someday, somehow, I thought, I’d get a good job and save up enough to buy one.
That day arrived late last year, when I found a C8 optical tube assembly (OTA) on sale for a price that seemed hard to beat. And not just any OTA: this was an Edge HD, quite possibly the best mass-produced Schmidt-Cassegrain on the market today. I snapped up the telescope – with a little help from my employer – and waited until I could use it. I waited long, because in cold weather, Schmidt-Cassegrains can take a long time to reach "thermal equilibrium:" the same temperature as the air around them. Until they do, air currents inside their tubes disrupt the view. In the winter, you have to leave your Schmidt-Cassegrain outside for quite a while before using it, and since I currently observe in urban parks that just isn’t possible for me. So I waited for warmer temperatures. Fortunately, they come early in Washington, DC. Tonight, with temperatures in the upper teens, I stepped out with my Edge HD for the first time. Aside from the temperature, conditions were far from ideal. The wind gusted from the southwest, so the “seeing” was far from perfect, and the transparency of the atmosphere also left something to be desired. Wisps of cloud drifted by from time to time, the first signs of a storm system that should be with us tomorrow morning. Yet it was a comfortable night overall, and I looked forward to observing with no risk of frost bite. I set up in my usual observing spot: out behind a police station, in a community garden. Bright street lights are far too close, so I can never develop proper night vision. Yet since I observe in the heart of a little vegetable labyrinth, I'm usually shielded from prying eyes and barking dogs. I have two mount/tripod assemblies that I can use with my C8: the Twilight I setup that I use with my lighter AR 102, and a Nexstar SE computerized mount that came with my (now dearly departed) C6. Both can theoretically handle weights up to around 18 pounds, but in practice neither can quite accommodate the 14-pound Edge HD, with its finder and eyepieces. Still, both are light and small enough for me to walk them the five or so minutes it takes for me to reach my observing sites. This time, I decided to roll out the Twilight I. I wanted to see what I could see with my OTA, and I just didn’t have the patience to deal with occasionally finicky electronics. To minimize the wobbling that usually plagues big telescopes on flimsy mounts, I placed my tripod on Celestron vibration pads. To my surprise, it actually worked fairly well. The telescope shuddered when I moved it and especially when I focused it, but that shudder was not as bad as I’d feared. After unpacking my telescope, I waited around 10 minutes before I lost patience and decided to observe, thermal equilibrium be damned. I snapped in a cheap, 30 mm Plössl eyepiece and wheeled my telescope over to the Orion nebula. The first think I saw when I looked through the telescope was a satellite streaking by. An auspicious start! When it left my view, the Orion Nebula emerged from the inky background. As you might expect, the difference between the Edge HD and my AR 102 was immediately striking. Where the little refractor shows a little arc of misty grey-green light, the bigger Schmidt-Cassegrain reveals delicate tendrils of nebulosity in a giant crescent around the Trapezium Cluster. Next, I reached for in a new purchase. I recently sold my Celestron refractor and used the money to buy a new diagonal and my first quality eyepiece: a 14 mm Explore Scientific 82°. After plugging in the eyepiece and thereby boosting my magnification, I turned to Venus. I was astonished. The AR 102 shows a small, flickering crescent blurred and distorted by chromatic aberration. At 145x, the Edge HD, by contrast, gave a razor-sharp view, even before it reached thermal equilibrium. Since Venus is nearing its closest approach to Earth, when it will be between the Sun and our planet, its crescent is even narrower now than when I last observed it. That made the effect of my sharp, Edge HD optics even more pronounced. There’s no sign of false color with the Schmidt-Cassegrain, so I could fully enjoy the pale, yellow-white atmosphere of Venus. I used a barlow lens to double my magnification to a whopping 290x – the highest I’ve ever used – and somehow the atmosphere (largely) obliged. The crescent flickered in the turbulence but overall remained razor sharp. Although it now filled much of my view, it lost little of its brightness. The view was now truly breathtaking. The atmosphere of Venus looks largely featureless, yet there was an almost magical quality to the zoomed-in crescent. It was amazing to think that this is a world roughly the same size as our own, but with an atmosphere so thick, and so choked with greenhouse gases, that a car would crumple and then melt on the surface. A hell-world deceiving me with the beauty of that delicate crescent. Mars is near Venus right now in the night sky, but it is actually much farther from Earth. As a result, it is roughly 200 times dimmer than Venus, and less than a tenth of the bigger planet’s apparent size. When I trained the Edge on Mars, I was not surprised to find a tiny, featureless globe. The wind picked up, and as it did the seeing worsened. The little red planet seemed to bob and weave across my view. I marveled at how small the disk looked, even at nearly 300x. Space is big. I kept my magnification high and turned to Rigel, a blue supergiant star some 863 light years from us that shines with the almost unimaginable brightness of some 200,000 (!) Suns. Several million years from now, it will explode in a brilliant supernova and its core will become a black hole. Rigel is actually at the heart of a solar system that contains several smaller stars. At 290x, I spotted one of its companions for the first time: Rigel B, actually another star system that orbits the bigger Rigel – Rigel A – at a distance equivalent to 2,200 times the distance between Earth and the Sun. Rigel B consists of two stars between three and four times the mass of the Sun, and one of these might actually be yet another star system consisting of two stars. It’s hard to imagine looking up from the surface of a planet orbiting Rigel Bb, with so many bright blue suns in the sky. Anyway, the Rigel B system is hard to spot with a telescope of six inches or less, so I was happy to glimpse it this time. I finished by taking another look at the Orion Nebula. I kept my magnification at 290x and screwed in my narrowband filter that, you'll remember, only lets in light that shines at the wavelengths of emission nebulae. Now the view was just overwhelming. My eyes were not fully night adapted, and yet: the detail in the nebula around the zoomed-in Trapezium Cluster was just incredible. Boiling grey-green mist. A few closing thoughts. First: this telescope hugely outperforms my AR 102. I expected as much, of course, and the comparison really isn’t fair given the very different roles (and costs!) of both telescopes. Yet I was surprised not so much by how much brighter objects appear through the Edge, but how much sharper they look. Second, the Twilight I mount can hold my C8 in a pinch. The view did wobble at high magnifications, especially during gusts of wind, but this is not a bad grab-and-go setup. It’s pretty amazing that such a powerful telescope can be so portable. Third: I’m beginning to grasp the appeal of “splitting” or “resolving” binary star systems. That’s good, because binaries are some of the few deep space objects that are easy to observe from urban locations. Finally: it sure feels great to have a really high quality eight-inch Schmidt-Cassegrain. I think I’ll keep it. I received my Twilight I mount yesterday, and my 4-inch, AR 102 refractor arrived a few days earlier. It snowed in the afternoon, but cleared up around sunset. At the same time, I scouted a new observing site, in the park just east of Sidwell Friends School. Bright lights from the school illuminate part of the park, but it's better than my usual observing site. Despite the bitter cold, I decided to pack my telescope and give it a go.
By the time I arrived at the park, it was only a few minutes to 9:00 PM. Mars and especially Venus were low on the horizon, glittering behind a tangle of trees. I spotted Mars through my finderscope, but I'm not sure if I ever had it in my telescope's field of view. It's awfully far from Earth right now and its apparent size to observers from Earth is tiny (just over 5 arc seconds). I used a 15 mm eyepiece, so the magnification through my telescope (which has a focal length of 663 mm) was only around 44x. Barely enough to make out a disk. The half moon was high in the sky - almost at zenith! - and of course it was a much easier target. I could now fiddle with the finderscope to align it with my telescope. I used a 33 mm eyepiece, so my magnification barely reached 21x. I could comfortably fit the whole moon into my view. It was almost painfully brilliant, but utterly breathtaking. The detail was incredible, and I could scarcely make out any chromatic abberation (an optical distortion common to achromatic refractors). By now, my telescope had cooled down to match the temperature of the air, so the image was crisp. It struck me that the optical quality of the telescope seemed higher than that of any other telescope I've used before. It's not a long list, but still: I was impressed. Orion was high in the sky, too, so I trained my telesope on my real target in tonight's skygazing: the Orion Nebula. At 44x, I could easily make out the Trapezium Cluster: four enormous stars at the heart of the nebula that may be moving around a huge black hole. The stars were glittering pinpoints. I could see obvious nebulosity, too, but there wasn't much detail amid the glare of the moon and the city lights. I screwed an Orion ultrablock narrowband filter into my eyepiece and had another look. The filter only lets in light that shines at the wavelengths of emission nebulae, such as the Orion Nebula. This time, the Trapezium was harder to discern. Yet by using averted vision - by using my peripheral vision, and thereby activating the light-sensitve rods in my eyes - I clearly made out two wings of boiling green gas. It was breathtaking. For a moment, I forgot how cold I was. Lastly, I added a barlow lens (doubling my magnification), screwed in a yellow filter, and turned back to the moon. At 88x, the detail on the lunar surface was spellbinding. I nearly lost myself tracing subtle shadings in the lunar "seas." Yet when the Northwest breeze picked up and the windchill dipped to -15°C, I realized it was time to go. With numb and borderline frostbitten fingers, I packed up my icy telescope. All in all, a great (but frigid) observing session. The AR 102 impressed me, as it has many other amateur astronomers. The telescope cooled quickly and afforded some remarkably crisp views that were a definite step up over my similarly-sized Celestron (which I'll now move to Winnipeg, where I often stay over the summer). The mount, focuser, and diagonal were also all superb. The straight through finderscope is predictably hard to use, however. It looks great, but I'll probably replace it either with a red dot or right angle correct image finder. Still, not a big deal. I also used a nebula filter for the first time, and enjoyed learning about its advantages and limitations. Moreover, I used averted vision more effectively than I ever have before. The yellow filter was a first for me, too. It helped me pick out some fresh details on the moon, but the false color was a little distracting. Perhaps I'll use a dedicated lunar filter next time. And most importantly: I observed a deep space object (DSO) from a big city for the first time. The didn't measure up to what I've seen with a similarly-sized telescope (a 6-inch reflector) in the countryside, but still: I was blown away by what I could make out. One thing I'll definitely need: a foldable camping chair or stool. Kneeling in the snow doesn't cut it. |
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