August 11, 2020

For me, it doesn't get much better than this.

---

I was quite tired after I last published on this blog, but the night of the tenth was clear again - and again the seeing promised to be better than average. With a week of uninterrupted rain coming our way, I had to step out again. This time I decided to try our rooftop, which was been a little too crowded to feel safe lately.

I decided to see whether the APM 140 was portable enough to haul upstairs. To my astonishment, the telescope slipped easily into the Gitzo carrying bag that I've been using for my Vixen refractor. That sliding dew shield goes a long way. It also barely felt heavier, and it suddenly dawned on me that, because the APM can sit well on the same mount and tripod, it's actually just as portable as the Vixen. Imagine that: a nearly six-inch-wide, portable refractor! 

To my relief, the rooftop was relatively empty. I unpacked and set up the telescope in under five minutes, and of course the APM acclimates so fast that it was immediately ready to go. Jupiter was up first. To my delight, I'd tuned in on time for another shadow transit - my third in three weeks! To think I'd never seen one before. This time it was plainly obvious that it was Io's shadow on the Jovian clouds; I could clearly make out the moon as a tiny orange disk. How the mind soars to imagine its volcanoes belching sulfur into the radioactive torus swirling around Jupiter. 

I switched to Saturn, but the planet was just a bit lower in the sky than Jupiter, and the difference in seeing was plainly noticeable. Turning back to Jupiter, I was struck by how much better - I'm afraid there's no other word for it - the planet looks through the APM than it does through the Takahashi FC-100DC, even when the smaller telescope has its focal extender screwed in. The biggest difference, I find, is in the color. Jupiter's reds typically look a pale pink through the Takahashi, but they are clearly red - in the case of the Great Red Spot, a vivid crimson - through the APM. 

I also noticed that my Delos eyepieces offered a notably better view then the Naglers, for what it's worth. Both made by the same company, of course, but the Delos seemed to have just a bit more contrast, and they were definitely easier on the eye to use. I'm thinking now that I should swap my 9mm Nagler for a 10mm Delos, if I can do it while breaking close to even. 

As I admired Jupiter with the 6mm Delos screwed in, for a magnification of 163x, the seeing suddenly stabilized for around 20 seconds, and the planet suddenly snapped into crystal-clear focus. I was taken aback; I almost couldn't believe what I could make out. It was a textbook view of the planet - in that it could have literally appeared as a Hubble photograph in a textbook, held at arm's length, while squinting ever so slightly. The Great Red Spot and the swirling, complicated clouds surrounding it beautifully framed Io's shadow, and the details in the cloud belts were so richly textured . . . I was just astonished.

When the seeing returned to normal, I could do nothing but pack up and leave. There are times in amateur, observational astronomy when you've had your fill and you need to step away to process it for a while. I packed up - again, in under five minutes - and stepped quietly downstairs, knowing I was sated for the week. 

​A note on the APM. Earlier this year, I would not have believed such a telescope was possible - or at least, I would not have believed I would ever own one. Here is a refractor that, at 5.5 inches in aperture, excels at just about every object, but somehow manages to be grab-and-go portable. It weighs just a few pounds more than my much smaller Vixen - which is itself light for its aperture - and so a relatively light mount and tripod can comfortably handle it. I can carry it with ease. Its focal length is fast enough for wide-field views, but slow enough for magnificent planetary observation. It offers absolutely sharp, color-free views and first-class mechanical quality, at least on par with my Takahashi, but somehow costs just a hair more than that much smaller refractor - and about the same as the Vixen. Somehow, it cools down just about as fast as they do.

​It's true that my APM has what I gather is an unusually high strehl ratio - in other words, its optical quality is better than average - so my experience with this model might be unusually good. Even so, tonight's look at Jupiter - not exactly the easiest object to view - made me wonder why anyone would need or want anything more expensive at this aperture. My cup was full, and I can't imagine that any other portable telescope would have filled it further.