First light for the Astro-Tech 66 - very impressive!

January 19, 2008 - AT66 - foreground- next to the Orion 80ED on the observing deck at Driftway Observatory.

Maybe I get too enthusiastic too easily. Maybe I'm still able to be surprised and thrilled. Maybe my expectations are overly low. And maybe I just don't know as much about astronomy and observing as I think I know and so I'm still learning. Whatever . . . the bottom line is this. My first look through the little 66mm scope made by Astronomy Technologies just blew me away. I bought it used on Astromart and I hope I didn't hurt the previous owners feelings when I wrote him the letter which follows. I just wanted to share my enthusiasm, but I never got a response from him/ Ah well . . .

Good morning Jeff:

Don't let the length of this note scare you - I'm well-pleased with the scope.

What an incredible little scope! I mean, I know it is beautiful to look at and I know these little guys are supposed to have great optics, but I was absolutely blown away last night by its performance under less than ideal conditions. As I probably told you, I spend every clear night giving free observing lessons. I've been an amateur astronomer for half a century. I now own about a dozen scopes, the best being a 15-inch Obsession - and that's one damned good scope - the Obsession. I also have an Orion 80ED - up to now my best refractor.

Last night I had people doing double stars with a 5-inch Celestron SCT and the 15-inch Obsession. I'd put the little AT66 out hoping to give it a test when I got a moment. (It was on a rather parallelogram shaky mount - intended for binoculars at low pwer, not a scope at 100X or more. ) Once most of the people left I started splitting some of the double-stars I had the other folks using the 5 and 15-inch scopes on. I was impressed. No it did not split Rigel - that splits nicely in the 15, but not the 5on this night.

But it gave me incredible views of stars like Almach and Castor. I used a 30mm 80-degree 2-inch eyepiece on it as a finder, then switched to a Hyperion 8-24mm zoom. But when I needed some power I went to a 3.5mm Hyperion with an apparent fov of 68 degrees. That put the little scope at around 114X - near it's theoretical limit. I didn't try to push it beyond there, but boy it handled that nicely. It was sitting right next to the 15-inch which was getting overwhelmed by conditions - 11-day moon and what I would generously call "average" seeing. The view of Almach, for example, was much better in the 66mm than in the 15-inch - no kidding. The 15-inch, of course, split this easy double with ease - but it showed large. fuzzy stars against a washed out background. The lack of light grasp in the 66mm meant the background was dark, despite the moon and the blue and gold colors stood out better than they did in the large reflector.

I went in about 10:30 pm - it was around 80% overcast by then - quite pleased. But as I pondered whether or not to get a 1X finder for this scope, I went down to a 1.25-inch diagonal - less cumbersome - and tried a 40mm Plossl in it. That gave me almost 4-degrees of Sky - it handled Orion's Belt with plenty of breathing room. I found that out when around 12:30 am I went out on the deck for a quick check of the skies. High skudding clouds provided a few clear spots which vanished fairly quickly with the fast-moving cloud cover. Still, I got excellent views of the moon,Mars, and Saturn. The moon was especially pleasing. We had been looking at it in the 15-inch with binoviewers - absolutely feels like you are in a helicopter - and had focused on the Pearl Ring which was right on the terminator. Beautiful sight. But now to my shock the 66mm was giving a very satisfying view of the same target, No, it was not outperforming the 15-inch. But boy, if the clouds had let me I could have sat on that a long time.

But here's what capped the session. I tried two doubles that challenge small scopes like the 5-inch. It splits them, of course, but not all that well. Now I went again to Castor. Perfect split. Man that fine focus is good and absolutely critical! Next I turned to Gamma Leonis. That was my real wow! Honestly, I have never seen that star split so textbook perfectly! Absolutely perfect little round dots! Charming! I know this scope won't do much with deep sky objects - but it's certainly winner. I'm well pleased - and, of course - will leave excellent feedback for you on AstroMart.

I went on to write the observing class this note which repeats some of the baove, but expands on it:

. . . some of you may have noticed a new telescope on the observing deck last night. This was a high quality, but very tiny, 66mm refractor and it's performance surprised the heck out of me. It also provided some lessons in telescope design, size, and use which I want to share here. Most amateur astronomers I know - and until last night, myself included - would not take such a small scope seriously. The smallest telescope most folks consider practical these days is 80mm. With an objective just 66mm in diameter (about 2.6 inches) this little dude just wouldn't be in the running. But several companies have come out with such small scopes in the past few years, so I decided to give one a try. This one is made by a new company, Astro Technologies, and is called an AT66. It generally sells for about $350 and is aimed at what is called the "grab and go" market. I picked it up used on Astromart for $250.

The basic idea behind these scopes is to produce a high quality scope that is extremely light weight, rugged, and doesn't require any extensive cool down period or fancy mount. In fact, you should be able to mount it on a good photo tripod. That's the case with the AT66. It's two major features are:

1. Excellent optics
2. A dual-speed focuser that makes fine focusing a breeze - smooth as silk - like what I have on the 15-inch Obsession.

Historically, the problem with refractors has been how to bend light of very different wave lengths so it all comes to focus at the same point. (This isn't a problem with reflectors, but reflectors degrade the image a tad because of the secondary mirror and its supports. ) Anyway, the first refractors were terrible at bringing all the colors together and what they produced was a lot of false color that surrounded any bright object they were pointed at. Eventually, the opticians learned how to produce an achromatic lens that brought two of the three main colors to sharp focus. The great bulk of refractors you see today use this kind of lens and they give very acceptable performance. But if you point them at a bright star, planet, or the moon you will see a green or purple fringes around it. Most people learn to ignore these, but the bottom line is the scope is not producing a truly sharp image because it is not bringing all three colors to sharp focus.

Enter the "apochromatic" telescope. These have appeared on the market only in the past couple decades and they are extremely expensive. For example, I have an 80 mm achromatic that you have used that typically cost about $125 on the used market. (New they're more like $250 now.) The semi-apochromatics - a scope of the same size, but using what is called "ED" glass - costs about $500. I have one of those I bought used. Very nice. But I've always considered a true apochromatic out of reach - just too costly for the slight improvement it might deliver. An 80mm true apochromatic can cost in the $1,000 - $1500 range - generally speaking at least twice as much as Astro-Tech and similar products that have come on the market in the past few years.

So back to the little AT66. It claims to be "apochromatic." Maybe it is. I have my doubts, but judging from what I saw last night, if it is not fully apochromatic, it's darned close to it. Of course I may just be lucky. Maybe I stumbled upon a good one. I haven't any idea what quality control at this company is like.

But what impressed me was this. After most folks left last night Joe and I turned this little scope loose on a few doubles, and Saturn rising low amidst the bare tree branches, and it did a real fine job. In fact, looking at Almach with it - and the 15-inch - I have to admit the view in the 66mm was preferable. Don't get me wrong. THIS DOES NOT MEAN A 66mm scope can out perform a 15-inch. But there is a good lesson here and it is simply this - bigger is not always better. It depends on what you're trying to see.

Believe me, the 15-inch will leave the AT66 in the dust when it comes to looking at nebulae and distant galaxies. But on Almach in average observing conditions with a sky brightened by moonlight, the 15-inch is simply too big. It showed two stars, very easily split, one blue and one gold. But the stars were fuzzy, large, and they were displayed against a washed out, grey background. Joe was having trouble seeing the color contrast, but he grudingly gave the fainter star a "faint blue tinge." In the 66 the same stars were bright, smooth, dots with extremely vivid colors (Joe agreed) displayed against a very dark background that enhanced the contrast. The 15-inch was gathering too much light for what we were trying to see - plus unsteady air -poor seeing - impacts the larger scope more than the smaller one simply because the larger scope is looking through a larger column of air. On a superior night with very good seeing (these are rare) and no moon, the 15-inch would have done much better.

But to get back to the little scope that could . . . as I packed things up for the night clouds were rolling in and there were few stars visible. I went inside, mounted the little scope on a small tripod, and played with different eyepieces and diagonal arrangements. I came up with a new combination and at about 12:30 am I was eager to see what it delivered. I thought the field of view might be up around three or four degrees and I was hoping there would be a break in the clouds and I could get a glance at Orion's belt - it's 3 degrees across. And there was. And this is what is meant by "grab and go." I threw on a coat, grabbed the little scope already on its tripod, and stepped out on the deck for a look. (Larger scopes involve significant set-up and take down time and must be in the cool hour half an hour or more for their optics to get to the same temperature as the air and thus deliver clean images. )

There were high clouds scudding past, with large gaps between them - but no surface wind. That to me means at least two layers of air moving at different speeds and that means terrible seeing conditions. But all I wanted to do was see how much sky I could gulp in using a 40mm eyepiece - and the answer was very close to four degrees - the belt of Orion with plenty of breathing room either side. That kind of wide field makes it easy to find things without having to use a special "finder" scope which would burden this tiny instrument.

But before I went in I couldn't help looking at some other stuff that was coming open in the gaps between clouds - like Saturn. Real nice. Then I switched to the moon and popped in a high-powered (114X) eyepiece. Wow! I won't say this was as good as what we saw with the 15-inch, but the pearl ring was outstanding. I got a folding chair and sat down. Very sharp, very obvious. Castor was high overhead and I know folks found that something of a challenge when using the 5-inch in the observatory. I pointed the 66mm at it. Wow again. The fine focus mechanism allowed me to really tweak the focus and see all three stars clearly. Better than I had seen them in the 5-inch. But then, these stars were higher in the sky at this hour, so that meant I was looking through less atmosphere.

So I turned to another more challenging double that was lower in the sky - this was one I had been viewing in the mornings last week - Algieba in Leo. That one really blew me away. Here I was facing what I considered awful seeing conditions. I was using a tiny scope with a bright moon over my shoulder, high in the west. I had just brought it out from a heated house and I was on a deck right next to the heated house. None of this makes for good observing conditions - all are factors that tend to cause problems. (Come to think of it, I had been looking at the moon and Castor right over the roof of that heated house.) Yet as I looked at Algieba, there were two very close stars with a color difference that is charming, but less dramatic than Almach, and my view was simply text-book perfect. No dancing. No reaching out of the light from one star to grab the light of the other. Just two, clean round dots. You gotta love it when it turns out that less equals more ;-)

Bottom line. You can have a lot of fun with a little scope like this and sometimes it will even outperform much larger, more expensive scopes. I hope that broadens your understanding of what's possible - I'm not trying to sell telescopes and certainly not any particular brand - but ihis experience was a lesson for me - and a very pleasant one. ;-)

Posted by Greg Stone at January 19, 2008 10:42 AM Comments? Please email me: gstone@umassd.edu