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Tuesday, November 21, 2017

Vixen A70lf Refractor Telescope Review

The Surprise Bargain

It was actually late 2016 when as I was browsing Amazon for what was affordable (to me) in the telescope and accessories section that I saw something I couldn't even believe. The Vixen A70lf 70mm refractor, as shown above, was on sale for only about $80. That's like half price. I spent the next hour scouring the Internet, double and triple checking that I was in fact looking at the model of Vixen telescope that I was sure normally sold for more like $160. I could see that I was looking at a Vixen telescope for sure, but maybe it was an introductory model, or a kids' model, not really the same as the $160 model.

But everything checked out. It was listed as the only one in stock, so I thought maybe they were just dumping it. I was sure it wouldn't sit around at that price for long, so I bought it.

Just a few days later, there it was again on Amazon, back at the original price. I can't explain it. I'm just glad I happened to look on the day I did.

A few days later my order arrived. It was packed kind of like a Russian doll, a big box within an even bigger box. When I unpacked it, sure enough it was the Vixen 2602 A70Lf Telescope. You might wonder why I was so fascinated about the prospect of owning a Vixen 70mm refractor.

The Long Time Desire

The urge for a 3 inch or so refractor started decades ago. I always read, back in the 60s, that for "serious" astronomy you needed either a 3 inch or larger refractor, or a 6 inch or larger reflector. I was kind of corrupted in my thinking back then to assume that those two telescope are more or less equivalent. They of course are not. No way does a 3 inch refractor deliver what a 6 inch reflector does. But a 3 inch refractor does deliver some nice, high contrast images, and has enough light gathering power to reach a lot of targets. So I've always wanted one.

But a good 3 inch or better refractor always seemed a bit out of reach compared to the cost of a much larger reflector, so I've always opted for the reflector. Newtonians generally. I started with a 6 inch f/12 back in high school. Lurched for a 10 inch mirror when in college, and built a behemoth telescope with that (I hadn't read about Dobsonians back then). Eventually got rid of the behemoth and settled for years for a homemade 8 inch DOB.

The First Buy -- Big Mistake

But the thirst for a quality refractor was always there. Then in the late 90s I saw an add for a Meade 90mm refractor on an equatorial mount. It was much less expensive that I expected, going for around $250. That should have set off red flares, no?

But I bought it. It was on a nice enough mount, and a solidly built telescope. It was an f/10, so there was certainly some visible chromatic aberration. What of it, I thought. Moon images seemed pretty nice with the thing. But when the chance came later that year, I found that images of Saturn weren't so good. Try as I could, I was not able to resolve the Cassini division. I thought I should be able to. The more I read, the more I was sure I should be able to. When I later got a Meade ETX 90, I found out for sure that a 90mm telescope definitely can and should resolve the Cassini division.

The Hint Of Greatness -- Small Refractors

Then I read about the influx of Chinese refractors that were being imported. I found that the one I bought was a Chinese import. For sure, today's Chinese import telescopes are pretty top notch, but in the 90s not so much. I got so frustrated with it that I took it off of the mount and put my Jaegers 50mm refractor on the mount. The Jaegers, a gift from a friend, was small but of excellent quality. While clearly not able to reach the stars as well as the 90mm Chinese import, in image quality it was more than a match. But alas, at the moderate tilt of Saturn's rings at the time, the 50mm couldn't quite reveal the Cassini division either.

So I was back to reflectors. Then around 2008, I ran across an astronomy egroup that was devoted to small telescopes, most particularly the 60mm refractor telescope. I joined that, and one of the members generously donated an old vintage Monolux 60mm telescope to me. It needed some tender loving care, but ended up being pretty nice. It easily beat the images of my old 90mm Chinese telescope. So now I knew that a "quality" small refractor could do pretty well. I remember watching a Europa transit with the Monolux, something that would have been a challenge for the 90mm Chinese import. But oh for that 3 inch threshold.

Enter The Long Sought (Amost) 3 Inch

Then along came the Vixen. I mounted it as shown above on my homemade Pipe-fitting Tripod.

Does The Vixen Measure Up?

First, lets just check out the telescope.

The focuser looks pretty substantial. And for a plastic focuser, it is pretty sturdy. But except for the draw tube, it is plastic. The draw tube is pretty long though, at least 6 inches. Yet I really wish it was made of metal.

The business end of the telescope, shown above, holds the quality 2 element objective. The lens cell, again a bit disappointing, is also made of plastic. It, like the plastic focuser, seems ample enough. For me though, a metal lens cell would be more reassuring. Looking through customer reviews, I found one who complained that the lens cell split at the narrowest point near a mounting screw. I've not had that problem, but I'm careful to not tighten them too much.

Of course the telescope comes with a lens hood, as shown above. There is an end cap that fits snuggly into the lens hood when the telescope is not in use.

The telescope also came with a few accessories. Enough to get any astronomer off and running, though in my case I had most of the accessories I already needed.

For eyepieces, the Vixen 70mm came with two PLOSSL eyepieces. One is a 20mm focal length eyepiece, giving a magnification of 45x. The other is a high power eyepiece of 6.3mm focal length, giving a magnification of about 143x. The Vixen seems able to be easily pushed to more like 165x, but the included eyepieces give a user a good place to start.

Also included is a prismatic 90 degree prismatic star diagonal, and an extension tube. If you intend to view without the star diagonal, you'll need the extension to make up for the lack of light travel distance through the diagonal.

A very solid mounting bracket with ringed clamps was included. The bracket is shown above. The clamps, padded on the inside, snuggly wrap around the telescope. It fits nicely with the Vixen tripod if the total package of telescope and tripod is purchases, but is even included if you buy just the telescope. It is the one accessory that is made of metal. It seems quite a sturdy mounting bracket for the telescope.

Ok, so 70mm is a bit shy of 3 inches. Just under a 1/4 inch shy. But that's pretty close. The Vixen is an f/12.9 telescope, having a focal length of 900mm. The Sidgwick criteria for acceptable chromatic aberration suggests that the focal ratio of a telescope divided by the lens diameter in inches should be 3 or greater. It turns out that the Vixen 70mm telescope's ratio is 12.9 / 2.76, or about 4.7. So the numbers say the Vixen should have quite acceptable CA (it does).

The Vixen is physically very light, seems to have a top-notch objective, has an f/12.9 focal ratio, shows virtually no CA, and at 36 inch focal length it still has a reasonable field of view. But all is not perfect. In the focuser image, notice what barely passes as a finder scope. It's a poorly implemented, poorly designed 24mm finder. Each time you use the telescope, you'll have to realign the finder as it never holds position. If you even slightly bump it you'll have to realign it. And it goes without saying that you can't see much through it.

I took the telescope out soon after I received it and got in some moon observing before winter set in. The limb of the moon showed virtually no CA effects. The crater views were crisp and high contrast.

I didn't get back to observing with the Vixen until this fall. On that outing I did get some more moon observing in, and as before, images were tack sharp and high contrast. But on that observing session, no planets were available. So I picked on the double double in Lyra. Some people call it the Lyra Double Double test. I've looked at the double double with many telescopes, and it does provide some indication of optical quality.

The double double, positioned not far from Vega, appears to be a single dim star to the naked eye. Even a finder telescope will reveal it to be a double star. But in a 60mm or better telescope, it is often seen to be two very close pairs of stars. In my long focus 60mm, I can make out all four components at something like 120 power. But one of the close pairs is very close and has stars of unequal magnitude, making the split difficult.

The Vixen handled it well. All four stars could be seen, and the first ring of a nice little diffraction pattern could be seen around the 3 brightest stars. So the Vixen seems to have a very good objective.

It should be said, however, that the double double test is also a test of atmospheric conditions, so if you get a poorer result than you expect should you view the double double, don't necessarily blame your telescope until you try on a couple of other nights.

The crude tripod holding the Vixen in the above image is as I mentioned my old pipe-fitting tripod. The iron tripod is used to hold a number of different telescopes, including my 50mm Jaegers refractor, my 60mm Monolux refractor, my 60mm long focus Carton refractor, my Vixen 70mm refractor, and my Meade ETX 90. It is a work horse.

On the evening when I checked out the Lyra double double, I also used the telescope to examine a healthy sampling of Messier objects. I didn't try to find them all with the supplied finder, I suspect that would have been a frustrating experience. Instead, I used the Star Pointer web utility. It is a handy cosmic target finding utility that lets one dispense with star-hopping, and get down to viewing. It is described on this blog on a different entry.

Star Pointer works with any telescope mount that has setting circles. It works with either equatorial mounts or altazimuth mounts. It works even with my old pipe-fitting tripod, as it has setting circles, as shown above. The setting circles in this case were printed out with a perl program, then glued onto 1/8 inch hardboard and coated with Modge Podge. Homemade, yes. Crude, maybe. Useful, certainly.

With this combination, the Vixen 70mm and the pipe-fitting tripod with its setting circles, I was able to see in a bit over an hour several targets, including M2, M73, M72, M15, M71, M27, M13, M92, M56, M57, M39, M31, and M34. I also viewed the double cluster in Perseus (Caldwell 14), and about four double stars, include Eta Cassiopeiae. That's not a bad haul in that time frame. And I only had to suffer using the finder once, when I used it to position the telescope on Polaris during alignment.

All of the targets showed nicely with the Vixen. I especially enjoyed M13 the globular cluster in Hercules, and the double cluster in Perseus. M13 was easily visible, with just a few sparklers visible at the periphery. The double cluster, super in my f/5 Newtonian but a little anemic in my 60mm telescopes, was very nicely displayed with the 70mm Vixen. With a 25mm eyepiece, the double cluster just filled the field of view, making a very satisfying target.

So what do you get with the Vixen A70lf telescope? Not a galaxy hunter, I admit. But a solid performer even if a bit lightly built with some plastic. You get good optics including the eyepieces and a good performing star diagonal. You get a solid cradle mount which you can adapt perhaps to your tripod, or hold onto should you buy a Vixen tripod later. Or, for a bit more cost you can get the whole enchilada, the Vixen Optics Mini2602 Mini Porta Mount and A70LF Telescope.

I'm pretty happy with the performance and how solid the marriage is between it with its light weight and my pipe-fitting tripod. I think it's going to become my favorite "grab and go" telescope.

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