If bigger is better, then it follows that smaller is worse, right? Not always. I’m referring to the latest addition to my telescope collection, a 65 mm refractor. Though it’s not very big, I’ve found it to be a very nice performer. And with only a sixty dollar initial investment, it represents some of the best money I’ve ever spent!
Late in 2007 a couple of us Lowbrows caught wind of a little scope that Bill Burgess of Burgess Optical Company was making available to folks. Originally, he was trying to develop and sell a small, lightweight 65 mm f/5.6 ED refractor that he was going to name the “ED 65 Backpacker”. The objective lens was to have one or both of the achromat’s elements made of extra-low dispersion glass (I believe FLP53), hence the “ED” in the lens designation. But Bill ran into trouble with the lens cells he had made up for his initial production run of around a hundred units. Apparently, the non-adjustable cell didn’t align the two elements correctly and virtually none of the units could be collimated. Rather than try to correct the defect and sell them as he originally intended, he simply decided to cut his losses and make them available to interested buyers for a song—only $25.00 shipped! Several Lowbrows took advantage of the offer, with yours truly being one of them. Here’s a picture of what the $25.00 got us (plus a lens cap and a small, soft carrying case that are not pictured here):
The only real drawback was that the scope arrived sans focuser. But we figured for a measly $25.00 investment for the guts of the scope we should be able to locate a commercially available focuser and still finish the scope for a very attractive price.
More about the focuser later. The first order of business was to figure
out how to modify the lens cell so that
we could collimate the scope. After all, if the lens couldn’t produce
an image worth focusing on, then we
wouldn’t need a focuser. The Internet to the rescue! Another Backpacker
purchaser Mike Overacker developed
and posted on the Internet detailed instructions for modifying the lens
cell. As of this writing those instructions
can still be found at
http://www.astronomyreviews.com/ed65/ed65fix.htm . The modifications involve adding thin, aluminum foil spacers to hold the front lens element stationary, drilling and tapping holes in the cell body to accommodate adjusting screws for centering the rear lens element, and replacing the metal mid-optic spacing ring with neoprene O-ring material. Fellow Lowbrow Clay Kessler, another Backpacker purchaser, works at a machine shop (in fact he’s part owner), and he graciously offered to do the drilling and tapping of the screw holes in the lens cell for us. Overacker’s instructions also indicated where to get the little adjusting screws and the O-ring material (http://www.smallparts.com), so after Clay did the machining, and a group order to SmallParts, we had everything we needed to modify our cells. Because Clay did the hard part for us, the rest of the assembly of the lens into its modified cell was relatively simple and straightforward.
Now on to the focuser. We didn’t have any luck finding a focuser to
fit the unusually small 70 mm tube used
on this scope. At least none that didn’t require machining an adapter
to make it fit. All the focusers we found
were made for a considerably larger tube. This time it was Bill Burgess
to the rescue. After a number of requests
by some Backpacker purchasers he made available a focuser to fit it for
under $35.00 shipped. It was a
decent, two inch, rack-and-pinion unit, with compression rings and a 1.25
inch adapter. So a number of us
jumped on that offer too. Installation wasn’t perfectly straightforward,
because it was ever so slightly oversized
for the tube. Again, as luck would have it, Mike Overaker posted instructions
for shimming and installing
the focuser, too. His instructions can still be found at:
http://www.astronomyreviews.com/ed65/ed65focuser.htm . Using his instructions, and a strip of thin brass I found at Rider’s Hobby, I was able to finish assembly of my scope.
Now if you know me then you know that I like to differentiate my scopes so that they stand out from the crowd somewhat. This little scope was no different. I really didn’t like the vanilla white color, and that dreadful lavender purple logo on the lens hood just had to go. But what color? I always liked the deep, anodized aluminum colors that Williams Optics uses on some of their scopes, so I checked my local auto parts store to see what kind of automotive colors they had. I found this nice, deep red spray paint that when applied over silver simulates anodized aluminum. Eureka!
Also, I was not too thrilled with the blackening of the scope’s innards. The tube had a single baffle inside, but the flat black paint they used wasn’t terribly flat. Moreover, the focuser had internal threads, but was left unpainted (you can see some of the sheen inside the focuser in the photo below). Too much opportunity for internal reflections.
I disassembled the scope, masked and sprayed the inside of the tube and focuser with KrylonTM ultra-flat black, and applied the silver undercoat and red topcoat to the exterior of the tube and lens hood. Some black flocking applied to the interior of the lens hood finished the scope off. It now has its own unique look, and that awful logo is gone forever! Below are some pictures of how I masked and painted everything, and the finished product:
Before evaluating the scope’s optical performance, I had to collimate the lens. It was trickier than I imagined it would be. As expected, the collimation was way off, with very comatic-looking stars across the field of view. But I found that a very small adjustment of the collimation screws had a profound impact on the resultant image. It was all too easy to overshoot and now have all the stars pointing in a different direction. My difficulty was compounded by the scope being mounted on my photo tripod. It just wasn’t solid enough to keep it pointed at the test star (I like to use Polaris because it stays put) while working with the adjusting screws. Fortunately, I had a spare, foot-long dovetail for my Vixen GP-DX mount, so I cut it in half, and mounted it to the bottom of the scope. That made all the difference in the world. With the scope mounted good and solid, I was able to crank the magnification as much as I needed to get the collimation as good as I could get it.
So how does the Backpacker perform? Very nicely in my opinion. It definitely displays a fair amount of false color around the moon, planets, and bright stars at high power. Still, the views are pleasing. It splits the double double, AKA Epsilon Lyrae, cleanly. Banding on Jupiter is easy, and Saturn’s rings are nice and sharp. But where it excels is at low to medium magnifications on deep sky objects. Now it only has 65 millimeters of aperture, so you won’t be hunting down 12th magnitude galaxies with it. But it works very nicely on big, bright, and chunky objects. I brought it with me to the Black Forest Star Party last fall, and had some very memorable views through it. The Pleiades was fantastic, and I could even make out the Merope nebula. M31 was a beautiful sight, too, as the entire galaxy fits neatly within the field of view. With a 24 mm eyepiece and an oxygen- III filter, the North America nebula was easily visible. And with that same setup, the field of view was large enough to hold the entire Veil Nebula end-to-end. Large open clusters were very nice, too, including the very large NGC 752 (the “BASS” cluster), which was simply gorgeous. And of course M42, the great nebula in Orion, was spectacular! The Trapezium was easily split into four stars, and the entire sword region and then some fit easily in the field of view. My biggest disappointment was that I couldn’t see the Horsehead Nebula silhouetted against IC 434 using a hydrogen-beta filter. (Now in case you’re thinking ol’ Scobel is losing it, don’t worry—that was supposed to be a joke!)
Here are a couple additional technical points. I measured the aperture in the lens cell and indeed it is 65 millimeters. I’m not exactly sure of the focal length though. It was advertised as f/5.6, which would put the focal length at 364 millimeters. I did not attempt to measure the focal length (I do mirrors, not lenses!) but I did an experiment with my camera’s exposure meter. The exposure reading with the scope attached, and with a camera lens set at f/5.6, matched exactly, so it must be pretty close to f/5.6. Also, none of my eyepieces come to a focus with just the focuser—there isn’t enough out-travel. So I bought a 1.25 inch diagonal on Astromart which did the trick. With it I can use all of my 1.25 inch eyepieces, plus it makes observing much more comfortable regardless of where the scope is pointing in the sky. I’m sure that the focuser was designed that way—you’d never want to use a small refractor like this without a diagonal.
I and others were thinking that a small scope like this ought also be ideal for astrophotography. I checked to see if my trusty old Olympus OM-1 film (yes, I said “film”!) camera would come to a focus. Much to my delight I found out that it does. I’ve since done some experimenting with it and come up with a few decent images. Nothing near as good as folks get nowadays using CCD cameras and DSLRs, but considering my comparatively miniscule investment I’m quite happy with my results so far. Here are a few sample images I shot with it from the dark skies of Cherry Springs State Park at last year’s Black Forest Star Party:
In case the above images whet your appetite, I’m planning a newsletter article on how I’m doing Astrophotography with the Backpacker. And of course I’ve been doing it “the Lowbrow way” (in other words on the cheap), so you may want to pay close attention should you want to do the same with yours. Stay tuned.
All in all, I just love this little sixty dollar scope. No, it’s not perfect by any stretch. High magnifications instantly reveal its optical shortcomings. And yes, there were additional costs, such as a couple dollars for small parts from SmallParts, twenty-five dollars for the diagonal, and about ten bucks worth of spray paint. But still I completed the entire scope for under $100.00, which is still pretty dang inexpensive. The real question is—how are the views? In my opinion, priceless!
Footnote: If you purchased one of these scopes and would like a helping hand getting it assembled and/or collimated, then just let me know. I would be more than happy to provide advice and/or help you out with it. — Doug