No, probably not the kind of glass recycling you are thinking of - the empty beer and wine bottles you put curbside for recycling... I'm thinking the camera lenses that you used to use with your old camera, somehow fitting on your new camera. Remember film? Back a generation or two ago, going back to high school, I had an old Pentax Spotmatic with screw-mount lenses. Then about 20 years ago when I got back into astro-photography, I upgraded to a couple manual Nikon cameras and had a pretty good collection of Nikon lenses mostly culled from the twice-annual camera swap meets we had in Tucson. Then just about 12 years ago as film was on the way out, I scored some eBay bargains in a medium-format Pentax 6X7cm with larger negatives for more detail. I'm not sure I shot more than a couple rolls of film, but I still had a few lenses from their system.
Well here I am in 2014 with a Canon XSi DSLR with APS sensor and EF lens mount. Normally I'd need to invest in an entirely new lens system. And for all-around shots, I highly encourage that, taking advantage of autofocus, various exposure modes, and fully taking advantage of all the camera features. But for astronomical applications, where long exposures and focal lengths are desired, the camera can be easily adapted to telescopes. And interestingly enough, all the lens systems I've mentioned above can also be used with my Canon camera! And another item to note, many lenses from these film days systems can be had for real bargain prices on Ebay!
Take a look at various camera's flange-to-focus measurements. It lists the distance from where the lens attaches to the detector focus. The Canon EF mount is near the middle with 44.0mm. Interestingly, all the lenses above, the ole' Nikon F (46.5mm), Pentax screw (M42 - 45.46mm), and Pentax 6X7 (84.95mm), all with longer flange-to-focus can be used with my Canon with the appropriate adaptor! The disadvantage of these adaptors is that you must focus manually, as well as shoot aperture priority (manual aperture setting). But for long-exposure astronomical imaging, who cares - you focus near the beginning of the night and checking occasionally is all you need.
I've had an adaptor to use my Nikon lenses on my Canon body for years. It has literally saved me thousands of dollars to use my old lenses - the fisheyes, fast telephotos and wide angle lenses I've collected. All these adaptors are found on E-bay, and just recently, after hearing good things about Pentax 6X7 lenses for astronomy, I ordered a $45 adaptor from E-bay. Of course, my order went to Hong Kong, and my shipment got caught up in the Chinese New Year, so it took a full 2 weeks to arrive, and when it did, as shown at left, there was some concern it survived the trip, but it appears to work fine. At right my Canon XSi body is shown at right, the Pentax 6X7 with the 165mm lens is humongous in comparison, and the new black adaptor is shown next to the lens. The Nikon lenses at left use the silver adaptor near them to go on the Canon body.
So with the new adaptor and lenses I hadn't used in over a decade, I had to go on an expedition! At the end of a work day, I loaded up the 3 Pentax lenses I had, a sturdy tripod, adaptor and lots of other gear for a sunset tour of downtown Tucson from "A" Mountain. The adaptor fits the Canon and Pentax lenses well and seem very snug. With the 165mm focal length, and some of the longish exposures used in deepening twilight, I used mirror lockup and a 2 second delay to minimize vibration. Fortunately, the adaptor has a threaded tripod adaptor near the center of gravity, which seems to work well.
First up in twilight, a stereo pair of downtown
seemed a natural, so used the 105mm Pentax lens for a pair of images of downtown taken about 40 meters separation and about a minute apart. They are oriented here for cross-eyed viewing. Cross your eyes slightly to look at the right image with your left eye and vice-versa. You should see 3 images, the center one of which should show stereo depth. It is easier to practice on the thumbnail before clicking on it to load the full-size version. Most of the frames are included in the left pair, and just the center section is in the right pair for higher resolution...
As it got a little darker and the light levels
stabilized, I took a 12-frame mosaic with the 165mm lens. The assemblage was put together with Microsoft ICE a free mosaic assembler that had no issues with the data set. Of course, the big advantage of a mosaic like this is while you have a wide image, you maintain the fine resolution of the original frames. Shown at left, it is VERY much reduced in resolution from the mosaic, nearly a factor of 10 in pixel width, because of the 1600-pixel-wide resolution limit of blogger. I think the mosaic is quite marvelous as I can't see any signs of vignetting or shadowing where the edges of pictures come together. I did not shoot wide open, but rather at F/5.6, mostly to decrease chromatic aberration. Of course, since the Pentax 6X7 lenses were designed for a much larger format, the thinking is that the illumination is "flatter" and vignetting would be reduced naturally... Something closer to the full resolution is shown at right, of the Bank of America Building at right (about 1.5 miles distant), to the University Medical Center at left (about 3.2 miles), and the Marriot Hotel on the west side of UA campus.
The sharp-eyed among you might have noticed a bluish "V" on the southern side of the Pima County Legal Services (formerly Tucson Federal Building). Fortunately I had also packed the little Meade 80mm F/6 triplet APO and did a closeup examination of the "V" which easily showed up in a couple second exposure, but I couldn't quite see it with naked eye. So of course, I do another 12-frame mosaic with the equivalent 480mm focal length lens, the reduced-resolution result of which is shown at left. Looking at the full-size mosaic, you can spot the variable image quality from the center to the edges of the individual frames, but it is less obvious here in this image. I had no clue what the "V" was - it is shown at right at something closer to full camera resolution. So now I can spot the "Modern Thai" that is projected onto the side of the building - Googling that returned with "V Modern Thai", a hip Thai restaurant near that block. So it is just advertising... Projected from near ground level, from my vantage on "A" Mountain, you can see the discontinuity caused by the offset in the south side of the building...
Well that is enough for now - at least I demonstrated that the ole' Pentax lenses work well with the new adaptor. It remains to be seen if they work as well for astronomy where they will be used closer to wide open to collect more light. Tiny errors in imaging quality or color correction will be enough to only make them useful when stopped down, less valuable for stars...