07-13-2015, 07:14 AM
Just to add a couple of points to the user side of "refractor" type telescope lenses; a lot of of nature photographers use telescope lenses basically because of their lower price point, eg. a 560mm F7.1 lens can cost in the region of $500-600. Usually they come with a "T" mount for which you buy the appropriate adapter for your make of camera.
Normally they are "all manual fixed aperture" and use a simple form of "rack and pinion" manual focus system, as such they're mostly suitable for photography in "hides" on a tripod where the shooter can wait unseen and has the time to focus and catch his shot. In spite of their simple construction (often only three elements) they are very sharp lenses and light, but their size (length) is about equivalent to their focal length. Modern telephoto lenses have a built in tele-converter to keep the lens compact which is why telescope lenses can get away a much more simple construction.
The "bokeh" is fine compared with mirror/reflector counterparts, which often result in awful and very distracting "donut highlights" as well as softer images and low contrast which pretty much counts them out for nature photography.
I have a semi-pro friend who uses one and he gets the most remarkable results out out of it, he actually prefers the fact that he does all manually!
However, with the recent lenses from Tamron/Sigma 150-600mm producing very good results for around $1,000 with variable aperture, image stabilization and fast auto-focus, unless you find a very cheap S/H telescope example suitable for DSLR photography, it is difficult to find a good reason to try one!
Normally they are "all manual fixed aperture" and use a simple form of "rack and pinion" manual focus system, as such they're mostly suitable for photography in "hides" on a tripod where the shooter can wait unseen and has the time to focus and catch his shot. In spite of their simple construction (often only three elements) they are very sharp lenses and light, but their size (length) is about equivalent to their focal length. Modern telephoto lenses have a built in tele-converter to keep the lens compact which is why telescope lenses can get away a much more simple construction.
The "bokeh" is fine compared with mirror/reflector counterparts, which often result in awful and very distracting "donut highlights" as well as softer images and low contrast which pretty much counts them out for nature photography.
I have a semi-pro friend who uses one and he gets the most remarkable results out out of it, he actually prefers the fact that he does all manually!
However, with the recent lenses from Tamron/Sigma 150-600mm producing very good results for around $1,000 with variable aperture, image stabilization and fast auto-focus, unless you find a very cheap S/H telescope example suitable for DSLR photography, it is difficult to find a good reason to try one!