On 25 Jul 2002 18:54:06 -0700, drsmithhm@hotmail.com (drsmith) wrote:

>I've lately been interested in stretching the high end of my telephoto. I've
>got a 75-300 Tamron lense for my Pentax bodies and the decision is primarily
>do I go with a 1.4 or 2x teleconverter(with the aforementioned zoom lense) or
>do I go for a quality 500mm f8 fixed lense. I'd definately be looking at the
>mirror type lenses since a 500mm straight lense is just a tad long.
>
>As for shooting, I do general purpose stuff. Times when I'd use this
>focal length is either for low power astronomy or those few times when the
>humidity drops and I want a really long close up(which can mean nature
>photos or landscape photos where it's not convenient to hike through a mile
>of crap just to get one shot. Ever see something interesting on the other
>side of a 600ft deep gorge? Well anyway...).
>
>I did take a quick look at spotting scopes with adapters, but that was far
>more expensive than what I'm proposing here. If you know of a setup that's
>more affordable, let me know. I have seen comet photos done with a 500mm
>that came out really good - I'd like to be able to do the same.

Fred's answer was a good one (above). Both Minolta and Nikon
(and Tamron, with the 350mm f5.6 only) made good mirror
lenses (there are probably others), but most are not very
good, including those with good reputations (I have not yet
seen a good Series I solid cat, for instance, and I have
tried a few...). Unfortunately, adding teleconverters to
zooms that reach 300mm or so has also produced poor results,
in my experience. There is a real need for ***GOOD***
compact cheap long tele lenses, even if slow, and there are
not very many in existence (the fast ones are generally very
good, but not compact or cheap). Best cheap long lenses I've
seen: various-label 400mm f6.3/6.9 preset teles (but not the
500mm versions), the older-style Nikkor 500mm f8 mirror
(even good on the TC14/14B [not C or A for a slow but tiny
700mm), the Tamron 350mm f5.6 (but it isn't very "long",
same with the Minolta 250mm f5.6 - but that one is TINY!),
and the Cosina 100-500mm f5.6-8 (but it was even slower
than rating, excellent to around 400mm, only OK at 500mm).
BTW, for night sky shooting, slow lenses would not work
unless you can mount the shooting rig on a device that
would accurately follow the earth's rotation (with a 500mm,
1/2 second exposures are too long for good sharpness
without this...). BTW, there are several photos on my
web page shot with the 500mm Nikkor alone, with TC14, and
even with the TC200...