Nikon used to make a 2000mm lens: http://tinyurl.com/39q6p . Where can
I rent this lens or a high-quality lens with Nikon mounts of similar
length for a day in New York City? (I'd consider using a shorter lens
with a teleconverter, but I'd prefer a longer lens.)

I'm not sure that this company rents lenses--it sells them, new and
used--but, if they don't, they can probably refer you to one that
does. I am in no way involved with this company, except as a satisfied
customer.

B&H Photo

Mailing/Street address:
B&H Photo
420 Ninth Avenue 
New York, NY 10001, USA 

Photo department:
800-972-5999 and 212-502-6200

E-mail for photo equipment:                                 
photo@bhphotovideo.com 

Web page:
http://www.bhphotovideo.com

Here's a company that rents equipment, but I've never dealt with them:
http://www.tamarkin.com

Here's a list of some some NYC photo rental companies:
http://www.newyork411.com/index.cfm?page=Listings&method=Category&sid=2001&cid=2031
I've never dealt with these companines, either (I might have bought
one lens from Adorama years and years ago, but I forget).


If you don't mind a little advice from a pro with years of experience,
a teleconverter is a poor substitute for a longer lens. If you're able
to find the real thing and can afford it, skip the teleconvertor.  :-)

dtc

P.S. Are you a pro? If so, you could contact Nikon to see if you can
sign up for their professional program. I joined Canon's years ago--I
had to apply, send copies of my work, plus a resume--and am able to
borrow lenses that I only rarely need.

Thanks for your comment.

Unfortunately, none of the rental companies I've found carry either
non-current lenses (like the 2000mm) or third-party lenses which might
solve the problem.

At the moment, we're likely to use a telescope with an adapter for
Nikon, which should work OK, but I'd prefer a lens designed for a
camera (although I don't know why).