RE: [APML] Piggybacked Canon FD 70-210mm f/4?

["Lane, Jason R" <jason.lane@navy.mil>]

Hi Bradley,

I've used an Olympus 70-210 mm f/4.5-5.6 zoom lens piggy-backed on my scope...to keep the zoom from slipping I cut a piece of a shish-ka-bob stick long enough to keep it at 210 mm.  This worked pretty good and is reusable so I don't worry about having to bring tape.

Chromatic aberrations aren't as well corrected in a zoom so there's blue flare present around the stars.  This is dependent on the lens design so you probably won't have the same amount that I did, but it's something you should be aware of.  I don't think it's too awfully noticeable unless you crop and blow up the picture like I did.  http://www1.iwvisp.com/opticman/astroimages/Pleiades.html is a good example of this.  Otherwise, the lens did pretty good and I didn't see any typically associated with photographing wide open at highest zoom setting.  

Good luck!
Jason

-----Original Message-----
From: Bradley Hope [mailto:bradley@thorngarden.net]
Sent: Sunday, November 23, 2003 8:34 PM
To: Discussion of Film Astrophotography
Subject: Re: [APML] Piggybacked Canon FD 70-210mm f/4?


Stuart - Alan - Richard

Thank you all for your input, it is much appreciated.

I just picked up the affore mentioned lens on eBay, listed as being in
excellent condition, for a whole $91 including shipping. If nothing else,
and it doesn't work out as an acceptable piggyback lens, I now have a decent
zoom lens for my Canon A-1..and I can pick up a 200mm lens later on for my
Nikon F2 (which is my primary astro camera).

If I'm happy with it (and I get some clear weather at some point in the
foreseeable future, which can be problematic around here as Mark de Regt can
attest to), I'll be sure and post some pictures taken with the Canon.

Again, thank you
Bradley

----- Original Message ----- 
From: "Stuart Heggie" <stuart.j.heggie@sympatico.ca>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Sunday, November 23, 2003 4:53 PM
Subject: Re: [APML] Piggybacked Canon FD 70-210mm f/4?


> Bradley, zooms are usually discouraged both because they tend to be slower
> and less sharp. I've used one and gotten good pics (it was a Minolta
75-200
> ostensibly made in the same factory that Minolta was subcontracted to make
> Leica's 75-200 - coincidence?).
>
> Anyway, it did a good job but was slow at f4.5; also, the zoom needs to be
> held down with tape or a heavy rubber band or something else you get the
> famous "warp to lightspeed" effect as the zoom mechanism drops under
gravity
> as you aim the lens up.
>
> Stuart

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