[vsnet-chat 5755] (fwd) Re: [AAVSO-DIS] Re: ST7E + photolens

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

Date: Tue, 24 Dec 2002 10:48:26 -0500
From: RA Kowalski <bitnik@bitnik.com>
Subject: Re: [AAVSO-DIS] Re: [vsnet-chat 5749] Re: ST7E + photolens

Maciej Reszelski wrote:
> 
> >     If you are trying to make survey-type observations with your CCD,
> > I can propose an alternative solution.  The PIXY program, used by the
> > MISAO project, is equipped with a function (proposed by the Kyoto team)
> > to process sequential images on a fixed mount and telescope.  With this,
> > you may be able to get survey observations with your fixed Dobsonian
> > mount.
> >
> >     We had experience with our 30-cm telescope (f/3.3 reducer) + ST-7E,
> > fixed on mount, which nearly reached 15 mag.  Yoshida-san can possibly
> > explain more about the details of this method.  You may even sleep during
> > your observation!
> >
> 
> Dear Taichi and Seiichi,
> 
> Yes I'm very interesting about this. I hope that Yoshida-san send me
> some more details about this. Current I make small adapter to my
> camera lens. I suspect that it will work ok.
> 
> Best regards,
> Maciej


To all,

While this conversation is moving off in a new direction, let me offer one small
suggestion on adapting small camera lens on to your ST-7 or 8. At a local or
online camera store, purchase one of several rear lens caps for the lens(es) you
want to use. Cut out the center circle of plastic so it is the slightly smaller
than the aluminium T thread ring. If you don't have any spares with your camera,
you can buy or machine, very short T threaded tubes. Once you have carefully
screwed the rear lens cap down the T ring until it is snug, you can attach your
camera lens. At about $4 -$5 new, you can have 30+ of these plastic rear lens
cap adapters for the price of one SBIG adapter. Granted you can't support long
lens this way, but for wide field they are perfect. This tip was shown to me by
Chris Bayus, of SMURFs...


The key to using a camera lens with your CCD is finding the correct distance
from the rear lens surface to the CCD. It'll always be different from what is
marked on the lens, so you'll also have to experiment to find focus. As you've
found, if your distances aren't right you can't reach focus. I suspect your
adapter is too long. Find the correct focal length first and then make sure your
adapter is close to that size.

-- 
Richard Kowalski
Quail Hollow Observatory         Minor Planet Mailing List
http://vsnet.bitnik.com/QHO        http://vsnet.bitnik.com/mp
761 Zephyrhills                  7392 Kowalski

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