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Re: [APML] 2 inch adapter and now focusers and such
Brian,
Now that you've seen the comparison of 2" vs 1-1/4", you may want to
consider a larger focuser, like 2.7". The 2.7" AstroPhysics focuser is
expensive, but absolute top quality. It uses a 2" adapter for eyepiece and
direct adapter to the camera, so only the t-adapter vignettes the light. It
also allows larger format photography for that massive CCD, film replacing
camera in the future. Mine allows off-axis guiding without any OAG shadow,
regardless of 35mm camera orientation.
Good luck with your SuperScope,
Don
> Hi Clay,
>
> Im starting to get picky on how Im building this thing now..
> Im getting the itch to make this scope into superscope, but I need to
start
> from scratch starting with the tubeing first so that I can adapt a decent
> focuser...maybe a megrez.
> I hear those are nice little focusers.
> I opened the B shutter with the film door open to see how much the frame
> gets cut between 1.25-2" and theres a huge differance.
>
> This is turning into a little bit of fun here:)
>
> I have 2 more main objectives to work with so the last two Ill be thinking
> of a bigger game plan.
> Hopefully Ill have this project done in time for summer.
>
> Thanks again,
> Bian
>
>
>
> > Brian,
> >
> > The length of the focus tube can hav an effect on vignetting and
exposure
> IF
> > it blocks part of the objective (forming an effective apature mask).
When
> I
> > built my 4" f6 refractor I wanted it to focus both a camera and my range
> of
> > eyepieces. This dictated a rather long draw tube. I used a 2" focuser
> for
> > a while but I eventually built a 3" crayford focuser. In this I have a
> > drawtube with a large inside diameter. I bring this to 2" at the end
> only.
> > This has worked out well. I have some pictures of the focuser parts and
a
> > description of the build process here:
> > http://www.gatecom.com/~ckessler/ATM%20Focuser.htm
> >
> > The refractor kit is described here:
> > http://www.gatecom.com/~ckessler/bw_optik_4.htm
> >
> > I hope this helps
> >
> > Clay Kessler
> >
> > ----- Original Message -----
> > From: "Brian Larmay" <astrobri@ameritech.net>
> > To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
> > Sent: Tuesday, March 04, 2003 3:39 PM
> > Subject: Re: [APML] 2 inch camera adapter question
> >
> >
> > > Thanks Frank,
> > >
> > > Does the length of focus, such as the focusing barrel/tube have impact
> on
> > > vignette or how long to expose for also?
> > >
> > > or....
> > >
> > > Should I make the main barrel of the refractor tube as close as
possibe
> to
> > > prime focus, so I dont have to have a long focusing barrel?
> > >
> > > This is hard to explain because Im making this refractor from scratch
> and
> > > Ive never built one before.
> > > I should really be going to ATM, but being that this scope is
> photographic
> > > in nature, I will ask here.
> > >
> > > Thanks,
> > > Brian
> > >
> > >
> > >
> > > ----- Original Message -----
> > > From: "Frank Parrotta (Navy Yard)" <FParrotta@TSC.COM>
> > > To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
> > > Sent: Tuesday, March 04, 2003 10:09 AM
> > > Subject: RE: [APML] 2 inch camera adapter question
> > >
> > >
> > > > Brian,
> > > >
> > > > As John has said, you really can't use the 1.25" if you want to
> > illuminate
> > > > as much of the 35mm frame as you can. However, you're still not
home
> > > free.
> > > > The camera T-ring will also vignette the frame as well - the amount
> > > > depending on the focal ratio. I find that the corners get pretty
dark
> > but
> > > > the central core of the frame is usable with some vignetting removal
> > > > processing. If you want to get an idea of just how much light
falloff
> > > > you'll have to content with, set up your scope with the camera
> attached
> > > and
> > > > aim it at an evenly illuminated source (e.g., blue sky, white
painted
> > > wall,
> > > > etc.). Set the shutter to "B" and open the camera back. Fire the
> > shutter
> > > > and look through the camera back opening (where the film would be)
and
> > > > notice the illuminated circle produced by the objective. Move your
> eye
> > > > around to the frame's edges and corners - the amount of the
> illuminated
> > > > circle that is obscured at each location will be proportional to the
> > > amount
> > > > of vignetting you will get at those locations. Hope this helps.
> > > >
> > > > Frank
> > > >
> > > > -----Original Message-----
> > > > From: Brian Larmay [mailto:astrobri@ameritech.net]
> > > > Sent: Sunday, March 02, 2003 3:40 PM
> > > > To: astro-photo@seds.org
> > > > Subject: [APML] 2 inch camera adapter question
> > > >
> > > >
> > > > Hi!
> > > >
> > > > What are the advantages photographically of a 2 inch camera adapter
> over
> > a
> > > > 1.25.
> > > >
> > > > Thanks,
> > > > Brian
> > > >
> > > >
> > > > My Photography
> > > > Nature: http://www.astrobri.com/nature_photography.htm
> > > > Astrophotography: http://www.astrobri.com/astrophotography_ind.htm
> > > > Storm chasing photography:
> > > > http://www.astrobri.com/weather_pictures_2002_season.htm
> > > > Northern Lights: http://www.astrobri.com/northern_lights.htm
> > > > Miscellaneous: http://www.astrobri.com/miscellaneous.htm
> > > >
> > > >
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