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Re: [APML] 2 inch adapter and now focusers and such
Hi Clay,
Its just a 280mm f 1:4.5 tominon copy lens, which appears to be a four
element objective with a stop in the middle.
I read somewhere and found only one bit of literature that it is a six
element, but I doubt that from what I can see.
Being a four element, wouldnt that make this an apochromatic instead of
achromatic?
I know its just a copy lens, but hey, why not<g>!
As far as facilities are concerned, notta..Im at the mercy of a very limited
budget right now, and I have access to nothing.
So as far as the 2" focuser...
I went to ace yesterday and brought my t ring with so I could find some thin
metal tubing to thread to it but with no availe..
I even went as far as...Hey...I can try to weld or solder this thing to a
makeshift drawtube over the whole T-ring itself so I get no
obstruction...again..lol.
By that time my wheels were turning too fast and I was getting ahead of
myself without draw plans...I need to make one of these....probably going to
end up with a few of them.
Well my brain is on overload due to no sleep last night so Im going to give
it a rest for a few hours
Thanks for your support Clay, Im sure I'll have more questions and Ill
contact you off list.
Thanks again,
Brian
> Brian,
>
> I know the feeling. What objective are you using for this scope? And, if
> you don't mind my asking, what facilities do you have access to to make
the
> various "parts and pieces". I went through a lot of the same decision
> processes that you are doing now when I built my first refractor. It was
> well worth it. It has become my most used astrograph to date and can take
> much better astrophotos that I can - even if it is a "lowly achromat".
>
> I second Don's recommendation for a larger than 2" focuser if possible.
> Don't forget - you may want to try medium format sometime in the future.
I
> did not find a large format commercial focuser at a reasonable price when
I
> was building my scope but there are more choices out there now.
>
> I don,t know where you are located. If I can be of help drop me a line
> "off-list".
>
> Clay
>
> ----- Original Message -----
> From: "Brian Larmay" <astrobri@ameritech.net>
> To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
> Sent: Tuesday, March 04, 2003 9:50 PM
> Subject: Re: [APML] 2 inch adapter and now focusers and such
>
>
> > 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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