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Re: [ATM] FOV by design: An iterative process?
Dominic-Luc Webb wrote:
> I have tinkered with numbers for some time, plugging numbers
> like ROC and radius into software, or direct trigonometry
> calculations, etc. The criteria we most frequently have used
> to constrain designs are things like magnification and
> sometimes magnitude. But what about constraining field of
> view (FOV)?
Constrain the effective focal length. EFFL + CCD chip size = FOV. For
instance, I played with this but I'll save my decision for the end of
this letter.
I started with selecting the imaging device I was going to use, a
Phillips Web cam, 640x480 w/ 5.6 micron pixels.
Next I decided I wanted to image 1/2 degree of the sky at a time.
(arbitrary, but it sounded like a good starting point).
What ever I built, it had to have an effective focal length of
315mm... (Yuk). I can't imaging the hand cramps one would get figuring
a 3" F/4 Newtonian primary. I played with building a 2 mirror
Schwartschild F/3 scope, but could not fabricate the F/8 primary that
required a conic constant of -11ish.
At this point I decided I had two choices, abandon the 1/2 degree FOV
imaging requirement, or get a new, larger, CCD chip.
If I kept the 1/2 degree FOV, and went with an Apogee U42 chip @ 2048^2
w/ 13.5 micron pixels, I need an EFFL of 3150mm (OK that's better, and
rather doable).
I started looking at the prices of said Apogee U42 CCD, then I decided
to by a BOAT and learn to fish..
I figure by the time I get skin cancer from being out in the sun
fishing, the price of a good CCD should be easier to swallow. Until
then, I also found out my wife likes to fish as much as I do, and
honestly I think she is better at it than I :-)
--
Take Care,
James Lerch
http://lerch.no-ip.com/atm (My telescope construction,testing, and coating site)
http://lerch.no-ip.com/ChangFa_Gen (My 15KW generator project)
"Anything that can happen, will happen" -Stephen Pollock from:
"Particle Physics for Non-Physicists: A Tour of the Microcosmos"
" Press on: nothing in the world can take the place of perseverance.
Talent will not; nothing is more common than unsuccessful men with talent.
Genius will not; unrewarded genius is almost a proverb.
Education will not; the world is full of educated derelicts.
Persistence and determination alone are omnipotent. "
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