From: Dale Eason 
To: James Lerch , Jeff Anderson-Lee
        , ATM List 
Reply-To: Dale Eason 


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Now I understand what I'm seeing in my test setup.  James, I'm glad you
talked about vignetting.  My test setup needs the mirror image centered
within 1/16 inch of the lens center and this if for an 8" mirror or
else the image is vignetted.  The lens is a large 35 MM camera zoom lens
F2.8.  But the adapter to connect it to the webcam is a small threaded
cylinder that replaces the webcam lens.  It has a hole drilled in it to let
the image shine on the CCD and is about 3/8 inch long.  The hole is about
3/8 inch.  I bet it is vignetting the image.

I didn't want to destroy the Web cam by taking it apart.  I also use it to
take movies of the moon through the scope.  But taking it apart would make
the ccd more accessible.

James Lerch  wrote:

----- Original Message -----
From: "Jeff Anderson-Lee"
>
> "Cary Chleborad"
> > Marshall electronics is a good place to get stuff....
> >
> > www.mars-cam.com
>
> Well maybe, but Supercircuits seems to have a better selection of B/W
> cameras at somewhat lower prices. You can even pick up a 6 to 60mm CS mount
> zoom lens for $160 or a 12.5 to 75mm zoom lens (1/2" C mount) for $280 or
> even an 8-56mm motorized zoom lens for $370 if you want to skip machining
> your own mount.
>
> http://www.supercircuits.com/store/home.asp

** WARNING **

Dave Bevel went the route of C/CS mount zoom lens (not sure which, C or CS,
and not certain which zoom range he selected) and was meet with unhappy
results (Vignetting)

I have come to the conclusion that there exists a relationship between the
F/Ratio of the camera optic and the F/Ratio of the mirror being tested. I
don't know what the relationship is, as I don't know how to calculate the
F/Ratio of my existing camera optics (I've taken apart several camera lens
sets, and there are just WAY to many lenses in there to make any sense of!)

I can offer a few data points on my cheap Sony camera (circa 1990's).

#1 F/4.5 mirrors are no problem
#2 F/4 mirrors require that the field lens is as close the KE as possible AND
properly oriented to avoid vignetting the edges of the image.
#3 F/3.8 was no Joy (could get 90% of the surface to illuminate, but not the
edges)
#4 F/2 was seriously no Joy, only getting a little more than half the mirror to
illuminate


I believe its possible to do without the lens, and just use the bare CCD if
we use a pinhole or point source light source. However this approach has
its own unique set of problems:

#1 Point source light, or really small pinhole = Lots of diffraction effects
#2 "Zoom" will need to be controlled by distance between KE and CCD
#3 The plane of the CCD must be kept perpendicular to the KE
#4 You won't get an image until everything is properly aligned
#5 Dust and stray light on the CCD must be addressed

Just my $0.02 worth, and while I'm tossing pennies around, let me relate some of
my experiences with video capture hardware.

WinXP and an Internal capture card often equals Trouble. Why, you might
ask, well M$ has two version of Video Capture technology, the old and the
new

#1 The old method is called Video for Windows. VFW is supposedly supported on
WinXP, and actually does work rather well with USB external capture
devices. However, most newer internal capture cards don't support VFW, or
kind of implement it and it doesn't work right..

#2 The "NEW" method is called DirectShow video capture, which
USED to be called
ActiveMovie (all part of the M$ DirectX technologies). On WinXP this is the
method supported by the internal cards I've played with (Pinnacle &
ATI). This will probably be the method used with FireWire and Digital Video
capture systems.

Here's the bad news, All three of the currently available Robo-Foucault programs
(Dale Eason's RTAFTc, Martin Cibulski's AutoFouc, and My RTAFT) all use the
older Video for Windows capture technology. If you have WinXP and an
internal capture card, be prepared for problems!

The good news is M$ has an SDK for DirectShow, the bad news is it almost
requires a career change to implement it! I've tinkered with it, and almost
have a method to support it with my Robo code, but the UI becomes rather
ugly!

Just something to thing about!

Take Care,
James Lerch



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Now I understand what I'm seeing in my test setup. 
James, I'm glad
you talked about vignetting.  My test setup needs the mirror image
centered within 1/16 inch of the lens center and this if for an 8"
mirror or else the image is vignetted.  The lens is a large 35 MM
camera zoom lens F2.8.  But the adapter to connect it to the
webcam is a small threaded cylinder that replaces the webcam
lens.  It has a hole drilled in it to let the image shine on the
CCD and is about 3/8 inch long.  The hole is about 3/8
inch.  I bet it is vignetting the image.
 
I didn't want to destroy the Web cam by taking it
apart.  I also use
it to take movies of the moon through the scope.  But taking it
apart would make the ccd more
accessible.James Lerch
<jlerch1{at}tampabay.rr.com> wrote:
----- Original Message -----
From: "Jeff Anderson-Lee"
>>
"Cary Chleborad"
> > Marshall
electronics is a good place to
get stuff....> >> >
www.mars-cam.com>> Well maybe, but
Supercircuits seems to have a better selection of B/W>
cameras at somewhat lower prices. You can even pick up a 6 to 60mm CS
mount> zoom lens for $160 or a 12.5 to 75mm zoom lens
(1/2" C mount) for
$280 or> even an 8-56mm motorized zoom lens for $370 if
you want to skip
machining> your own
mount.>>
http://www.supercircuits.com/store/home.asp;** WARNING
**Dave Bevel went the route of C/CS mount zoom lens
(not sure which, C or CS, andnot certain which zoom range he
selected) and was meet with unhappy
results(Vignetting)I have
 come to the conclusion that there exists a relationship between theF/Ratio
of the camera optic and the F/Ratio of the mirror being tested. I
don'tknow what the relationship is, as I don't know how to
calculate the F/Ratio ofmy existing camera optics (I've taken
apart several camera lens sets, and thereare just WAY to many
lenses in there to make any sense of!)I can offer a few
data points on my cheap Sony camera (circa 1990's).#1
F/4.5 mirrors are no problem#2 F/4 mirrors require that the field
lens is as close the KE as possible ANDproperly oriented to avoid
vignetting the edges of the image.#3 F/3.8 was no Joy (could get
90% of the surface to illuminate, but not theedges)#4
F/2 was seriously no Joy, only getting a little more than half the mirror
toilluminateI believe its possible
to do without the lens, and just use the bare CCD if weuse a
pinhole or point source light source. However this approach has its
 ownunique set of problems:#1 Point source
light, or really small
pinhole = Lots of diffraction effects#2 "Zoom" will
need to be controlled by distance between KE and CCD#3 The plane
of the CCD must be kept perpendicular to the KE#4 You won't get
an image until everything is properly aligned#5 Dust and stray
light on the CCD must be addressedJust my $0.02 worth,
and while I'm tossing pennies around, let me relate some ofmy
experiences with video capture hardware.WinXP and an
Internal capture card often equals Trouble. Why, you might
ask,well M$ has two version of Video Capture technology, the old
and the new#1 The old method is called Video for
Windows. VFW is supposedly supported onWinXP, and actually does
work rather well with USB external capture devices.However, most
newer internal capture cards don't support VFW, or kind
ofimplement it and it doesn't work right..#2
The "NEW" method is called
 DirectShow video capture, which USED to be calledActiveMovie (all part of
the M$ DirectX technologies). On WinXP this is themethod
supported by the internal cards I've played with (Pinnacle & ATI).
Thiswill probably be the method used with FireWire and Digital
Video capturesystems.Here's the bad news, All
three of the currently available Robo-Foucault programs(Dale
Eason's RTAFTc, Martin Cibulski's AutoFouc, and My RTAFT) all use
theolder Video for Windows capture technology. If you have WinXP
and an internalcapture card, be prepared for
problems!The good news is M$ has an SDK for DirectShow,
the bad news is it almostrequires a career change to implement
it! I've tinkered with it, and almosthave a method to support it
with my Robo code, but the UI becomes rather ugly!Just
something to thing about! Take
Care,James
Lerch Do
you Yahoo!?
http://pa.yahoo.com/*http://rd.yahoo.com/evt=1207/*http://promo.yahoo.
com/sbc/">SBC Yahoo! DSL - Now only $29.95 per month!
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