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Need high resolution scanner for unusual project

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Anonymous   03-17-2005 at 10:16:08 PM

Archived from groups: rec.photo.digital (More info?)

 

I am a neophyte when it comes to scanners. Please help if you can. I have
organized an engineering project at a military academy. It involves a very
large lens (11" diameter, 160 degree field of view, f/2.8) The diameter of
the image is 4.5". We will be photographing the night sky. Would like to be
able to image stars. Although the main purpose may be to scan the sky for
obscuring clouds for a large observatory.

We are converting the lens to an all-sky camera. If I could afford it I
would use a CCD and a precision scanning table and piece together the
image. But as a class project I don't have that kind of budget.

So I need some expert or at least experienced advice. Can a flat bed
scanner be used to scan a focused image? If so what type of scanner has the
highest resolution and the highest bit depth.

I have seen a reference to grain reduction software how does this work.
Please reply to this forum or directly to me at mickey.schmidt[at]usafa[dot]
af[dot]mil

Mickey Schmidt

--
Message posted via http://www.photokb.com

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Anonymous   03-17-2005 at 10:16:09 PM
- 0 +

Archived from groups: rec.photo.digital (More info?)

 

You are going to have two problems, first when photographing the night
sky the exposure times are normally in the many seconds to minutes, the
scanner uses a very bright light source and scans at hundreds of lines
per second, so you will simply not have enough light. The second
problem that you will have is that you really need a field lens to make
this work, a lens close to the focal plane that refocuses the light
from the objective lens onto the imagine lens of the scanner, otherwise
you will end up with a very small image circle. Putting in a field
lens with out messing up the image is not easy.

Scott

Reply to Anonymous
Anonymous   03-18-2005 at 01:51:45 AM
- 0 +

Archived from groups: rec.photo.digital (More info?)

 

Considering who you are working for and where the school is located I would
think that there would be observatories and government facilities that could
help you. The might have some old stuff laying around. I wonder what night
vision equipment might do. Bring the light in, boost it, and shoot the
resulting green image.

"Mickey Schmidt via PhotoKB.com" <forum@PhotoKB.com> wrote in message
news:e23cb06586a74b19b940221e980df75e@PhotoKB.com...
> I am a neophyte when it comes to scanners. Please help if you can. I have
> organized an engineering project at a military academy. It involves a very
> large lens (11" diameter, 160 degree field of view, f/2.8) The diameter of
> the image is 4.5". We will be photographing the night sky. Would like to
be
> able to image stars. Although the main purpose may be to scan the sky for
> obscuring clouds for a large observatory.
>
> We are converting the lens to an all-sky camera. If I could afford it I
> would use a CCD and a precision scanning table and piece together the
> image. But as a class project I don't have that kind of budget.
>
> So I need some expert or at least experienced advice. Can a flat bed
> scanner be used to scan a focused image? If so what type of scanner has
the
> highest resolution and the highest bit depth.
>
> I have seen a reference to grain reduction software how does this work.
> Please reply to this forum or directly to me at
mickey.schmidt[at]usafa[dot]
> af[dot]mil
>
> Mickey Schmidt
>
> --
> Message posted via http://www.photokb.com

Reply to Anonymous
Anonymous   03-18-2005 at 01:19:27 PM
- 0 +

Archived from groups: rec.photo.digital (More info?)

 

"Mickey Schmidt via PhotoKB.com" <forum@PhotoKB.com> writes:

>So I need some expert or at least experienced advice. Can a flat bed
>scanner be used to scan a focused image? If so what type of scanner has the
>highest resolution and the highest bit depth.

A normal flatbed cannot be used for this, because it has its own lens
system that images the platen onto its CCD. To make it work, you'd need
a rather strong large diameter field lens located near the scanner focal
plane in order to redirect light from your prime lens into the scanner
lens.

However, there's another possibility: the Canon LiDE scanners do not use
a conventional optical system. They have a sensor array that's actually
8.5 inches long, and a lenslet array to transfer the image from paper to
sensor at actual size. If you take one of these, disable the LED
illumination, and remove the lenslet array, you have what amounts to a
8.5x11 inch B&W scanning camera back.

You'll still have angle of view issues (the sensor is at the bottom of a
well, assuming that the light path is always perpendicular to the sensor
plane, while your light will be arriving on various diagonal paths).
But at least this is a plausible starting point.

Dave

Reply to Anonymous
Rob   03-19-2005 at 02:34:00 AM
- 0 +

Archived from groups: rec.photo.digital (More info?)

 

Mickey Schmidt via PhotoKB.com wrote:
> I am a neophyte when it comes to scanners. Please help if you can. I have
> organized an engineering project at a military academy. It involves a very
> large lens (11" diameter, 160 degree field of view, f/2.8) The diameter of
> the image is 4.5". We will be photographing the night sky. Would like to be
> able to image stars. Although the main purpose may be to scan the sky for
> obscuring clouds for a large observatory.
>
> We are converting the lens to an all-sky camera. If I could afford it I
> would use a CCD and a precision scanning table and piece together the
> image. But as a class project I don't have that kind of budget.
>
> So I need some expert or at least experienced advice. Can a flat bed
> scanner be used to scan a focused image? If so what type of scanner has the
> highest resolution and the highest bit depth.
>
> I have seen a reference to grain reduction software how does this work.
> Please reply to this forum or directly to me at mickey.schmidt[at]usafa[dot]
> af[dot]mil
>
> Mickey Schmidt
>
Have seen a one of those hand scanners which scans pages used as a
panoramic camera. Think they actually altered the focal length to
infinity and mounted it on a stepper motor. You may want to google up
some more info.

Reply to Rob
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