Astro version of Canon 20D

Chris L Peterson wrote in message ...
On Mon, 14 Feb 2005 18:25:30 -0500, "matt"
wrote:

not sure which IS Canon binos you're referring to . I opened a couple of
them and they have a moving lens not prism. One of the objective lenses
moves in some sort of yoke arrangement , with 2 degrees of freedom. Both
eyes are moved simultaneously by the same linear voice coil type actuator.
The control electronics have nothing to do with optics (no image motion
sensing per se) and derive their feedback signal from an Analog Devices
piezo accelerometer .

I don't know if Canon uses different approaches, or if it has changed
recently. A few years ago I examined a corrector that was essentially a
variable prism- two flats with a flexible bellows between them, filled
with oil, and driven by a pair of actuators. This is the type of
mechanism I used for my tip/tilt corrector. The other approach would
work too- it looks like what SBIG has adopted for its new large format
tip/tilt device.

_______________________________________________ __

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


the binos I opened were less than a year old and up to 50mm aperture . The
objective looked like an air spaced doublet in which the inner lens was able
to move sideways and up/down .
The piezo accelerometer was a dual axis chip , the ADXL variety .
Electronics looked simple.

Funny how SBIG and Starlightxpress decided to take a step backwards and made
the newer tip/tilt devices even slower than the AO-7, completely eliminating
any chance of correcting atmospheric turbulence . They should be called
integrated guiders not adaptive optics . I guess not only Meade is allowed
creative using of technical terms for the purpose of marketing .


best regards,
matt tudor

On Mon, 14 Feb 2005 20:43:17 -0500, "matt"
wrote:

Funny how SBIG and Starlightxpress decided to take a step backwards and made
the newer tip/tilt devices even slower than the AO-7, completely eliminating
any chance of correcting atmospheric turbulence . They should be called
integrated guiders not adaptive optics.

Yes, that's probably what they should be called. I'm not sure if it
matters about being a little slower, however. You can't correct for
atmospheric turbulence in any case, since the reference star is just too
far away, and the FOV of the imager is too large. Adaptive optics works
over small angles, and requires large apertures (at least meter-class)
to get enough light to correct at high speed (either from an artificial
star or the target itself).

With the FAA freaking out about 5mW laser pointers, I can't imagine what
would happen if amateurs started making their own artificial reference
stars! g

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On Tue, 15 Feb 2005 00:10:19 GMT, "Gary Honis"
wrote:

I and a few others have used a coated clear glass window from Edmunds
Scientific Optics. (Part No. 32741):
http://www.edmundoptics.com/onlineca...productID=2402

It has worked out well. The glass would need to be cut as explained on my
site.

I have heard from Andrew Lutley who has ordered a higher spec glass from
Edmunds for his modification, the B270 optical window - Stock No: T45-57:
http://www.edmundoptics.com/onlineca...productID=1755

Hutech has decided not to sell already cut glass to those doing the
modification.

The advantage of a clear glass window is that the CMOS imaging chip is open
to all wavelengths for imaging. Cut and pass filters can be used in the
optical train as needed and a color correcting filter can be used for normal
daylight photography.

Canon has got to offer a filter when they sell this camera.
Unless you want to loose 80% of the utility, buy a second
camera, or just use it for astronomy.
-Rich

RichA wrote:
On Tue, 15 Feb 2005 00:10:19 GMT, "Gary Honis"
wrote:
The advantage of a clear glass window is that the CMOS imaging chip is open
to all wavelengths for imaging. Cut and pass filters can be used in the
optical train as needed and a color correcting filter can be used for normal
daylight photography.


Canon has got to offer a filter when they sell this camera.
Unless you want to loose 80% of the utility, buy a second
camera, or just use it for astronomy.
-Rich

What 80% loss of utility are you talking about?

All we're doing here is removing the IR cut filter from the chip inside,
and putting it on the removable SLR lens, which has 58mm filter threads,
for of all things, filters. ;-)

SPaul

I think Rich meant that when Canon sells the 'a' version, they should
sell it with an external IR filter so it can be used for terrestrial
photography as well.

Mark


Stephen Paul wrote:

What 80% loss of utility are you talking about?

All we're doing here is removing the IR cut filter from the chip
inside,
and putting it on the removable SLR lens, which has 58mm filter
threads,
for of all things, filters. ;-)

SPaul

I now understand. Thanks.

Moving on....

Mark wrote:
I think Rich meant that when Canon sells the 'a' version, they should
sell it with an external IR filter so it can be used for terrestrial
photography as well.

Mark


Stephen Paul wrote:

What 80% loss of utility are you talking about?

All we're doing here is removing the IR cut filter from the chip

inside,

and putting it on the removable SLR lens, which has 58mm filter

threads,

for of all things, filters. ;-)

SPaul