Converting Canon Rebels, etc, to astro cams

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RichA - 28 Apr 2005 02:02 GMT

The early gens of Canon's and Nikon's DSLRs are dropping toward
the $500 and under mark on the use market.
If anyone is thinking of removing the sensor's infrared filter
window for astronomy, you can buy a screw-on (the lens of the camera)
replacement from B&W filters. The part number is 489.
-Rich

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Stephen Paul - 28 Apr 2005 04:05 GMT

> The early gens of Canon's and Nikon's DSLRs are dropping toward
> the $500 and under mark on the use market.
> If anyone is thinking of removing the sensor's infrared filter
> window for astronomy, you can buy a screw-on (the lens of the camera)
> replacement from B&W filters. The part number is 489.
> -Rich

You can get a variety of filters for them here:

http://www.maxmax.com/aXNiteFilters.htm

http://www.maxmax.com/aXRay58mmFilters.asp

The CC-1 is the color correcting filter for use after removing the IR block
on the CMOS sensor. There's more to it though than just pulling the IR
blocker and popping one of these into place. You also need to add a piece of
optical glass where the IR blocker was, in order for the auto-focus to work
properly (so I read).

I keep the CC-1 permanently on the 15-38mm lens for non-astro use. With this
filter, the camera really does work in full auto-mode with excellent
results. But, now that there's no limit on the CMOS sensor itself,
supposedly you can also do some other neato stuff too, like IR imaging.

What I'd like to know, is the thread diameter on the inside of my EOS
T-Ring?

It seems like it might be the same as a 2" eyepiece filter thread. Anyone
know?

-Stephen

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RichA - 28 Apr 2005 08:48 GMT

>> The early gens of Canon's and Nikon's DSLRs are dropping toward
>> the $500 and under mark on the use market.
[quoted text clipped - 14 lines]
>optical glass where the IR blocker was, in order for the auto-focus to work
>properly (so I read).

I know. You woudn't want to leave the sensor exposed anyway.

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Stephen Paul - 28 Apr 2005 12:39 GMT

>>> The early gens of Canon's and Nikon's DSLRs are dropping toward
>>> the $500 and under mark on the use market.
[quoted text clipped - 19 lines]
>
> I know. You woudn't want to leave the sensor exposed anyway.

How come?

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RichA - 29 Apr 2005 04:34 GMT

>>>> The early gens of Canon's and Nikon's DSLRs are dropping toward
>>>> the $500 and under mark on the use market.
[quoted text clipped - 21 lines]
>
>How come?

They already have dust issues with DSLRs and that's before removing an
IR filter.
-Rich

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Stephen Paul - 30 Apr 2005 20:39 GMT

>>>>optical glass where the IR blocker was, in order for the auto-focus to
>>>>work
[quoted text clipped - 6 lines]
> They already have dust issues with DSLRs and that's before removing an
> IR filter.

That's what I thought. I have the glass over sensor and it has some dust
that I am convinced is under the glass. I can't blow it off or gently sweep
it off with a Q-tip. Right now I wish I didn't have the glass, so I could
get at them. Taking the camera apart to get at the optical window is a job.

Thank goodness for flats. But still, in order to get an even better image, I
need to take half the frames with the target object shifted a bit, so that I
can get the data blocked by those "flecks". Doesn't help for non-astro
though. I am going to need to get it cleaned.

For now I'm not too worried about it. I'm just a part time hobbyist, and
still gratified by the simple joy of getting novice level results. I have
other issues to work out that are more important. Like focus and tracking.

I just bought a Stiletto IV, but haven't had the chance to use it yet. I
have to say, it was a lot more robust than I expected. It's weight is
comparable to the Rebel, for which it's calibrated. I can't wait to see if
it indeed makes focusing easy.

As for tracking accuracy, I have a feeling that's not going to be as easy
and (relatively) cheap to solve, as it was to simply buy a Stiletto. ;-)

G11's are hardly inexpensive for a part time hobbyist, with a family.

But anyway,
Stephen

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Space Forum / Amateur Astronomy / April 2005

Converting Canon Rebels, etc, to astro cams