Meade DSI question

My son is trying to get his new Meade imager working, and he said that the
preview pic (Jupiter) is OK, but when he takes a pic, the image goes to an
over-exposed white blob!

He has tried exposure times down to 6/1000 to no effect, but doesn't know
where else to look......instructions seem a bit light on, and we have
found some tips by other users, but this one his him stumped.

FWIW, I am starting out with a converted web cam.

Adrian.

Adrian wrote:
My son is trying to get his new Meade imager working, and he said that
the preview pic (Jupiter) is OK, but when he takes a pic, the image
goes to an over-exposed white blob!

He has tried exposure times down to 6/1000 to no effect, but doesn't
know where else to look......instructions seem a bit light on, and we
have found some tips by other users, but this one his him stumped.

FWIW, I am starting out with a converted web cam.

Adrian.


Sounds like a daytime picture. You can not take any pictures in the day time
with it.

steve

It looks like a daytime pic, but I assure you it was night or he wouldn't
be able to see Jupiter....its on the other side of Earth during the day.
Thats why it is puzzling. The preview pic looks fine.
Adrian.


On Thu, 07 Apr 2005 18:30:40 -0400, Steve Sherman
wrote:



Adrian wrote:
My son is trying to get his new Meade imager working, and he said that
the preview pic (Jupiter) is OK, but when he takes a pic, the image
goes to an over-exposed white blob!
He has tried exposure times down to 6/1000 to no effect, but doesn't
know where else to look......instructions seem a bit light on, and we
have found some tips by other users, but this one his him stumped.
FWIW, I am starting out with a converted web cam.
Adrian.


Sounds like a daytime picture. You can not take any pictures in the day
time
with it.

steve



--
Using Opera's revolutionary e-mail client: http://www.opera.com/m2/

You didn't mention the type of telescope you're using. If the scope's past a
certain size then you'll always overexpose with the brighter planets.

You mentioned you started off with a web camera, so I assume you've done some
planet imaging before trying the Meade imager, true or false?

If true, then I assume you successfully got focused and correctly exposed images
with the web camera.

If all this is true, then it sounds like the camera's gain is not set correctly,
and I mean the gain set at the factory. To check this, try putting a mask in
front of the telescope and try imaging Jupiter again. A mask can be made from a
thick black sheet of paper that covers the entire front end of the telescope,
blocking all light from getting in except for a hole in the mask. Secure it
temporarily with scotch tape; this is only a test after all. Start off with a
1-inch hole. If you still get over exposed but focused images, then send the
camera back to the factory. If you don't see an image or the image is faint and
focused, then you'll need to use a mask when imaging the brighter planets.

Good Luck !

--- Dave
--
----------------------------------------------------------------------
Pinprick holes in a colorless sky
Let inspired figures of light pass by
The Mighty Light of ten thousand suns
Challenges infinity, and is soon gone




"Adrian" wrote in message
newspsowenhymm1wqna@accounts...
It looks like a daytime pic, but I assure you it was night or he wouldn't be
able to see Jupiter....its on the other side of Earth during the day. Thats
why it is puzzling. The preview pic looks fine.
Adrian.


On Thu, 07 Apr 2005 18:30:40 -0400, Steve Sherman
wrote:



Adrian wrote:
My son is trying to get his new Meade imager working, and he said that the
preview pic (Jupiter) is OK, but when he takes a pic, the image goes to an
over-exposed white blob!
He has tried exposure times down to 6/1000 to no effect, but doesn't know
where else to look......instructions seem a bit light on, and we have
found some tips by other users, but this one his him stumped.
FWIW, I am starting out with a converted web cam.
Adrian.


Sounds like a daytime picture. You can not take any pictures in the day time
with it.

steve



--
Using Opera's revolutionary e-mail client: http://www.opera.com/m2/

Thanks Dave,

You didn't mention the type of telescope you're using. If the scope's
past a
certain size then you'll always overexpose with the brighter planets.


Sorry, I think it's a Meade 6" refractor, and Jupiter looks OK in the
preview though.


You mentioned you started off with a web camera, so I assume you've done
some
planet imaging before trying the Meade imager, true or false?


Its my son, so false, he has started with what he figured was the best for
his pocket!




If true, then I assume you successfully got focused and correctly
exposed images
with the web camera.


I have, in a fuzzy way with my scopes! (Small ones) And with a converted
Logitec webcam. But I am learning...but that's another subject!




If all this is true, then it sounds like the camera's gain is not set
correctly,
and I mean the gain set at the factory. To check this, try putting a
mask in
front of the telescope and try imaging Jupiter again.

We will certainly try the mask idea thanks, I feel silly not thinking of
it myself.
Is it possible for the preview to look OK, but a picture to over-expose?


Your response is much appreciated.

Adrian.

Hi Adrian !

"Adrian" wrote in message
newspsowljagum1wqna@accounts...

Thanks Dave,

No problem. Just inquiring and commenting. ^_^

----------------------------------------------------------------------

You didn't mention the type of telescope you're using. If the scope's past
a certain size then you'll always overexpose with the brighter
planets.


Sorry, I think it's a Meade 6" refractor, and Jupiter looks OK in the preview
though.

OK. Time to put the ol' brain in high gear.

By preview, I take it to mean you're seeing a "live video" image on the
computer. If this is correct then there's probably some sort of automatic gain
and exposure control being used on it, but this is just a guess.

If this is the case, then obviously the problem isn't the camera hardware.

Since I don't own this camera, and since Meade tends to go their own way when it
comes to doing things done by others especially electronics and software, I can
only take a shot in the dark (hah!) on how they've set up their camera software,
but here goes.

One possibility is that although the software allows you to slide the exposure
time control, there's another switch somewhere that selects for manual vs.
automatic exposure control. Look around the menus and the various windows and
see if this is the case.

The same possibility might exist for the gain control. By the way, you want to
set gain as low as you can, and exposure as fast as you can, and still get good
images. Gain needs to be set low so that noise is inhibited. Exposure time
needs to be set fast so that the cleanest possible images are captured. Seeing
makes situation bad, but one needn't make it worse by capturing a lot of it per
image.

----------------------------------------------------------------------

You mentioned you started off with a web camera, so I assume you've done
some planet imaging before trying the Meade imager, true or false?

Its my son, so false, he has started with what he figured was the best for
his pocket!



If true, then I assume you successfully got focused and correctly exposed
images with the web camera.

I have, in a fuzzy way with my scopes! (Small ones) And with a converted
Logitec webcam. But I am learning...but that's another subject!

In this case, focus as precisely as possible. No software can completely clean
up a poorly focused image. I use a Hartmann mask. Looks like a regular mask
but with two or more holes in it placed just within the outer edge of the mask.
When a telescope is out of focus, it splits into multiple images by the mask.
Focus is achieved when the multiple images coalesce into one. this technique is
very precise for most telescopes and works fast.

----------------------------------------------------------------------

If all this is true, then it sounds like the camera's gain is not set
correctly, and I mean the gain set at the factory. To check this, try
putting a mask in front of the telescope and try imaging Jupiter again.

We will certainly try the mask idea thanks, I feel silly not thinking of it
myself.
Is it possible for the preview to look OK, but a picture to over-expose?

Yes, very much so, for the reasons I outlined above.

But I believe now, that I know the situation better, that there's nothing wrong
with the camera but there is something you're not controlling on the computer
end. So other than to use a Hartmann mask to get the focus as precise as
possible (and I highly recommend this for ANY imaging or photographic project) I
no longer think using a mask will help determine the source of the problem.
Check ALL the controls to see how the exposure and the gain are set, and whether
there is an automatic/manual switch for both somewhere.

----------------------------------------------------------------------

Your response is much appreciated.

Adrian.

You're very welcome ! Hope you get this thing working.

Good Luck !
--- Dave
--
----------------------------------------------------------------------
Pinprick holes in a colorless sky
Let inspired figures of light pass by
The Mighty Light of ten thousand suns
Challenges infinity, and is soon gone

Adrian wrote:
My son is trying to get his new Meade imager working, and he said
that the preview pic (Jupiter) is OK, but when he takes a pic, the
image goes to an over-exposed white blob!

He has tried exposure times down to 6/1000 to no effect, but doesn't
know where else to look......instructions seem a bit light on, and we
have found some tips by other users, but this one his him stumped.

FWIW, I am starting out with a converted web cam.

Adrian.

Hi,

Guessing here, but:

If you are using some sort of autoexposure, this will explain it. The same
thing happens with a webcam such as the ToUcam. The automatic exposure
assumes an an average grey image, but a planet in the night sky is far from
that (black sky, bright planet). If the planet is relatively small in the
frame (depending on magnification), an autoexposed frame is bound to
overexpose a planet.

So I would do
- Make sure auto-exposure is disabled
- Reduce gain as necessary
- use short exposure time

If the planet is still overexposed, try increasing magnification.

I haven't used the DSI, but I think an over-exposed white blob is s sure
sign of using auto exposure, particularly if the frame contains a lot of
black sky. With webcams you disable the automatic exposure settings in the
camera driver. My guess is that the DSI is similar.

Still, I think an unmodified ToUcam would be better on the planets than the
DSI....

Clear skies
Carsten A. Arnholm
http://arnholm.org/
N59.776 E10.457