Image Statistics? - Help!

I've made a similar post on one of the Yahoo DSI usergroups, apologies if
this is a duplicate for any of you.

With the recent weather I've taken to modifying a relatively untested brand
new Meade DSI CCD Imager. (Just couldn't help myself...)

Initial feelings with the cooled DSI are that the reduction in temperature
(at room temperature) is around 10 to 15 degrees. Without an accurate
temperature guage thats fit for purpose I'm having to guesstimate this from
sense of touch relative to items left in the cold outside and items from the
fridge etc..

I'm not too sure but the fan seems to just cope with the heat-load at room
temperature as the fan's heatsink remains decidedly hot to the touch while
the DSI heatsink is pretty cold. I'm guessing that efficiencies will
increase in cooler (denser?) air outside.

I've taken a number of 15 minute dark BMP exposures with:

a) no cooling
b) just the fan
c) Peltier cooling and fan

I've no scientific means of analysing the noise statistics and as such have
only been able to observe the following:

1) Histogram enhancement that is replicated across all three images just
about show a visual difference in the number of hot pixels. The pixel values
across the frame are reduced by small amounts when using the 'dropper' in
paint shop pro, to measure.

2) 'Image Information' from the Autostar Image Processing shows a max value
of 65 041 @ 14?? for BMP(a) and 22 332 @ 12?? for BMP(c)

3) The 'number of colours used' from paint shop pro shows 14287 for BMP (a);
8290 for BMP (b) and 5497 for BMP (c).

I'm not sure what these values may represent in terms of noise but the
measurements for (2) and (3) demonstrate a similar reduction of about a
third for the values on BMP (a) and BMP (c)

If the noise has been reduced by about third, this would offer a noise
reduction of about 5db (if using 10log?).

Although technically savvy to some degree, this isn't an area that I've got
much expertise and would welcome the advice/guidance of anyone with the
relevant experience.

Thanks and regards


Chris

Wasn't it Chris Taylor who wrote:

With the recent weather I've taken to modifying a relatively untested brand
new Meade DSI CCD Imager. (Just couldn't help myself...)

Initial feelings with the cooled DSI are that the reduction in temperature
(at room temperature) is around 10 to 15 degrees. Without an accurate
temperature guage thats fit for purpose I'm having to guesstimate this from
sense of touch relative to items left in the cold outside and items from the
fridge etc..

I'm not too sure but the fan seems to just cope with the heat-load at room
temperature as the fan's heatsink remains decidedly hot to the touch while
the DSI heatsink is pretty cold. I'm guessing that efficiencies will
increase in cooler (denser?) air outside.

I've taken a number of 15 minute dark BMP exposures with:

a) no cooling
b) just the fan
c) Peltier cooling and fan


If you want to do some serious statistical analysis of the noise, then
one way forward would be to obtain the free "Wide Histogram" plugin from
www.reindeergraphics.com and use it in your Paint Shop Pro. It allows
you to export the histogram data into a text file suitable for importing
into Excel, SAS or any statistics package.

The Wide Histogram itself displays the mean, median and standard
deviation of the values without needing to export the data into a stats
package. Set the mode to "Luminosity" (because you're likely to be more
interested in the brightness of the noise rather than its colour) and
compare these stats.

Paint Shop Pro's own histogram palette displays median and mean, but
seems to work only on a selected range and only gives one decimal place
for the mean, which may not be sufficient for a very dark image.


--
Mike Williams
Gentleman of Leisure

"Chris Taylor" wrote in message
...

I've made a similar post on one of the Yahoo DSI usergroups, apologies if
this is a duplicate for any of you.

With the recent weather I've taken to modifying a relatively untested
brand
new Meade DSI CCD Imager. (Just couldn't help myself...)

Initial feelings with the cooled DSI are that the reduction in temperature
(at room temperature) is around 10 to 15 degrees. Without an accurate
temperature guage thats fit for purpose I'm having to guesstimate this
from
sense of touch relative to items left in the cold outside and items from
the
fridge etc..

I'm not too sure but the fan seems to just cope with the heat-load at room
temperature as the fan's heatsink remains decidedly hot to the touch while
the DSI heatsink is pretty cold. I'm guessing that efficiencies will
increase in cooler (denser?) air outside.

Hi Chris,

If your heatsink is decidedly hot to the touch, you will get significantly
more cooling by fitting a bigger heatsink/fan. With a peltier cooler, most
of the job the heatsink has to do is disssipate the extra heat generated by
the current the peltier takes. If your cooler is working well, expect to see
frost on the cold side! To see what I mean, take a look at my indirect
cooled camera (not DSI) here.

http://www.leadbeaterhome.fsnet.co.uk/1004xcam2.htm

Of course, your next problem may be dealing with the dew/frost that
condenses on the ccd.

Robin

----------------------------------------------------------------------------
-
Robin Leadbeater
54.75N 3.24W
http://www.leadbeaterhome.fsnet.co.uk/astro.htm
----------------------------------------------------------------------------
-

"Mike Williams" wrote in message
...

If you want to do some serious statistical analysis of the noise, then
one way forward would be to obtain the free "Wide Histogram" plugin from
www.reindeergraphics.com and use it in your Paint Shop Pro.

Hi Mike

Thanks for the usefull info.

I've visited reindeer graphics and the software appears to be compatible
with adobe photoshop rather than paint shop pro? I downloaded the plug-in
and dropped into the plugins folder of paint shop pro and can see no
difference to the program's operation.

Am I doing something wrong?

Regards


Chris

"Robin Leadbeater" wrote in message
...

"Chris Taylor" wrote in message
...
If your heatsink is decidedly hot to the touch, you will get significantly
more cooling by fitting a bigger heatsink/fan. With a peltier cooler, most
of the job the heatsink has to do is disssipate the extra heat generated
by
the current the peltier takes.

Hi Robin

The DSI's design has offered an unusual (if limited) approach. The
cold-finger (006?) is encased with the electronics and is part of the
existing cast-heatsink.

I've shaved a few of the fins/protrusions from the outside of the existing
heatsink and mounted the peltier on the outside (behind the finger). To the
peltier I've mounted a small CPU heatsink and CPU fan. Making the peltier
sandwiched between two heatsinks. The CPU heatsink gets pretty hot , while
the DSI heatsink gets cold. The CPU heatsink cools quickly via the fan when
the peltier is switched off. I'm aware that the DSI heatsink will dissipate
some of the surrounding 'warmth' into the peltier, thus limiting its
efficiency, but the DSI heatsink is getting pretty cool. I'm sure a better
design will present itself in the long run but with the present lead-times
on the product, I'm trying to limit any lasting damage to the operation of
the camera given the American-Led Coalition effort required to get this one.

I've pasted a link showing a pic of the arrangement (last night still in
prototype phase) be aware that the link offers a 1meg jpg.

http://homepage.ntlworld.com/chris.t...eltiertest.JPG

When the mod is completed, and I've found a way to quantify the success (or
failure) of the mod I'll probably document it and post it to the website
thats been so long in the making...

Thanks for the feedback.

Chris

Wasn't it Chris Taylor who wrote:

"Mike Williams" wrote in message
...

If you want to do some serious statistical analysis of the noise, then
one way forward would be to obtain the free "Wide Histogram" plugin from
www.reindeergraphics.com and use it in your Paint Shop Pro.

Hi Mike

Thanks for the usefull info.

I've visited reindeer graphics and the software appears to be compatible
with adobe photoshop rather than paint shop pro? I downloaded the plug-in
and dropped into the plugins folder of paint shop pro and can see no
difference to the program's operation.

Am I doing something wrong?

These sort of plugins were originated by Adobe, but many graphics
packages support them. I use them in PSP and Irfanview.

The place to put them is different for different versions of PSP.
Use File=Preferences=File_Locations=Plug-ins to see which folder to
put your plugins in and check that the folder is enabled.

When you put WideHisto.8BF into the folder and restart PSP you'll find
that there's a new menu entry in Effects=Plugins=OPTIMAX called "Wide
Histogram".

--
Mike Williams
Gentleman of Leisure

"Robin Leadbeater" wrote in message
...

If your cooler is working well, expect to see
frost on the cold side! To see what I mean, take a look at my indirect
cooled camera (not DSI) here.

http://www.leadbeaterhome.fsnet.co.uk/1004xcam2.htm

Of course, your next problem may be dealing with the dew/frost that
condenses on the ccd.

Hi Robin

Thanks for the advice on this. I managed to get a larger heatsink and fan
onto the DSI and you're right, frost and dew are now my biggest issues...

I'm now considering a variable fan, or a duty cycle on the peltier to
control this.

Regards


Chris