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 Long
exposure deep sky image taken with a modified colour webcam.
The previous spacecam long exposure mod
takes what is a cheap insensitive camera and increases
the exposure time to 4 seconds which puts it on a par
with low light video CCD's.
This mod goes one step further by starting with a good
CCD based webcam and making possible exposure times
limited only by tracking precision. Maybe we will soon
see a ST4 guided cooled vesta picking up GRBs!
Strategy and applicability.
The vesta's sony CCD is controlled by a Phillips
SAA8115hl though a NEC PD16510 driver. The mod obtains
long exposures selectively blocking the charge transfer
pluses and stopping sub pulse before they reach the
driver. Although developed on a vesta this modification
should be equally applicable for any ccd driven with the
PD16510. (Apparently this includes 675 680 and 690 from
Philips).
Datasheet for the
16510
The exposure is controlled using a line from the PC's
printer port and the image is recovered over the normal
USB connection. If the control lead from the PC is not
connected the camera will output images as normal; except
in making the mod you will disable the shutter (if used
without the PC controlling the exposure this is
equivalent to a 1/25sec shutter). Alternatively a switch
may be added to re-enable the shutter function allowing
planetary imaging.
If you are interested in making the modifications,
firstly read though these instructions with the webcam
PCB in front of you. The mod is not difficult to make but
does involve soldering on a small scale (its more a
question of confidence than skill!). If you decide your
soldering is not up to the task it would be possible to
have the modification to the camera PCB made by an
electrical repair company and do the control board
yourself. Remember the cheapest alternative for one shot
colour deep sky imaging costs £600.
If you are going to do the work yourself then a gadget to
hold the PCB behind a magnifying glass is going to be a
great help.
The tools you are going to need include. Fine tipped
soldering iron, solder wick, multimeter, magnifier, and
patience.
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The Poor Meadow Dyke Galleries are now open. THE
GALLERIES |
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See the full range of Atik cooled CCD cameras for
astronomy on the Atik Website
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