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(meteorobs) Canon T70 Secrets Part 2



Hi all, 

Here some info for meteor photographers that are using the Canon T-70
and want to know
more about this camera. 

Now some more details on the T-70 triggering. 

First the T3 connector. This connector is build on the grip of the T-70. 
Canon makes two attachable cable's for it: 
1) The T3 adapter (T3 male -> female 2,5 jack plug) 
2) The T3 electronic cable-release (T3 male ->2 way(lock)release button) 

The connections on the female socket connector that is built in in the
grip of the Canon
T70 is as follows: 

TRIGGERING o o GROUND (higher in the socket) 
            o  ACTIVATING MEASURING(same as pressing the release button
have down) 

We have used three systems in the past but I find the latest developed 
system excellent to use during the Leonids. 

System 1 has been developed by Hans Betlem and Koen Miskotte in 1984. 
Use the triggering (make/brake contact) from the controlling T70 flash
contact to trigger a
electronic relay that will sent a make/brake signal to the T3 adapter to
the other T70
camera's or to activate a constant power supply that will open/activate
the shutters of the
other camera's (shuts as Canon A-1, AV-1, AE-1 or similar) used since
1985 and is
currently only used by Hans. Advantages: you can trigger as many
camera's as you want
(other types also). It is an electronically isolated triggering system
and can't run wild.
Disadvantages: it is using additional power (no power no photos) you
will have to have
spare parts for fixing brake-downs. 

System 2 has been developed by Robert Haas in 1989 and is still in use
by Casper ter Kuile
of meteor observing team Delphinus station 1. Use the triggering
(make/brake contact)
from the controlling T70 flash contact that will sent a make/brake
signal to the T3 adapter
of the other T70 camera's. Only two additional camera's can be connected
to the
controlling T70 flash contact and your make/brake signal disappears or
will not be reliable
anymore. 

System 3 has developed by Robert Haas in 1996 (especially for the
Leonids) and has been
successfully used during the 1997 Perseids and 1997 Leonids campaign by
the Delphinus
meteor observing stations 1 and 2. This system 3 is a very tricky one
but if used correctly it
will be the best ever... 

Connect the T3 adapter from the controlling T70 to a closed signal ring. 
MAKE SURE THAT THE TWO MAIN CONNECTOR RINGS CAN NEVER IN ANY
WAY CONNECT WITH EACH OTHER. The triggering signal will be enhanced by
all the
T70's and will trigger whit out any delay. All shutter's will be
triggered exactly at the same time.
At the moment all our new systems are being used in this way. 

Advantage: no additional power supply needed. 

AND NOW FOR THE BIG EXTRA ON SYSTEM 3: 
Just every camera in the signal ring can trigger all the others. So if
you use two
programmed command backs 70 (one off) you may change the program of a
fully
equipped camera battery in 2 SECONDS from 36 exposures with an
exposuretime of 10
minutes to 24 exposures with an exposure time of 2 minutes (or what ever
you like). You
can even trigger another camera battery (it should be configured like
system 3) and another
etc. 

Used New Systems: 
Sky watch camera Battery's 
CAMERA'S ON ZENITH: 4 x T70 with 50mm 1,8 canon FD lens 
CAMERA'S ON MID BATTERY: 7 x T70 with 50mm 1,8 canon FD lens 
CAMERA'S ON LOW BATTERY: 9 x T70 with 50mm 1,8 canon FD lens 

Example programming of the Canon Command back 70 command sequence: 

EXPOSURE TIME 9 MIN 58SEC 
INTERVAL TIME 2 sec (The Save Transport time of a T70) 
TOTAL EXPOSURES 36 

OR AS A STORM APPEARS...............................Only System 3. 

EXPOSURE TIME 1 MIN 58SEC (reducing the total meteors so that you can
easely
identify the photographic ones) 
INTERVAL 5 MIN (taking samples in time from the total activity) 
TOTAL EXPOSURES 36 

Greetings from The Dutch Meteor Observation Team Delphinus 
Member Dutch Meteor Society (DMS) 

with best regards 

Robert Haas