Re: Shutter timing

[Tom Droege <droege@wwa.com>]

Chris,

This does not work.  Here is why.  The delay - typically ten seconds - can 
occur anytime.  Suppose I record when I send the command to the stamp to 
open.  There might be a 10 second delay before it actually opens.  Suppose 
I record the time I get the ack.  This might have been delayed 10 seconds 
after Windows got around to telling me about it.  I have considered 
this.  I think there is no solution until we get a real time operating 
system.  Or at least something that works around Windows.

I run with Windows because my present system for reading an image is Image 
Scientist.  It is convenient to switch back and forth between a DOS window 
and Windows to read the images.  Things would work better under a DOS only, 
preferably in an old version of DOS.  But I am testing and convenience is 
more important than the best possible data.

Tom Droege
At 05:19 PM 6/19/00 -0700, you wrote:
>Tom writes,
>
> > Also per the notes, this does not guarantee that all images
> > are of comparable length.
>
>Tom,
>
>I know about your problem with serial port timing.  One thing I
>am doing that you could maybe do in your BASIC software is to
>record the _actual_ times.  In other words you capture the wall
>clock time just after the shutter opens and just after it closes
>even if the open and close times get messed up by the OS.  So the
>final FITS files header would record the actual rather then intended
>exposure time.  This would likely only require a few small mods to
>both your QBASIC program and to the raw-to-fits program. (I'd
>suggest the QBASIC program would write out any housekeeping data
>after the pixel array.)
>
>My Linux based software will record the time (of day) when the STAMP
>sends an ACK.  I am designing things so that the software is "ACK
>driven".  The Linux software can queue up STAMP commands far faster
>then the serial link could deliver them.  My serial port handler
>queues outbound commands at any time and issues them to the STAMP
>whenever the STAMP sends an ACK or a power up version message.
>
>
>--
>   Chris Albertson
>
>   calbertson@logicon.com                  Voice: 626-351-0089  x17
>   Logicon, Pasadena California            Fax:   626-351-0699