"Eric" wrote in message
...
Robin Leadbeater wrote:
"Eric" wrote in message
...

Nice job, Robin. I wonder if a BW TV camera would be able
to pick this up on a 16" telescope...

Eric.


Hi Eric,

You would still need some sort of strobe technique as the frame rate
would
not be fast enough to catch the 30/sec double pulse. I suspect it would
not
be sensitive enough either. I have a very sensitive camera and it needs
a
few seconds exposure to catch the mag 16 pulsar. To catch it in a
1/60sec
frame I estimate would have needed at least 100x more light ie an 80
inch
scope. I would not mind having a try though if you know where I can
borrow
one ;-)

I'm just writing things down quickly - 29.804 Hz and 30.0 Hz gives a
0.196 Hz beat frequency. This is about 5.113 s. At 30 fps, that's 153ish
frames. If I average 9 frames at a time, I get 17 frames per beat
period. 9 frames at 30 fps is about 1/3 s exposure. I know we can get
the central star in the ring with a 1s exposure, so if I gather frames
for 30ish seconds, I might be able to pull it out of the noise.

Have I missed anything really terrible ?

Eric.

Hi Eric,

If Pat's figure (up thread) of 40 photons in a 3.9m scope is right you are
going to be down to less than 1 photon per video frame in a 16inch so it
could be tough to pull it out of the noise. But the big problem is that your
video shutter is open for 1/30 sec for each frame so there will be only a
few frames without the main pulse in them. (2 in 300 I think, even if the
pulse is very sharp) Another complication is the pulsar actually produces a
smaller intermediate pulse. (ie a pulse every 1/60 sec, alternately large
and small) which will degrade the on/off difference further. Can you see the
(mag15?) ring central star in a stack of 1/30sec video frames? If so you
will know you are at least in the right sensitivity ballpark.

Robin