Isnt that what we(I) use a big black hat for???
Maybe, if you are there for the whole 30 mins with your eyes on the sky, and
you are vigillant enough pick up those faint satellites as well! Personally,
when my setup is taking a series of exposures, maybe for an hour I sometimes
nip in for a cuppa, or look at another part of the sky or have some hanky
panky with the missus !
Ian.

"Robert Geake" wrote in message
...
Additionally there is much less chance of a plane or satellite
(gust of wind, brief cloud cover etc) ruining the shot during the 30th
minute of exposure! (just throw out the short exposures that are ruined).

Isnt that what we(I) use a big black hat for???