ASTRO: breaking up an exposure into subexposures: how to get the same s/n ?

here's something I threw together today to look into how much I am
complicating my life by using more and shorter exposures instead of fewer
and longer exposures

"Richard Crisp" wrote
....
here's something I threw together today to look into how much I am
complicating my life by using more and shorter exposures instead of fewer
and longer exposures


Richard,

I'll take a look. Thanks for posting. Your tech stuff is always helpful.

I find that short exposures work best for me because of factors that can
mess up exposures - stuff like wind gusts, astronomers with big feet,
visitors hitting the counter-weight, short periods of bad seeing, passing
clouds, etc. If I take fifteen one minute exposures I sometimes lose one to
three from one of these problems. The loss from read noise is a small price
to pay to insure that an hour of imaging is not lost to a wind gust or
someone walking into the dome and hitting the scope.

Also, with the 1301E, if I go too much longer than 60 seconds with an
exposure, some of the stars start over-exposing - even in red or green.

George N

those are all factors
indeed!


"George Normandin" wrote in message
...

"Richard Crisp" wrote
...
here's something I threw together today to look into how much I am
complicating my life by using more and shorter exposures instead of fewer
and longer exposures


Richard,

I'll take a look. Thanks for posting. Your tech stuff is always helpful.

I find that short exposures work best for me because of factors that can
mess up exposures - stuff like wind gusts, astronomers with big feet,
visitors hitting the counter-weight, short periods of bad seeing, passing
clouds, etc. If I take fifteen one minute exposures I sometimes lose one
to three from one of these problems. The loss from read noise is a small
price to pay to insure that an hour of imaging is not lost to a wind gust
or someone walking into the dome and hitting the scope.

Also, with the 1301E, if I go too much longer than 60 seconds with an
exposure, some of the stars start over-exposing - even in red or green.

George N

George Normandin wrote:

"Richard Crisp" wrote
...

here's something I threw together today to look into how much I am
complicating my life by using more and shorter exposures instead of fewer
and longer exposures



Richard,

I'll take a look. Thanks for posting. Your tech stuff is always helpful.

I find that short exposures work best for me because of factors that can
mess up exposures - stuff like wind gusts, astronomers with big feet,
visitors hitting the counter-weight, short periods of bad seeing, passing
clouds, etc. If I take fifteen one minute exposures I sometimes lose one to
three from one of these problems. The loss from read noise is a small price
to pay to insure that an hour of imaging is not lost to a wind gust or
someone walking into the dome and hitting the scope.

Also, with the 1301E, if I go too much longer than 60 seconds with an
exposure, some of the stars start over-exposing - even in red or green.

George N


At Hyde we had to go to all fork mounts. We had a GEM with an 8" scope
at first. But after hearing many streams for profanity from guys who
caught the crotch high counter-weights a few times -- even a couple
volunteers who should have known better got nailed by them -- we went to
a fork mounted 12.5" scope. I was sorry to see that old 50's era Cave
go as it had fantastic optics!

Right after I put in the Paramount here with the 6" f/4 I ran into the
shaft one night when doing a T-point map run. I didn't have any CCD so
a friend was at the eyepiece while I was running the computer. While
the friend was centering the star on the cross hairs I walked into the
chest high shaft without its rubber protector on. Broke cartilage
joining ribs to breast bone knocking me to the floor. But the star just
jumped a couple seconds of arc then went right back to dead on the cross
hairs. That's when I knew the mount was solid. But it was two weeks
before I could take anything but very shallow breaths! Now I run from
inside so am safe from that shaft. I also put on the end piece. Though
that's more for preventing flat toes from a falling counterweight it
does spread the pain over a larger area. Not sure if that's better or not.

Rick

--
Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".

ouch

that must have hurt

keep that "foot saver" on the cwt bar too Rick...


"Rick Johnson" wrote in message
...


George Normandin wrote:

"Richard Crisp" wrote
...

here's something I threw together today to look into how much I am
complicating my life by using more and shorter exposures instead of fewer
and longer exposures



Richard,

I'll take a look. Thanks for posting. Your tech stuff is always
helpful.

I find that short exposures work best for me because of factors that
can mess up exposures - stuff like wind gusts, astronomers with big feet,
visitors hitting the counter-weight, short periods of bad seeing, passing
clouds, etc. If I take fifteen one minute exposures I sometimes lose one
to three from one of these problems. The loss from read noise is a small
price to pay to insure that an hour of imaging is not lost to a wind gust
or someone walking into the dome and hitting the scope.

Also, with the 1301E, if I go too much longer than 60 seconds with an
exposure, some of the stars start over-exposing - even in red or green.

George N


At Hyde we had to go to all fork mounts. We had a GEM with an 8" scope at
first. But after hearing many streams for profanity from guys who caught
the crotch high counter-weights a few times -- even a couple volunteers
who should have known better got nailed by them -- we went to a fork
mounted 12.5" scope. I was sorry to see that old 50's era Cave go as it
had fantastic optics!

Right after I put in the Paramount here with the 6" f/4 I ran into the
shaft one night when doing a T-point map run. I didn't have any CCD so a
friend was at the eyepiece while I was running the computer. While the
friend was centering the star on the cross hairs I walked into the chest
high shaft without its rubber protector on. Broke cartilage joining ribs
to breast bone knocking me to the floor. But the star just jumped a
couple seconds of arc then went right back to dead on the cross hairs.
That's when I knew the mount was solid. But it was two weeks before I
could take anything but very shallow breaths! Now I run from inside so am
safe from that shaft. I also put on the end piece. Though that's more
for preventing flat toes from a falling counterweight it does spread the
pain over a larger area. Not sure if that's better or not.

Rick

--
Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".

"Rick Johnson" wrote

At Hyde we had to go to all fork mounts..... Right after I put in the
Paramount here with the 6" f/4 I ran into the shaft one night when doing a
T-point map run. I didn't have any CCD so a friend was at the eyepiece
while I was running the computer. While the friend was centering the star
on the cross hairs I walked into the chest high shaft without its rubber
protector on. Broke cartilage joining ribs to breast bone knocking me to
the floor.......

Rick, et al:

I keep trying to remind people that safety of people is the first
consideration, equipment second, and any observations or classes are a
distant third.

The counter-weight (painted black) on the OGS 100 GEM is about the size of
my head! A long time ago we did put a tennis ball on the end of the big
steel screw that the weight is on and more recently someone has gone around
and put glow-in-the-dark strips on stuff including the counterweight. There
are still problems: a week ago I was testing the scope during the day time
and the last user had not shifted the tube weights so the metal nose cover
nearly hit me on the head when it fell off - although surprised I was able
to catch it. Our biggest recurring problem results from poor dome design:
the switch to open the slit door plugs into the wall, which means that if
you forget to pull the plug out and rotate the dome you will rip the plug
off, or at least bend it. Several people have been knocked on their behinds
when plugging in a damaged cord and gotten hit with 110v ac. I recently
noticed that the plug was damaged yet again! It seems that the Staff can't
resist rotating the dome when they take people on tours during the day, but
the fail to look to see if the slit motor is plugged in.

....and then there are big Dob's and their &()*&)* ladders, but that's
not a subject for an imaging group!

George N