Seeing effect help: 4" vs 8"

"Ron B[ee]" wrote:

...

The question then is: Has the mirror cooldown? The night time
temperature is around 70-75d F. while the day is 90d or over. It's
hard for me to believe that after 3 hours, the mirror hasn't cool yet.

You may look for a double thermometer at Radio Shack

Catalog #: 63-1035 is offered now for $20
63-1023 is what I got last year but is not online now

David

Say, that looks cool David. So do you tape the "plug" from the
thermometer to bottom of the mirror?

Thanks,
Ron B[ee]
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"David" wrote in message
...


"Ron B[ee]" wrote:

...

The question then is: Has the mirror cooldown? The night time
temperature is around 70-75d F. while the day is 90d or over. It's
hard for me to believe that after 3 hours, the mirror hasn't cool yet.

You may look for a double thermometer at Radio Shack

Catalog #: 63-1035 is offered now for $20
63-1023 is what I got last year but is not online now

David

In every nights so far this week, seeing prevents the use of 400x with the 8-
incher, 300x was just barely at times, while 200x was pretty much ok. The 4-
incher view was good (but obviously dimmer) at 176x.

Most nights I find that seeing limits me to 250-300x in my 8" Newt.
It's only on very good nights that I can use 400x. This is near the
Gulf Coast where seeing is much better than average for the country.
But transparency isn't.


It's hard for me to believe that after 3 hours, the mirror hasn't cool yet.
If not, then what is it? Why is frequency of wave faster in the 8-incher
than the 4-incher? Could this be what David Knisely refer to as "resolve
the seeing"?

Yeah that's probably what it is. In bad seeing I can see these waves
pretty easily even at low power on the moon. It's a good indicator to
skip the planets that evening.

However, do you have an open mirror cell (can you see the mirror from
the back of the scope)? How is the mirror mounted in the cell? With
an open cell, an 8" mirror should equilibrate in less than an hour in
the summertime. In the heart of winter, perhaps three hours. A fan
would cut these times to about a third or fourth. With a closed cell,
however, the mirror may *never* reach equilibrium if the temperature
keeps dropping.

Ritesh

"Axel" wrote in message
om...
However, do you have an open mirror cell (can you see the mirror from
the back of the scope)? How is the mirror mounted in the cell? With
an open cell, an 8" mirror should equilibrate in less than an hour in
the summertime. In the heart of winter, perhaps three hours. A fan
would cut these times to about a third or fourth. With a closed cell,
however, the mirror may *never* reach equilibrium if the temperature
keeps dropping.

Ritesh

Thanks Ritesh. Yes, I can see the back of the mirror through the cell.
It's quite opened.

Ron B[ee]