How do you check seeing conditions?

I have a pretty good telescope and a pretty good location for observing,
considering it's close to San Francisco. Earlier this week, we had some
warm temperatures, and I expected great evening viewing, but it was not
to be the case. Seeing was so bad that I couldn't locate Uranus or
identify Neptune (star hopping, you know), even though I was pretty sure
I had them in the field. When I looked at Mizar, the close double
looked like a couple of Brillo pads--fuzzy, blue and bumping into each
other.
I checked the collimation on my scope *twice* because I couldn't believe
how bad everything looked, but the collimation was within tolerances.

Tonight, we had cooler temperatures, and our regular star party was
fogged out, so some of us moved to a nearby location that was away from
the fog, and we had clear skies overhead.
I checked Mizar again and the close double appeared as two distinct
points, clearly separated (you could drive a truck between them).
Seeing was better, but before I could locate my targets (Uranus and
Neptune) the fog returned and we were closed out once again. I did
manage to show some newbies a few of the eye-candy Messier objects
(Lagoon, 57, 31, 13, and so on) until the fog finished us off.

So Mizar, at this point in my learning curve, is a pretty good indicator
for me of seeing conditions. I don't know how to qualify seeing
conditions--I think it's on a 1-10 scale, isn't it?
But I am curious about how the more experienced observers gage seeing
conditions--are there particular objects you view to get a ballpark
figure? The Epsilon Lyra?
I think this would be good information to know, since most observing
reports include a reference to seeing conditions.

What are the benchmarks?

Regards,
Uncle Bob

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"Manuel Joseph Din" wrote in message
...

I have a pretty good telescope and a pretty good location for observing,
considering it's close to San Francisco.


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There's an article on the Pickering Scale, which is the 10 point scale
you're referring to, at: http://www.cloudynights.com/howto/seeing.htm as
well as some other places.

I only tend to record good or bad seeing, the two point Kreuzer scale, which
you're free to use! :-) I usually get the transparency off Crux, because
it's right outside my front door. 10 points is too fine a gradation for my
humble purposes, there's also a 5 point version around (Antoniadi?) but as I
say 2 works fine for me.

Regards, Michael
--
Non, Je Ne Regrette Rien. E.P.

So Mizar, at this point in my learning curve, is a pretty good indicator
for me of seeing conditions. I don't know how to qualify seeing
conditions--I think it's on a 1-10 scale, isn't it?
But I am curious about how the more experienced observers gage seeing
conditions--are there particular objects you view to get a ballpark
figure? The Epsilon Lyra?
I think this would be good information to know, since most observing
reports include a reference to seeing conditions.

What are the benchmarks?

Regards,
Uncle Bob

Seeing conditions are a function of several variables. The atmosphere.
Your optics and its thermal characteristics. Local disturbances. Tube
currents. Assuming that your optics are close to or at thermal
equilibrium with the atmosphere, and you are not looking over a hot
parking lot or rooftop, etc., then you can begin to consider the
atmospheric seeing quality. For planetary observers, a quick guage is
the amount of power that can be put on a particular planet compared to
its theoretical limit. And don't let folks tell you that you cannot put
more than 60 or 70 X per inch of aperture on the planets. With excellent
optics (you DO have excellent optics, right?), 80, 90 and perhaps
occasionally 100 X per inch can be achieved. In that instance, you have
a 10 evening on your hands.

Double star observers usually point to a double that might be close to
the theoretical resolving power of their aperture and if it splits, then
same thing ... a good night.

Deep sky observers ... ahhh, what do THEY know, right? LOL Even on a bad
night, a fuzzy, barely noticable blob is still .... a fuzzy, barely
noticable blurrier blob.

Bart Fried

Manuel Joseph Din wrote:

I have a pretty good telescope and a pretty good location for observing,
considering it's close to San Francisco. Earlier this week, we had some
warm temperatures, and I expected great evening viewing, but it was not
to be the case. Seeing was so bad that I couldn't locate Uranus or
identify Neptune (star hopping, you know), even though I was pretty sure
I had them in the field. When I looked at Mizar, the close double
looked like a couple of Brillo pads--fuzzy, blue and bumping into each
other.
I checked the collimation on my scope *twice* because I couldn't believe
how bad everything looked, but the collimation was within tolerances.

Tonight, we had cooler temperatures, and our regular star party was
fogged out, so some of us moved to a nearby location that was away from
the fog, and we had clear skies overhead.
I checked Mizar again and the close double appeared as two distinct
points, clearly separated (you could drive a truck between them). Seeing
was better, but before I could locate my targets (Uranus and Neptune)
the fog returned and we were closed out once again. I did manage to
show some newbies a few of the eye-candy Messier objects (Lagoon, 57,
31, 13, and so on) until the fog finished us off.

So Mizar, at this point in my learning curve, is a pretty good indicator
for me of seeing conditions. I don't know how to qualify seeing
conditions--I think it's on a 1-10 scale, isn't it?
But I am curious about how the more experienced observers gage seeing
conditions--are there particular objects you view to get a ballpark
figure? The Epsilon Lyra?
I think this would be good information to know, since most observing
reports include a reference to seeing conditions.

What are the benchmarks?

Regards,
Uncle Bob

__________________________________________________ _____________________________

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