FreeLists / az-observing / [AZ-Observing] Re: FWHM measurements for Phoenix skies, anyone?

["Steve Coe" <stevecoe@xxxxxxxxx>]

Matt;

I am in agreement with AJ, I think that the number of evenings that I =
have
had truly excellent seeing in my backyard is about 5 nights and almost =
never
for the entire night, more like an hour or two.  So, I think spending a =
lot
of money on a long focal length imaging system that you will be using =
inside
the city is a waste.  I would think that either a refractor of 700mm or
less, or using the Hyperstar system would provide better results.  My
opinion, but I have a lot of nights in my observatory when trying to =
split
anything less than 2 arcsec is just not possible at any magnification.

Hope that helps;
Steve Coe


-----Original Message-----
From: az-observing-bounce@xxxxxxxxxxxxx
[mailto:az-observing-bounce@xxxxxxxxxxxxx] On Behalf Of Matt
Sent: Sunday, May 20, 2007 9:17 PM
To: az-observing@xxxxxxxxxxxxx
Subject: [AZ-Observing] Re: FWHM measurements for Phoenix skies, anyone?

AJ,

It seems from my research that, for imaging, anything sub 2 arcsec (as
measured during critical automated focusing, I think) is considered very
good to excellent.  I wonder how often we get that here with our low
humidity.  BUT, turbulence from the giant urban heat island we live in =
may
offset our "Arizona Skies."

I am planning on doing some patio imaging.  It can be done RGB with an =
LP
filter or by going narrowband (O3, Ha, S2).  My choice of scope and =
camera
may be influenced by the typical local seeing, but  I just don't know =
enough
yet to make an educated decision.  The monetary investment is =
substantial,
so I am trying to figure out as much as possible in advance.

Matt



-----Original Message-----
From: az-observing-bounce@xxxxxxxxxxxxx
[mailto:az-observing-bounce@xxxxxxxxxxxxx] On Behalf Of AJ Crayon
Sent: Sunday, May 20, 2007 9:01 PM
To: az-observing@xxxxxxxxxxxxx
Subject: [AZ-Observing] Re: FWHM measurements for Phoenix skies, anyone?

Matt, this will, probably, generate, quite a bit of discussion.  I =
haven't=20
done anything scientific to answer your question, but I do have quite a =
bit=20
of experience observing from my back yard, near 35th Ave and Thunderbird =
Rd.

Over the years the closes double that I remember splitting with my 8"=20
telescopes is 3".  When I say my 8" telescopes that means the f6 =
Newtonian=20
that I owned for about 20 years.  It also references the new SCT =
purchased=20
around the beginning of this year.  The 3" split was not something that=20
could be done on a consistent basis, only if the observing conditions =
were=20
good.

My guess as to why, over 20 years, this kind of observing didn't =
deteriorate

is because most of the urban sprawl was north of my position.  Most of =
my=20
observing is to the south or west, the east being right smack dab into=20
Aurora Phoenicis.

Any reason for settling on the 2+ arc seeing condition?

Hope this helps,
aj

----- Original Message -----=20
From: "Matt" <mluttinen@xxxxxxxxx>
To: "'AZ-Observing mailing list'" <az-observing@xxxxxxxxxxxxx>
Sent: Sunday, May 20, 2007 8:25 PM
Subject: [AZ-Observing] FWHM measurements for Phoenix skies, anyone?


Hello,

Anyone (crazy enough) out there do enough urban imaging to get a feel =
for an
average FWHM over Phoenix? Is it usually 2+ arcsec (or worse) or do we
sometimes get below that?

I am about to jump off the imaging cliff and want to know what I am in =
for.

TYIA,

Matt

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