[AZ-Observing] Picketpost Mountian Site Report

Last night, Peter Argenziano and I tried out the Picketpost Mountain
trailhead parking lot as an observing site.  Provided it doesn't turn out
to be popular among the usual urban recreational types during Winter
months, the site has good potential for general use.

It is a 50-minute drive to the trailhead from the intersection of I-10 and
I-60, as long as your departure is not between the hours of 4 and 7 p.m.
Monday through Friday.  This is an easy drive, as there are only three
traffic signals along the way, and only the easiest of mountain passes to
traverse along the way.  Access is free to all, as the trailhead is
contained in Tonto National Forest, incidentally, about as far south as you
can go in the Tonto.

Peter found the best spot, indicated as parking for horse trailers, where I
would estimate a dozen scopes and vehicles could be comfortably set up on
reasonably level ground.  The parking lot sits in a small depression, and
the horizon in all directions is elevated several degrees, except to the
southeast, where Picketpost Mountain very scenically looms.  There are no
local lights visible from the lot.  I did find that I underestimated
traffic noise from US-60 on my previous stay.  It is quite audible, as the
highway is over the ridge only a half mile away, but nothing like the
thunderous roar from Boyce Thompson Arboretum.

I thought the low setting would mean consistently terrible seeing
conditions, but at least the one data point of last night proved that it's
not always of the several-arcsecond variety.  At 375x, my 13-inch cleanly
split of ADS 10217, a pair of 8th-magnitude stars separated by 1.4" (1996).
 Lambda Ophiuchi, a binary with a current separation of 1.4", was a
difficult split due to the unequal components.  I bet this is about as
steady as the site gets, so in the interest of consistency with many other
observing reports, "I'll give it a 7."

Next, I tried a naked-eye limiting magnitude test for the zenith, where
Corona Borealis was culminating.  I could hold HD 141527 and HD 139761
(mags. 5.9 and 6.1) 100% of the time.  In the 50% detection level were HD
139389 and HD 141465 (mags. 6.5 and 6.4).  Based on past tests, I think the
site is somewhere between 0.5 and 1.0 magnitudes brighter than natural.
And based on the visibility on the trip and nearly total lack of water
vapor, I bet it was also about as transparent as this site gets, so let me
give it a 7 for transparency.

If you insist on pointing near the horizon, you will be disappointed.  20
degrees to the east and west of due south are small glows of Tucson and
Florence.  A small dome with little breadth appears in the northeast from
Florence.  Then there's the big masterplanned community robbing the western
third of the sky of stars.  So horizons get, you guessed it, a 7.

The Picketpost Mountain trailhead parking lot appears to be a very good
nearby observing site in all respects for East Valley residents.  While its
darkness doesn't quite match Vekol to the south, it is a good compromise
for those weeknight observing trips.  All in all, I'll give the site 3 1/2
stars (out of 5).

Tom

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Tom Polakis
Tempe, AZ
Arizona Sky Pages
http://www.psiaz.com/polakis/
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