Mount Lemmon Sky Center’s ‘Sky
Nights’ Observing Program
The cultured and likeable city of Tucson in southern Arizona
is a real epicentre for astronomy, professional and amateur. Home to ‘Optics
Valley’, including AU’s ‘Mirror Lab’ which makes many of the world’s largest
professional mirrors, Tucson is surrounded by mountain-top observatories like
Kitt Peak and Mount Graham with world-class research programs.
One of the lesser known, but closest to Tucson, is the
University of Arizona’s Observatory on Mount Lemmon, one of the sites that
comprise their Steward Observatory.
The Mt Lemmon observatory used to be a military early warning
radar facility and still hosts a couple of (empty) geodesic radar domes, but
was taken over by the university in the 1980s to host a range of professional
telescopes, including the 60” and 40” telescopes of the Catalina Sky Survey
that looks for Near Earth Asteroids.
The university also has an active outreach program at the
observatory through its Sky Center, which offers
tailored individual programs on its RC Optical 32”, but also regular public
viewing ‘Sky Nights’ that include a session on the telescope with some unusual
additional activities. This is my experience of one of these sessions.
I originally included more details on the scope and observing
session, but this article ended up too long, so I’ve split the telescope review
out here.
Catalina Highway from Tucson to Mount Lemmon.
View from the Iron Door Restaurant parking lot used by SkyCenter visitors, looking north towards Oracle and
Biosphere 2.
Sky Center sessions start at these
locked gates: you can’t drive all the way.
Getting There
Tucson has an international airport and Mount Lemmon is easy
to access from it without going through central Tucson. Similarly, hotel prices
in Tucson can be high, but places east on I-10 are cheaper and easy to get to
from Mt Lemmon. Whilst you’re there, the Tucson area has lots of other
space-themed visits, including Mirror Lab, Pima Air and Space Museum and Kitt
Peak.
The Sky Center is about 45 miles
and 1.5 hours’ drive from central Tucson or I-10, but that’s no hardship
because the Catalina Highway up to Mt Lemmon is one of the most scenic drives
in the southwest.
The drive starts among giant Saguaro cacti and ends up among
snowy (in winter) pine forests, via numerous curves, huge views and some
spectacular rock ‘hoodoos’ by the wayside.
Towards the top of the Catalina Highway, you also pass –
almost unseen but quite close to the road – a couple of domes belonging to
another Steward Observatory site, mount Bigelow, including the one containing
the 61” NASA telescope (through which one of my guides reported amazing solar
system views).
The drive up through the Catalina Mountains ends, and the
viewing night begins, at a locked gate just past the Mt Lemmon Ski Valley and its
big parking lot. But the ski area parking closes at dusk and the Sky Center advise you to park across the road at a smaller
(free) parking lot that serves the Iron Door Restaurant.
My ‘Sky Night’ session in late January started at 15:45 when
two minibuses with chains arrived at the locked gate and we were ushered
onboard for the drive up the steep and snow-covered road to the observatory.
The Sky Center warn you to dress
warmly and they weren’t kidding. It had been in the 60s down in Tucson, but by
the end of the night at the 9,157 ft altitude of the observatory it was in the
low 20s and felt much colder on deep snow and with wind chill. You’ll need more
than jeans and a thin puffer!
Snow chain equipped minibuses take you up to the dome for the
Sky Center 32” Schulman Telescope.
Activities
Orientation and First Observing Session
The minibuses dropped us at the observatory and the guides -
Will (a graduate astronomer and keen amateur too) and Gustavo (an electrical
engineer at the Large Binocular Telescope) - gave an orientation talk about the
history of Mount Lemmon.
They also pointed out several interesting sights around,
including Biosphere 2 clearly visible in the valley to the north and the Large
Binocular Telescope dome on snow-capped Mount Graham in the distance opposite.
The latter is very distinctive and I was really interested to see it through my
bino’s (it’s not an easy facility to get to see otherwise).
After that, we were ushered into the Sky Center
dome whose slit was already open and where they introduced us to the telescopes
– a 32” truss-tube Ritchey Chrétien built by RC Optical, on a
remotely-controllable fork mount, and a piggy-backed SkyWatcher
Esprit 150ED triplet apochromat refractor for wide-field views.
They (bravely, I thought) passed around the expensive
eyepieces we would using later: a 31mm Tele Vue Nagler giving about 206x
magnification in the 32” and a 21mm Ethos giving 50x in the refractor.
Then – unusually given it was still broad daylight – we
viewed the bright star Deneb (Alpha Cygni) and also a pale but surprisingly
sharp and detailed Jupiter!
Daylight viewing with the Sky Center’s
Schuman Telescope – a 32” F7 by RC Optical.
Introductory Lecture and Dinner
A snack meal at the main building, just down from the
observatories, was included in the price. It followed the initial viewing
session and was preceded by an introductory astronomy talk and slide show.
Thereafter, we were each offered a pair of 10x50 binoculars
to use for the rest of the evening (though I opted to stick with my trusty
Canon 12x36s) and a complimentary red keylight for
getting around whilst maintaining that all-important night vision.
Sunset and the Green Flash
The next part of the program was a complete surprise and (for
me) a unique experience. We were led out to a snowy slope in front of one of
the domes facing west. The deep orange of the setting Sun was sparkling prettily
off the snow and we looked to the left of it to find Kitt Peak National
Observatory silhouetted in the far distance, its solar tower and the dome of
the 4m Mayall telescope clearly visible despite being 55 miles away.
We then waited and shivered as the sun sunk onto and then
past the horizon. At the very last moment, just as the final remaining sliver
of the Sun’s limb was about to set, the guide instructed us to look at it
through the binoculars.
This really surprised me. It’s not something I would have
dared to do otherwise, but it was worth it because I clearly saw the famous
‘green flash’ for the first time and even a hint of even-rarer blue too. This
is caused by refraction and is something I’d looked for many times but never
seen. The exceptionally clear skies, unobstructed horizon - and yes the binoculars - all helped, but apparently it’s far
from guaranteed even so.
Please don’t repeat this experiment unsupervised! The guide
knew precisely when it was safe to look: a few seconds too soon and it could
blind you!
Waiting for the green flash.
Dark sky binocular viewing outside the Schulman dome.
Catalina Sky Survey up and running across the way from the
Schulman Dome.
Two guests view through the Schulman 32” RC and the 150ED
simultaneously!
Dark-sky Telescope and Binocular Viewing
As darkness fell under very transparent skies, we made our
way back up to the dome and started with some guided binocular viewing of easy
deep sky objects like the Andromeda galaxy and Orion’s Great Nebula, whilst the
dark skies sparkled overhead and various other observatories opened for the
night and began whirring around.
Then it was back into the dome to view a number of objects in
the 32” Schulman telescope and its piggy-backed 150mm Esprit apochromatic
refractor. There was plenty of time at the eyepiece on both scopes and plenty
of chairs to sit on in between. Adding to the comfort factor, the dome does
have a small warm room.
The guides were both informative and relaxed. We were allowed
to tweak the Feather Touch focuser for ourselves, and even try a spot of
impromptu imaging through the eyepiece with our phones, something I’d never done
at a public session before.
We started with views of bright stars and Jupiter again, the
latter showing much more detail this time. After that it was a good selection
of deep sky objects. Highlights included seeing Jupiter’s cloud belts in quite
strong colours, internal structure in the Crab Nebula and lots of fine
structure in M42 through the 32”.
The Esprit 150ED with its ultra-wide Ethos eyepiece did provide
a beautiful low-power overview of the objects we were viewing in detail with
the 32”. Orion’s sword region encompassing the entire Great Nebula and
virtually the whole of M31 showing hints of a spiral structure, were especially
memorable through the refractor under Mt Lemmon’s dark sky.
For a full description of the 32” viewing experience and the
object list, see my separate review of just the telescope and viewing session here.
My Rocket Fuel Dump Imaging Accident
So there I was, with my Canon EOS 6D MkII and 20mm F1.8 Samyang lens, taking long exposure
photos of the sky, the watchers and the domes for this article. Meanwhile, everyone
else was enjoying binocular views.
I was pleased with some of the photos and tweeted them at the
Sky Center later that evening, who promptly asked
what the nebula was to the right of Rigel, that looked much the size and
brightness of nearby M42.
I confess that I hadn’t even noticed it, but on inspection I
was puzzled too, speculating that it might be a fuel dump or rocket stage
ignition; and so it proved. I asked my readers for
help and Victor Boesen discovered that this was in fact a fuel dump from the
USSF8 Atlas V launch! My tweet about it went semi-viral and ended up in a
re-tweet from Tori Bruno, the CEO of ULA who make the Atlas V (that’s my 15
seconds of fame over).
Inspection of all the images I took that night show it in
five taken over two minutes between 02:25 and 02:27 GMT. You can spot it in one
of the other photos above. Tellingly, those images show it fixed relative to
the stars as it moves with the turning Earth.
USSF8 Atlas V fuel dump.
Leaving the Schulman dome for the drive back down to our cars
at the Iron Door parking area in the minibuses.
Exit Via the Gift Shop!
At the end of the evening, we went back into the main
building to collect our things, warm up and purchase a few souvenirs (I added
to my collection of observatory beanies). Then they drove us back down the icy
road to our cars for 9 pm.
The drive back down the curves of the Catalina Highway
allowed some evocative views of the Tucson lights (see below).
Summary
The Mt Lemmon Sky Center experience
was a little different from viewing nights I’ve done on otherwise similar
telescopes at McDonald and Kitt Peak.
The list of objects viewed with the 32” RC telescope at Mt
Lemmon was a bit shorter, but that’s because those other viewing nights were
limited to just the telescope viewing, where the Sky Center
experience adds in binocular viewing – of the deep sky, of the observatories around
and that bucket-list sunset green flash.
I also really liked being allowed to get best focus for
myself and the opportunity to try some phone imaging. The guides were
particularly knowledgeable, enthusiastic and friendly too.
Finally, Mount Lemmon is easier to access (much more so than
remote McDonald). Overall, one of my best astronomy outreach experiences to
date!
A ‘Sky Night’ at the Mount Lemmon Sky Center
is a unique, varied and hugely enjoyable public viewing experience that’s easy
to attend and ranks amongst my all-time favourites.
Lights of Tucson on the way back down from Mount Lemmon.