Winter Solstice. Been cold observing lately?

[gary]

The freezer suits last weekend certainly got a workout. Whilst observing
with Andrew Murrell and Rod Berry, I noted the temperature had dropped down
to +0.4C and has been reported in this forum recently, it is not uncommon for
observers at these latitudes to be observing in sub-zero temperatures at this
time of year.

The Bureau of Meteorology web site has links to Antarctic weather
which can always be interesting to look at this time of the year around
the winter solstice.

If you have been coming in from a night's observing of late and think it has
been cold, consider for a moment what it would be like at "Dome A" where just
in the last 24 hours the minimum temperature was a reported -69.4C. Last week
it was a jaw dropping -77C. You can check out the Dome A temperature graph here -
http://www.aad.gov.au/weather/aws/dome-a/index.html

It can also be fascinating looking at the webcams at the Antarctic bases.
For example, take a took at this timelapse movie taken from Mawson Base
yesterday. Watch the local time in the top left and watch the sun rise and
just skim over the horizon followed later at night with the glow of the Moon -
http://www.aad.gov.au/webcams/mawson/timelapse.mpg
And you thought the day was short in Sydney. :lol:

A live webcam image from Mawson can be found here with links to webcams
to other bases appearing on the same page -
http://www.aad.gov.au/asset/webcams/mawson/default.asp

So next time you are out observing in the cold, take heart with the fact that 'cold' is
only a relative thing. :thumbsup:

[AstralTraveller]

It will get colder soon. As a child I was taught that 'as the days lengthen so the cold strengthen". Not to mention the increase in windy days.

I notice that the Dome A air is stable (ie the warm air is above the cold air) - at least near the surface. So the seeing should be good!!

[GTB_an_Owl]

I guess some people just don't feel the cold Gary - do they :thumbsup:

well the smart ones anyway :D

I had to visit the daughter last week in Coffs - so no observing for me - much the pity

geoff

[pgc hunter]

Yes, the temp on the scope was 2.5C at 11pm last night. Wouldn't be surprised if it touched the negatives around sunrise, but by then I was long in me toasty warm bed :D

Coldest I had so far is 0.6C just before sunrise on May 23. Seeing was awesome that night though.

[Ric]

Blimey, -69ºc now that's cold but the viewing on a good night must be awesome.

I'll never complain about a -5ºc night again.

[gary]

Hi Ric,

I note today it reports that in the last 24 hours that the minimum at Dome A was -71.4C.
That would certainly help with mirror cool down times.

At the South Pacific Star Party in May, we had a couple of visitors from the Yukon.
I asked Kelly, who was a flight instructor, what are some of the funny and not
necessarily intuitive things that happen to materials when you live and work in
these very cold environments. He mentioned that you park your car overnight
and it gets so cold that the rubber in the tyres becomes so stiff that the flat
spot on the bottom of the tyre where it rests on the road remains flat when you
begin to drive off. The car then bumps up and down as the flat spot hits the
road - a bit like driving over continual speed bumps. :lol:

[gary]

Hi Geoff,

Hope you have been keeping well.

At the South Pacific Star Party in May, several people were admiring our freezer
suit attire and feeling the Ilford cold, were asking where they could buy one. I told them
to see Geoff at the vendor's hall in the morning. But, alas, you didn't get up
there this year.

[GTB_an_Owl]

Yes - i was sorry i had to miss Ilford Gary
but circumstances meant i had to settle for a few days at Lostock with those mad pony club fellas

geoff

[Ric]

Hi Gary

I think the mirror cool down times would be in the order of a few seconds at that temperature.

[AstralTraveller]

I imagine that taking a mirror from room temperature straight to -70 would result in a cracking sound. Surely that would even stress pyrex or zerodur.

I once discovered what happens when one puts too much liquid nitrogen in a nice (expensive) agate mortar and pestle. We did manage to glue it together but I never tried that trick again.

[Ric]

I was having a quick look around the Antarctic divisions website and didn't see any mention of visual astronomy.

Do they actually do any visual/imaging or is it that cold that scopes and gear would just freeze to the point of seizing up or worse.

I have this vision of some poor scientist walking around with an EP frozen to their eyelid waiting for it thaw enough to remove.

[gary]

Hi David,

A close friend and fellow engineer has worked for a major observatory for about the
past 27 years. He likes to tell me the story about the time back in the early 80's
when the observatory procured a new infrared sensitive CCD.

Anyway, this particular CCD was the same model as that used by the US spy satellites
for detecting the heat plumes of Soviet ICBM's. The Cold War was still in
full swing and suffice to say, procuring such sensitive military technology required
US DoD export approvals including signatures by officials up to the
ministerial level. Costing a sizable chunk of the observatories annual budget,
an American from a large US defense contractor flies out of the US with this
state-of-the-art CCD in his brief case basically hand-cuffed to his wrist lest it fall
into the hands of the Reds.

When it arrived at the observatory, the CCD was carefully mounted on a substrate
and then it was cooled down with liquid nitrogen. That's when things went awry.
The differential contraction of the CCD compared to the substrate it was mounted on
caused the incredibly expensive CCD to crack. There was nothing to do but to
ask the man with the brief case whether he could please fly back to America and
bring them another.

[gary]

Hi Ric,

The Australian Antarctic Division has conducted astronomical research there.
See http://www.aad.gov.au/default.asp?casid=244

Several years back, Wildcard Innovations was contracted by the Anglo Australian
Observatory in Epping to write some of the software that was part of their IRIS 2
Inrfrared detector. One morning in the tea-room, I asked one of the AAO engineers,
"how was your weekend?". Peter, who had been one of the brains behind the design
of the Kecks, then causally replied that he had flown to Christchurch, donned a
survival suit and flown by US military plane to the U.S. base at the South Pole,
worked on a telescope there and then flown back. I stood there stunned.
He had provided the best "what did you do on the weekend" response I had ever heard. :)

Some time ago, investigations were being done by several teams including
French, Italian and an Australian team out of UNSW.
At the time, they were investigating a place known as Dome C which was looking
like one of the best places on Earth from which to observe.
See http://www.phys.unsw.edu.au/nature/

There has even been amateur astronomy conducted at Dome C.
See http://www.gdargaud.net/Antarctica/AstroAntar.html

It sure would be a fabulous experience.

[Jen]

:eyepop::eyepop: -77 degrees :rolleyes: holy crap thats cold :cold::cold::cold:

[astroron]

Gary what a great read on the amateur astronomy at dome C:thanx::thumbsup:
The lowest temp I have observed at Cambroon is -7:cold:possativly warm compared to down there:lol::lol:

[Ric]

A very interesting read Gary, thanks for the links

I agree that "what did you do on your weekend" would be pretty hard to beat.

Cheers

[gary]

Dome A hit a minimum -80.3C in the past 24 hours, just 2.2 degrees shy of the
coldest ever recorded there.

See http://www.aad.gov.au/weather/aws/dome-a/index.html

However, the temperature has dramatically risen today and is only in the high minus sixties. :lol:

[Ric]

Only -80.3ºc :eyepop:

And I struggle riding to work in -4ºc.