|
|||
| Joint Astronomy Centre |
|
|
|
| Show document only |
UKIRT News
Back to Contents
Primary Mirror Aluminising : Summer 1998Justin GreenhalghChief Engineer, Joint Astronomy Centre, HiloThe primary was aluminised during end of May/early June this year. The object of the exercise, as always, was to provide a fresh coat of aluminium on the surface so as to maximise reflectivity and minimse emissivity. However this year was special because (a) we had not done it for 5 years, and there weren't all that many people around who had seen it done and (b) we ended up doing it twice! (read on).
 The next step was to coat the primary, which is done in a large vacuum
tank. The evaporative coating process consists in simply boiling small
samples of aluminium in carefully-selected places in the vacuum chamber;
in the absence of air the atoms drift in a straight line and stick to the It's interesting to know just what went wrong, as it illustrates how tricky the procedure is. Extra aluminium had been put onto the tungsten filaments which are used to do the evaporation; one would think this would result in a thicker coating. In fact, the aluminium melted and dripped off (fortunately, not onto the mirror) before it could boil, resulting in a thinner coating. The solution was to put LESS aluminium on the filaments: more of it was retained and a thicker coating resulted. So things went rather better the second time around (which is just as well; by this time the staff had been at the summit working long days for over a week, and knew that the tricky part – putting it all back together – was yet to come, and were not in the mood for much more; plus scheduled science was only a few days away and the mirror was still about ¼ of a mile away from the telescope!).
Back to TopDouble White Dwarf ResolvedSandy LeggettUKIRT Support Scientist, Joint Astronomy Centre, Hilo
This pair of stars are separated by 0.7 arcseconds and consist of two very cool white dwarf stars with Teff ~ 4900 Kelvin, which translates to an age for the system of about 7 Gyr. Clearly, the two stars are easily resolved, due to the excellent seeing conditions which were better than 0.3 arcsec (FWHM) on that particular night. The image serves as a clear indicator of the continued success of the
Upgrades Programme in delivering a telescope which is able to take advantage
of some of the best seeing conditions that Mauna Kea has to offer.
Back to TopView from the TopThor WoldTelescope Systems Specialist, Joint Astronomy Centre, Hilo
The El Niño phenomonon is finally over, at least for things at
sea level. The weather up top continues to be very good for the most part.
This past winter was the driest ever, and the amount of time lost to weather
was a record low. Our time lost to faults continues to be low as well.
This is primarily due to our outstanding staff, who are very diligent about
preventative maintainance and lending a hand at all hours over the phone
to find work-arounds for problems. Thanks to all of you, you know who you
are! You make my job MUCH easier.
All of the moisture is still being trapped below 7000 feet (the last cattle guard on the access road). Above this, we have not had a soaking rain since November. All the grasses are totally brown. The mamane trees are beginning to become very stressed, and some are dying. This will no doubt put stress on the endangered palila bird, which depends on the mamane for its sole source of food. Perhaps when some tropical systems or remnants thereof come into our area, we may get some real moisture at that elevation. Until then, the area around Hale Pohaku is looking bad. The meteorologists are beginning to talk now about La Niña, which is of course the opposite situation: a cold and wet winter. The situation at sea level is certainly cooler than the last couple of years and has returned to its favorite Bog Climate. The drought in Hilo ended on March 26, and it has been nice and wet since. Well...nice may not be quite the right term. One extreme to another! We have had quite enough moisture to regain our water tables, thank you. The situation with Saddle Road is that they are finally beginning to resurface and repair the last stretch of terrible road on the Hilo side; the 19-23 mile mark area. Of course, they waited until the dry weather was over with before trying this. Typical. This is the first significant work in the last 6 years of our current mayor's term. He seems to have a dim view of Saddle Road, compared to his predecessors. Anyway, at least it is finally getting done, so the transit from Hilo to Hale Pohaku will at least be consistently smooth. The potholes in this last section were becoming Legion, and better described as Cauldron Pits. At this writing, the work is now down to about the last two miles of the five mile stretch. The outlook for the upgrade of the whole of Saddle Road is somewhat in limbo. It seems the EPA is concerned that the east side of the Saddle is a 'wetland' and the Environmental Impact Statement did not address this to their liking. Pardon me, but while I do agree that East Hawaii is wet, it is not what they would term a 'wetland'. I mean, so the area gets 200 inches and more a year in places. It does not have the sort of ponds, swamps and lakes that support wildlife as on the mainland. Although the pasture on Humu'ula Ranch had greened up since the return of the rains, they have mercifully not restocked the pasture with the usual black car-eating cows. It appears they are allowing the pastures to go to seed first. I have not missed not having cows in that stretch now for the last 6 months! The Hawaiian Homes lease on the ranch expires in the year 2000. I have no idea what will become of the area. (To explain what Hawaiian Homes is about would be far too much to deal with in this space). Suffice to say it is unlikely the ranch will exist anymore after 2000 and the land will be divided up for other uses. Maybe the notorious black cows will be history. Spring was only late April through May at that elevation. The pasture grasses are again brown and parched. The reservoir just above the ranch houses has remained nearly empty. Your Vacation Resort Hale Pohaku remains unchanged. If anything, the slow deterioration of 'amenities' continues. When I was thinking of what to write for this space, it occurred to me that I have LIVED nearly five YEARS of my life in that place. An utterly depressing thought. As in the last article, I just cannot bring myself to get further into this. More and more observers are making comments about the conditions at HP in their observer's reports. Up top, we anxiously await the arrival of UFTI. There have been rumblings that it should have been named USTI, but then people might confuse this with UIST. There appears to be progress at last, and we are hoping for it to be shipped to Hilo towards the end of August, meaning it may well fit into the current schedule (revised many times) in September. We have purchased a new CCD camera for the fast guider, which has increased sensitivity. While we have not yet fully characterized its performance, it has been able to guide on stars down to magnitude 18. This makes it a bit hairy for the observers, as those stars are not visible on the TV, yet the guider is merrily working fine. (You guys will just have to have more confidence in us!). When I wrote for the last newsletter, it appeared that Tom Geballe was going to move to Gemini. Of course, I did not want to speculate at the time...but had a pretty good idea what was going on. We shall all miss Tom, although he promises to return to observe for the next few years. Just a few days ago, he was lamenting that he will not have an echelle to play with, so he will continue to have to come back to observe with CGS4. Since the new Gemini headquarters office is right next to JAC, he is only going to be across the parking lot. And, since we will share the staff lounge with Gemini, no doubt Tom will still haunt the halls at JAC. Tom is being replaced by Andy Adamson. I have worked with Andy a lot over the years (yes, I AM getting old!) and look forward to having him as The Boss. I think he will do a super job. The impression amongst the staff is that Andy is kind of like another Tom. (I hope you consider this a compliment - both of you!). So, here is hoping that La Niña does not spell a horrid winter
for observing. We all know how vicious the weather can get up on top of
this mountain. Considering this, I urge all that are coming out to observe
to be extremely safety-conscious. I have witnessed enough idiocy through
my many years, and am not in the mood to see or hear about any more!
Back to TopPeopleDeparturesJoanne Griffin left UKIRT at the end of August to go to the mainland to further her education. Joanne and her technical knowledge will be sorely missed at UKIRT – just ask the Instrument Support Scientists!Tom Geballe is leaving UKIRT in October to become a Gemini
Support Scientist. Words cannot fully express the loss to UKIRT, but his
staff wish him good luck and fortune in his future endeavours. His obituary
can be read in this issue’s TOP
END.
ArrivalsYaguang Yang arrived in May as the new Telescope Control Software Engineer. Yaguang comes to us from Siemens Macroelectronics Inc. in Vermont.Andy Adamson, as many must know by now, will be replacing
Tom Geballe as Head of UKIRT Operations & Director of Science. Andy
will be arriving late in September, from the University of Central Lancashire,
to take up his position in October.
Back to Top...And FinallyThis issue we have a flashback photograph of the UKIRT control room, kindly provided by Sandy Leggett. The photograph was taken at some uncertain time in the mid-1980’s. Some of the observers seen in the picture may seem familiar to you. From left-to-right we have : Andrew Zadrozny, Mike Selby, Richard Wade, Matt Mountain and Tom Geballe.It’s not only the control room that has undergone a lot of changes since
this picture was taken, but also UKIRT instruments have come and gone.
The whiteboard, just visible on the right hand side of the photograph,
shows the status of the various instruments available at the time, including
CGS2, UKT5, 6, 7, and 12 and two instruments called the 2-Banger and 8-Banger!
Back to Top |
around the edge of the mirror - the anchorage points can be seen on the
mirror. In the third photo you can see the mirror cell, sans mirror. The
aluminium cylinders are the pneumatic supports which are connected together
in three sectors and form the so-called "pneumatic whiffle tree". You can
also see parts of the active optics system around the edge of the cell.
In the background, incidentally, is the new roll-up door which was fitted
last year to replace the previous model that buckled in the summit winds.
first
thing they hit. The art comes in knowing just where to put the samples,
and how much to use in order to obtain the right thickness of coating.
When the coating thickness is measured, it's always a tense time. Sadly
this time, for the first time ever, the art went wrong for us. The coating
came out at around 400-500 Angstroms, compared to the desired value of
around 900 Angstroms, and so after an emergency telephone conference with
the folk at CFHT is was decided to strip the new coating off and do it
all again.
