Invar buttons everywhere

The clean room dress code's strictly enforced, even for local wildlife...

With various workshop jobs in progress, the redundant astronomers set off to explore two of the newer telescopes on site: SLODAR & MoNet South.

The latter was painfully close to getting going earlier in the week when the roof mechanism suffered the same catastrophic failure MoNet North experienced a couple of years ago :(

Meanwhile, back at SALT, the main task for the day was to attach custom made Invar buttons to all the SAC mirrors. These cleverly shaped, thermally invariant bits of SAC bling will enable us to make repeatable measurements of the mirror positions using the Faro Arm.

The backs of M2 & M4 are both painted black so small patches of the paint had to be stripped off before the buttons could be glued on.

While I was quietly enjoying a manicure from Francois, Darragh proclaimed himself cameraman & snapped a few pics. He's subsequently pulled rank & insisted that at least one of his shots make it into the blog, so here it is!

Actually, Francois was dabbing tiny blobs of epoxy onto the backs of the buttons. They were stuck face-down on strips of duct tape that would later be used to hold them in place while the epoxy cured.

For those hard to reach places, an advanced applicator system (consisting of a lump of Prestik on an allen key) was successfully employed...

The backs of M2, M3 & M4 each got 6 buttons while M5's 6 had to go around the outside edge of the mirror. The pic below shows the first button in place on M4 & no, the vertical streak wasn't an accident - that's how the mirror was painted (it can also been seen in one of the shots in the 19 April post).

The M3 set would've done a chiropractor proud for the level of back-mangling involved - well done James!

Eben stopped by during the course of the evening & showed us his latest work of art - an absolutely incredible piece of craftsmanship!

Clean room dentistry & fashion

The Faro Arm will be attached to a convenient location from which it can reach as many of of the required measurement points as possible. If it's necessary to uproot it & move to another position, the 2 coordinate systems can easily be related to each other by referencing a common set of points.

The similarities between a visit to the dentist & the interventions needed to rotate the NRS simulator super-structure by 90 deg were startling. The process involved loud drilling, ineffective suction & an inordinate amount of duct tape. Regrettably, the vacuum cleaner seems unlikely to make a full recovery & so an extensive rock-paper-scissors tournament will be required to establish who breaks the news to Willa in the morning :(

From Acting Acting Tech Ops Manager to Chief Swarf Sucker in less than 24 hours - oh how the mighty have fallen!!

The 16 segments removed from the primary mirror array for the SAC take-down have been lurking quietly in the spectrometer room, but now they need to go back in so that the edge sensor testing programme can resume.

Some of the segments have clearly seen it all, but as bad as they look right now, they at least will do considerably better than the vacuum cleaner after some TLC.

A special thank you to our lovely model for the instructive clean room fashion tutorial this evening!

& the Cool Toy Of The Day is: Faro Arm!

James arrived today with a magic blue box... Our new Faro Arm - a portable coordinate measuring machine that'll allow us to determine the positions of all the SAC mirrors & various other essential bits to within tens of microns. A truly remarkable piece of equipment!

Meanwhile, next door in the spectrometer room, Peter M & Dave C were busy hauling SALTICAM & all its electronics out of the payload - preparing to send it back to Cape Town for its long-anticipated upgrades.

Astronomers at observatories are contractually obliged to feign dismay at the sight of a beautiful sunset, but with our telescope comprehensively out of action, we get to shamelessly relish the absolutely incredible displays Sutherland's been producing lately...

Interferometer Day

Today was a real treat getting acquainted with our beautiful bambino Buccini interferometer! It was installed on top of the NRS simulator super-structure & fired up to produce fringes. Very cool indeed!

A "long weekend" indeed

Although not quite as intense as last weekend, there's still plenty going on at SALT... :)

With all the gear installed & made to work, we pronounce the M4/M5 wavefront test "commissioned" - the age of pinhole astronomy is near!! Coming soon: live video of all your favourite aberrations (get your Zernikes here).

Also, M5 had its reflectivity measured before & after a trial make-over. A special mirror cleaning goo was applied to a small patch near the edge of M5 & allowed to dry before being peeled off to remove dust & dirt from the mirror surface. Later this was also tried on one half of a badly mangled surface relief grating - stay tuned for the results!

After spending most of Sunday recording a TV interview, Charl & Seb helped us with some essential clean room redecorating & then had to remove an unwelcome visitor from the workshop (Shireen, Darragh - skip the rest of this sentence & the image below): a baby Spotted House Snake.

In addition to the welcome improvement in the weather, we also enjoyed a really spectacular crescent moon on Sunday evening!

Looking more like an ICU patient now!

A huge amount of progress was made today in getting the clean room set up & attaching the patient to all the life-support systems it will need over the coming weeks. This included connecting the dial gauges to the PC, installing pneumatic isolators on the feet of the NRS simulator, attaching the simulator's super-structure, securing a camera to the super-structure platform, taping down all the cabling & testing the x-y-z stages on both the pinhole & the camera.

Having done all this, it was time to remove the cover from M5, the mirror that's most exposed to the environment. Dr O'Donoghue displayed nerves of steel during this delicate process & the author/photographer admits that seeing M5 like this for the first time was something of a religious moment :)

In stark contrast to the day's clean room action, fun was also had squelching around in the mud this afternoon while lowering the 30m weather mast!

Installing the gear for the M4/M5 wavefront test

Nope - this isn't a scene from an ER episode... Before departing for Cape Town, the gang donned their super-stylish clean room gear to help James & Janus install the gear for the M4/M5 wavefront test.

The tube is used to locate a pinhole (mounted on precision stages) just below the vertex of M5. The pinhole acts as a point source which the 2 mirrors then image & the resulting wavefront is measured by a Shack-Hartmann camera mounted at the focus.