The combination of Blogger Fatigue (27 posts in as many, busy, days) & too much going on up here means that we're overdue for a catch-up. Quite a lot's happened since the First Light post about a week ago so here's the highlights package... First of all - Hamish in a clean suit (+ beak!) for a full tour of the tank :)
Before our 2nd night on-sky, we needed to tweak the position of the exposure meter to optimally align the images from the various modes. While working on this, Jürgen noticed that the lens that focuses the image onto the photomultiplier was the wrong way around & hence not quite playing the game.
That was a simple fix & then it was a matter of much frustrating fiddling in the dark to improve the alignment of the fibre ends at the double scramber (for the High Stability Mode). After all that we could use the exposure meter to check that the situation was indeed vastly improved for both the HS mode fibres.
During the course of Sunday night (29 September), David (Buckley) decided that pancakes would hit the spot & provide a fine send-off for David (Bramall) & Jürgen who were leavng the next day (courtesy of the overworked Luke Tyas Airport Shuttle). Dr Buckley devised this crafty solution to address the SALT kitchen's dire need for an egg-beater.
Perhaps this treatment of an electric drill serves to counteract Eben's previous abuse of a smoothie machine in the process of making of a batch of black powder? Either way, the pancakes were excellent - thanks David!
Plenty of progress has been made with the software & so we're now able to take simultaneous images in both the red & the blue channels using the HRS LabVIEW GUIs. However, we were dismayed to find that the blue camera has undergone a significant focus change for no apparent reason & so this issue remains under investigation. We also struggled with poor seeing, FIF guider problems & eventually the payload software crashed on us as well, so Not a great night!
More seriously though - the news the next morning (Monday) was that the right-hand Y bearing on the tracker turns out to be badly damaged & hence the telescope would be out of action until a miracle could be arranged. Fortunately, the Tech Ops team is well versed in miracle production & pretty soon a dramatic plan had been hatched & was being executed. This involved amputating the lower section of the damaged rail so that the ruptured bearing could be extracted.
Here's Ray eyeing the situation, noting the relative positions of the fibre cable & the electric hacksaw that was used to cut through the slide.
Mechanicals Strydom & Wiid in action!
Cleaning the edge up with a dremel tool & a vacuum cleaner... One can't overstate the importance of wearing safety specs at a time like this, right Eben?
& there you have it - that extra piece of rail that was only ever going to be in the way. With this "upgrade", the right-hand Y bearing is now & forever serviceable!
The damaged bearing (just to the left of the vertical plate) could then be removed.
Here it is, along with the extra piece of rail, on the table in the SALT kitchen.
A closer look reveals where the ball bearings have been escaping from! Very Very ugly & scary to imagine how these 8 mm balls could've popped out while the tracker was somewhere over the primary mirror...
Thanks to Keith for sharing Tech Ops wisdom about how to go about delicate tasks up on the payload. Apparently tools such as 2.5 mm allen keys, or verniers as shown here, can be held between one's nose & upper lip while using arms & legs to prop oneself in the appropriate position.
This was valuable information as the HRS guider needs to be removed for some modifications so we would need to detach all the fibres from the FIF before heading for Cape Town on Thursday morning. Each fibre would receive a label & a protective cap before being stored in the fibre holster next to the FIF.
For HRS II we'll figure out some clever, painless way to attach/detach the fibres!
The sky fibres for the High & Medium Resolution modes pose a particular challenge & were awarded "special" names during the extraction process.
All the fibres now have caps on & are safely tucked away. That's it for now... what remained of the HRS team (Ray, Luke & I) drove down to Cape Town the next day.
We stopped for a Fantastic lunch at Glen Carlou on the way down before dropping Ray off at the airport. Travel safely Ray & happy teaching, we'll see you out here again in November!
The tracker was back online by Thursday evening - Hugely Well Done guys!! That's really Great stuff :) Luke & I will go back up to Suthers on Monday with the bits to fix the guider & to keep going with various commissioning tasks & tests.