Monday, September 16, 2013

First HRS-in-Sutherland frames & the FIF & guider on-sky!

With both CCDs cooled & ready to go, it's Show Time!  We selected the Low Res mode & fed a halogen light source into fibres A & B...

Switch to the red camera PC & fire the shutter!

Whooo Hooo!  We have an échellogram :D  The double traces are due to both the star & sky fibres being illuminated at the same time.

The light distribution's not quite what it should be so the red fold mirror had to be adjusted.  Tilting it in the horizontal plane shifts the orders vertically & gets the right wavelength range onto the detector.

& then vertical tilting of the mirror shifts the whole échellogram horizontally.  The 2 frames below show successive images after making such an adjustment (looking better on the left).

Ray consults his notes & confirms that the red channel images are back to what they looked like in Durham :)

Now for the blue arm!  Same treatment, but we're not getting the results we expect.  We need to translate the pupil mirror beyond the stage's travel in order to get the orders in focus, & even then, we end up with a focus gradient.  & the orders are more tilted than they should be.  Hmmm...

Time to get back in the tank to retrace our steps & confirm that everything makes sense.  By blasting light in through the LR mode fibres we can use a screen to examine the beam footprint on each successive surface to check that it's centred all the way through the system.  First we see the white patch on the collimator mirror.

Then follow it to the grating where it forms an ellipse on the tilted grating surface.

Then after bouncing back off the collimator, the strip of dispersed light comes to a focus just in front of the dichroic.

On the other side of the dichroic we see only the red (well, orange actually) component that gets transmitted.

This diverges & lands on the red pupil mirror.

Which then reflects the light to the red fold mirror.

This in turn directs the beam it into the red VPH cross-disperser.

& then on into the red camera barrel.

Since we know the red channel's happy, we can now compare all the footprints of the blue (turquoise!) beam & adjust the optics to get things centred again.  This was necessary since we did a lot of fiddling in trying to get rid of the mysterious tilts.  Here we see the beam reflected from the dichroic hitting the blue pupil mirror.

Then the blue fold mirror.

& the blue VPHG.

Before disappearing down the blue camera barrel.

This exercise got the various optics back to their nominal positions but - alas, we're still not getting good images in the blue...  Eddy meanwhile did his best to stay out of all this optical trouble by burying himself in a pile of LabVIEW.

This is the monitoring GUI that displays the status of the instrument, including its various mechanisms, sensors, configurations & the exposure meter.

Having done all we could with the halogen light source, we connected up the Thorium Argon lamp so that we could take arc exposures which provide more useful focus information.

The red channel yielded a pretty healthy looking arc, albeit with some of the brightest lines saturating.  There's also some stray light thanks to these frames being taken with the tank open.

But again, the blue arm's not doing so well...  There's a focus gradient in both the vertical & the horizontal.  The lower intensity of the arc frames also revealed a lot of structure in the bias.  Some work to be done here to figure out what's going on!

So much for the day's action - now for the night-time news...  The weather wasn't exactly on our side, but we did get a chance to briefly go on-sky with the Fibre Instrument Feed (FIF) & its auto-guider before the humidity got too high!  Here's the SALTICAM view of the first field we looked at to find a brightish star.

Flipping the payload fold mirror switches from the SALTICAM port to the FIF bay & we see stars!  They're out of focus, but they be stars :)

Thea adjusted the telescope's focus (& noted the offset between the SALTICAM & FIF focus positions so that the guys can shim it out tomorrow) & then they switched from the FIF acquisition camera to the guider's camera.  Darragh had bet that the 2 would not be parfocal & so he promptly owed Ockert 2 beers :)

Extremely proud parents Janus & Ockert admire their handiwork while proud Oom Darragh looks on :)

There was just enough time to quickly check the orientations (moving the star to the left here means moving it up over there etc) & also to mark where one should put the star on SALTICAM for it to appear in the FIF field of view. 

Unfortunately the dewpoint-delta (the difference between the temperature inside the dome & the dewpoint) soon went below the 2.5 C limit so we had to close up... 

Frustrating to have to pack it in early, but Great to get on-sky for first-light on the guider (recall that first-light for the FIF on its own happened back in July) & to have everything perform Beautifully! :)  Very cool indeed O & J!

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