Saturday, November 16, 2013

HRS Science Verification observations underway!

Jürgen did some final tweaks to the optical alignment on Tuesday after the necessary modifications were made to the new baffle.

Having successfully tested things on Tuesday & Wednesday nights, all that remained was to brick up the rest of the thermal enclosure on Thursday morning.

David & Jürgen went after this & by the time those of us that had observed all night came up after lunch, Her Royal Spectrographness was completely entombed in grey styrostone bricks for the first time!  With that, the system could finally set about stabilising properly...

We've been fortunate to have good weather & a fairly well-behaved telescope for much of the week & so we've been able to tackle a number of the HRS Science Verification observing proposals.  The honours for the most impressive acquisition image have to go to Marcin Hajduk's binary central star of the planetary nebula LHA115-N61 in the Small Magellanic Cloud.

This V = 14.5 magnitude object yielded HRS's first emission line spectrum.  The image below shows a section of a 20 minute red channel frame that was obtained in Medium Resolution (MR) Mode.  It contains strong features due to H-alpha, sulphur, nitrogen & helium, visible as the bright blobs in the horizontal rows known as orders.  A number of sharp lines from atmospheric emission (night sky lines) are also visible & are repeated in both the object & sky fibres, the latter appearing immediately below each object order.  The features in the sky spectrum will be used for accurate background subtraction when cleaning up the object frames.  The tiny, randomly distributed, white specks are spurious features caused by cosmic rays striking the detector.

We've also taken a bunch of evening & morning twilight flat fields with sky illuminating both fibres at once.  This is what the Sun & our atmosphere look like in High Resolution (HR) Mode in the red channel: exceeedingly nifty!

But then the weather began packing up on Friday night.  The seeing deteriorated spectacularly from a stable 1.5" to >5" within a matter of minutes as the wind swung around to the dreaded south east quadrant.  It's been downhill since, but we hope to get back on-sky on Sunday night, before Sean & Jürgen leave us on Monday.

The bad weather's had its advantages too though as it allowed plenty of time to take the necessary calibration frames, including internal (HRS) arcs, external (SALT calsys) arcs, flat fields, dark frames & biases for the various instrument modes.  The image below shows the High Stability (HS) Mode fibre pair illuminated with the SALT calibration system's flat field lamps.  This was done while the iodine cell was in the beam - hence the enormous number of narrow absorption (dark) lines towards the top of the frame.

The red internal Thorium-Argon (ThAr) arc frames (belonging to the HS mode) used to saturate horribly due to some extremely bright lines.  These have now been reduced to something manageable through the introduction of a small turquoise filter on the front of the lamp - thanks Jürgen!

Midst all this & to break the monotony of being sentenced to writing quick-look software, Luke's acquired a fine black marker pen which has taken his egg art to a whole new level.  He's particularly proud of this week's Minion egg & promises more exciting characters in the coming days :)

Fingers crossed the weather clears up soon & we can get back on-sky tomorrow!

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