October 2016
most of the night by observing Band 4 or Poor Weather proposals ( if available ).
Band 4 programs can be submitted at any time during the semester and are most welcome during periods of bad weather ( see the following News for Users item ). If you have a science case with bright targets that can handle Cloud Cover = 70 % and above ( or any ), any Image Quality , and any Water Vapor ( with no restriction on Sky Background — or any Cloud Cover and Water Vapor ( with no restriction on Image Quality and Sky Background ) — then consider submitting a Band 4 / Poor Weather program today . More details on the proposal submission process can be found at this link .
Winter Blasts Maunakea
The tilt of our planet ’ s axis has once again delivered an extended period of weather not conducive to astronomical observing on Maunakea . Starting in late November a series of fronts , troughs , and low-pressure systems have produced overcast skies , wind , and significant snow , ( with drifting ) at the Gemini North site ( Figures 3 and 4 ). In the one month period from mid-November until mid-December , 16 nights were entirely lost to weather , and an additional four were more than half lost . Overall , during this period we have only managed to obtain science for about one-third of the available time . As this issue goes to press the weather is improving !
January 2017 | 2016 Year in Review
October 2016
The “ Super Seeing ” ( LGS + P1 ) Mode
In 2012 , Gemini commissioned a new observing mode for ALTAIR ’ s Laser Guide Star system ( known as LGS + P1 ), which added the option of using a peripheral wavefront sensor ( PWFS1 or P1 ) for the Natural Guide Star tip-tilt focus measurement . This mode does not provide diffraction-limited resolution , but instead gives “ Super Seeing ” by reducing the natural seeing point spread function Full-Width at Half-Maximum ( PSF FWHM ) by a factor of 2-3 . The major benefit of this seeing-improver mode is that it increases the LGS sky coverage to almost 100 %. While the limiting magnitude of P1 is R = ~ 14 ( less than the R = < 17 magnitude for the conventional LGS mode ), this is more
GeminiFocus
Figure 3 ( left ). This image is a screenshot taken from the UH88 camera pointed at the Gemini North telescope , dated Monday , December 19 , 2016 .
Figure 4 ( right ). An image taken from Hilo on December 19 , 2016 , of a snowy Maunakea . Image credit : Joy Pollard
Figure 5 . Comparison of estimated sky coverage for LGS + P1 ( red ) compared with conventional LGS ( black ). Note that sky coverage refers to the percentage of sky with guide stars above elevation 40˚ at Gemini North .
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