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Earthshine blog

"Earthshine blog"

A blog about a telescopic system at the Mauna Loa Observatory on Hawaii to determine terrestrial albedo by earthshine observations. Feasible thanks to sheer determination.

Hohlraum lamp flat fields

Bias and Flat fields Posted on Oct 26, 2011 16:33

There is an ‘integrating sphere’ in the dome at MLO and we can now use it for flat field observations. Preliminary results suggest that the problems with gradients are as procounced as with other methods, and that the ‘interference pattern’ seen in VE2 with other methods are different when seen using the lamp.

The ND0.9 filter was also used and flat fields attempted – but maybe the shutter is prone to sticking during long exposures and the low temperatures we had today (4-5 degrees C).

The lamp is at Altitude 4 degrees and Azimuth 291 degrees. Some experimenst should be performed to find the best alignment.

Sunglint Map

Showcase images and animations Posted on Oct 26, 2011 15:35

The reflection of the Sun travels across the Earth as seen from the Moon. Since a majority of the earthshine originates near the sunglint it is of interest to map the position of the sunglint.

Below is a map of the footprints of the sunglint for all observations we have so far, from Hawaii. Since almost all the observations are morning observations the sunglint is East of Hawaii and has travelled across South America, Mexico and even North America (the last one may be an error and relate to observations of the Moon from Lund).

A few evening observations have been performed and they correspond to sunglint positions in the Indian Ocean, South-East Asia and Australia.

Close parallel tracks are separated by one day.

On the map below I show all the sunglint positions for the year 2011 – at half-hourly intervals. Times are selected for the Moon being up and the Sun being down. Blue points have Moon’s illuminated fraction less than 25% – i.e. acessible with the CoAdd technique.

The assymetry between the two ‘patches’ is not yet understood by me.