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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.

Diffraction-limited optics

Optical design Posted on Oct 03, 2011 02:03PM

According to theory, the aberration for a lens in a circular aperture, like ours, is given by the Airy function which is proportional to (BESELJ(r,1)/r)^2.

For a single wavelength the function looks like this:

Theory also predicts that assymptotically the envelope of the Airy function should go as 1/r^3, which is also plotted on the graph above.

For mixed-wavelengths as in our case the curve becomes smooth(er) and we should expect to see our PSF as a 1/r^3 envelope. Steeper envelopes than this should not be observed in correctly analysed optical systems. This has bearing on the 1/r^2 ‘King profile’.

FW stuck

Mechanical design Posted on Oct 03, 2011 01:02PM

Stuck Filter Wheel hindering further observations:

Two dome flats showing a stuck FW. A script was used to get these images. In between the images we used the manual Engineering Mode to ‘do the homes’ (i.e. to force each wheel and stage to traverse its range and find its home position). Apparently the “Large Rotary Stage” is still stuck after doing this.

What the Skycam saw

Observing log Posted on Oct 03, 2011 08:29AM

A selection of Skycam shots to show what you can see. From top left : a hazy night, a very hazy night (ice crystals?), a very clear night, water on the sky cam and the laser star, the skycam on a wet afternoon and the crescent moon on a bright sky just before sunset.