Tuesday, April 8, 2025

Daylight progression on the moon. A triple-star spectrum.

 Monday's moon:


 Tuesday's moon:


 The progression of sunlight over three days, Clavius crater:


 


The progression of sunlight, Plato crater:




Mizar and Alcor in the handle of the "Big Dipper" form a naked-eye double star that resolves into three apparent stars in small telescopes.  A spectrum for each star can be obtained simultaneously with a diffraction grating:


 The rainbow spectrum for Mizar (top star) consists of two closely spaced spectra corresponding to each component (Mizar A and Mizar B).  All three stars, Mizar A,B and Alcor are classified as A-type main sequence stars.  All exhibit strong hydrogen absorption lines, which are evident in the picture above and more clearly seen in the intensity plot below:

The red-dash lines mark the wavelengths of the hydrogen-Balmer series.

 All images were obtained with an Orion 80mm ED f/7.5 refractor.

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