Harvard University Astronomy Lab and Clay Telescope

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Visual Observations of Albireo

How easy is it to see the color difference between a hot vs. a cool star? The visual "double star", Albireo, is the perfect example. Albireo is the "foot" of the Cynus cross (of which Deneb, in the Summer Triangle, is the "head").

Procedure:

• Slew the telescope to the RA/DEC for Albireo at coordinates RA= 19:30:43 DEC=+27:57:40 using TheSky software.
• First, look through the Finder Telescope. You should see a bright star, just barely "double".
• Next, look through the main eyepiece with the reticle and rotate the reticle so the line with the tick marks runs between the two stars.
• Measure the angular separation: count the number of tick marks between the two stars (Each tick mark is ~5.7arcsec).
• Now, using the hand paddle, move the telescope to determine which way is N (i.e. push S button and star moves N) and E (push W button and star moves E). Make a quick sketch (which you will hand in with your report!) to show which star is "red" and which star is "blue" and label the directions N, E (with 2 arrows: one pointing up and the other to the left) to show the orientation you observed. Enter everything in the table (pdf or docx).

Analysis:

• Calculate the angular separation of the two stars in arcseconds from your tick mark measurement. Use the conversion factor of 5.7 arcseconds/ tick mark. Combine your several measurements (in tick marks) to report the average and uncertainty (rms) of your measurement.
• Make sure to hand in your quick sketch with your report.