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Open Star Clusters


Open, or galactic, star clusters are found in the spiral arms of the Milky Way.  They usually have younger stars which are often more blue in color.  

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Many open clusters are difficult to image on a small CCD chip which is mounted on a big telescope.   These two images were taken with a small telescope or a camera lens in order to capture all of the cluster stars in the images!


Compare filtered images to find any very red stars among the many bluish stars in NGC 884, an open cluster in Perseus.

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Adler Planetarium's  HOU teachers took images of NGC 884 in red, green and blue filters using the TIE Mt. Wilson 24 inch telescope with an SBIG ST-6 CCD.   Compare the colors of the cluster stars by using Auto aperture or Find to record and compare brightness counts.  Make a chart to record the position of each star on the images and the brightness counts in red, green and blue.  Tally by color as many stars as you can analyze.  Describe the distribution of stars by color in the open cluster, NGC 884. 

Note: Image exposure times are in a ratio of red:1, green:2, blue:3 as recommended by the telescope operator to adjust for the red sensitivity of the SBIG ST-6 CCD chip.   The green image was further altered to create a more accurate color balance among the images. 


Compare B and V images of M36 in Auriga.

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HOU Educators: Download .fts images.
Yerkes 2 inch refractor, image of double cluster in Perseus:  n884_869.fts
Oil City Astronomical Society's Pleiades image:  m45_ocas.fts
Yerkes 2 inch refractor, Pleiades image: pleiades.fts
TIE Mt. Wilson 24inch Reflector's red, green, and blue images:  NGC884
Yerkes 24 inch reflector, images of M36 in Auriga:  M36

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01/09/2000

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