Dept. of Physics & Astronomy, Macalester College, USA
Introduction
Methods
For this project a large mosaic spanning the middle third of the cluster was made by combining images from 27 overlapping frames. Each frame was captured in three color filters: Red (R), Visible (V), and Blue (B), on a SBIG (Santa Barbara Instrument Group) ST-8 CCD camera, and all observations were carried out on Macalester's 16-inch Cassegrain reflector telescope, built by DFM Engineering on the nights of April 17th and 22nd, 2006. A dark frame was recorded for each exposure for a duration equal to the exposure time to correct for noise caused by the CCD electronics. Exposure times for the different filters were 10s for R, 16s for V, and 48s for B. A mosaic was made of all the frames for each color channel using ver. 5.41 of SBIG's CCDOps software, and Iris ver. 5.31, a free digital image processing program designed for use in astronomy. After the image mosaics were made for each of the three color filters, CCDOps was used to combine them as the red, green, and blue color channels in a final RGB color montage, shown above. The final picture is composed of 81 smaller images spans 75 minutes of arc horizontally and 32 minutes of arc vertically, and includes approximately 100 stars, some of which may be foreground or background stars.
Links
Messier object 44, also known as the Beehive Cluster, or Praesepe, is an open cluster located in the constellation Cancer (RA 08:40:19, DEC +19:41:48). It has an apparent magnitude of 3.7, allowing it to be seen by the naked eye. The cluster spans approximately 100 minutes of arc on the night sky at a distance of 577 light years, for a linear size of about 16.8 light years. Due to its brightness and large size, this cluster has been observed for millennia.
Methods
For this project a large mosaic spanning the middle third of the cluster was made by combining images from 27 overlapping frames. Each frame was captured in three color filters: Red (R), Visible (V), and Blue (B), on a SBIG (Santa Barbara Instrument Group) ST-8 CCD camera, and all observations were carried out on Macalester's 16-inch Cassegrain reflector telescope, built by DFM Engineering on the nights of April 17th and 22nd, 2006. A dark frame was recorded for each exposure for a duration equal to the exposure time to correct for noise caused by the CCD electronics. Exposure times for the different filters were 10s for R, 16s for V, and 48s for B. A mosaic was made of all the frames for each color channel using ver. 5.41 of SBIG's CCDOps software, and Iris ver. 5.31, a free digital image processing program designed for use in astronomy. After the image mosaics were made for each of the three color filters, CCDOps was used to combine them as the red, green, and blue color channels in a final RGB color montage, shown above. The final picture is composed of 81 smaller images spans 75 minutes of arc horizontally and 32 minutes of arc vertically, and includes approximately 100 stars, some of which may be foreground or background stars.
Links