We have been commissioning a new camera over the past few months, called Spectral (although it is an imaging camera not a spectrometer). One of our science interns (BJ Fulton) has been following an open cluster monitoring program and has been among the first people to use the spectral camera on Faulkes Telescope North for science. BJ is particularly interested in finding out the mass of the stars in these clusters.
The images attached (click on them to zoom) are standard RGB composites produced in Adobe Photoshop. Red is composed of 6x300 second exposures in the SDSS-I band filter. Green is 6x300 second exposures in the SDSS-R filter and Blue is 1x300 second exposure in the SDSS-G band filter. There is also a luminosity layer on top to help bring out some of the fainter detail that is an ultra-deep SDSS-I band image composed of approximately 16x300 second exposures (depending on the cluster). Total exposure time of about 2.5 hours.
BJ and Nairn Baliber are looking for photometric variability of the very young stars in these young clusters. At early ages, these stars have very strong magnetic fields which produce large star spots on the surface of the stars. As the star rotates, these star spots will move across our line of sight and can be seen as a slight decrease in brightness. This puts better constraints on their models of star and planet formation. These particular images will help to estimate the masses of the stars being studied.
The spectral camera has a chip twice as large as any other camera on our 2m telescopes, at 16 Megapixels (4096x4096 pixels square). Despite being a bigger chip it has a faster readout time than the Merope camera which is also mounted on the 2m's, at 6 seconds (compared to Merope's 20+ seconds). The field of view is significantly larger than previous cameras at around 10 x 10 arcminutes. Since we now have 4 times as many pixels the quality of the images is much higher.
These images were taken with the autoguider enabled which is now much more routine. This means we can use much longer exposure times and observe fainter objects. We have also warped the secondary mirror with about 40 lbs/sq-in of force at the edges to make M2 have a mild potato chip surface to compensate for a slight optical distortion called astigmatism present on the primary mirror. Both of these measures have made stars in the images smaller and rounder.
If you own a copy of Adobe Photoshop and would like to make your own color images from our public data archive, using our making color images activity .
Many thanks to BJ Fulton for the information on the observations and making the color images.
