Friday, August 17, 2012

M74 a Grand Design Galaxy

M 74
5x2 min expousres binned 2x2 @ f/10 12" SCT
© Billy Vazquez
M74 is a beautiful galaxy on the constellation Pisces.  The image presented here was taken at VAO in the morning of August 16th.   They are 5x2 min exposures binned 2x2 on Johnson R filter at f/10 on the 12" SCT.   FWHM for the night averaged 2.7".  Bradon Doyle generated interest in this galaxy and we collaborated to obtain this image for scientific research.  The image was colorized in GIMP but no streching or other post-processing effects were added.  The image was callibrated with darks and flat fields.   The image was taken on a cooled KAF8300 CCD cooled to -10 degrees Celsius.

Monday, August 13, 2012

Orion Parsec KAF8300 CCD Linearity Test

The main camera of the VAO is an Orion Parsec that has a KAF8300 CCD.  One of the issues with this camera is the possibility of non-linearity as it fills the pixel electron well.   The KAF8300 uses Anti-Blooming circuitry to drain current as the pixels fill up.   This has the desirable effect of eliminating blooming from bright stars in your image while increasing your dynamic range.   The downside of this technology is that it lowers the quantum efficiency of the CCD since there is additional electronics in each pixel to drain the current out.   More importantly, it adversely affects photometric measurements as the pixel fills up.  The measurements at higher ADU counts will show non-linear response.   Therefore, in an attempt to quantify these deviations from linearity for my camera, I have performed a linear test.   The test is simple enough.  Take flat exposures of increasing time steps and plot the counts vs time as you can see from the plot I present here.   Notice that the asymptotic error of the linear fit is of the order of 0.39% or about +/- 12 ADU. 

Thursday, August 9, 2012

M 52 an open cluster but how far is it?

M 52
3x5 minute exposure, Stromgren y
© Billy Vazquez
M 52 discovered by Messier in 1774 is shown here in an unguided co-added 3x5 minutes Stromgren y filtered exposures.   This image is part of a battery of tests I am excercising on the observatory in preparation for a a new science run that will use Stromgren filters for stellar and luminosity classification.   I am glad to report that the Stromgren y filter which peaks exactly where the Johnson V filter does, is performing well in initial tests.   It is also an opportuinity for you to glimpse at a cluster with a controversial history about its true distance.  Reports vary considerably in the literature and mostly attributed to interstellar extinction.

Friday, August 3, 2012

Maia a Star in the Pleiades Cluster

Maia in Pleiades
5 min unguided exposure
© Billy Vazquez
The Pleiades Cluster also known as the Seven Sisters will always make one of the favorite astronomers stops.   Why you say? Well is bright, can be seen with the naked eye and it harbors these beautiful Blue B stars.   More importantly, there is interstellar dust that reflects the light of this enormous stars, making it look nebula like.   Well not everything is forever and astronomers have determined that in about 250 million years this cluster will be stripped away of its stars by gravitational forces.   The image I show you today is one of the many tests I am performing on my renovated observatory.  Maia one of the Pleiades stars is smacked in the middle ( more or less a bit southeast ). A 5 minute raw unguided exposure, on a full moon night, which is why you can barely see any nebulosity. Still a very nice image, with full width half maximum of 2.1 arc seconds.