How Deep Did I go?

    *for another depth study click here

On January 10, 2001, under a full moon, I pointed the NGT-18 into the double cluster to image to take a quick one second image of NGC 0884 using the ST-9E.  I did this with the following result:

I then image linked the image using TheSky and got the following:  77 stars from the database were linked to the image.

I then checked for use by the astrometric algorithms used in CCDSoft and found that the 77 stars were usable for that purpose.

I use this algorithm to identify quality star points.  The star at line 79 represents the dimmest star that was usable for this purpose.  GSC3694:1871 is the dimmest star found having sufficient accuracy to be used for astrometry in this image.   The star is 14.17 magnitude according to the GSC catalog.

Ever wanting to increase my knowledge of my tools, I pulled the image into AIP4WIN, my latest image processing tool. 

This wonderful package is very powerful.  For example, The Centroid Extractor scanned my image, and created a database of all the stars it found using normal sensitivity.  The number was 212.   I used a 6 pixel wide radius for the extractor.  The beginning of the list of centroid's (stars) is shown in the image below.  The list is sorted by raw magnitude, brightest stars first.

At the tail end of the list are found the dimmest stars.  The last one, shown below has a raw magnitude of 14.4. (see the data log).  I marked the location of this star on the image.  It corresponds  to a star found in the USNOA2.0 catalog.   Notice how the raw magnitude of 14.41, the red magnitude of 14.2, and the integrated magnitude of 14.73 pretty much agree?  If I had taken the image with a Johnson Cousins Red filter, I could have directly calibrated the magnitudes of the other stars (in red) on the image.