id	summary	reporter	owner	description	type	status	priority	milestone	component	version	severity	resolution	keywords	cc
1291	skycells needs to allow for overlapping edges.	kpat.jhu	eugene	"A buffer of 15 pixels on all edges of the sky cells from the stacks are masked. I found this first in MD08, a quick check by Mark Huber and I of MD09 and MD07 showed the same effect. The anomaly is illustrated on the PS1 wiki at

http://ps1sc.ifa.hawaii.edu/PS1wiki/index.php/Stack_Anomalies#Edges_of_sky_cells_are_masked

The effect was noticed when examining a galaxy at the edge of a sky cell. Examination of the RA,DEC values of the pixels indicates that the sky cells meet seemlessly - little or no gap nor overlap in the vertical edges of the sky cells. However, with this 15 pixels masking of each sky cell edge we lose a strip 6 arcsec wide (2 * 15 * 0.2 arcsec/pixel) of un-imaged sky. It would be good to turn off this unnecessary masking.

In a reply to my original post, Paul-Price noted that some masking is needed for convolution purposes (presumably to remove convolution edge effects).  That may be, but it would then seem that a better way to proceed is to make the sky cells bigger and then trim unnecessary masked pixels before making the final product.

Note - I am not familiar with IPP so my pick for ""component"" is a guess, and I have not picked keywords.

-- Gerhardt Meurer"	defect	assigned	normal		Ohana		normal