2MASS Previous Dithering Patterns

82.80" step size and -0.11 camera rotation

83.22" step size and 0.0 camera rotation

82.80" step size and -0.11 camera rotation

This is the pattern that we currently are using. The J pattern is not too bad, but the H and K dithering is bad, with dithering occurring in only one dimension. In addition, the K dither effectively has only 4 dithers instead of 6, as 2 of the dithers fall on top of other dithers.

Array Rotations:

Band	Array Rotation (o)
J	0.377
H	0.441
K	0.335

Using the following plate scales:

Band	Plate Scale ("/pixel)
J	1.9966
H	2.0060
K	1.9839

gives the following step sizes in pixels:

	Single Frame step in pixels		6th frame step in pixels
Band	In-scan	Cross-scan	In-scan	Cross-scan
J	41.47	0.27	248.82	1.64
H	41.27	0.32	247.65	1.91
K	41.74	0.24	250.41	1.46

The resulting dither patterns are:

(Click on graph for bigger and better image.)

(Click on graph for bigger and better image.)

(Click on graph for bigger and better image.)

(Click on graph for bigger and better image.)

83.22" step size and 0.0 camera rotation

This is the pattern that we started out with.

• The J pattern is a one-dimensional dither pattern with effectively only three dithers instead of six, since 3 of the dithers fall on top of other dithers,
• the H pattern is not too bad but has only 0.5 pixel spacing in the in-scan direction, and
• the K pattern is a one-dimensional pattern oriented such that there is no in-scan dithering.

Array Rotations:

Band	Array Rotation (o)
J	0.489
H	0.551
K	0.452

Using the following plate scales:

Band	Plate Scale ("/pixel)
J	1.9966
H	2.0060
K	1.9839

gives the following step sizes in pixels:

	Single Frame step in pixels		6th frame step in pixels
Band	In-scan	Cross-scan	In-scan	Cross-scan
J	41.68	0.36	250.08	2.13
H	41.48	0.40	248.90	2.39
K	41.95	0.33	251.68	1.99

The resulting dither patterns are:

(Click on graph for bigger and better image.)

(Click on graph for bigger and better image.)

(Click on graph for bigger and better image.)

(Click on graph for bigger and better image.)