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I don't completely understand the different coordinate systems available. See: http://iraf.noao.edu/projects/ccdmosaic/imagedef/imagedef.html
I believe DTM/DTV are the ones we should assume are default, but I'm happy to be corrected.
Header Key | AmpInfo | Description | Default |
|---|---|---|---|
EXTNAME | name | Name of Amp: '0,1' | |
DETSEC | BBox | Bounding box of physical pixels in in assembled coordinates | |
| GAIN | Gain | Gain value of this amp e-/count | 1. |
| RDNOISE | ReadNoise | Read noise in counts | 0. |
| SATURATE | Saturation | Value of saturation threshold in counts | |
| DTM[1-4] check mod 90 rotation | ReadCorner | Location of first pixel read in assembled coordinates | LLC |
| LINCOEFF | LinearityCoeffs | Coefficients of linearity fit | 0., 1. |
| LINTYPE | LinearityType | Type of linearity: This could map to a method for applying non-linearity correction | POLY |
| NAXIS1, NAXIS2 | RawBBox | Bounding box of raw data (including prescan, overscan regions) in raw coordinates | |
| DATASEC | RawDataBBox | Bounding box of raw data in the raw frame | |
| DTM[1-4] | FlipX | Flip x axis when assembling? | False |
| DTM[1-4] | FlipY | Flip y axis when assembling? | False |
| DTV1, DTV2 | RawXYOffset | Offset of to apply to assemble raw frames in a mosaic | 0,0 |
| BIASSEC[1] | HOverscan | Bounding box of horizontal overscan in raw coordinates | |
| BIASSEC[3] | VOverscan | Bounding box of vertical overscan in raw coordinates | Empty BBox |
| BIASSEC[2] | Prescan | Bounding box of prescan region in raw coordinates | Empty BBox |
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| Camera Config | Description | Default |
|---|---|---|
| name | Name of the camera | 'FileCamera' |
| plateScale | plate scale at the focal plane (arcsec/mm) | 1. |
| radialCoeffs | radial coefficents that describe a radial polynomial distortion | I think the following produces no distortion [0, 1, 0] |
Implementation of use case
I implemented the plotting use case outlined above. The code can be found here. The results from commit 102320d are all shown below.
This shows an assembled flat provided by Jim C. The segments are labeled. Note that a bias correction and rudimentary gain correction have been applied. This agrees with an assembled flat he provided shown here:
Below is plotted an untrimmed version. The green box are raw data boundaries, the red box is the overscan region and the blue box is the data region.
The above images were produced using bounding boxes and offsets calculated in the code. This makes the plotted images match the orientation from Jim's example. If I use the bounding boxes in the header (commit 280194e), I get a good assembly, but it is flipped about the y-axis. I'm not sure how important that is or what I'm missing in the headers, but I believe that the above orientation does not imply that the serial direction is +ve in the +ve x direction.
Questions
Below is a list of questions to be addressed as a result of this requirements document. These are just here for historical reasons. These answers will be fleshed out in the design above.
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