Virus Health Check checkbias

## checkbias - Check hetdex bias images

### Purpose:

Check the given images if they conform to the HETDEX standards for a HETDEX bias observations. This tool can run in addition to the purely bias recipe specific tests also the header conformity checks provided by checkheader.

##Options:

`-N, --npixels <bool> [FALSE] Check for the correct number of pixels in the file.`
See VirusHealth::validate_size() for more details.

`-K, --keywords <bool> [FALSE] Check that the header keywords are correct.`
See VirusHealth::validate_keywords() for more details.

`-O, --overscan <bool> [FALSE] Check the rms of the overscan.`
See VirusHealth::validate_overscan() for more details.

`--ovc_stddev <FLOAT> [0.2] Expected standard deviation of the overscan.`

`--ovc_mean <FLOAT> [1.0] Expected mean of the overscan.`

`--max_ovc_dev_rms <FLOAT> [0.1] Maximum relative deviation for standard deviation of overscan.`

`--max_ovc_dev_mean <FLOAT> [0.1] Maximum relative deviation for mean of overscan.`

`-E, --exptime <bool> [FALSE] Check that the exposure time is at least 6 minutes long.`
See VirusHealth::validate_exptime() for more details.

`-F, --flatness <bool> [FALSE] Check that the average and the rms of the bias frame measured at four subsections of the image and the overscan is below the maximum allowed deviation.`
See VirusHealth::validate_flatbias() for more details.

`-B, --bias <bool> [FALSE] check mean and rms of bias frame.`
See VirusHealth::validate_refbias() for more details.

`--bias_stddev <FLOAT> [0.2] Expected standard deviation of the bias.`

`--bias_mean <FLOAT> [1.0] Expected mean of the bias.`

`--max_bias_dev_rms <FLOAT> [0.1] Maximum relative deviation for standard deviation of bias.`

`--max_bias_dev_mean <FLOAT> [0.1] Maximum relative deviation for mean of bias.`

`-m, --maxdiff <float> [0.1] Maximum allowed difference between the measurement subsections, or between the bias frame and the reference bias frame.`

### Example:

Run all tests on a file:

> checkbias -N -K -O -E -F -R masterzro.fits 20120908T192750_001LL_zro.fits