Functional QUICK LOOK Requirements

General requirements

• control will be by GUI inputs (ie, graphical buttons, text boxes) and/or mouse;
• mouse button functions will be continuously updated/displayed;
• default parameters should be accessible for user modification and resetting to nominal values.

Quick-look operations must be easy to use. As they may be less self-explanatory than the image display operations, there should be an "on-line help" button to provide detailed descriptions of the procedures and operations.

There must be hardcopy capability (with proper stamp) for any plots or text output generated by the quick-look operations.

List of Quick-Look Operations

General Image Analysis:

• Row/column plots; average over many rows/columns;
• Averaged row/column plots for a user-specified region (mouse drags out box to specify the region).
• Plot along an arbitrary vector. These coordinates should appear on the plot abscissa: absolute x, absolute y; relative distance from start. The plot must be labeled with vector (x1,y1), (x2,y2) length and position angle. The width of the data strip along the vector (eg, 1,3,5 pixel) should be user-selectable;
• Print out array of pixel values in small (eg, 9 x 9 pixel) box;
• Statistics within a box; user drags out box of desired size. The list of possible values should include:

    number of pix     mean         rms about mean      sum
    nx,ny of box      median       min                 max
    location          mode         coords of extrema
    percent of values above/below 3,4,5 sigma
  

  It should also be possible to see a histogram, and to select the same stats above with/without (a) sigma clipping and (b) "masked" regions (eg, bad pixels) excluded.

Direct Image Analysis:

• Centering on cursor-selected feature (positive or negative). Different algorithms for centering are: centroiding; edge-weighted centering of features of known width; location of peak (positive or negative) pixel. All three (and other?) center values could be displayed. For interacting with other operations (eg, PSF analysis below) the centering algorithm could be user-specified.
• Radial profiles;
• PSF/object analysis: sky, peak, FHWM, rms to gaussian fit (or other PSF fit), S/N estimate, approximate magnitude (based on standard zeropoints or local calibration -- see Note 1). There should be a "clip CRs" option in this analysis;
• Cursor readout of celestial (and other) coordinates, including updating the coordinate zeropoint by marking reference objects (this means there must be a "private" WCS for this function);
• Ability to measure distances (a "ruler"): drag out vector, display length in pixels and arcsec, and angles (wrt image, north, horizon).
• Various graphic overlays:
  • circles (of specified radius);
  • coordinate grids (eg, RA-Dec; Alt-Az);
  • catalogued object positions;
  • slitmask outline.

Spectral Image Analysis:

• Cursor readout of approximate wavelength (by individual slit) plus celestial coords along slit. Slit/object ID must also be displayed;
• Calculation of approximate redshift upon identification of a spectral feature, and overlay of rest-frame wavelength scale;
• Overlay of object positions;
• Statistics of spectral line profiles: FWHM, rms to gaussian fit, skewness;
• Simple spectral extraction (with options of displaying object+sky, object, and/or sky). Must include a S/N calculator. Extraction should also list FWHM of object along slit. Traced location of object peak (or center of object window) as a function of wavelength should be shown on image display (see Note 2).

Calibration Analysis

• Analysis of stellar images on a focus frame;
• Analysis of images to compute gain and read-out noise.

Note 1: "Standard" magnitude zeropoints for typical conditions must be tabulated for each filter. Coupled with gain and exposure information (and filter ID), this enables quick estimate of throughput and/or transparency. However, we should also have the ability to specify "private" zeropoints appropriate for, eg, a particular image taken under poor conditions. Under these conditions, a star of known magnitude is selected and a zeropoint is calculated, and added into a "user" section of the zeropoints table.

Note 2: Quick spectral extraction may be best provided by easy access/interface with more sophisticated spectral extraction routines in the automated spectral reduction package.

Design Notes