Fields Processed by Photo

Stages in running Photo
A series of images that take you through a run of photo
Photo's estimate of the Smooth Sky Background
A field with rich cluster of galaxies (z = 0.134), showing photo's estimate of the background, binned 4x4

Stages in running photo

A series of images of a 512x512 pixel region (100x100arcsec) of Run 745, camCol 3, Field 455; the i' band is shown. All images have a histogram-equalisation stretch.

Raw

The raw frame; the amplifier split is clearly visible, along with bleed trails and a horizontal line due to the star crossing the serial register. Some cosmic rays are visible near the end of the top-left diffraction spike

Corrected

The corrected frame; interpolated pixels are shown in green. Saturated pixels, bad columns, and cosmic rays are all visible. The next image shows the green overlay removed.

Corrected (No mask)

The same as the previous image, except that the green overlay is removed.

Bright Objects Detected

The same as the corrected image with BRIGHT detections (in blue) added.

Faint Objects Detected

The same as the previous image with faint detections (in red) and subtracted bright-star pixels (in yellow) shown. See the next image if you don't like the overlays.

Faint Objects Detected; no overlay

The same as the previous image, but with the overlay removed

Measured Objects

The same as the previous image, but with object's bounding boxes shown; see the next image if you don't like overlays. A large `sky' object appears in the top right; the small empty boxes are objects detected only in some other band.

Measured Objects, no mask

The same as the previous image, but with the overlay removed.

The frame reconstructed from Atlas Images

The pixels assigned to each object are taken from the atlas images, with a constant background (the stippling is a GIF artifact).

The frame reconstructed from Atlas Images including sky

The background is reconstructed from the 4x4 binned images; the objects are (as in the previous image) taken from the atlas images.

Photo's estimate of the Smooth Sky Background

This is an entire field (run 756, camCol 3, field 748) in the r' band, showing a cluster of galaxies at z = 0.134.

Measured Objects, with mask

The complete field, with no local sky subtraction performed but with detected objects marked (cf. this image).

Measured Objects, no mask

The complete field, with no local sky subtraction performed.

The background light level

The frame with detected objects removed, binned 4x4 and with the local sky added back in. The bright stars are clearly visible, as is the cluster of galaxies. It is not clear if this is due to the resolved galaxies or the unresolved background cluster light.

The background light level in g'

Photo's estimate of the `local sky' in g' for part of run 756 (fields 736--759; column 1 at the top. The cluster in the previous image is in column 3, field 748). The stretch is linear.

The sky is determined in 256x256 pixel (100x100 arcsec^2) patches with centres spaced every 128 pixels; this is then subtracted from the frames before the faint object finder is run, and the objects measured. Some residual flat fielding problems are also visble.


The background light level in g' for the corresponding frames of run 756

The area around the cluster, zoomed a factor of 2; cf. the corresponding frames of run 745

Note that some details of the sky background differ between the runs (e.g. ghosts of stars that are just off the frame).


The background light level in g' for fewer frames of run 745

The area around the cluster (in fields 461-462), zoomed a factor of 2; cf. the corresponding frames of run 756