John Robens' Summer 2008 Progress page

How did I get to this image?

1. Basic CCD Reductions

Biases: I started off combining the bias images and then subtracted off the combined bias from each image using ccdproc in IRAF.

Flats: Then I combined the dome flats using flat combine and divided all images by the flat using ccdproc.

2. Improving the background flatness

The blanks were combined and smoothed over using boxcar. This created one smoothed image which was applied as an illumination correction.

3. Analysis: possible OC's in blank fields

I searched the blank images near the region of the HI detection comparing to the SDSS.

Nothing found yet, but further reduction is planned (smoothing, etc.)

4. Analysis: possible OC's in the tail region

Combining the Images

We have 10-11 10-minute exposure images that are shifted with respect to one another

All the images have the same bad columns from the CCD chip, so those were removed (fixpix).

Next I determined background values for each image and subtracted the background

I then chose one image as a reference, found the position of some prominent stars and determined the average shift of each image based on the stars.


I aligned all the images according to their shifts.

The next task was to match the point spread functions of the images (psfmatch), to correct for seeing variations.

I tried to combine the images, using cosmic ray rejection techniques within the IRAF task combine. The combined image still contained residuals of cosmic rays.

Then I went back and removed the cosmic rays from the original images using various cosmic ray tasks until they were all removed without affecting the stars (xzap task)

I re-matched the point spread functions, and the convolved images were combined to get to the final image shown.

Status

Began analyzing the final combined image of field 1 that you see on the progress page.

Currently in the process of matching the point spread functions of field 3

Field 8 has yet to be reduced

Look into methods to reveal fainter structures

Measure the brightness or upper limit to brightness of any feature



Back to Progress Page


background image from www.quidquam.com (tangled-galaxies)