CCD_BLINK.CL INSTRUCTIONS

Open IRAF and DS9.
Make new directory "AGBLINK".
Copy the IRAF program "cdd_blink.cl" into AGBLINK.
Copy any ANDICAM ccd images with which you are going to work into AGBLINK.
Go to the DSS website
Choose "Retrieve from" POSS2/UKSTU Red, POSS2/UKSTU Blue or POSS2/UKSTU IR.
Input the "RA" (hh:mm:ss) and "DEC" (dd:mm:ss) of the ANDICAM observations.
Input a "Height" of 8.0 arcminutes and a "Width" of 8.0 arcminutes.
Choose "File format" FITS
Click "RETRIEVE IMAGE"
Save the image to disk into the directory AGBLINK, giving the DSS image an easily recognizable name such as dss_R.fits, dss_B.fits or dss_IR.fits.
Decide which images in AGBLINK are to be compared. Compare ANDICAM R-filter images to POSS2/UKSTU Red DSS images. Compare ANDICAM B-filter images to POSS2/UKSTU Blue DSS images. Compare ANDICAM I-filter images to POSS2/UKSTU IR DSS images.
Run the program ccd_blink.cl in IRAF (make sure you are in the AGBLINK directory and type the command "cl < ccd_blink.cl"). The first thing the program does is show all the files avaliable in AGBLINK.
Follow the program instructions as they appear →
- Enter the full filename of the DSS image (example: dss_IR.fits). The program magnifies the DSS image by a factor of 2.72 in x and y in order to match the pixel scale of the ANDICAM images. The DSS image is also rotated slightly.
- Enter the full filename of the ANDICAM ccd image to which the DSS image is being compared (example: ccd012345.0123.fits)
- Select 1 star in the ANDICAM ccd image (which will be displayed in frame 2), move the curser over that star and press "c" to select and then "q" to move on to the next step. You can move freely between frame 2 and frame 1 (in which the DSS image is displayed) in order to identify a common star, but make sure you first select that star in frame 2.
- Select the SAME star in the DSS image (displayed in frame 1), move the curser over that star and press "c" to select and then "q" to move on to the next step. The DSS image is then shifted so that the selected star has the same physical pixel coordinates as it has in the ANDICAM ccd image.
When the program ends there should be a magnified/shifted DSS image displayed in frame 1 and the ANDICAM ccd image displayed in frame 2. Use the DS9 function "frames → match frame → physical" to align the two DS9 frames.
You may now blink between frames 1 and 2 to search for any new sources. Zoomed in to look over the images in detail, realigning each time using the DS9 function "frames → match frames → physical".

CAUTION: DSS images may have a lower limiting magnitude than ANDICAM exposures so dim stars that are absent in DSS images may appear in the ANDICAM exposures. It may, therefore, not be possible to differentiate between a dim star and a dim afterglow using this procedure. Dim afterglow can be confirmed if the source decays between multiple observations.
CAUTION: This alignment procedure is NOT perfect, you may especially notice slight rotation between the images. However, the alignment will be close enough so that new sources are evident.

BINIR_BLINK.CL INSTRUCTIONS

Open IRAF and DS9.
Make new directory "AGBLINK".
Copy the IRAF program "binir_blink.cl" into AGBLINK.
Copy any ANDICAM ir images with which you are going to work into AGBLINK.
Bin the ANDICAM ir images.
Go to 2MASS Quicklook website.
In the field "Coordinates or Object Name:" input the RA and DEC of the ANDICAM observations (hh:mm:ss dd:mm:ss).
In the field "Subimage Size (arcsec):" input 300.
In the field "Band" select J,H or K.
Press "Submit", this will open a new internet browser.
Above the sky image on this new webpage, there is a "Download" option followed by the name of a fits image (typically ji??????.fits, hi??????.fits or ki??????.fits). Click on this image name and save the file to disk in the directory AGBLINK.
Decide which images in AGBLINK are to be compared. Compare ANDICAM J-filter images with 2MASS J images, etc.
Run the program binir_blink.cl in IRAF (make sure you are in the AGBLINK directory and type the command "cl < binir_blink.cl"). The first thing the program does is show all the files avaliable in AGBLINK.
Follow the program instructions as they appear →
- Enter the full filename of the 2MASS image (example: ji012345.fits). The program magnifies the 2MASS image by a factor of 3.69 in x and y in order to match the pixel scale of the ANDICAM images.
- Enter the full filename of the ANDICAM binir image to which the 2MASS image is being compared (example: binir012345.0123.fits). This image is rotated by 90 degrees to match the "North up, East left" orientation of the 2MASS images.
- Select 1 star in the ANDICAM binir image (which will be displayed in frame 2), move the curser over that star and press "c" to select and then "q" to move on to the next step. You can move freely between frame 2 and frame 1 (in which the 2MASS image is displayed) in order to identify a common star, but make sure you first select that star in frame 2.
- Select the SAME star in the 2MASS image (displayed in frame 1), move the curser over that star and press "c" to select and then "q" to move on to the next step. The 2MASS image is then shifted so that the selected star has the same physical pixel coordinates as it has in the ANDICAM binir image.
When the program ends there should be a magnified/shifted 2MASS image displayed in frame 1 and the rotated ANDICAM binir image displayed in frame 2. Use the DS9 function "frames → match frames → physical" to align the two DS9 frames.
You may now blink between frames 1 and 2 to search for any new sources. Zoomed in to look over the images in detail, realigning each time using the DS9 function "frames → match frames → physical".

CAUTION: ANDICAM ir image MUST BE BINNED
CAUTION: You may need to re-display the images (particularly the 2MASS images), setting z1 and z2 to appropriate levels in order to insure you are getting good image contrast.
CAUTION: 2MASS images may have a lower limiting magnitude than ANDICAM exposures so dim stars that are absent in 2MASS images may appear in the ANDICAM exposures. It may, therefore, not be possible to differentiate between a dim star and a dim afterglow using this procedure. Dim afterglow can be confirmed if the source decays between multiple observations.
CAUTION: This alignment procedure is NOT perfect, you may especially notice slight rotation between the images. However, the alignment will be close enough so that new sources are evident.

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