YALO - Reduced images

Examples of Reduced YALO IR data 

Good YALO reduced images from March 2001

The following images are the final reduction images for SN2001X. The data was taken from 20010323( 23/4 March 2001). The data were taken as:

  • 45s exposures in JHK at each dither position
  • Two dither positions with dither=40 (20" throw)
  • The telescope was moved 1.0s of time W between each series. No guide star was used.
  • Series 1,2,3 - JHK; Series 4 - HK; Series 5 - K. Total exposure (J,H,K)=(270,360,450)s


The data reduction was described in the notes given in this web page. In particular, I reduced the JH data using a single averaged sky, averaged across the two dither positions. The K image was reduced keeping the two dither positions separate to reduce the fringing. I used flat fields taken at the two dither positions, and reduced the data to [OZF] keeping the dithers separate.

The supernova had the following approximate magnitudes in these data:
JHK = (3450,4100,3350 ADU/45s) = (14.9,14.7,14.4)

The reduced J image.

SN2001 J

 

The H image. The dark edge on the right is a result of averaging all the skies together across dithers. If I reduced the H data for each dither independently, this edge would disappear.

SN2001 H

 

The K image. Note the absence of fringing. You can see a small amount of print-through in the skies as a vertical white streaks above and below the bright objects. This is because only 5 images went into the sky median.

 

Here is what the K image looks like if the sky is averaged across all dither positions. Note the fringing and the obvious problems that remain with the vignetting. I am not convinced yet that the vignetted area in the image above is photometrically flat. The sky has subtracted but this does not mean that the photometry will be correct in that region. I will still assume that only for x<650 is the field photometrically flat.

 

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