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Observation by Paul Leyland: An experiment in super-resolution.

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Paul Leyland

Observer

Paul Leyland

Observed

2018 Nov 09 - 01:55

Uploaded

2019 Sep 22 - 16:47

Equipment
  • 0.4m Dilworth-Relay
  • SBIG-8 with AO-7 autoguider
  • No filter
Exposure

75 seconds in four subs of 5, 10, 20, 40s

Location

Tacande Observatory

Target name

ES 1128

Title

An experiment in super-resolution.

About this image

I freely admit this is not a classic pretty picture; it is the result of a crude attempt to improve the angular resolution of an optical train by post hoc image processing.

ES 1128 is a double star for which, according to Gaia, the separation is 3.247 arcsec with a PA of 172°28'

My telescope has a diffraction-limited resolution of 0.3 arcsec and the camera used for the image above had a plate scale of 0.71 arcsec per pixel. The minimum exposure time is 0.11 seconds so lucky imaging was not an option. Typical seeing radius is 2 to 3 arcsec. Only on the very best of nights could I reasonably expect to resolve the double.

The right-hand frame shows the stacked images at a four-fold zoom; that is each 4x4 block of squares represent a single CCD pixel. The stars have a FWHM of 5 CCD pixels which corresponds to 3.6 arcsec, so the seeing radius is about 1.8 arcsec --- a good night. The brightest star is not obviously a double.

The left-hand frame is the result of a quick and dirty deconvolution. The simg program was used to find the stellar PSF and then to run 10 iterations of Richardson-Lucy deconvolution. The increased noise and loss of sensitivity is apparent  but so is the duplicate nature of the bright star. There isn't quite clear sky between the components but it's pretty close.

The double star is fairly easy to measure. I make the separation to be 0.5±0.25 pixels in RA and 4.0±0.25 pixels in Dec. Converting to angular measure, the separation is 2.9±0.35 arcsec and the PA is 173°. Agreement with Gaia is satisfactory.

I'm fairly sure that more careful image processing can improve on this result; that will have to wait for another rainy day!

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