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Observation by Paul Leyland: Caliban (Uranus XVI)

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Paul Leyland

Observer

Paul Leyland

Observed

2020 Jan 13 - 23:00

Uploaded

2020 Jan 17 - 23:06

Objects

Uranus

Equipment
  • 0.4m Dilworth-Relay
  • SX Trius Pro 814
  • No filter
Exposure

356 30-second subs, median added (2h58m total)

Location

Tacande Observatory, MPC J22

Target name

Caliban (Uranus XVI)

Title

Caliban (Uranus XVI)

About this image

Caliban is an irregular outer satellite of Uranus discovered with the Hale 5m at Palomar in 1997 and is estimated to be 72km in diameter.  At a MPC-ephemeris V magnitude of 22.2 it is likely the faintest I can manage in my program to image satellites in the outer solar system. Even with three hours exposure, unfiltered for maximum sensitivity, the signal to noise ratio is barely 3. The image above has used truncated histogram equalization to maximize the contrast.  Stacking was made markedly easier because the satellite is near a stationary point as observed from the earth, moving less than two arcseconds during the 3-hour exposure.

The only reasons why I am certain of the identification are that it lies exactly at the predicted position and there is no other object of comparable brightness at that position in any images taken to that limiting magnitude which I have been able to find.

Caliban was predicted to be at 02:01:03.0 +11:44:22 throughout the observation.  The brightest star in the image, to Caliban's upper left, is Gaia-DR2 2574537812519595520, with g-magnitude of 17.04, at 02:0107.3 +11:45:49.  The 2 stars below Caliban are magnitude 19.78 and 19.18 in Gaia-DR2.

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