Observation by Paul Leyland: Bare detection of (50000) Quaoar

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Paul Leyland


Paul Leyland


2021 Aug 12 - 14:07


2021 Aug 12 - 14:07


50000 Quaoar

  • 0.4m Dilworth Relay
  • Starlight Xpress 814 Trius Pro
  • No filter

6480 seconds, 55 subs stacked on predicted motion of Quaoar


Tacande Observatory, MPC J22

Target name

(50000) Quaoar, a Trans-Neptunian Object


Bare detection of (50000) Quaoar

About this image

I have my doubts as to the wisdom of posting this one because the object is at the limits of detectability under the conditions last night ---poor to moderate seeing and fair to middling transparency. It is being posted as an example of how a little lateral thinking can make the almost indistinguishable recognizable, given prior knowledge of a position

The TNO (50000) Quaoar is currently in a dense part of the Milky Way and close to the open cluster NGC6055. It is also magnitude 18.9 and there are a lot of 19th magnitude stars in that part of the sky. Luckily its position is known to within an arc-second. At the time in question it was about 3" from its three nearest neighbours and 5" from the fourth. Working clockwise from Quaoar the companions are 19.6, 18.0 and 18.2 in Gaia's G-band.

With the eye of faith something can be seen on the image stack in exactly the expected position. Plotting a contour map of the isophotes makes it much easier to see; it is the marked bump in the image above. Other bumps mark the positions of faint field stars.The other two images show the stack and the corresponding portion of the DSS2 images with Quaoar marked with a purple +. Note that the images are only 53" high so the plate solver doesn't stand a chance.  For the record Quaoar was located at 18:16:05.4 -15:16:42 when the images were stacked.

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