British Astronomical Association
Supporting amateur astronomers since 1890

BAA Images Alex Pratt

Observation by Alex Pratt: Video astrometry of comet C/2017 T2 (Pan...

Uploaded by

Alex Pratt


Alex Pratt


2020 Jun 01 - 22:00


2020 Jun 05 - 13:52



  • C11 f/10 @ f/3.3
  • Watec 910 video camera
  • IOTA-VTI GPS time inserter
  • OccuRec (recording)
  • Tangra (reduction)

Generally 0.64s



Target name

Comet C/2017 T2 (PanSTARRS)


Video astrometry of comet C/2017 T2 (PanSTARRS)

About this image

Comet C/2017 T2 (PanSTARRS) has been trundling through the northern constellations for several months and I've been doing astrometry of it since late October 2019. I've obtained 90 measures of its position on 32 nights. The comet reached perihelion on May 4 when it was 1.6 AU from the Sun.

I downloaded all astrometry for this period from the MPC website (including my own) and processed them with online Find_Orb to determine the RA and Dec residuals for each observation. The attached plots show the astrometric residuals (arcsec, in RA and Dec) for all CCD measurements (in grey) and video measurements from my location, Z92 (in black). It's interesting to see the comet's movement in recent weeks, meandering around its mean nominal position.

C/2017 T2 is now nicely located above the Plough asterism and I hope to measure it for some weeks yet.

Files associated with this observation
Like this image
Copyright of all images and other observations submitted to the BAA remains with the owner of the work. Reproduction of work by third parties is expressly forbidden without the consent of the copyright holder. By submitting images to this online gallery, you grant the BAA permission to reproduce them in any of our publications.