British Astronomical Association
Supporting amateur astronomers since 1890

BAA Images Alex Pratt

Observation by Alex Pratt: (41) Daphne occults UCAC4 452-022234

Uploaded by

Alex Pratt


Alex Pratt


2020 Dec 31 - 00:59


2021 Jan 07 - 10:50


41 Daphne

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

0.08 s



Target name

(41) Daphne and UCAC4 452-022234


(41) Daphne occults UCAC4 452-022234

About this image

Shortly before 1am on 2020 Dec 31, the mag. 11.9 ~200 km diameter main-belt asteroid (41) Daphne occulted a mag. 13.2 star in Monoceros, detectable as a mag. 0.3 drop in brightness for up to 12.9 s. I was inside the predicted shadow zone and recorded a 10.86 s dip:

    D  - 00 59 15.94 ± 0.10

    R  - 00 59 26.80 ± 0.08

My NEMETODE colleagues Michael O'Connell (Kildare, Ireland) and William Stewart (Ravensmoor, Cheshire) were also fortunate to be in the shadow path, using similar equipment and with good skies. Our timings were submitted to the Planoccult list-server and Eric Frappa (European Occultations Coordinator) accepted them for the Euraster database.

They can be viewed here, also with a link showing our chords against the shape model (derived from light curve inversion). A mathematical shape model is dimensionless; chord timings allow the body's dimensions to be estimated. They also give high-quality astrometry of the asteroid at the mid-time of the occultation, measured against the latest Gaia star positions. Good Pro-Am science conducted from back gardens with relatively simple equipment.

Files associated with this observation
Like this image
Tim Haymes
Tim Haymes, 2021 Jan 08 - 12:19 UTC

I good result Alex. The small one-third magnitude drop is a consideration when planning observations.  This made the observation best suited to electronic detection.  Your video light curve illustrates this very well.

The chords are shown here (for the record) - The event for me was hidden by the house!

20201231-Daphne_crd+DAMIT131.gif (1443×1103) (