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Occultation of UCAC4-410-143659 by Triton, 05 October 2017

On 05 October 2017, the star UCAC4-410-143659 (magnitude +12.7) was occulted by Neptune‚Äôs principal moon Triton. The event was predicted to occur at 23:49 UT as seen from the UK. At this time, Triton, at magnitude +13.7, was at a distance of 29.1 AU (4350m km) and presented an angular diameter of 2.3 arcsec.

Using a 235 mm Meade SCT and Canon 60Da camera (6 s exposure at ISO 1000) I obtained the two images below, at 22:56 UT (left) and 23:54 UT (right), respectively one hour before and immediately before disappearance. (Although the second image was taken shortly after the predicted event time, disappearance had not, at that time, occurred.) Due to wind and a neighbour's tree, I was unable to record the disappearance itself.

In the images, the large bright blob is Neptune (250 times brighter than Triton). The fainter object to the right is Triton and the object further to the right is UCAC4-410-143659, approximately one magnitude brighter than Triton. The second image shows Triton and the star just starting to overlap, at the resolution of my equipment.

20171005_2256_Triton_occ_MOM.png 22:56 UT.

20171005_2354_Triton_occ_MOM.png 23:54 UT.

Mike O'Mahony