Astroblog: How to see the new comet C/2025 R2 (SWAN) from Australia.

Wednesday, September 17, 2025

How to see the new comet C/2025 R2 (SWAN) from Australia.


North-western sky on Tuesday, September 17 as seen from Adelaide at 19:35 ACST (90 minutes after sunset, click to embiggen). Comet C/2025 R2 (Swan) is just above Mars. The inset is the approximate binocular view of the comet at the time.	North-western sky on Saturday, September 20 as seen from Adelaide at 19:35 ACST (90 minutes after sunset, click to embiggen). Comet C/2025 R2 (Swan) is just above Mars. The inset is the approximate binocular view of the comet at the time.	North-western sky on Tuesday, September 17 as seen from Adelaide at 19:35 ACST (90 minutes after sunset, click to embiggen). The track of the comet over successive nights is shown (ignore the magnitudes, the comet is around magnitude 7).

Comet C/2025 R2 (Swan) is (very) recently discovered comet that is around magnitude 7 (binoculars only), but it is well placed near some very bright guide stars so it will be easy to find (especially Mars and Spica this week). it is currently a dim dot in 10x50 binoculars. It will brighten a bit as it climbs higher into the darker skies, but will not really reach visual magnitude.

For this week it is relatively low above the horizon, and sets an hour after astronomical twilight, so you have a narrow window to observe. https://www.aerith.net/comet/catalog/2025R2/2025R2.html see also https://www.minorplanetcenter.net/mpec/K25/K25RA2.html for an ephemeris.


Black and White printable chart of the western sky starting Tuesday, September 17 as seen from Adelaide at 19:35 ACST (90 minutes after sunset, click to embiggen and print). The track of the comet over successive nights is shown (ignore the magnitudes, the comet is around magnitude 7).	Black and White printable chart suitable for binoculars of the comet for September 17 to September 23. (90 minutes after sunset, click to embiggen and print). Use in conjunction with the spotters chart.	Black and White printable chart suitable for binoculars of the comet for September 23 to September 30.(90 minutes after sunset, click to embiggen and print). Use in conjunction with the spotter chart.