Comet Tsuchinshan-ATLAS (C/2023 A3) is a lump of dirty space ice. But it's a special lump of dirty space ice, as it's forecast to swing by the Sun and become bright enough to be seen by the naked eye at night in mid-October.

However, comet brightness predictions are always tentative. Comets may be significantly brighter or dimmer than advertised. So how bright will Comet Tsuchinshan-ATLAS get (as judged by me)?

The categories are pretty subjective, so here's a breakdown:

Great comet

A generational comet that is a stunning sight at night and may even be visible during the day, like Comet McNaught in 2007. Alternatively, it may be very bright over a long period of time, like Comet Hale-Bopp in 1996-97. In either case, it's impressive enough for even the general public to appreciate, with extensive news coverage.

Pretty bright

The comet is pretty easily visible to the naked eye. It should attract the interest of people that are moderately into astronomy or nature, and may start to capture the attention of major news sites. Examples include Comet NEOWISE in 2020 and Comet Lovejoy in 2011.

Disappointingly dim

The comet is never easily visible to the naked eye. Because light from comets is more diffuse, this usually occurs when the comet's magnitude is dimmer than around 4. Examples include Comet ZTF in 2023 and Comet ISON in 2013, which both reached peak magnitudes of around 5 for most observers.

Since the resolution of this market could be subjective, I will not bet on this market.