Bright & uncertain

Forums Asteroids Observing Trans Neptunian Objects, etc Bright & uncertain

Dr Paul Leyland

To be quite honest, I don’t know. I’ve not tried to find out. It would not surprise me to find a few in the 19-20 range but fainter than 20 are likely to be more common.

That said, I can take measurable images at  magnitude 20.5 unfiltered in 51.5 minutes (see for an example) and 22.2 in 178 minutes (see with a 0.4m on a decent night.

Owners of smaller scopes need to multiply by the square of the aperture ratio. A 30cm, say, takes (0.4/0.3)^2 as long — 92 minutes and 316 minutes (5h16m)  respectively. The figures for a C14 (0.356m) are 65 minutes and 225 minutes, or 3h45m.

I accept that over five hours is almost certainly too long for most people. Nonetheless observers equipped with telescopes in the 30-40cm class should be able to do useful research by measuring objects which are significantly below mag 21.