[Wavytone]

The original question concerned refractor optics, not reflectors.

In some respects salt would be OK as far as the lenses are concerned, however putting salt anywhere near the metal bits of the OTA will ruin them very quickly, especially aluminium or brass parts, regardless of whether they are machined, cast, painted or anodised.

And before anyone chimes in about aluminium boats in seawater, they survive the salt only thanks to a sacrificial electrode (dissimilar metal) creating an electrolytic battery that protect the aluminium.

But don't let me stop you trying, and destroying your scope in the process...