You might like to consider something similar for around the price of an ED 100
take a look at
https://www.bintelshop.com.au/Product.aspx?ID=6967
You seem to not be considering imaging based on your specs for a bumpy road/mobile life and a non goto setup. If you were, the above link would not be too appropriate. But it will find objects quickly enough, has a little more apeture than an ED100, and could be setup without a tripod.
Ideal camperscope for a campervan.
cheers,
Doug