I did a shoot out between a 100mm f/9 synta ED doublet and 127mm mak.
They were about the same on planetary/lunar detail
The 100/9 can go wider because of the shorter FL and ability to handle 2 inch eyepieces, so in general
it is a more versatile scope.
I have just purchased a 80mm synta ED, but now the planets are gone, and I can't really
compare 100 vs 80 for planetary detail.
You would be losing whatever premium optics gives you, and I have never viewed through one
to no how much I would be giving up.
Besides text book resolution calculations, there is also exit pupil. I find I stop seeing more detail
at about EP=.7mm. The 100 then gets you 150x, where the 85 is 120x
According to DessertSky the DV1 is recommended for a 100 f/7. The 100 f/9 might be pushing it.
My 150mm f8 dob is better than either the 127mak or 100ED, if you want to go there.
It is not a giant leap, just a step better.
Edited by vtornado, 10 January 2020 - 02:42 PM.