[Wavytone]

Peter, you already have a 150mm f/10 Mak. A smaller refractor will do absolutely nothing of use for you, IMHO, unless you want to use it as a very big finder, or guide scope.

FWIW I have a 102mm ED doublet APO refractor, an Alter M703 (7" f/10) Mak, and a Skywatcher 180mm f/15 Mak.

My refractor does produce a good diffraction pattern with only the barest hint of colour - surprisingly better than I expected, however f/7 is too short to be much good on planets (the combination of f/15, cassegrain optics and longer eyepieces is much better) and for DSO's disappointing except in very very dark skies. Katoomba airstrip is ok for fun, but IMHO its not that dark compared to really good sites.

My refractor doesn't get much use, frankly because the two maks do significantly better on DSO's (aperture), planets (where high agnification resolution counts) yet small enough to be dead easy easy up. When I do take I out, it usually ends up serving asa very big finder 4 degree field) for the f/15 Mak, which once aligned, can stay at medium to high power. An expensive luxury, perhaps.


A 120mm f/7 won't be noticeably better - having looked through a couple.