6" f/8

Can a 6" f/8 Newtonian be as good as a 4" ED/APO when it comes to planetary, binaries and globular clusters?
Has anyone tried this Sky-Watcher (Synta) 6" f/8 OTA? I`d like to buy this OTA and mount it on my EQ3 or possible my Vixen Porta....
/Magnus

Magnus Ahrling said:

Can a 6" f/8 Newtonian be as good as a 4" ED/APO when it comes to planetary, binaries and globular clusters?
Has anyone tried this Sky-Watcher (Synta) 6" f/8 OTA? I`d like to buy this OTA and mount it on my EQ3 or possible my Vixen Porta....
/Magnus

A 6" f/8 is a very good alternative to a 4" APO. It does give up the low power, wide field views. If the optics are good it will do better than any 4" scope on the Moon, planets, and most deep sky objects. The good old 6" f/8 is a very cost effective way to get a nice scope.

Things might be a bit closer on double stars - refractors tend to give tighter star images at very high powers, and often split doubles at lower powers than a comparable reflector.

Clear skies, Alan

Magnus:

I think others have given you some good information but I have to add my two cents simply because I have three 6 inch F/8 Newtonians and I enjoy each one.

Two are Criterion RV-6's. RV-6s were made from 1958 until about 1978 and featured a pedestal mount with an AC drive motor, a hand figured Pyrex(??) mirror in a lightweight Phenolic tube with an simple aluminum mirror cell. The focuser is adequate but could be better. They seem to be something of a classic and have of a reputation for having quite good optics. When the seeing permits, mine give nice tight star images with good contrast on the planets.

View wise, there is a temptation to call it "refractor like" but the truth is, I don't have a refractor that provides RV-6 level views though I am sure they exist, just not in the $200-$400 price range. I have a wonderful clear memory of probably delta cygni at 300x with beautiful diffraction rings and the companion shining brightly.

As far as a mount, I have an EQ-3 with Vixen wooden legs. I have been tempted to try the RV-6s on it, they are quite long so even though the OTAs only weigh about 8lbs, they may be too much for the mount.

Anyway, 6 inch F/8 Newts are a real treat.

jon