Whatever happened to RFT's ?

[Wavytone]

Watching the current vogue for small fast refractors (4" f/7 or thereabouts) and big dobs, I have noticed no-one mentions Rich-Field Telescopes these days - the ideal weapon of choice being a 6" f/5-7 Newtonian.

One reason I suspect the "grab & go" refractors are popular is they are coming close to the parameters identified 50 years ago in the ATM books which result in maximising the number of stars you can hope to ever see in a single field of view. A 150mm f/7 Newtonian or APO f/7 refractor with say a 2" 40mm widefield eyepiece would be about the ideal, I suspect.

So - I'm curious - does anyone bother with RFT's these days, or not ?

[Starkler (Geoff)]

RFT's are at their best in dark skies, and as time goes on , less and less people are living under them.

[Wavytone]

Mmm... still doesn't make much sense... sky background detracts from all extended objects and the effect is pronounced in all fast scopes - in that respect we should all be using scopes round f/10 or slower to so that we have a maximally dark background in the eyepiece.

All the dobs at f/5 or faster will be equally disappointing in anything less than a very dark site...

... so why are the vendors all pushing f/4 to f/5 Newtonians, when they're a fairly poor choice in urban skies ?

Hmmm..