Some weeks ago I bought, at auction, a 60mm refractor c/w a sturdy-looking equatorial -- it looked like it had been run over by a tractor, but I paid what I think a 60mm refractor is worth --UKP5 (about $8). Having straightened and cleaned things, I decided to try to improve the transmissivity of the unbloomed objective by replacing the air (& 3 spacers) with thickened cedar oil.
The first attempt was a disaster -- owing entirely to my attempt to mate the crown (biconvex) with the flat surface of the flint (plano-concave). Having eventually realised why the oil was refusing to stay near the edge of the doublet, I cleaned the flint and tried again.
The result is better than I had dared hope -- everything is _so_ much brighter. We'll have to see what transpires over a couple of seasons -- it's blissful unremitting heat-wave (in UK terms) at present -- winter should show if it's going to do anything untoward.
I realise 60mm is not exactly representative, but it has given me enought confidence to try it with the 112mm I am working on at the moment.
Clear Skies, Steve <sft@aegis1.demon.co.uk>