102mm ED doublet vs C14

As a general rule, my Vixen ED102 f/6.5 rides my C14 to provide wide fields. I have occasionally seen it do other things that gave me pause. For example when watching a moon emerge from behind Jupiter on a night of poor seeing, the refractor seemed to do a better job of giving good definition between the moon and Jove right at the limb.

So I have gradually come to think that small scopes can indeed outperform big ones in bad seeing conditions.

But last Friday night The C14 trounced the 102mm on splitting Rigel. The seeing was poor. The refractor just wouldn't show the dim companion. I'm trying to figure out why. Maybe in bad seeing the dim companion star image gets smushed that the effective surface brightness of the seeing disk is diminished, enough that the small aperture can't pick it up? Maybe the brightness of Rigel would also diminish the contrast.

Anyhow the C14 showed a clean split. The C14 as a rule does pretty well with doubles, though I don't go double hunting often enough to have bagged any sub arc second specials. Izar was virtually unsplittable later that night by either scope. On Rigel I pushed the refractor through a variety of magnifications from 40x to 180x.

Both scopes were thermally equilibrated obviously the C14 takes longer to cool than a 4" doublet.

Thanks for any insights,

Greg

Greg: You experience is similar to mine... Rigel is a favorite and I will give it a go several times a night most anytime it is visible.

With a scope 8 to 10 inches or larger, it really doesn't seem to matter how bad the seeing is, the companion will be there. In the late fall with Orion rising in the early evening, I have to wait for it to clear the backyard fence, but even with a scope that is cooling and Rigel near the horizon, the companion is there, strong and steady.

Sometimes I chuckle when I am out there with my 12.5 inch F/4.06... The image is far from stable, Rigel is swirling flashing, no way I tell myself, but the secondary is there, waiting. Sometimes I get a good split before it has completely cleared the fence..

With a refractor, my current 4 inch is an NP-101, there is no doubt it takes better seeing... the secondary is not so bright, it's a tiny spec, and any disturbance seems to cause problems...

But the main thing... you had clear skies

Jon