Today, setting up my C8 again for some comet hunting I tried even harder for stars in daylight and set a new benchmark! As a hint I've now managed to see all 8 planets during the daytime
The seeing and transparency seemed quite good - although a bit of haze in the west - and I could plainly see Jupiter and its 3 brightest moons around 5:30pm. Mag 6.5 callisto was a bit harder, especially since it was well away from Jupiter itself, but once found it was seen with ease.
However, with the sunset getting closer I decided to go for a harder target, mag 7.9 Neptune! I centred the scope on a nearby mag 5.9 star, which was plainly visible, and at that point - judging by how easy the star was to see - I went for the planet. To my amazement at 6:10pm I succeeded in finding Neptune! From my location I calculated the centre of the sun to be 0.5 of degree above the horizon and local sunset to be around 2-3 minutes later.
NOTE: I am going to try to make a metal pointer/reticle at the field stop in the eyepiece (this allows the eye to be trained more readily at infinity) so perhaps its possible to see fainter still
Terry