Adrian,
Myself, no I have not tried the Pentax 20X60 SP binos. I have tried another set of binos that was also 20X, and from that experience I can only share a word of caution.
Such high magnification binos are pretty much entirely a tripod situation. Hand held you not only need to rest your arm somewhere to have any chance of using them, and even then it will not be an easy proposition.
Such high magnification can make aiming the binos difficult. The field of view is also very narrow, 2.2deg from what I've been able to find about these Pentax ones. Remember the higher the magnification, the narrower the field of view will be. This was the main aspect of why I didn't like the 20X binos I did use. Binos are a different proposition from a telescope - they are supposed to be for rich field view in astronomy, and the narrower the field of view, the less of the sky you actually get to see.
Astro is not all about magnification! This is a trap most new players fall for! Many times when using my scopes for deep sky objects, I'm pushing the lowest practical magnification I can get from any given scope of mine. The use of high magnification is not best in most instances, with many conditions dictating how high you can go and why. Binos are in a way the opposite, in that high magnification is not what you want! Instead, high mag binos are a more specialized niche of binos use, and not one I honestly would recommend for someone new to astro.
In all sincerity, I would advocate you look at a set giving between 7X and no more than 10X for a couple of reasons:
1, It will be much easier to aim the binos. Even on a tripod set up (more talk about this later!), lower magnification is a lot bloody easier to aim, and when panning it is much easier to find your way again if you lose you way across the sky.
2, If the astro bug does not bite, binos in this range of magnification is MUCH easier to use for terrestrial, with high magnification being just too impractical
3, You won't see more. Not for you any time soon. High magnification is just too specialized, they really are.
The binos I have now are 11X70. Before them it was a 10X50 set that I had for many years until my kids dropped them one day - crap happens. When looking for a replacement set I looked at a 20X80 set, yes much bigger in size than 20X60, but the bulk was not the killer issue, it was entirely the 20X magnification - just wayyyyy too much to be practical. The set I settled on ended up being the best compromise for larger aperture from the 50mm I had to something that was both more manageable when holding them by hand (20X is next to impossible) and a field of view that was also practical and useable - 20X is too narrow and just too specialized.
I have looked through larger astro specific binos too, 25X100 and larger that friends of mine have. The views these instruments provide is gorgeous, no doubt, but it has not made me reconsider getting high mag binos...
As for a tripod mounting, the often sold "bino tripod adapter" is bloody aweful and actually dangerous for astro!
These put the binos way above the pivot point of the tripod head, meaning that when you want to view something high up in the sky, you need to put a huge amount of torque on the head clamp to stop the binos from tipping back, an the higher you aim the greater the torque/force you need to exert on clamp, which does not do the clamp any good, and leaves the binos susceptible to tipping back and even tipping the the tripod over if the do fall back with some force.
These bino adapters are fine for terrestrial viewing, but not for astro.
A much better solution for astro is a simple little rig made from a strip of plywood! The binos are attached not on top but slung underneath the plywood strip. This places the binos in line with the altitude pivot of the tripod head, meaning there is no undue force placed on the tripod head and the clamp would need bugger all tightening up. In fact, with the rig I made I leave the clamp totally unengaged/open and I can freely move the binos and they remain nice and steady for me.
There are more complex bino holders, but these are more expensive and significantly larger, but they do work very well.
Whatever tripod system you do use, you will need to be seated for astro.
Alex.
PS: to give you a further idea of a field of view comparison with 20X60 binos, the pics of the sketches below, 20X60 binos will produce an image "hole" roughly of half the diameter of the sketches. You now begin to see how you are actually losing the broader detail by increasing magnification. Higher magnification binos are very much a niche instrument, not one I would recommend for newcomers to astro. Using high mag binos is a lot more complicated than just sticking them on a tripod too.
Alex.