Hi Sancho, I went through the same thing a few years ago when I got my ATS 80HD.
I did a bit of research and found that someone in the US had posted on BF about his quest to find the best high mag eyepieces for his (same) scope. Based on his findings I bought the Swaro Astro adapter (now no longer in production) and a used 5mm Televue Nagler eyepiece from Ebay.
This eyepiece gives 92x on the 80mm body, which is useable in good light, but a stable support is needed to get the best from it, with no wind to cause vibrations. If it is windy, forget it. Accurate focussing is also very critical at this mag, but when sharp it is very sharp, just as Swaro's own eyepieces are. FOV is a wapping 82 degrees I think, but to get this you have to press your eye so tight up against the lens that it's uncomfortable. Eye relief of this EP is very short! Too short for my comfort, and the exit pupil is very small.
To calculate the mag of an astro eyepiece on a terrestrial scope, divide the focal length of the body by the FL of the eyepiece. In this case:
460mm divided by 5mm = 92x
If you wanted something less powerful then a 6mm eyepiece would give 76.66x, and so on.
If you wanted to go down the same route, then you'd have to acquire a used astro adapter if possible, or talk to someone like SRB Griturn, or perhaps knock something up yourself! I remember reading somewhere on BF about someone making an astro adapter for their Kowa 88mm using plastic tubing.
A couple of things to bear in mind though:
Some astro eyepieces will not focus to infinity on the Swaro scope
I also tried a Baader 5mm, but returned it very quickly-didn't find it as sharp as the TV
Televue also make a range of Radian EPs, with longer eye relief, but I'm not sure if they reach infinity focus on my/your scope
Henry Link (I think?) also recommended the TMB Planetary eyepieces, which are much cheaper than the TV ones, but I'm not sure how well they work, if at all?
Lots to think about, and to be honest, I only use my TV eyepiece rarely. I have the 20-60x zoom which I find enough for 99% of occasions, but with max 50x I can feel your need! Ace Optics of Bath have an astro dept and sell some of the TV eyepieces I mentioned. They might be able to help you out re. which eps will work, as they also sell terrestrial scopes like yours.
Best of luck, and do ask if you have any more questions.
Steve
I presume you saw this thread already:
http://www.birdforum.net/showthread.php?t=190087