Mariusz, Mark,
Just for clarification, the Kowa DA10 outer sleeve thread is 61mm or thereabouts. 61mm step rings are hard to find, so you're forced into either buying one of Kowa's AR rings or having one custom made by, for example, SRB Griturn (see above).
The filter thread on the Nikon 11-27.5mm and 10-30mm lenses is 40.5mm. Unfortunately, Kowa don't make an AR40.5 ring, and so the options are to either have one custom made as described above, or buy a larger Kowa AR ring and use that in conjunction with a step ring to get to the required 40.5mm.
An advantage to using a Kowa AR58 in this way, rather than, say, an AR52, is that the AR58 is wide enough to become a mere extension of the DA10 outer sleeve and thereby allow close placement of the lens to the eyepiece. Conversely, if you used an AR52 along with a 40.5-52mm step ring you might find that the presence of the AR52 would prevent the lens being able to get close enough to the eyepiece, ie by not being wide enough to slip over the inner sleeve of the DA10.
Re. the 18.5mm lens: I haven't got it but I believe it has a 40.5mm thread as well, and is suitable for digiscoping. I read that it's Neil's current favourite lens for digiscoping with the V1 and V2.
Another thing to consider with the zoom lenses on an angled scope is zoom creep. To prevent this, I use a bit of plastic cut from an old pill bottle which fits around the inner barrel of the lens when extended. Others use elastic bands for the same purpose.
Hope this all makes sense. It's not as complicated as it might sound.
David
