William Optics Zoom II 7.5-22.5 mm: First impressions

[michael.h.f.wilkinson]

I am still on sick leave (some bug causing headache, fatigue, slight nausea and a sore throat), but as a consolation I was at home when the postman brought a William Optics Zoom II 7.5-22.5 mm I had got from ABS-UK. It had caught my eye, because clones of it (Astro-Professional or Omegon Flat-Field zoom) claimed an eye relief of 18-19mm. As I had sold the second-hand Lunt zoom (7.2-21.5) because of its short eye relief (14-15mm: fine for most, too short for me with my glasses), this was an excellent opportunity to enter the world of zoom EPs mainly for solar use (without breaking the bank).

The EP came with original box, caps and all paperwork, and the only sign it had been used at all were some slight marks on the 1.25" barrel from the screw that holds it in the focuser. Big deal. It is a fairly big EP, but is surprisingly light, without giving any impression that it is flimsy. It feels more solid (and is a bit heavier) than the Lunt Zoom. I gave it a quick spin just now in the Lunt LS35, and the views are very good, easily a match for thefixed focal length EPs I tried, except for some slight glare around the 17mm mark. At 14mm all the detail visible in the Radian 14mm was there, without any loss of brightness. At 8.5mm it compared well with the Pentax XF8.5, and at 20mm It fared nicely against the MaxVision 20mm. The only difference there was a slight internal reflection off a baffle. This light seemed to have entered through the eye lens, as it appear to e white, rather than red.

This is in fact very similar to my experience with the Lunt, with one big exception: eye relief. It might be a bit shorter than the rated 18-19mm, but it is certainly long enough for me. Well pleased. I will make a more full comparison later, but it looks like I have found my ultimate solar EP set: just one zoom. If so, the former ones may have to go

[Lorne]

Sounds a good first impression, I managed to pick up a pristine used one from the classifieds on here last August. I bought it, not for the advertised eye relief, but mainly to fill the gaps in my eyepiece set. I found over the past dark season it was my most used eyepiece along with my 28mm. This surprised me as I have always been happy with my Nirvanas and SPLs. No 82* views but for viewing the planets and singling out individual moon features the wide view isn't necessary. Very easy to use as the zoom can be quickly tweeked to keep the view crisp as the seeing conditions change. I wont be rushing to get rid of any EPs in my box though as I like my wide views of DSOs too much! 

[Pig]

Great review Michael, it seems you have found the perfect zoom

[Pete Presland]

nice review, sounds like it was made for the job! i am in  the market for a zoom for my PST so its nice to hear the opinion of other users of solar scopes.

[michael.h.f.wilkinson]

I also had a run in the APM 80mm F/6 in white light. The image was very sharp indeed, and there was little or no shift in focus over the entire zoom range. This was easier to judge in the APM than in the LS35 with its helical focuser.  An added bonus of the zoom in white light viewing is not having to unscrew the solar continuum filter from one EP and screw it back into another when swapping EPs. You can continuously adapt magnification without hassle.

I noticed some glare at the longer end, but not much more than the MaxVision 20mm. It is unsurprising that some glare occurs with such a bright target and multiple filters (ND + Solar Continuum)

[michael.h.f.wilkinson]

I have been using the WO Zoom with the LS35 on the light photo tripod with its rather more wobbly mount compared to the solid Vixen Great Polaris used in the first tests. This provided a better comparison with the Lunt Zoom in terms of eye relief. With the Lunt, the light tripod was unusable, because my glasses kept bumping into the EP, causing horrible vibrations. Using the WO Zoom, this happens only occasionally, and the light tripod is a viable option: not as good as the home brew alt-az, and nowhere near the Vixen GP, but usable nonetheless. Ideal for lightweight travel. Have not yet been able to use it on stars and planets.

[Christhorpe]

Can these still be bought brand new ? I like the William optic products but I haven't come across this before. Nice review.

[michael.h.f.wilkinson]

Can these still be bought brand new ? I like the William optic products but I haven't come across this before. Nice review.

These are no longer sold under the WO brand, though they still have it on their web page:

http://www.williamoptics.com/eyepiecesDCL/zoom2_features.php

as a discontinued product. TS do supply one that looks identical and has the same specs:

http://www.teleskop-express.de/shop/product_info.php/info/p1933_Flatfield-Zoom-7-5mm-to-22mm---1-25----8-Element.html

Astroshop.eu also have one under their Omegon brand, but that is more expensive

[Christhorpe]

Thanks for the information Michael.

[steph]

Thanks for this nice review ! I owned this zoom since 2007 and use it with small 80mm triplet APO and WO erecting prism : great terrestrial view, no CA , good ER and no distortion. I own also a Nikon NAV SW 14mm for WA viewing and this ocular isn't sharper at center, it's better at the edge, wider. I didn't notice internal reflexion with my setup.
Did-you try it for planets ?