My review of the reducer II and III on the M90 and ZS66SD
- Hi folks,Haven't posted in a while here, but have tried to keep up with what's been going on. I ended up taking delivery of one of the first units to ship here (kudos to Daniel and William for a record shipment from China - 3 days!!). However, weather and work have conspired against me, I was determined not to post until I tested both scopes and both reducers. Well, here's my impressions of the new reducer and a mini review (with pics):First off, the desing of the new reducer is very clever! The nosepiece comes off like before, but now there is also a ring from sct thread to a larger thread. Daniel informed me the larger thread is to accomodate the larger focusers and cameras. Very nice I would say, because it uncovers the rest of the lens, which is much larger than before. The whole assembly actually is larger (but not longer) than the V2 reducer.
The version 3 definitely has improved vignetting... actually, none you can detect in a photo unless you do pixel peeping. To me that is good enough, the rest is easily corrected with a flat. I honestly don't see how anyone would fuss about vignetting with aps chips and this reducer.
Star tests. First one I tried was the Megrez 90FD. The pics I have are original, untouched, full size jpegs. They're pretty large, around 5MB each, so beware looking at them through a slow connection. Click on the magnifying class for the full version btw.Here is the star test using version 2.
And here is using version 3:
Aside from the small shift in the image (my fault) the images show
very similar star fields. The old version 2 overcorrects a little
bit, while the version 3 seems to undercorrect slightly and also shows
a little astigmatism. I think, and I may be wrong, that one or 2 mm
of spacing might make the v3 perform better. All in all, I give the
v3 a slight advantage, since the corner stars, although oddly shaped,
are better aligned when stacking than the v2 oval ones. I use
DeepSkyStacker to do my stacking, so it is possible it is more of a
function of the stacking program than the quality of the stars.
Nevertheless, the improvement is enough for me to say it is a keeper.
Second test I did was on the ZS66SD, and this was really a big surprise to me. Daniel has mentioned several times that the V3 reducer was not ideal for the shorter focal length scopes like this one. The surprise to me was that it actually performed better on the ZS66 than it did on the M90! :o Here are the two pics to demonstrate:First off, the old V2:Second, the new V3:First off, I have been having an on/off issue with the V2 reducer not staying flat in the focuser. Dont know why, and in this instance it did it again. As you can see, the bottom of the V2 image shows a bit out of focus. Still, you can see the overall distortions around the edges, showing still some field curvature combined with a bit of coma. The V3 image is very impressive though. First off, it actually shows improvement in vignetting. That is very good news. Second, the edge stars, although showing a bit of overcorrection, look much better than the V2 edge stars. Personally, I find the results from the V3 reducer to be overall better as far as the Zs66SD is concerned.One more thing of note. The V3 reducer requires 2.5" longer focuser travel then the V2. I see this as another advantage, because it makes it suitable even with longer tube scopes. With the V2, there's not a whole lot of focusing room when it's mounted on the ZS66. With the V3, the focus is right about in the sweet spot, with plenty of clearance either way. Very nice extra touch.Well, that's my mini review. I think the V3 is a keeper for both scopes, while the V2 will shortly go for sale.Thanks and clear skies,Daniel