Have been trying to get a chance to do a more thorough test of the 50mm f/3.8 CCD finder.
Finally had a cloudless night with somewhat reasonable transparency. Not great, but reasonable. I could see a decent number of stars with naked eye, but I was not able to easily see the principle stars of Cygnus.
The main challenge for me was to avoid the distraction of just looking around because it has been weeks since I have had even half way reasonable conditions. The Milky Way was of course quite stunning. One of the top five nights since owning the Mod 3 binocular, so I had trouble pulling myself away from the Mod 3 at 1x and 3x.
I did not like using two of these CCD finders for the Mod 3 by the way.. There is just enough play in the mounting of the Mod 3 pods that the very long CCD finder tubes don't stay collimated unless I further flex the pods against the bridge and I just don't want to do that.
Perhaps I can find a "Natural" alignment for the tubes (maybe rotating and marking them) where they settle at the correct angle, but for now, I am simply using the PVS-7, which is kind of sad because I bought them for the Mod 3.
That being said, even the PVS-7 views of the Milky Way were very sharp last night using 1x and 3x. In fact, last night, even the green Milky Way was simply crazy good!!!
I used the PVS-7 for the testing though because it was just easier to manage one lens when changing filters.
The lens is yielding about 7x.. Stars are not pinpoint sharp but they are decently sharp with the 650nm Deep Sky IR Pass filter. I have settled on this filter for most viewing because unlike the 680nm, you can still see Nebula with it and at f/3.8, the sky is already darkened so the filter does not seem to provide as much benefit as it would at f/1.2 or f/2.This lens puts up a view that seems to be better than my much heavier 200mm f/2.8 zoom when it comes to star sharpness. I tried a full aperture 680nm and stars did not appear any sharper, but again, stars were still decently sharp and much better than I had hoped for.
Even with just the 650nm IR Pass filter, I could quite easily see the shape of the Swan nebula and the Eagle was easily visible. The Lagoon was only just visible and the Trifid was only hinted at and only because I knew were to look.
The darker structure of the Milky Way is so large that it much of it does not stand out well at 3x, but I could see the texture of the folds and ripples pass though the field as I swept around. Very enjoyale!
H-a results were quite excellent! I have used a variety of SLR lenses with more aperture and I had expected that the 50mm f/3.8 would struggle to show these nebula very well, but I am more than ever convinced that my older zooms are simply not passing light as efficiently as this little cemented doublet.
The lens put up a quite excellent view of the Logoon and Trifid that I don't think has been matched by my f/2.8 zooms. There was considerable structure and extension and the nebula really popped out from the starry background. With the H-a, stars are very sharp.
Even at 7x, the Trifid was big enough and shown well enough that I could see one prominent and irregular lane, but to small to resove the smaller branches.
Now I can see much more structure in it with the Comet Catcher, but here, the beauty (as with Peter's recently posted picture) is seeing both the Trifid and Logoon in the same true field.
Swan was also very nice. Even at 7x, the shape is quite well defined and I was able to see some of the knotting that follows behind and below the duck's tail. This was the best view I think I have had of the swan using any kind of attached, hand held lens. Small, but not at all difficult to see these kinds of details. Once again, better in the Comet Catcher, but you don't get the much bigger context of the rich stars around it (even with the H-a, there is a lot going on in the field).
Even North American was better than the 200mm f/2.8 zoom. I could see the shape quite easily and the Pelican was also visible but not nearly as good as with the 3x afocal lenses, and indeed this is one of those targets that looks utterly fantastic in the 3x lenses, and one of the reasons I am so attracted to those lenses.
I only have one H-a filter, so I can't really get the most out of the Mod 3 binocular, but I am going to fix that pretty soon.
I do very much like the helical focusers. Mine are kind of grainy, but my guess is that they will break in. it is very nice though to have such slow, precise focusing. In this kind of scope, even with filters, stars to not seem to have a very distinct best focus, so I have to rack back and forth a bit to find the smallest blur diameter, and the helical focuser makes that pretty easy to do. (With H-a, star focus is very precise by the way).
I am very pleased with this lens vs the SLR lenses I have been using. Stars are sharper and in spite of the slower focal ratio, it seems to do as well or even better on nebula. There has to be some amount of transmission loss and absorption on these older SLR zooms. My result has been much better than I had expected as far as Nebula go, and stars are indeed sharper.
My guess is that if I could afford a very fast 200mm ED lens, I could get a better result, but for now, I am getting a really pleasing performance, so I am going to stand pat for the time being.
An excellent buy in a longer hand held lens. These sell for about $80, and this would be money well spent for most PVS-7 owners that don't want to tie up a lot of money in a super fast long focus ED lens.
Edited by Eddgie, 06 September 2016 - 08:45 AM.