Stratus vs. Expanse?

To be used in an 8" f/6 Dob. I can get the full set of Expanse EPs for less than the cost of two Stratus EPs.

I've owned Naglers, Pans, and Pentax XLs and loved them all, but now I'm trying to take a much more modest approach to this hobby. Casual observing only.

Also, am I correct that Hyperion EPs' are pretty much the same as the Stratus, and that Antares W70s are the same as the Expanse? Any reason to favor one brand over another?

I'm thinking that I'd be best equipped with three pieces... 21mm for sweeping, 12-13mm for 100X, 5-6mm for 200X. I am leaving out 8-9mm which is a nice fl as well in an 8" Dob. That's why I lean towards the Expanse... I can get the whole lot for $200... Hmmmmm.... I hate these decisions.

Thanks,
Dave

Dave:

This is my thinking/experience. Over the years I have owned the 6mm, 9mm, 15mm and 20mm Expanse/W70's/Whatever and some I have owned more than one example. I also owned a 13mm Stratus.

Expanses: The 15mm and the 20mm seem much like Erfle's I have owned, quite good at F/13 but poorly corrected at F/6, the edge is just nasty. The 6mm and the 9mm are "negative-positive" designs, they have Smyth/barlow-like front section so they are quite well corrected at the edge even at F/5. Unfortunately both examples of the 6mm I owned were soft and had serious ghosting. That leaves the 9mm which IMHO is a real winner, definitely worth owning. I have measured the effective AFoV via Drift Timing at 70.5 degrees, it is really quite Nagler-like. I has quite ample eye relief, it is definitely worth owning.

I suggest though you consider the TMB/BO Planetary Eyepieces. These are $59 and come in about every focal length you could want between 2.5mm and 9mm. They are quite similar to the 9mm Expanse but with a 60degree AFoV and a nice twist up eye cup. Great values, I currently own the 4mm, 6mm and 9mm, and they are good planetary as well as all-around eyepieces.

For the longer focal lengths, well that's a problem IMHO. I was not happy with the 13mm Stratus. It is a big eyepiece, about the 16mm Type 2 Nagler, it does have good eye relief and provides a nice "big field of view" because of the eye relief and the generous field lens. But I was quite dissatisfied with the edge correction. The eye piece is quite sharp in the center but about 2/3-3/4 the way to the edge, the stars really become distorted, quite rough looking. And this is not just in an F/5 Newtonian but very noticeable in an F/7 refractor. Everyone description I have read notices this. The edge of the field also shows a bright background, I found this particularly distracting.

Since it was about the same size as the 16mm Type 2, sometimes I would put the 16mm Nagler in the focuser instead of the Stratus at which time I would tell myself: "This eyepiece is really quite good, sharp to the edge, no bright ring, I must be seeing things." Then I would dawn on me I was not looking through the Stratus.

Now obviously a Stratus is not a Nagler, even an old Nagler, but to my eye the flaws were sufficient that I would suggest looking for something else, maybe something with a narrower field of view, a used 32mm TV Plossl or Ultima. Or maybe an inexpensive 30mm GSO SuperView for scanning and a decent something in the 18mm range...

Others certainly will have different experiences and thoughts... Many seem to be happy with the Stratus/Hyperions so a combination of the Stratus with the TMB/BO's might be the ticket.

Jon