A match made in heaven...Genesis and 31mm Nagler

[Arneb]

@Stu I hope to one day as I'm sure it would be a wonderful pairing and I feel almost duty bound to make it happen. The 34mm and 40mm Maxvisions are doing sterling service in the meantime. The ES92 17mm and NP101 is a special pairing too. Certainly enough to keep me out of the clutches of the Ethos range, for now at least.

And here's one of the 90s ads with images similar to those I found so enticing:

https://televue.com/televueopticstalk/wp-content/uploads/ST_1995DEC_p2_GenesisSDF_RenaissanceSDF_Pronto.jpg

[Stu]

18 minutes ago, Littleguy80 said:

Great combo, Stu and fab report. I debated more than once on the big Nagler. Originally I plumped for an ES82 30mm which I did really like. It was quite a big heavy beast though. Recently I sold the ES and got an APM UFF 30mm. It’s really nice and light and gives a 4.2 degree FOV with my 80mm refractor. I think the lightness of the APM makes it a better match to the little frac. One thing that helped with my decision to sacrifice some FOV was the AERO ED 40mm I have. Again, very light weight for a 40mm eyepiece. It gives a nearly 5.5 degree FOV with the refractor. Both of these are great for sweeping across star fields or observing big objects like the Veil.

Long story short, I completely agree that the wide field views from these eyepiece and little fracs are something to be treasured  

Looks like an excellent choice Neil, and as you say, much better suited to a smaller frac. The Genesis is actually reasonably heavy so the big Nag feels quite ok in it.

One thing I don’t quite understand is how eyepiece performance can be described in isolation from the scope it is being used in. Ultimately a short focal length scope will have more field curvature than one with a long focal length, so an eyepiece optimised for one surely can’t work as well in the other? I think that’s why I was careful to say the Nag worked well in the Genesis, and just that the ES 30mm wasn’t as good in the Genesis from that perspective. It will likely perform well in a scope with different field curvature characteristics.

[Captain Scarlet]

21 hours ago, Stu said:

I do think so. I almost felt like a bit of a gooseberry! 🤣

If you’re really lucky they’ll breed and you can retire selling off the offspring!

[Louis D]

14 hours ago, Stu said:

Which scope is that in Louis? As I understand it, scopes and eyepieces have curvature, so the best results are where these cancel each other out. If they reinforce then results can be bad.

The Genesis is a Petzval, and well known for a flat field, so I assume the 31mm Nag has a flat field too. There is some discussion elsewhere about the longer focal length Pentax XWs. I’ve seen a number of reports of field curvature in them, but do wonder if that is because they are designed to counter FC in shorter focal length spotting scopes, so are less good in longer focal length scopes?

That's in my AT72ED with TSFLAT2 and 8" Dob with GSO CC.  The 30mm APM UFF is also dead flat as well in both.

By way of comparison, the 30mm Wide-Field III clone has loads of field curvature in either.  I once moved it well back from the diagonal in the AT72ED with a 2" extension and racked in my focuser to overcompensate the field flattening, and then the 30mm WFIII had a pretty flat field and just residual astigmatism at the edge.  It's a shame it doesn't have a built in field flattening element at the bottom because it would actually make a pretty decent 80 degree eyepiece.  I was able to achieve similar results for my 14mm Pentax XL with about an extra inch of spacing.

Edited April 15, 2021 by Louis D

[Louis D]

11 hours ago, Stu said:

I think the Genesis came first Chris, they were produced between 1988 and 1993 I think. There is a nice history here:

http://www.company7.com/televue/telal.html

The Nag 31mm came along in 1999 apparently.

http://www.company7.com/televue/index.html

 

Here's Tele Vue's own history table documenting the introduction (but not discontinuation) of each product.