2” eyepieces with a 66mm scope

[RobertI]

My 66mm Zenithstar comes with a 1.25” visual back but can take SCT accessories. So I wondered, if I fit my SCT 2” diagonal, could I also use my Panaview 38mm 2” eyepiece without vignetting? So I set it all up and was delighted to see it reaches focus and there doesn’t seem to be any vignetting. This gives 10x magnification and an expansive 7 degrees. The downside is an exit pupil of 6.5mm which might be a bit on the large side. But it will be an interesting experiment to compare this setup with my 10x50 binoculars and see how the views compare. My guess is I will prefer the binoculars, but we’ll see! I have to say the combination of tiny scope and huge diagonal and eyepiece is slightly comical. And it’s pretty damn heavy now too. 
 

 

[dave34]

It looks like a small bundle of fun to me, i think i want one.

[Stu]

Snap @RobertI, I used to do exactly the same with mine! This was back in October 2013. I actually prefer the views through a widefield scope. Having the 90 degree diagonal helps with viewing comfort, and the views through a decent scope/eyepiece tend to be better edge correction than most binoculars. Have fun!

EDIT you don’t really need a finder with your combination! 😀

[RobertI]

2 hours ago, Stu said:

Snap @RobertI, I used to do exactly the same with mine! This was back in October 2013. I actually prefer the views through a widefield scope. Having the 90 degree diagonal helps with viewing comfort, and the views through a decent scope/eyepiece tend to be better edge correction than most binoculars. Have fun!

EDIT you don’t really need a finder with your combination! 😀

That’s good to know Stu, I’m looking forward to using it. Yes, the finder is there because I was using this for EAA and needed a quick way of aligning. It actually makes a very useful handle! 
 

The Panaview and diagonal are very heavy but the focuser seems to be able to handle it ok and I always have the focus lock.

Edited November 29, 2022 by RobertI

[michael.h.f.wilkinson]

That is a lovely kind of set-up. I often use my APM 80mm triplet with a 2" Amici prism and the Nagler 31T5, yielding 5.3 deg FOV at 15.5x magnification. I did a comparison with the views in a pair of Helios Apollo 15x70 bins here:

The bins have the definite edge in portability, but the 80 mm triplet beats them for visual impact

[RobertI]

37 minutes ago, michael.h.f.wilkinson said:

That is a lovely kind of set-up. I often use my APM 80mm triplet with a 2" Amici prism and the Nagler 31T5, yielding 5.3 deg FOV at 15.5x magnification. I did a comparison with the views in a pair of Helios Apollo 15x70 bins here:

The bins have the definite edge in portability, but the 80 mm triplet beats them for visual impact

Thanks Michael, just read your comparison post - made interesting reading. I am not expecting the edge of field aberrations to be that good with the Panaview but daytime testing looks promising. I forgot that I have a 2” UHC so that could be fun on some larger emission nebulae - perhaps I’ll have a stab at Barnard’s Loop?

[Louis D]

For balance with heavy 2" eyepieces in my 72ED, I have to clamp the dovetail bar almost directly under the focuser knobs, so the scope is cantilevered on a long bar.  The other problem I have is the focuser slips under the 3+ pound 2" load despite cranking up the focuser default tension screw under the pinion and roughing up the flat of the focuser tube.

[RobertI]

19 minutes ago, Louis D said:

For balance with heavy 2" eyepieces in my 72ED, I have to clamp the dovetail bar almost directly under the focuser knobs, so the scope is cantilevered on a long bar.  The other problem I have is the focuser slips under the 3+ pound 2" load despite cranking up the focuser default tension screw under the pinion and roughing up the flat of the focuser tube.

Thanks Louis, this “extreme” setup is not without its problems it would seem. The balance point in mine is actually further away from the focus knob, at the end of the silver dovetail - I think the added weight of the rings and the finder help to move the balance point forward. I’ve never been a fan of the focuser on this scope, but I adjusted it recently and it seems to be holding the load ok - the test will be in the field of course.

[Stu]

I remember having similar problems to @Louis D at the zenith, I had to support the eyepiece from underneath to maintain focus! It was ok at lower altitudes though.

[Highburymark]

Nice set up Robert!
I love widefield views with small refractors. Don’t have a 2” diagonal anymore, just T2 prisms and mirrors - but still see sharp field stop with 60ED/APM 100 degree 20mm and Panoptic 27mm, my only two 2” eyepieces.

[RobertI]

Thanks Mark - a 100 degree eyepiece with a 60mm scope - that must be a nice wide field! 

[Louis D]

1 hour ago, Highburymark said:

Nice set up Robert!
I love widefield views with small refractors. Don’t have a 2” diagonal anymore, just T2 prisms and mirrors - but still see sharp field stop with 60ED/APM 100 degree 20mm and Panoptic 27mm, my only two 2” eyepieces.

Which end do you look in? 😁

[Don Pensack]

Many years ago, I did a review of a telescope that people also asked which end to look through.

It was an 80mm refractor designed to be usable ONLY with binoviewers (and could be used without the OCA).

 

Edited November 30, 2022 by Don Pensack

[RobertI]

32 minutes ago, Don Pensack said:

Many years ago, I did a review of a telescope that people also asked which end to look through.

It was an 80mm refractor designed to be usable ONLY with binoviewers (and could be used without the OCA).

 

Interesting. Was that a commercial scope or a DIY project Don? 

[Louis D]

Sounds a bit like the Tele Vue Bizarro, except that it was an 85mm scope.

[RobertI]

19 minutes ago, Louis D said:

Sounds a bit like the Tele Vue Bizarro, except that it was an 85mm scope.

Not come across that one before, seems like a great concept to me. Not sure about the name though!

[Don Pensack]

5 hours ago, RobertI said:

Interesting. Was that a commercial scope or a DIY project Don? 

It was a William Optics short tube 80mm scope

From 2006:

https://www.cloudynights.com/articles/cat/cn-reports/telescope-reports/cn-report-william-optics-zenithstar-80-st-r1390

Edited December 1, 2022 by Don Pensack

[Louis D]

Wow, that scope seems to have been massively overpriced for an 80mm f/6 achromat with single speed 2" focuser by 2019 pricing standards.  I would have thought it would have had ED glass for that price.

[RobertI]

12 hours ago, Don Pensack said:

It was a William Optics short tube 80mm scope

From 2006:

https://www.cloudynights.com/articles/cat/cn-reports/telescope-reports/cn-report-william-optics-zenithstar-80-st-r1390

Thanks for the link Don. A nice idea by WO but poorly executed in some places by the look of it. It’s interesting that the binoviewer can be used without the GPC in this setup. The Bizarro referenced by Louis includes an inbuilt correcting lens that Televue claim is essential to prevent aberrations from the prisms, or something like that. Neither product seemed to last, perhaps the price, getting into bino-telescope territory?

[Don Pensack]

11 hours ago, Louis D said:

Wow, that scope seems to have been massively overpriced for an 80mm f/6 achromat with single speed 2" focuser by 2019 pricing standards.  I would have thought it would have had ED glass for that price.

Huh?  $699 included the binoviewer, scope, diagonal, minus violet filter, OCA, 2 eyepieces and a case.

That is cheap even by today's standards.

[Louis D]

I was referring to kit #2:

2) Kit with OTA only (1-speed focuser) $328

That seems high by 2005 standards for a fast achromat with a single speed 2" focuser.  Generic ST80s were going for about $100 or so with a 1.25" single speed focuser.  I can't imagine a 2" single speed focuser added $228 to the price.  When I started reading the review, I had assumed it had ED glass to account for that price increase.

[Don Pensack]

Louis,

The only one near $100 was the Orion Short Tube, but the William optics scope I reviewed was higher end in every way--finish, optical correction, focuser (rotatable!), lens, etc.

Back in 2006, it wasn't considered essential to have a 2-speed focuser on f/6+.  It still isn't, though that is the way the market has gone.

The William Optics Zenithstar series had an ED lens and that was well known at the time.  ED wasn't considered a big thing to advertise.  William Optics called it a 'semi-apo' because no 2 lens scope can be truly apochromatic.

Today's Zenithstar II 80mm has an ED lens and is $679.   That price also got a binoviewer, diagonal, 2 eyepieces and a minus violet filter back then. 

Most 80mm ED refractors of quality back then were $699-$799 with an occasional one at $499 on sale and $399 on closeout.  I never saw a quality scope for $100, and the company I worked for at the time sold a LOT of refractor scopes.

 

[Franklin]

I've been reading this thread with interest, as I have a similar set up and it doesn't disappoint for super low power, widefield viewing.

I drove this little rig out to the Peaks in the summer and scanning through the Cygnus region was awesome, a 2" Baader UHC-S in the nose of the diagonal worked well too.

 

[RobertI]

7 hours ago, Franklin said:

I've been reading this thread with interest, as I have a similar set up and it doesn't disappoint for super low power, widefield viewing.

I drove this little rig out to the Peaks in the summer and scanning through the Cygnus region was awesome, a 2" Baader UHC-S in the nose of the diagonal worked well too.

 

Very jealous of your lovely little Vixen scope, I think that combination must be getting on for 8 degrees FOV? 😲

Edit: Just worked out it's closer to 10 degrees!

Edited December 2, 2022 by RobertI

[Franklin]

21 minutes ago, RobertI said:

Just worked out it's closer to 10 degrees!

9 or 10 degrees? It all depends on whether the LVW 42 is taken as 72deg or 65deg. Mine is the older version and has 72deg printed on it but the more recent versions have 65deg?

Either way it's very wide and with a magnification of only 7x the exit pupil is 7.7mm, so it really needs a dark sky. There is some unavoidable curvature towards the outer of the field, but the views are stunning, nonetheless.