TS and Orion US bino viewer - zero backfocus, no corrector needed

[25585]

https://www.amazon.co.uk/Orion-Premium-Linear-BinoViewer-Telescopes/dp/B07CG8GBL8/ref=sr_1_31?ie=UTF8&qid=1528288991&sr=8-31&keywords=diagonal+correct+image

 

 

TS model looks the same

 

[Highburymark]

I looked at one of these - interesting product - also available under other brands - I think for a fair amount less than £440. Not the most beautiful of designs but it offers something new

[Merlin]

Some years ago, I made a similar binoviewer, which I still have, using a 50/50 mirror beam splitter and three first surface mirrors from redundant SLR cameras.

The budget binoviewer works, but produces a ghost image to the left of the main image. This matters with bright starfields, as it doubles up on the number of stars in the field, but the viewer is okay on the Moon and planets because the ghost image doesn't intrude directly on the main image.

The ghost reflections originates from the uncoated surface of the beamsplitter and is quite faint. Question: how does Orion avoid a ghost image in its mirror-type binoviewer?

 

[25585]

Just arrived today, I bought the cheaper TS pair (well half as my brother part-paid as a birthday present).h

These red & black jobs are what Baader's new Maxbrights will be competing against I reckon. It will be interesting to see if Baader design a pair with the same zero backfocus etc.

[25585]

23 minutes ago, Merlin said:

Some years ago, I made a similar binoviewer, which I still have, using a 50/50 mirror beam splitter and three first surface mirrors from redundant SLR cameras.

The budget binoviewer works, but produces a ghost image to the left of the main image. This matters with bright starfields, as it doubles up on the number of stars in the field, but the viewer is okay on the Moon and planets because the ghost image doesn't intrude directly on the main image.

The ghost reflections originates from the uncoated surface of the beamsplitter and is quite faint. Question: how does Orion avoid a ghost image in its mirror-type binoviewer?

 

TS page says mirror & lenses combination for their branded model. But only 22mm field stop.

[Louis D]

Also sold by APM as Tecnosky Horizon.  Here's the internal light path diagram:

CN had a discussion on it and the Orion some time back.

I also see that Orion has a 1.25" Pentaprism Diagonal with an optical path longer than a 2" dielectric diagonal.  I wonder if anyone has tried it out yet to see how it compares to the typical Amici prism correct image diagonal.

[25585]

On 06/06/2018 at 14:31, Louis D said:

Also sold by APM as Tecnosky Horizon.  Here's the internal light path diagram:

CN had a discussion on it and the Orion some time back.

I also see that Orion has a 1.25" Pentaprism Diagonal with an optical path longer than a 2" dielectric diagonal.  I wonder if anyone has tried it out yet to see how it compares to the typical Amici prism correct image diagonal.

Thanks Louis. A no-fuss bino viewer & suitable for Newtonians especially, has a big appeal. I'll read those threads with interest.

Orion guy in the video

Says the lenses are Lanthanum, mirrors are dielectric coated & that an Orion pentaprism should be used for correct image as a diagonal inverts. The pentaprism video;

The pentaprism on its own inverts an image, so refractor & catadioptric users get the same orientation as a Newtonian user. Could be good as a finder diagonal for the latter scope.

https://www.telescope.com/Orion-125-Pentaprism-Diagonal/p/130301.uts

[AndyH]

i read about a similar pentaprism some years back, but my interest waned when i saw the quoted 120mm optical path. Looks nicely made though.

Here's the (in japanese)Kasai Trading page....

http://www.kasai-trading.jp/dxpentaprism317.htm

 

I look forward to folks opinions on these new types of binoviewers. They sound like an interesting design.

 

Andy

[Stu]

5 hours ago, Louis D said:

Also sold by APM as Tecnosky Horizon.  Here's the internal light path diagram:

CN had a discussion on it and the Orion some time back.

I also see that Orion has a 1.25" Pentaprism Diagonal with an optical path longer than a 2" dielectric diagonal.  I wonder if anyone has tried it out yet to see how it compares to the typical Amici prism correct image diagonal.

Thanks Louis. Interesting design, has anyone actually tried them out yet, any reviews around?

My concern would be complexity, things going out of alignment and possible loss of performance vs standard due to the increased number of air to glass surfaces.

@25585, would be great to hear your comments when get a chance to observe with them.

[Louis D]

Everyone be aware that they have only a 17.3mm clear aperture which is considerably less than the 22mm of most budget binoviewers.  Thus, don't expect to use these with eyepieces having large field stops.

[niallk]

Hmmm.  Interesting... very interesting.

Field stop ok for how I'd want to use them; would theoretically work in my Lunt 50mm and my 15" dob I think - both where my Maxbright BV is challenged.

Dammit, I feel temptation and I've been doing well in terms of no purchases this year! It would tip me back towards buying EPs too.

I saw these advertised under a brand name I didnt recognise earlier this year. Interesting to see the design being rebranded by Orion/TS: it must have merit!

I await your reports with great interest, @25585

[Merlin]

Ah! So the viewer uses a pentaprism beamsplitter. There's the difference. Mine has a flat beamsplitter, hence the ghost reflection from the back face.

[25585]

15 hours ago, Stu said:

Thanks Louis. Interesting design, has anyone actually tried them out yet, any reviews around?

My concern would be complexity, things going out of alignment and possible loss of performance vs standard due to the increased number of air to glass surfaces.

@25585, would be great to hear your comments when get a chance to observe with them.

I don't have those, just the conventional type. I did consider them, but for the price, I am not a commited bv user yet. Need more hours experience to decide.

[Stu]

1 hour ago, 25585 said:

I don't have those, just the conventional type. I did consider them, but for the price, I am not a commited bv user yet. Need more hours experience to decide.

Ah, ok. I read your post saying they had just arrived thinking, well, that they had just arrived  but I see you were referring to the standard TS ones

I think these are great for the money and have a pair currently. Let us know how you get on with them. Binoviewers can be a little like Marmite.....

[25585]

2 hours ago, Stu said:

Ah, ok. I read your post saying they had just arrived thinking, well, that they had just arrived  but I see you were referring to the standard TS ones

I think these are great for the money and have a pair currently. Let us know how you get on with them. Binoviewers can be a little like Marmite.....

Will do certainly ☺ I chose them on all the recommendations on SGL. They seem well made but not too heavy. No clear sky for a few nights but soon as there's a moon....

[Stu]

37 minutes ago, 25585 said:

Will do certainly ☺ I chose them on all the recommendations on SGL. They seem well made but not too heavy. No clear sky for a few nights but soon as there's a moon....

Excellent. Which scope to try them in first though?

[25585]

11 hours ago, Stu said:

Excellent. Which scope to try them in first though?

It will be my trusty TV Genesis, then Equinox 80. Using a pair of TV 40mm Plossls initially. I know those very well so can assess what effect the TS will have.

Large exit pupil light loss will be cut down noticably by bino viewers I presume.

[Stu]

33 minutes ago, 25585 said:

It will be my trusty TV Genesis, then Equinox 80. Using a pair of TV 40mm Plossls initially. I know those very well so can assess what effect the TS will have.

Large exit pupil light loss will be cut down noticably by bino viewers I presume.

Will you need a barlow or GPC to reach focus with these do you think? Which diagonal will you be using?

If you are try to use them natively then you will likely run into vignetting issues as the open aperture on the binoviewers is probably 23mm (?) and the 40mm field stop is 27mm

I do use 40mm Plossls (Celestron Omnis) in mine but use a barlow element to reach focus with the PST Mod. I don’t seem to see vignetting with this combination.

As for Exit pupil, if you are using them natively then I think you will still be losing light with an oversized Exit pupil even when binoviewing.

[25585]

1 hour ago, Stu said:

Will you need a barlow or GPC to reach focus with these do you think? Which diagonal will you be using?

If you are try to use them natively then you will likely run into vignetting issues as the open aperture on the binoviewers is probably 23mm (?) and the 40mm field stop is 27mm

I do use 40mm Plossls (Celestron Omnis) in mine but use a barlow element to reach focus with the PST Mod. I don’t seem to see vignetting with this combination.

As for Exit pupil, if you are using them natively then I think you will still be losing light with an oversized Exit pupil even when binoviewing.

I will try no Barlow to start with, but if one is needed have an Abbe 2x. Diagonal would be 2 inches until I find a good 1.25, looking for a correct image type to cover terrestrial use, but the Tak prism otherwise.

Both scopes I mentioned are 500mm, if the 40s have too large exit pupils in the bv, I can use Baader Eudiascopic 35s.

[Stu]

11 minutes ago, 25585 said:

I will try no Barlow to start with, but if one is needed have an Abbe 2x. Diagonal would be 2 inches until I find a good 1.25, looking for a correct image type to cover terrestrial use, but the Tak prism otherwise.

Both scopes I mentioned are 500mm, if the 40s have too large exit pupils in the bv, I can use Baader Eudiascopic 35s.

May take some experimentation but should work fine. Amici Prism will take more back focus though I think.

[Ricochet]

10 hours ago, Stu said:

I do use 40mm Plossls (Celestron Omnis) in mine but use a barlow element to reach focus with the PST Mod. I don’t seem to see vignetting with this combination

I would think there must be some vignetting. I can't think how a barlow before the binoviewer would change that. The 30/32mm (?) Plossls supplied with my binoviewer aren't 50° because the clear aperture doesn't allow it. I think you can use the approximation below to work out what will vignette: 

fl(e) x AFoV = 57.3 x CA 

[Stu]

1 hour ago, Ricochet said:

I would think there must be some vignetting. I can't think how a barlow before the binoviewer would change that. The 30/32mm (?) Plossls supplied with my binoviewer aren't 50° because the clear aperture doesn't allow it. I think you can use the approximation below to work out what will vignette: 

fl(e) x AFoV = 57.3 x CA 

You may be right, I will check properly next time. It has never been something which has troubled me though.

[25585]

14 hours ago, Stu said:

May take some experimentation but should work fine. Amici Prism will take more back focus though I think.

Is the Tak prism diagonal an Amici one? 

[Stu]

8 minutes ago, 25585 said:

Is the Tak prism diagonal an Amici one? 

No, just a standard prism.

[25585]

This one seems reasonably priced https://www.teleskop-express.de/shop/product_info.php/info/p291_TS-Optics-1-25-inch-Erecting---Amici-Prism---90----upright-andcorrect-image.html