The Zeiss Primo Star binoviewer

[spartinix]

A while ago I decided not to buy a modified Zeiss mirror-binoviewer.

 

As this model has been modified by amateurs for years I thought I'd give it a go myself.
I ordered one from a Zeiss dealer, but they can also be ordered here for about 360; model 415500-1401-000:
https://www.micro-shop.zeiss.com/en/uk/shop/search/binocular tube?page=3

 

Once received, I removed the 3 screws attaching it to the microscope deflector and
started to measure it up for designing the modification parts.

Initially I was only going to adapt the binoviewer on the telescope side only.
After all, microscopic eyepieces come highly recommended and the hassle of switching
eyepieces can be avoided by combinations of barlows, Powermates, Glasspaths or some
powerswitch system.

A few weeks ago I decided to modify it completely, as it was suddenly announced that this
binoviewer plays nice with 27mm fieldstop-eyepieces after all.

The telescope-side part arrived recently, it attaches to the original rotating ring at the back of the binoviewer.
No removal of parts needed, and no loosening and tightening of a set screw to rotate the unit.

The part has an internal M42x0.75mm 'T2' thread for most common accessories like 1.25" and 2"
nosepieces and various OCA's / GPC's.
The part has also an M48x0.75mm external thread which can accept M48 accessories, such as 2" extension
tubes (no undercuts!) for 2" focusers.
The adapter is 15mm in thickness.

The eyepiece-side parts, the eyepiece holder sockets; accept the common Baader T2/1.25" eyepiece holders.

These parts can get relatively expensive depending on the choice of material and finish IF you only
have one piece made at some CNC-service.
So, in a collective buying effort with some others I made the order for 5 pieces per modification part
and even at that quantity, the bulk prices for these kinds of small parts gets ridiculously low.

The prototype eyepiece holder sockets I received proved good, am now awaiting the actual parts.

Feel free to pm me for the design files if you wish to go diy on this one (no charge).

Some renderings of the complete model I made, with and without Baader Clicklock #2458100 1.25"/T2 eyepiece holders.

Edited January 24, 2021 by spartinix

[spartinix]

Some more pics and screenshots.
 

 

[Highburymark]

Very nice! Interesting to read about your modification.
I’ve recently bought a pair of Zeiss ‘apo’ binoviewers to replace my Mk V which sadly proved too heavy for my lightweight set up. Must say they are superb - very sharp, and transmission is excellent, and zero false colour even in murky seeing. 
Look forward to hearing about how your new binoviewer performs.

[spartinix]

They are indeed very good.
I've been using mine for a few months now, with microscopic eyepieces, and before, with a temporary homemade telescope-side photographc T-ring-adapter.

A binoviewer too heavy is where it all started for me.

[spartinix]

Baader-Zeiss Micro M42 Bayonet dovetail-ring connection to mount on the original rotating ring connection with three M3 panhead screws of 5mm length (first screenshot).

No binoviewer dissasembly required.

The main advantage is faster switching between mono and binoview-mode, in particular for refractors and SCT's, IF used with Baader Quickchanger, T2-diagonal, and Clicklock eyepiece holder(s) and Baader ChangeRing (also dovetail-ring) for mono configuration.

Baader has now introduced the M48 Quickchanger, ChangeRing and accessories;

https://www.baader-p...ter-system.html

Baader-Zeiss M48 Micro Bayonet dovetail-ring connection to mount on the original rotating ring connection with three M3 panhead screws of 5mm length (second screenshot).

PM for cad files.

 

 

 

[Louis D]

8 hours ago, spartinix said:

The main advantage is faster switching between mono and binoview-mode, in particular for refractors and SCT's, IF used with Baader Quickchanger, T2-diagonal, and Clicklock eyepiece holder(s) and Baader ChangeRing (also dovetail-ring) for mono configuration.

Not seeing it.  I just pull the 1.25" diagonal and 2" to 1.25" adapter and binoviewer with associated OCS/GPC bits for reaching focus out of the focuser and replace it with a 2" diagonal and eyepiece to switch between modes.  On my Dob, I just pull the binoviewer and OCS/GPC bits out of the focuser and put an eyepiece in its place.

On my Mak without OCS/GPC focus help, it takes forever to move the mirror enough to reach focus with just a diagonal and eyepiece after pulling out the binoviewer.  Thus, I don't switch modes on it during an observing session.  I don't see how the quick changer would help unless it has an extension tube incorporated in it to match the backfocus of the binoviewer.

Am I missing something here?

[spartinix]

With my dob, I also just pull out the binoviewer and OCS/GPC out and in goes the eyepiece, with or without adapter depending on 1.25" or 2" barrel.

I don't have a refractor or SCT but if I had, I'd have the choice to change fast between mono and bino IF I had two diagonals as in your case and if I were using an OCA/GPC.

IF I had only ONE diagonal, then preferably a T2 diagonal, and IF I used a BV at native focal length without OCS/GPC, then I'd have the Quickchanger permanently mounted on the diagonal and use a ChangeRing/Clicklock combo to switch to mono.

In both cases it's of course possible also to have two OCS's; between the bv and the eyepieces.

I should have also mentioned the 'native mode' condition (if the OCS was a Barlow or Bravais lens it could be left for mono too of course unless for low power viewing).

Edited March 12, 2021 by spartinix

[Louis D]

Yes, I bought a dielectric 1.25" diagonal with a rigid case to safely hold the BV weight while minimizing the optical path length.  I normally use a 2" diagonal for mono viewing because I have so many 2" eyepieces.

[Highburymark]

On 12/03/2021 at 07:24, spartinix said:

With my dob, I also just pull out the binoviewer and OCS/GPC out and in goes the eyepiece, with or without adapter depending on 1.25" or 2" barrel.

I don't have a refractor or SCT but if I had, I'd have the choice to change fast between mono and bino IF I had two diagonals as in your case and if I were using an OCA/GPC.

IF I had only ONE diagonal, then preferably a T2 diagonal, and IF I used a BV at native focal length without OCS/GPC, then I'd have the Quickchanger permanently mounted on the diagonal and use a ChangeRing/Clicklock combo to switch to mono.

In both cases it's of course possible also to have two OCS's; between the bv and the eyepieces.

I should have also mentioned the 'native mode' condition (if the OCS was a Barlow or Bravais lens it could be left for mono too of course unless for low power viewing).

Should have mentioned, among my favourite astronomy memories was a holiday in Loutro, south Crete. Only reachable by boat, it’s about as secluded as destinations go in Europe. At the time I only took a pair of 15x70 binoculars!! Even so, views were incredible with ink black skies and a perfect southern vista over the Mediterranean. What I’d give to go back with a 4” refractor.

[spartinix]

That part of Crete is indeed very dark. And if you can observe from a few hundred meters above sea level in that area you get the best of both worlds; great seeing as well as transparency.
About 30 miles south is the island of Gavdos btw, which is arguably the darkest place in the EU.

It's true, in some places here one can content himself with just a pair of binos or even a few hours of naked eye observing.
Some of the Milky Way's dark clouds can be seen as if hovering in the foreground over de brighter sky background and Milky Way stars.

[Nicu Barbieru]

I am intending to buy one Zeiss Primostar Binoviewer (415500-1401-000)
Could you please help me with the necessary draws for building (CNC) that eyepiece holder sockets?
For the telescope side I would need also a bayonet dovetail-ring connection adapter for my Baader T-2 Quick Changer.
Baader has such an adapter who can match the mentioned binoviewer or I have to build one ?
Otherwise could you send me the files (CNC) to build this  bayonet dovetail-ring connection ?
(to mount on the original rotating ring connection with three M3 panhead screws of 5mm length).
See attached please.

I am waiting for your answer here or in: barbieru@gmx.net

Thank you very much
Nicu Barbieru

 

[spartinix]

Some pictures of the finished binoviewer.

The designs are available for who wants to make/order parts.
NOT for commercial purpose. The CAD software licence does not allow it.
I'm keeping track of this.

Also, there are vendors enough I'd say.
They all sell secondhand stuff and charge way too much.

It's much cheaper to do it yourself.

PM me for advice and more information.

 

Edited October 6, 2021 by spartinix

[Highburymark]

Very nice - looks like you’ve done an excellent job

[Highburymark]

Those Denk Plossls look pretty good too. Beautiful coating.

[spartinix]

Thanks! I started the second collective buying initiative for these.
Prices should be very interesting.

Contact me asap for joining.

[Highburymark]

One of the features of my Zeiss binoviewer when using a GPC is it produces significantly higher magnification than my other pair - a Maxbright II - even with the same eyepieces. Haven’t measured the precise increase, but clearly there’s a longer light path between EPs and barlow. Today for example, using a TV85 and 24mm eyepieces with 2.6x GPC for solar, I was getting around 62x with the Maxbright and I’d guess around 80x with the Zeiss.

[Louis D]

The optical path length through prisms is shorter than through a series of mirrors.

[Don Pensack]

2 minutes ago, Louis D said:

The optical path length through prisms is shorter than through a series of mirrors.

Regular 90° prisms, yes.  Amici prisms, no.

[Louis D]

1 hour ago, Don Pensack said:

Regular 90° prisms, yes.  Amici prisms, no.

Which is what are found in prism based BVs that we are discussing.

[spartinix]

 

5 hours ago, Highburymark said:

One of the features of my Zeiss binoviewer when using a GPC is it produces significantly higher magnification than my other pair - a Maxbright II - even with the same eyepieces. Haven’t measured the precise increase, but clearly there’s a longer light path between EPs and barlow. Today for example, using a TV85 and 24mm eyepieces with 2.6x GPC for solar, I was getting around 62x with the Maxbright and I’d guess around 80x with the Zeiss.

 

Yes, the path is easily 25-30mm longer, depending on the particular configuration.

Here's the path of the mirror binoviewer.

[Arneb]

A really interesting thread this. Very tempted to give this a go myself. A question though for anyone who has done this conversion, how are the original microscope eyepiece holders attached? I presume they are threaded on and it's just a case of unscrewing them, but wanted to check before I grab a pair. Thanks.

 

[spartinix]

Hello Arneb

The holders are one unit with the plates in which the screws visible in this picture attach them to the binoviewer.
No threads; the holders must be bored out to ~31.7mm to accept 1.25" eyepieces or adapters to accept T2 eyepiece holders must replace them.

The original holders are actually the best configuration to collimate the binoviewer easily (with the 3 screws connecting to the body).
This is one mistake btw Nicu Barbieru made (see above).
He asked me for designs for personal use but went commercial with incomplete designs and temporary collimation instructions I gave him.
He stated in private that he would make the adapters himself so I figured I'd give him what I had at that point and he would figure out the
adjustments for precise collimation.

There's a bit more to it than just replacing the original holders to achieve good collimation though, so buyer beware.

The original holders can be fitted with supreme quality Zeiss W-PL, S-PL, OPMI and Leica microscope eyepieces for the absolute best optical
quality, in combination with a corrector or not (Powermates highly recommended).
The only thing needed then is a telescope connection adapter, which is the easiest and least expensive part.

In the meantime, a second project round is almost finished now with new designs and a new dovetail allowing shorter optical path.

Anyone is free to contact me on the availability on updated designs and new parts regarding collimation as well.

The binoviewers can not be purchased new anymore though, since the mothership microscope has been upgraded by Zeiss.
Not that most adapted binoviewers sold were new rather than refurbished models but anyway.

Edited March 13, 2022 by spartinix