Kutter binoculars 120/f31

[Chriske]

f/31, so planetary and Moon observations only.
Busy grinding the optics.
And at the same time designing the telescope itself.
This is V1. The light leaving the secondary tube passes through the primary tube at an angle of 11.30°
The yellow transparent cone is to guide me where I need to cut that oblong hole in the secondary tube.
The focuser is a new design that has never been done before. It goes up the small upper tube. I'm not planning using 2" eyepieces at all in this scope.

 

Edited March 11, 2019 by Chriske
Change of concept

[Gina]

That looks ideal for planetary imaging.  Following with great interest...

[Peter Drew]

Also following with interest. I've had some experience with a 6" Yolo version. These TCT's (Tilted Component Telescopes) do have excellent false colour free, high contrast images. Like folded refractors they can be a challenge to collimate initially.   ?

[Chriske]

Optics well done en tuned these Kutters are superb telescopes.
In our local observatory there use to be a 10" version. Focal length 5 meter.  Moon at primary focus fitted just on the negatives of my 6x6 camera.
It was a 'real' Kutter. To correct residual coma and astig there was a correcting lens installed tilted about 20°. Focal plane is tilted about 7°.
As you can see in the drawing, Focal plane of my 120mm kutter is tilted almost 4°, also to correct residual errors. But not all is corrected(there's no correcting lens in mine) But all ray's stay well within the Airydisk, no problem there.

Another one one my wish-list is a Gregorian. Two concave mirrors, one is a parabola and the secondary is an ellipse.

Gregorian 150/f25

Compared to a (very long)Newt of the same size F=2000mm

[Chriske]

17 minutes ago, Peter Drew said:

Also following with interest. I've had some experience with a 6" Yolo version. These TCT's (Tilted Component Telescopes) do have excellent false colour free, high contrast images. Like folded refractors they can be a challenge to collimate initially.   ?

Good optics too that yolo. In the early days I've written to Mr Leonard. Was no mail in those days.
Same as the other long scopes..

This one is not 12" but a 6"

 

[Robert72]

Superb project Chriske.  I would like to try my hand at an obstruction free scope one day.

[Chriske]

It's not very difficult to make this type of telescope.
There are a few different types of Kutters.
Actually the one I'm making right now is not really a Kutter telescope,  it is called a Neo-Brachy telescope.
Kutter read about it and improved the concept. The most important change he made was adding a correcting lens between secondary mirror and eyepiece(somewhere in the middle).
The Brachy version I'm making is a anastigmatic one. Advantage of this type is : There's only one mirror-set to make. Meaning the concave mirror is the primary(of course) and the tool is used to make the secondary. Both mirrors have the same curvature and on top of it both these mirrors can stay spherical.
A Kutter's primary mirror on the other hand  is a parabola(50%), so in fact elliptical. The secondary can stay spherical. The corrector is a plano-convex lens. Convex side is very shallow, and that lens is also wedge shaped.
There are other possible configurations but the one I'm building right now is the closest to the Kutter version. I do like it very much.

Unfortunately these 'planet-killers' can't be taken outside very often. They need steady skies. If the atmosphere is quiet and steady they will give you breathtaking superb images. Nothing can compare with it..! Because of it's long focus contrast is very high.

In the past I've already made a couple of these scopes mostly 150mm. Disadvantage is it's size. A Brachy is always on the long side.
I also made this one almost 2 years ago. I also was busy making a bino version of that one, but it's on hold now.
It will look like this :

[Chriske]

Hi,

Lots of things have changed these last days while drawing.
First of all I've added three fans to cool the scope very quickly.  Powerpacks in the scope. It's a near open scope, so it's handy to dry optics with these fans if necessary.
Added also is a laserpointer. These scopes are very difficult to aim without an aid. (I never use finderscopes) - ( I use my lasers very cautiously, never point at people, planes, etc. And when I lit them it's only for a few seconds. It's tool, not a toy..!)
It's not a classic focuser. I didn't want to mount  a large focusing-device on top of that most upper tube. So I designed a Crayford-like focuser. I call it : 'Inversed Crayford'. (Maybe it's been done before, don't know) The focuser is nothing more than a tube containing 6 ball-bearings and a focusing rod. In fact just the same as a regular Crayford. Point is, while focusing I move the focuser itself +eyepiece up and down. This way it has a more 'elegant' look.
That eyepiece sits angled in it's focuser, it's part of that Kutter design. Eyepiece is tilted 3.86° away from the observer.
To insert the eyepieces I'll be using on-axis adapter. Purpose is to mount eyepieces in the exact centre of the optical train. So there's no thumbscrew required at all. These adapters are 'springloaded' in both ways, in- and outward. Also own design.

That's it for now, still some more drawing to do...

[Chriske]

Cutting the oblong hole in the secondary tube. That hole is in fact a cone shaped cut in a cylinder.  Even in Inventor not an easy task. For every other Kutter that oblong hole is different.
But once I have that drawing, I can print that part of the tube to use that printed part as guide to draw that hole on the StSt tube itself. To be sure I need to enlarge that hole a bit, taking care the light-path coming from the primary is not partly blocked.

[Gina]

Mmm.... Tricky.

[Chriske]

The secondary holder needs a angled cut to allow free passage of incoming rays from the sky to the primary mirror. It's a very close fit.
The very last thing after collimation is to free that incoming lightpath from the secondary holder. To do this one of the adjustment screws of the primary mirror must be installed in the meridional plane. When done the angle of the primary mirror is automatically correct(ed).

[Chriske]

8 minutes ago, Gina said:

Mmm.... Tricky.

I know, but I love this kind of stuff..., I love the challenge.
It's a rewarding instrument. It beats a long refractor of the same size easily.

[Gina]

Oh yes - I like a challenge too - as you know.

[Robert72]

Did you mention that these are AD Inventor models? Nice quality.

[Chriske]

Indeed Robert,

All is done in Inventor. It's an old one. I got it from my employer about 10 years ago. Still use it every single day. It was in fact part of my job.
Although it's an old one it does what it's suppose to do and more...
The most rewarding item is 'Assemblies'. It gives you the ability to see in and outside to inspect  the project. It also detects collisions if needed. There's also a strain-detector.
There's in fact to much to mention...love it.
There's only one minor point. It does run only in Win.(I'm Linux user) So I run Inventor in a VirtualBox.  Using it in a VB I don't see any difference, it's in fact as fast as in a 'normal' Win.

[Chriske]

I always try to hide wires in project like this. It looks  better.
In this case I need to hide the wires of the laser(sitting in front of the eyepiece holder).
I need to make 'corridors' in the parts itself. For my laser there was no other way than to lead the wiring very close to the top of that part. After installing the laser I cover the corridor with a very narrow ring.

[Chriske]

Added a cover to hide the electronics
- Contact-points power-packs
- Fan
-7815
-DC -DC converter

 

 

Edited February 21, 2019 by Chriske

[Chriske]

Just ordered a small diagonal mirror for my Kutter. (Orion Optics UK) cost 70£
After ordering and paying(paypall) I now need to pay an extra 10£ before they send that mirror.
Is this a normal way off working..?

And what is 'Sales Carriage'..?

 

 

Edited March 11, 2019 by Chriske

[Chriske]

My pal Marc decided to make himself a Gregorian telescope(instead of a Kutter)
That Greg will be 250mm f/24. Also planetary observing only.

A few days ago my single Kutter-telescope I drew was almost ready to start printed . And at the same time I was left with an extra set of 120mm Kutter optics. (I was making 2 sets of Kutter-optics simultaneously)
So I started thinking about that extra set of optics and what better solution than make myself a Kutter-bino...
With a focal length of 3720mm it will be challenge, I know. But I made a few big Newt-bino's in the past, so why not....

This is what I have so far. A lot of parts I already drew for that single-version can be reused. Lucky me...

 

 

[Chriske]

I want to install a dual-speed focusing unit, so a new setup is required here.
This is what I got so far.
in this new version there's a timing belt involved. Left is done right one still to draw.

[Chriske]

This is what I got so far.
Still to design is the IPD adjusting unit before I'll start printing.

[Chriske]

IPD-adjusting-unit done.
the bleu(transparant) part is a fixed part. Turning the red knob the light brown parts(together with the focusers) move in opposite directions.

 

 

[Chriske]

Next step is to add a(3) SevSeg-display to that IPD unit. I could use a simple ruler to indicate how far the two eyepieces are separated but I chose not to and go for a electronic version. And it looks cool imo.
Yesterday we tried to  upload firmware to a Nano to drive these 3 displays. All we got was some weird looking 'figures' on the SSD-units(while turning the potentiometer - it's a 10rev pot btw)).
Think we made some wrong wirings between that Nano and the 3 SSD-units. I want to install 3 SSD-displays separated by a dot.

[Chriske]

After a few attempts we succeeded to have these three sevseg units working properly. Was not easy to find the correct settings.
Turning the potentiometer knob, I can adjust the IPD from 55mm to 78mm. That is, not the IPD itself yet, just the readings from the LEDdisplay of course.
I even can adjust the brightness of the display. Very handy.

[Chriske]

Meanwhile printing and has started.
Busy printing the template for that strange looking oblong hole in the secondary tube. When done I only have to lay it at the correct spot on the tube and draw were I have to cut and grind away.
I need to print it in two pieces because my printsurface isn't long enough.
That oblong hole is almost 20" long. 455mm to be exact.