NC16 Construction

The first thing before starting the manufacturing of the telescope is to identify the providers for the key parts. After searching though internet I decided to go for the following providers:

Optics: Huygens optics (www.huygensoptics.com). They are located in the Netherlands and have the capability to manufacture large parabolic mirrors. I talk with them to optimize the manufacturing tolerance and adapt the optical design to their capabilities. They will manufacture the parabolic primary and hyperbolic secondary.

Corrector lenses: Both lenses were manufactured by Focus Photonics (www.focusphotonics.com) in the Netherlands.

Carbon fiber tube: Klaus Helmerichs (http://www.klaushelmi.de/index.html). I highly recommend him. There is not too much providers of carbon tubes and he is delivering high quality, very well finished, and high specs carbon tubes up to 460 mm diameter.

Mechanical parts:

Focuser: the focuser is the model OK3-Z from ASA. It has 15 mm travel range and 3" internal diameter. The focuser has an internal temperature sensor to correct for temperature focus shift.

The primary and secondary mirrors The hyperbolic secondary mirror is the most complicated part of all optical components. Manufactuing the hyperbolic mirror has the problematic of testing a convex surface. The testing method used during manufactuing is a null test through the back side. The back side was polished to an sphere. The outcoming wavefront reflected from the hperbolic side saw from the back side though the spherical shape is spherical. A null test on this way is very sensitive to radius deviation, as well as to small variations to the conic constant. I decided to start with the manufacturing of the secondary, and before sending it for coating, performing profile measurements. The measurment result (done with Sensofar's Plu-apex), determines the shape of the primary and the optical design of the corrector lenses. Click on the PDF file to read a full report of the mirror quality before sending for coating.	Click for complete report of the secondary mirror
The tube The tube was made by Klaus Helmerichs (http://www.klaushelmi.de/index.html), in Germany. The tube is made unidirectional 1.5mm inner layer carbon fiber, 8 mm of nomex sandwich and 1.5 mm additional carbon fiber outer layer. The outermost layer is made of twill carbon fiber and a clear coat. Total weight of the tube is only 4 Kg.
The primary mirror Beginning of july 2012 the mirror figuring and polishing was finished. The work has been carried by Huygens Optics. The mirror is made of 46 mm thickness Supermax by Schott, with parabolic shape and a focal length of 1400 mm (F3.5). It has a central hole of 100 mm diameter. Testing of the mirror show a better wavefront PV error than lambda/25, with less than 2.5 nm rms shape error. The mirror is now send for coating.
The primary mirror arrived at end of july. During august and september most of the mechanical parts were machined and I started to assembly them. The picture on the right shows the primary cell with the floating points and the primary baffle.
The cassegrain mirror holer. I finally manufactured 0.5 and 1 mm thickness vanes. Both seems to work very fine, but the 1 mm looks stronger. Theoretically, 0.5 mm vanes diminishes the strelth ratio down to 0.99, while 1 mm to 0.98. Both are above 0.96 meaning that it should not be apreciable difference between both.
Nearly all the mechanical parts tested and ready for anodyzing.
The two meniscus lenses. Diameter of the lenses is 80 mm, with an average shape error of 3 fringes.
First assembly with the cassegrain configuration. I experimentally check the center of gravity and total weight of this assembly. It matches very well with the CAD simulation.
All parts are now anodized. Here it is the newtonian spider, without the diagonal mirror.
My second son, Esteve, holding the cassegrain secondary cage.
The mirror main cell completed by 18 of November 2012. The hyperbolic mirror has been send for aluminizing. Once it will be back the telescope will be ready for aligment and checking optical quality.

The primary and secondary mirrors

The hyperbolic secondary mirror is the most complicated part of all optical components. Manufactuing the hyperbolic mirror has the problematic of testing a convex surface. The testing method used during manufactuing is a null test through the back side. The back side was polished to an sphere. The outcoming wavefront reflected from the hperbolic side saw from the back side though the spherical shape is spherical. A null test on this way is very sensitive to radius deviation, as well as to small variations to the conic constant.

I decided to start with the manufacturing of the secondary, and before sending it for coating, performing profile measurements. The measurment result (done with Sensofar's Plu-apex), determines the shape of the primary and the optical design of the corrector lenses.

Click on the PDF file to read a full report of the mirror quality before sending for coating.

Click for complete report of the secondary mirror

The tube

The tube was made by Klaus Helmerichs (http://www.klaushelmi.de/index.html), in Germany. The tube is made unidirectional 1.5mm inner layer carbon fiber, 8 mm of nomex sandwich and 1.5 mm additional carbon fiber outer layer. The outermost layer is made of twill carbon fiber and a clear coat. Total weight of the tube is only 4 Kg.

The primary mirror

Beginning of july 2012 the mirror figuring and polishing was finished. The work has been carried by Huygens Optics. The mirror is made of 46 mm thickness Supermax by Schott, with parabolic shape and a focal length of 1400 mm (F3.5). It has a central hole of 100 mm diameter.

Testing of the mirror show a better wavefront PV error than lambda/25, with less than 2.5 nm rms shape error.

The mirror is now send for coating.

The primary mirror arrived at end of july. During august and september most of the mechanical parts were machined and I started to assembly them. The picture on the right shows the primary cell with the floating points and the primary baffle.

The cassegrain mirror holer.

I finally manufactured 0.5 and 1 mm thickness vanes. Both seems to work very fine, but the 1 mm looks stronger. Theoretically, 0.5 mm vanes diminishes the strelth ratio down to 0.99, while 1 mm to 0.98. Both are above 0.96 meaning that it should not be apreciable difference between both.

Nearly all the mechanical parts tested and ready for anodyzing.

The two meniscus lenses. Diameter of the lenses is 80 mm, with an average shape error of 3 fringes.

First assembly with the cassegrain configuration. I experimentally check the center of gravity and total weight of this assembly. It matches very well with the CAD simulation.

All parts are now anodized. Here it is the newtonian spider, without the diagonal mirror.

My second son, Esteve, holding the cassegrain secondary cage.

The mirror main cell completed by 18 of November 2012. The hyperbolic mirror has been send for aluminizing. Once it will be back the telescope will be ready for aligment and checking optical quality.