Astrophotography by Philipp Salzgeber

 

 

Philipp
Salzgeber

Wolfurt / Austria

A 150 mm altazimuth mounted telescope



DSCN1640After Seeing "Bebra" the 3kg travel telescope made by Patrick Woitala, I started longing for a similar device. Since no such telescope is commercially available, what else could I do but building a small altazimuth mounted telescope myself.

Here are some pictures of the finished scope...

additionally here are the results of different optical tests (including interferometric and ronchi-tests) before and after the refiguring of the mirror by Stathis Kafalis: optical bench report

and here are some images of the building process: building the 6-inch dob

Because I am new to amateur telescope making, I wanted to keep the financial risk low and ordered a used 150mm parabolic mirror of "average quality" (1/4 Lambda p/v Strehl ~0,8) together with the main mirror I bought a used secondary mirror. I paid 90 € for both mirrors together.

here is a short list of my design goals:

  • portability (holiday)
  • cheap
  • easy to use
  • interesting project

after some thought and many scribbles I decided on a design which allows a 45 degree angle for the eyepiece and uses only four trusses. After obtaining aluminium tubes (12mm) I found 6 and 8 mm carbon tubes intended for kite-building and decided to use those for my project.

I have to thank a lot of people who provided tips, plans, ideas or presentation of their own telescopes, here is an incomplete list: Patrick Woitala, Stathis Kafalis, Martin Trittelvitz, Chuck Fellows, Barry Leger, Dirk Mohlitz...)

Here are some images of the telescope (click on the images for enlarged version):

Standing on the base plate is the laser collimator I use everytime I use the scope Beside the collimator you may notice a black disc this will be used as a baffle behind the secondary.  
  With the bigger altitude bearings the scope is well balanced without counterweights.  
closeup of secondary holder, notice the curved single-vane spider. The secondary is oversized, it will be replaced.. At the lower end I used a Exel T-Joint (the same as used on the upper end), but to make it fit, I had to cut away a part. The builder and owner of this still not finished telescope: Me!
Wing nuts for tool-free collimation, ventilation holes and counterweights Sliding focuser, I will change the position of the spring to make the movement more smoothly View through the focuser without eyepiece, a baffle behind the secondary needs to be added.

 

Here are some images of the scope with earlier, smaller altitude bearings:

     

The first observations with this telescope included M3, M51, M13, Jupiter, M44, NGC4565. During this first-light observations I found out that something was wrong with the optics. The images are not sharp. On Jupiter only two cloud bands were visible, and M13 was only mottled, far from resolved (see the optical bench report). My 130mm Vixen Newton telescope has much better optics, and the Vixen was interferometrically tested, and I know it has a lambda/2 mirror...

Stathis Kafalis has kindly refigured the mirror, and now the quality is quite good.

I have added another page with some images of the construction process: building the 6-inch dob.

 


All images Philipp Salzgeber

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