Ultra-portable Newton 200mm f/5


A very portable telescope, transportable as airplane cabin luggage (respects carry-on luggage allowances for most airlines). Its high-quality ⌀ 200mm optics make it a powerful instrument!

Optical Specifications:

  • primary mirror:
    Portable 200mm Newtonian telescope

    The assembled 200mm portable Newtonian telescope, side view.

    • ⌀ 200mm
    • focal length: 1000mm
    • focal ratio: f/5
    • precision: Strehl ratio > 0,95, usually around 0,98-0,99 (supplied with optical test bulletin)
    • glass substrate: fine-annealed Schott Borofloat 33 (low thermal expansion)
  • secondary mirror:
    • minor axis (⌀): 46mm (for other sizes, please ask)
    • central obstruction: 23%
    • surface precision: λ/20 (supplied with optical test bulletin)
    • diameter of 100% illuminated field: 0,59°
    • diameter of 75% illuminated field: 1,67°
    • MoonLite focuser, other focusers possible on demand

Mechanical specifications:

  • weight (telescope + mount / transport box): 11,2 kg (finder and eyepieces not included)
  • transport:
    The telescope packed and ready for transport

    The telescope packed and ready for transport

    • 55*35*23 cm and 9,1 kg for the box with the optical assembly components
    • 96*5*2,5 cm the aluminium bars (x2 for two bars ; 1,4 kg together)
    • ⌀ 35 cm, h=6 cm and 0,7 kg for the azimuth orientation mechanism
  • materials:
    • premium birch plywood, lightweight and tough, beautiful look
    • aluminium for the two connecting bars
  • finishing:
    • transparent (shows the wood grain): water and UV resistant varnish, 3 coats
    • other: please ask

Detailed description:

This is the first model that I managed to make compact and lightweight enough to take it as cabin luggage in an airplane. The optics are housed in two octogonal ‘boxes’ (optical assemblies), one for the primary mirror and the other for the secondary mirror and focuser. Two aluminium bars, one on each side, connect these two boxes.

For altitude orientation, two large disks are attached to the aluminium bars. Teflon pads ensure smooth and precise movements. During transport, these disks double as protective covers for the optical assemblies. Azimuth orientation is ensured by a circular base attached to the bottom of the rocker box, turning on teflon pads attached to the feet.

During transport, the rocker box doubles as a transport case, housing the optical assemblies, the altitude disks, the finder, eyepieces, a star atlas, warm gloves, a lamp and whatever other accessories you may have. Only the two aluminium bars and the round base for azimuth motion need to be transported as checked luggage, the optics and all other sensitive parts travel safely with you as cabin luggage.

Assembly or disassembly take about 5-10 minutes, depending on how much practice you have. The only tool you need is a 5mm hex key. Collimation after assembly is easily achieved in about 2-3 minutes with a laser collimator.

The optics:

I decided to make my own primary mirrors, this way I can control the optical quality. It would have been a shame to put a low-quality, mass-produced mirror in such a nice telescope. From experience, I can make my 200mm mirrors to about λ/16-λ/18 on the wavefront, much better than what I could have gotten ready-made. I decided to buy the secondary mirrors, but I made no compromise and got the best ones out there.

I had the chance to compare my telescope on several occasions side-by-side against mass-produced scopes of the same diameter (I won’t name any manufacturers but you can probably guess them). On Jupiter, both my telescope and the other showed the main cloud bands and the largest of the round ‘hurricanes’, but in mine I could also see smaller features, ‘turbulences’ at the boundaries between different cloud bands and the image overall had better contrast.

On Saturn, I compared my telescope with a 250mm from a large Chinese manufacturer. Both telescopes showed the Cassini division, however mine showed it perfectly crisp while the other was fuzzy. In my telescope, I also managed to see some large, low-contrast features inside Saturn’s atmosphere, while in the other telescope they were invisible despite the larger diameter optics.

On deep-space objects I get similar results: I can resolve individual stars better in globular clusters or I can make out more structure in galaxies or nebulae.

Image gallery