For those observers that might feel a bit intimidated to dive right into a 17.5 inch reverse binoscope I might suggest a more modest project of a 6 inch F5 side by side binoscope, which, under dark skies, provides truly amazing views at 25X to 40X magnification. The one shown here uses a simple construction of 0.75 inch aluminum angle and 3D printed parts. To keep the design as simple as possible and weight to a minimum (only 5Kg) there are some compromises and one of these is that although the IPD can be adjusted from 54 to 75mm it is not adjustable "on the fly" and it takes about 5 minutes to do this. So this is a "personal" binoscope which may be a show stopper for some and in this case a more complex design is necessary to make the upper OTA have a sliding configuration (see the 114mm binoscope). One of the real advantages of this design is that both OTAs and the focusers are all assembled in one very accurate cage so the two OTAs are inherently parallel which makes the image merging very simple. The final (very small) merging adjustment is accomplished by manually reaching around the back of the upper OTA (while viewing) and very slightly adjusting the upper primary mirror adjustment screws.
- Watch on my youtube channel "petertinkerer W" for the assembly of this binoscope. It takes less than 30 minutes which includes the mirror alignment.
All the .stl files are available on Tinkercad. Search for "Full Assembly 150mm Offset Binoscope". Its Public and freely available
Approximate cost breakdown:
1) Two 6" F5 Parabolic Mirrors from Agenaastro~$300 (or buy two spherical 150mm F5 mirrors for $120 from Aliexptress which work very well up to 37.5X using 20mm eyepieces)
2) Upper 35 mm secondary ~$15 from Aliexpress
3) Lower 54mm secondary ~ $25 from Aliexpress
4) Aluminum frame ~ $50
5) General hardware: Vinyl light covers, velvet sheets, glue, nuts&bolts, 3D filament, etc, ~$45
6)Two 32mm Plossl eyepieces $45
Total cost of Ultra Light (5Kg) 150mm Binoscope ~$480, ($300 if you use spherical mirrors which work very well up to 40X)
The Dobsonian Alt-Azm mount costs about $100. At a dark site this binoscope provides amazingly bright views of the night sky with 6.4mm exit pupils at 23.4X using 32mm eyepieces and 4mm exit pupils at 37.5X using 20mm eyepieces.
