My 200mm/F6 bino is now operational and but for a few tweaks is working well. Just need to get the hang of using it, especially collimating in the dark after transporting. Thanks to all who gave me advise, intentional or otherwise, these last 2+ years of design and build. This is my first ATM project, hence most of the time has been consumed with research and the evolution of design. There are a number of innovative risks that seem to have paid off OK. I think it was Mark Suching who advised me to keep it simple and I will succeed. Given my background, that would be very difficult for me as an engineer, but at last I got there.
Here's a partial desciption: The tripod (which telescopes up 500mm for viewing the horizon) weighs 9.2 kg (20lbs), and the OTAs with frame weighs 22.3kg (49lbs), totalling 31.5kg (69.5lbs). The EPs at zenith are about 1,300 off ground, and about the same with the tripod extended for the horizon. The EPs are 2" wide angle and the minimum IPD 56mm. The primary mirror separation is about 480+ minimising body heat turbulence. The OTA assembly detaches from the tripod (hexapod) mount at COG by means of loosening one M8 cap screw, and the individual OTAs detach from the frame by means of two M6 cap screws each and the handlebar/IPD adjustment fixture screws.
The construction is of CF OTA tubes and other bits, heaps of machined and anodized aluminium, all stainless screws, Tufnol fittings, and Tufnol and Vesconite bearings, and NO wood.
Thanks for the comments. Took it to the Central Star Party near Hastings this last weekend but never got to see even one star! Being a semi-retired toolmaker/machinist helped a lot but I had great resource of all the ATM and bino makers on the web for ideas. On the aesthetics, I still think it hard to beat Jaques Civette's bino http://www.astrosurf.com/altaz/460_bino_e.htm
Am I right in thinking that IPD adjustment is handled by the two tubes swinging on that enormous hinge running between them ( very similar to a standard refracting binocular design ) ?
Hi Mark, yes the design for IPD was inspired by the small bino design. After much consideration, as there are several methods to choose from, I figured that since the scope was small enough, I could get away with it. And it does work well. The handlebar has LH & RH threads in the ends and the anchors pivot on the tufnol brackets. The small pressure exerted in IPD adjustment does slightly affect the merged image but is corrected by simply easing it back.
Thanks for the compliments. Hey, I think we've got some clear sky at last--catch you later
On the use of Tufnol:
This is an engineering thermoplastic that has been in use since the days of Bakelite. I found that it works well in bearing applications with aluminium (I used 6061 throughout), and that the combination works particularly well in the mount where a smooth yet firm operation without slip-stick is required. The one caution is that although water is a good lubricant with it, it does absorb a small amount which affects dimensional changes. So where I used it for structural applications, I painted the exposed edges to seal.
Tufnol works well in the tripod bearings between the tubes. However, because of the larger sizes and the cost of buying pieces that size, I found scraps left around the machine shop, machined them to fit together and glued the pieces with high strength Araldite. The larger bearing comprises eight bits. Then I was able to machine, split and screw the bearing without difficulty.
Another composite I used was Vesconite, a black oil-less bearing plastic. I used this for the top and bottom bearings on the frame hinge, and also as part of the azimuth bearing running between aluminium, Tufnol and stainless surfaces.
Awesome piece of gear, far out, and a mighty accomplishment indeed Keith
It was mentioned to me to make one when I was grinding a few 6"; 8" & 10" mirrors back in the '90's day - way out of this ducks league to put a bino-scope together !
To be honest, I never thought it would've been possible - speshly back then ..
Definitely an Eye-Opener & a privilege to have seen this, not sure if there are any such equipment over here Sth QLD Aus, but if I ever get over to NZ, id try for a looksies through this
