interesting mount?

[blink138]

this sounds very interesting ................ no price given though
just seen it on the astronomy technology today magazine

http://www.rainbowastro.com/new/theme/basic/content/product-135.php

pat

[bojan]

Tis is with harmonic drive....
Probably expensive.


However, ebay is listing used harmonic drives fo ~US$100 & up.. Interesting for DIY

[blink138]

phwoar yes a good read on CN's nearly U.S4k though!
pat

[bojan]

3D printed version of Harmonic drive (Strained Gear):
https://hackaday.com/2017/01/17/3d-printed-strain-wave-gear-needs-your-help/

[AstroApprentice]

Here's the Aus distributor with pricing for the RST-135 & 150 models:
https://www.siderealtrading.com.au/product/rst-135-compact-harmonic-drive-telescope-mount-head/

[Wavytone]

Harmonic drives - and this specific mount - been around for a few years, and there is a very nice video showing what it can do traversing a scope in a circle around the perimeter of the sun. Key points:

1. No backlash - zip, nada, none at all.

2. Extremely compact and lightweight compared to a GEM for the same payload.

3. Although the mount head is mechanically very stiff the lack of balance around the axes means significant forces are transmitted to whatever is supporting it - and these change as the scope moves. The inevitable result is flexure, which effectively means pointing errors around the sky.

Bolting it firmly to a block of concrete or granite would be the only real way to eliminate this.

4. Periodic errors are significant so for imaging at any serious focal length autoguiding is a must to deal with this and #3 above.

5. Expensive.

Great for visual, great for a travelscope (solar eclipses), Ok for short focal length imaging but problematic for long focal length stuff.

[FlashDrive]

Check here also

http://www.rainbowastro.com/new/theme/basic/content/pricelist.php

Col.

[AstroApprentice]

Anyone interested in the Rainbow strain wave gear mounts is likely to benefit from reading the current discussion/ongoing review of the RST-135 on CN:
https://www.cloudynights.com/topic/666852-rainbowastro-rst-135-review-the-ideal-imaging-mount/page-6
Particularly from post #131 onwards warning of the back driving issue if the mount is accidentally powered off - a rather sobering thought...

[The_bluester]

I don’t think I could live with a mount that did something other than just stop if the power failed.

[troypiggo]

I wonder if you could add a counter-weight anyway to ameliorate the flexure issue mentioned by Wavy above.

[Wavytone]

Periodic error is huge with all harmonic drives - ok for visual but for AP you need an autoguider.

[troypiggo]

Understood, and if imaging would always guide. Was more talking about the flexure only.