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Comment by donkeybeer | Hacker News Reader

So is the accuracy and stability he achieved better or worse than the commercial mount?

Short answer: it's in the same ballpark as other mounts of the same size. The theoretical accuracy for RA is 0.198″ (65,536 steps and 100:1 reduction) and for DEC is 0.253″ (256*200 steps, 100:1). In practice many things will reduce this accuracy: seeing, proper polar alignment, sturdiness of the wedge and tripod all account for some loss in accuracy. My highest achieved accuracy was probably around 1″ during brief moments, I'm sure with excellent seeing this could reach <1″ performance.

So do you think that complex mechanism ended up no better than the normal mounts? It could be execution too, I am no good at experiments and sometimes even "proven" designs end up a bit subpar, so it could be the design was alright.

Not sure what you mean with complex mechanism. The mount has a similar architecture to other commercially available mounts like the HEM15 iPolar for example.

Oh ok. I didn't know harmonic drives were standard in commercial mounts.

They have become popular in the last few years. They are smaller, lighter and thus more portable than traditional mounts. They also don’t need to be balanced with a counter-weight (although they usually allow for a counter weight to increase payload capacity, they don’t need to be perfectly balanced). This all saves in set-up time.

One disadvantage compared to traditional mounts is that they absolutely need guidance, and with a pretty fast guide loop at that (like 0.5s). You can’t do long unguided exposures with a strain wave. But anyone who’s serious about astrophotography is guiding anyway so that’s not really a big deal.

I am a bit idly curious since I plan to build a telescope sometime. Nothing as complex as this, just a manually guided dobson.

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