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My Astrotrac TT-320X mod

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#1 Jarno

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Posted 06 October 2012 - 11:13 AM

A couple of months ago I bought an Astrotrac TT-320 as a simple, transportable system to get into astrophotography. There are already plenty of reviews of the TT-320X on the 'net so I'll just say that it does what it promises. But being an engineer I was annoyed by some things that I consider to be design flaws, one of which I have now addressed.

To use the TT-320 you'll need a wedge or something similar to align it with Polaris. I opted for Astrotracs own TW3100 wedge which is a fine, albeit pricey, piece of engineering. The connection between the wedge and the TT-320 could be a lot better though. Unless you intend to transport the wedge and TT-320 as one piece (which is certainly possible) you're expected to unscrew three tiny M3 Allen bolts. Imagine doing that at 3AM in freezing temps while wearing gloves, you're just asking to lose the bolts or ruin the threads. What were they thinking at Astrotrac? :shrug: So, here's what I came up with:
Posted Image

What you're looking at is a standard Vixen dovetail system with a few threaded holes in the dovetail bar to attach the TT-320. Instead of fumbling with an Allen key I can now detach everything in seconds. An added benefit is that the center of gravity now lies more to the left of the picture, almost exactly above the center of the tripod. I was concerned that there might be too much flex in the clamp but it turns out to be a very stiff connection. And if I should get any flex I'll just slide the dovetail down until the flex is gone. The best part of all is that absolutely no modifications were made to the Astrotrac components, just a few holes in the dovetail bar. :thewave:

The next thing on my to-do list is the lousy polar scope attachment. It's held in place with magnets but from the bottom up, which means that the magnets have to work against gravity. Bump the polar scope slightly and it'll come tumbling down, maybe even poke you in the eye along the way. I'm trying to figure out an easy way to fix that, stay tuned for more. :scratchhead:

#2 Mkofski

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Posted 06 October 2012 - 01:08 PM

I don't have or plan on buying an Astrotrack but that is a great mod!

#3 core

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Posted 06 October 2012 - 10:45 PM

Thanks much for sharing the mod! I had the same frustration with their design after I got the TT-320X as well (in my case, with the pier and and all) - wonderful mount, wished they'ed incorporated a tool-less setup! It's a little worse with the pier - should I decide to store/transport the mount with the wedge, or the wedge with the pier plate? iirc I've seen another quick (dis)connect mod using Manfrotto plates, but your solution's definitely cheaper, and adds a new feature of adjusting the balance.

Do update on the Polar scope mod; I'm already having issues with centering the reticle as it is!

#4 Jarno

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Posted 08 October 2012 - 02:33 PM

The problem with using camera plates is that they have rubber on them which always causes flex, I prefer solid metal connections.

Regarding the polar scope issue, I think I'll have a screw connection machined. Then the scope can be inserted the normal way but you also screw on a securing ring at the backside, no way the scope can fall out then. Or maybe I'll scrounge up another polar scope to mod.






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