Sky Watcher Star Adventurer, Part II

I had an old counterweight shaft and counterweight for an EQ1 mount lying around (the EQ1 had already broken some years back and I had thrown it away).  The shaft has a large-pitch thread on one side, and an M6 tapped hole for the toe saver on the other side.

I drilled out the M6 tapped hole with an 8mm bit, then epoxied an M8 bolt into the hole.  I then cut off the head of the bolt leaving the M8 threaded portion exposed.  A more robust solution would have been to drill out the M6 hole with a 6.5mm or 7mm bit, then use an M8 tap to cut threads into the hole.  The M8 bolt would then screw into the threaded hole, a more secure fastening than just epoxy.  But I did not have an M8 tap handy.   The epoxied bolt seems secure enough (I used Araldite brand epoxy) and hasn't wobbled through a 2-hour plus testing session.

With the stock EQ1 counterweight, the Stellarvue SV80ED still would not balance; however the result is much more in balance than having no counterweight at all.

However, the counterweight did not really improve the guided performance, or reduce the periodic error to in any meaningful way (and I did not expect it to).  Guided performance is still around 2" RMS, which I believe is the best this mount is capable of.  Hence it should be used at a pixel scale of 4" to 6" per pixel, or 200mm to 300mm focal length.

A longer sampling period has confirmed that the worm fundamental is 10 minutes, hence the worm wheel has 144 teeth (like the Vixen Polaris, Great Polaris, and CG-5).  This was confirmed by a poster on Stargazers Lounge who tore down the Star Adventurer.  The fundamental is about 30" peak-to-peak.

I got a better polar alignment this time (as shown in the minimal DEC drift in the graph above) and in the process noticed that the polar scope is pretty well-aligned - better than my PASILL3.  It's not perfect, but it's good enough that I'm not going to mess with it.


Mark Kilner said...

Thanks for posting this info - it's really helpful. If possible, can you tell me the diameter of the base of the equatorial wedge? I'm thinking of getting the Star Adventurer package and I've got a tripod similar to yours, but it's got a spur that sticks up (for the azimuth screws to lock onto). I'm concerned this might get in the way.


orly_andico said...

Hi Mark, the base is about 80mm in diameter, and exactly fits the base of a Gitzo tripod.

Unknown said...

Thanks for the post. Just what I was looking for. Didn't purchase the counterweight hoping the one I had would fit, it didn't. I'll try the method you would've done. Quick question, where did you get the...idk clamshell (maybe it's called), the piece your scope is sitting in and fastened to the sky watcher? I've been looking for something like that too and haven't had much luck. Probably about 4-5 hrs searching online and I'm pretty good at finding things. Example, this blog, lol. Thanks for the help, looking forward to your response.


orly_andico said...

It's a Stellarvue 90mm clamshell which is now discontinued.

Alternatively Televue makes a 3" and 4" one (that would be 76mm and 100mm internal diameter).