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Assistance needed with Giro Alt-Az Mount

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#1 kvcook

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Posted 27 September 2020 - 08:00 PM

Hoping someone here on CN has this Giro mount and can help me with a question.  I think, but am not certain, this was called the Giro Mini-DX or a similar name.  I purchased it maybe half a dozen years ago to use with my AstroTrac, to balance out telephoto lenses and small scopes.  The last time I used it was for viewing the last total solar eclipse here in North America, and I did not notice anything unusual about it back then.  It has been sitting unused in a closet since then.

 

Last week, when I got it out and loosed the azimuth lock (the lever on the base with the red button), the bottom plate separated from the alt-az head when I lifted the assembly up.  Once the azimuth lever was loosened totally, nothing held the bottom base plate on.  It is possible this is the way it was designed, and I either always had the azimuth lock tightened or had the head mounted onto a tracker or tripod for use, and so never before noticed this aspect of the design.  But it seems odd.  

 

The second photo shows this baseplate removed with the bearing surfaces both facing up.  There is a plastic washer with some light grease to smooth out the azimuth motion.  The central azimuth axis is a smooth cylinder with no ridge that would keep the assembly together when the azimuth lock is released.  The three holes on the bearing surface of the bottom plate penetrate all the way through to the bottom surface of that plate, and are not threaded.  So I don't think these three holes were intended to somehow secure the bottom plate to the rest of the alt-az head.

 

The third photo shows the bottom side of the base plate (i.e., the surface that would connect to the tripod screw).  The central hole is threaded to accept a 3/8-inch tripod screw.  The three small outer holes are unthreaded.  On the same shelf where I had this stored, I noticed this small brass cylinder or pin, approx 4x4mm in size.  However, it is not a press fit into any of these three outer-rim holes; possible it could be hammered in, but that seems a strange way to assemble this head.  And I only found this one brass pin, not three.  This pin also does not fit into the hole in the plastic washer that forms the bearing surface (and would serve no obvious purpose there).  It is possible this brass pin came from something else in the closet and is unrelated to this Giro head.

 

So what am I missing here?  Seems odd the bottom plate of the alt-az head is totally unsecured to the rest of the head when the azimuth lock is released, but it is possible I just never loosened that lock enough to notice this.  I appreciate any insight that a current or former owner of this head can offer.  Thank you.

Attached Thumbnails

  • Giro-1.jpg
  • Giro-2.jpg
  • Giro-3.jpg


#2 Hesiod

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Posted 27 September 2020 - 11:55 PM

It is normal.
You have to "split" the head in order to secure it to the Astrotrac (first have to remove the plate with the 3/8 screw from it), that is the purpose of the 3 holes in the bottom piece.
The brass pin belongs to the head too: likely it came out when turned the azimuth locking lever.
You should put it back in the lever' s hole from the inside (so will be the brass pin "to clamp" the top half piece).
If have not ever done this, I suggest to apply a thin layer of grease before reassembling the head.

#3 kvcook

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Posted 28 September 2020 - 10:07 AM

Thank you, Hesiod, that all makes sense now.  Because I started using the AstroTrac with a conventional ballhead screwed onto the 3/8" stud on the AstroTrac, I just did the same with the Giro head.  I had bought that Giro assembly at an astronomy show back in Pasadena CA a few years ago (it was supposed to be the West Coast competitor to NEAF) and it did not come with any instructions (this was an unboxed display model).  If I understand you correctly, those three allen-head screws on the camera side of the AstroTrac should be removed and then used to secure the Giro baseplate to the AstroTrac, at which point the rest of the Giro is secured to the baseplate with the azimuth locking level holding the assembly in place? 

 

Thank you also for telling me where that little brass pin goes.  I think I will use a small dab of silicone adhesive to secure it to the end of the screw, so it doesn't become separated again.  You have no idea how much time I spent looking for two more of those brass pins, thinking there were supposed to be three of them in the baseplate.  On the bright side, my astro gear closet has not been this clean in years. lol.gif

 

Having just recently sold the AstroTrac, I now have to decide whether to keep the Giro rig.  While I don't need it for use with the AstroTrac, I have to admit it was a pretty nice and simple alt-az mount to use with a small AT65EDQ scope for visual use, and it might be worth keeping for just that purpose.     KEVIN



#4 Hesiod

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Posted 28 September 2020 - 10:27 AM

Almost...the three Allen screws on the Astrotrac has to be removed together with the round plate, but to link the head a different set of screws would be needed (the same M4 used to link the tracker to the wedge).

Then the top part is kept in its place by gravity, and a gentle "pinch" by the clutch lever:

gallery_215679_8115_97502.jpg

IMHO not the most brilliant solution: it works (even if with ample margins for improvements) at my latitude of 45°, but am not so sure would use it closer to the equator

 

 

 

Anyway, the small alt/az head is quite nice, but very sensible to balance. If do not have the original counterweights anymore can use the standard Vixen ones (with 20mm bore):

gallery_215679_8115_85751.jpg



#5 kvcook

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Posted 29 September 2020 - 10:26 AM

Thanks, Alberto, this helps a lot.  I doubt I will be using the Giro much anymore for tracked photos, but may still use it as a conventional alt-az mount as it is simple and smooth.  I still have two of the original counterweights - sometime I should experiment with how large of a scope it can safely carry.  And I may look into the longer M4 just for an added measure of security.  Thanks again for your help.  Kevin




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