Author Topic: Parallax or Quality Control or . . .?  (Read 1803 times)

Brian

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Parallax or Quality Control or . . .?
« on: March 04, 2012, 05:09:46 PM »
A person on Amazon reviewed one of the Suunto compasses (MC-2DLIN), said this   http://tinyurl.com/85ssum9  :

". . . Overall the compass is a well made example of a classic design and first impressions are very good. However, on close examination of the compass needle capsule it is clear that the alignment arrow in the base of the compass capsule and the parallel alignment marks/declination scale indicator are slightly offset. This indicates that the two scales are not concentric. . . ."

This concerned me because I have a Suunto M3 Global (it's all Lyle's fault . . . ;)), and  I assumed that the capsule, baseplate and declination adjustment are the same — or almost so — in the two compasses.

So I tested my M3 using a map-reading grid (in lieu of the graph paper the reviewer had used) and wrote a reply to the effect that at first, it did seem to me that there was a QC issue, but when I moved my head around a bit, it seemed I could make the problem disappear from where it had been but reappear elsewhere, and I wondered if it might not be a case of parallax.  (Lyle stresses the need to eliminate parallax when discussing proper compass use.)

Anyone have any thoughts on this?   If I'm wrong, I'd really like to know it so I could correct what I've written there.

Thanks all.
« Last Edit: March 04, 2012, 05:11:43 PM by Brian »

Lyle Brotherton

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Re: Parallax or Quality Control or . . .?
« Reply #1 on: March 04, 2012, 05:55:35 PM »
I would confidently say parallax Brian.

Just to check, I have set my M3 on my desk and rotated the body, then aligned the guide lines and found no error.

An exercise I get folk to do, is to assume the Brace position, and whichever way north is pointing, move the orienteering line parallel with the needle using the two guide lines on the M3 to lie either side of the red needle. Then, I ask them to lean forward and view directly down onto the compass and check that their bearing is exact – it never is (unless is directly ahead of them).

« Last Edit: April 08, 2012, 07:18:52 AM by Lyle Brotherton »
“Opinion is the medium between knowledge and ignorance” - Plato

Brian

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Re: Parallax or Quality Control or . . .?
« Reply #2 on: March 04, 2012, 08:02:27 PM »
Thanks again, Lyle.

I would have bet the farm that parallax is the issue.  The guy who posted the review replied to me and said that he'd ruled out parallax (not stated in his original review), and there's another reviewer who claims he's seen the same ±2 degree "offset" in several of these units, and who says it does not exist in the Global version.

So I've written to Suunto to ask their take on the matter, and I'm ordering myself a Suunto MC-2DLIN so that I can make my own judgement.

This can get expensive, but I really can't leave this alone.  I need to know.

Lyle Brotherton

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Re: Parallax or Quality Control or . . .?
« Reply #3 on: March 04, 2012, 08:06:52 PM »
Brian, hold off ordering, I have various compasses that I bought and used for my research, I will mail you the some of the Suunto ones.
« Last Edit: March 05, 2012, 07:13:16 AM by Lyle Brotherton »
“Opinion is the medium between knowledge and ignorance” - Plato

Brian

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Re: Parallax or Quality Control or . . .?
« Reply #4 on: March 04, 2012, 09:19:56 PM »
Wow!  Thanks!  I really appreciate that!