rcaffin
2003-07-05 10:15:30 UTC
There is a version of this in the test folder with one known error -
a prize to the first person to find it. :-)
------
Owner Review - Recta Compass DO 150
Roger Caffin
Product Information
Manufacturer: Recta (Switzerland)
Year of manufacture: early-mid 1990s
Manufacturer URL: www.recta.ch
Listed weight (2003): 23 gm (0.9 oz)
Weight in use: 26 gm ( 0.9 oz) with cord loop
Dimensions: 52 x 95 x 12 mm (2" x 3.75" x 0.5")
Product description - general
This is a small oil-filled compass with an rotating capsule, set in a
small rectangular plastic base. The base includes a low-power 22 mm
(~5/8") plano-convex magnifying lens and engraved scales on the
underneath along the two sides - one metric, one imperial. (The
current model shown on the web site has a third scale across the
front edge, and they may be slightly different scales.) There are
holes in the two rear corners for a loop of string, and those corners
are rounded and curved up slightly to minimise any tendency to dig
into your body when the compass is hung around your neck. The DO 110
unit is identical except it does not have the moulded-in lens.
The outer ring of the capsule is black with white graduations in one
degree increments. It rotates in the base and the base has a North
mark, so the capsule may be set to compensate for the local magnetic
declination. (The North mark is invisible in the image here having
lost its pigment years ago.) There is a form of coarse knurling
around the capsule which allows a good grip for ease of rotation. The
base of the capsule is transparent with parallel red lines aligned N-
S relative to the outer scale. There are two red bands on the lines
closest to the pivot, one on each side, which allow me to align the
compass needle parallel to the lines with about one degree accuracy.
The needle is marked red at the N end and white at the S end. The
pivot appears to consist of a hardened steel pin set in the base and
a jewel (sapphire) watch bearing set in the needle. (The Swiss have a
lot of experience with such watch bearings.) There is a slight recess
in the plastic lid which forms the top of the capsule, and this
matches the top of the pivot boss on the needle. It serves to limit
the movement of the needle off the pin when tilted, and is shown in
the diagram below. There is no fluorescent paint on the needle.
Product description - technical
The needle is about 29 mm (1.1") in length, 2 mm (0.7") wide and
about 0.5 mm (0.025") thick. The length appears to be quite
sufficient to give it adequate magnetic torque to overcome any
friction at the pivot. The low thickness lets the needle rotate
fairly quickly through the oil, but there is enough drag that the
needle is only slightly under-damped at typical room temperatures.
The oscillation dies in about two full cycles. Under very cold
conditions the oil becomes a little more viscous and the damping
increases slightly, but since I normally hang my compass around my
neck inside my clothing it doesn't normally get that cold.
The pivot boss is of medium size, about 4 mm (0.15") in diameter. It
is hard to measure the height of the pivot point above the plane of
the needle: I estimate it to be about 2 mm (0.07"). There is a solid
ring of metal below the needle around the pivot, shown in the diagram
as the 'Lower weight'. This is quite important for the usability of
the compass in different countries around the world.
The capsule is retained in the base by a small wire spring right
around it. This spring can be removed (with care and some difficulty)
to separate the capsule from the base. This allows the rotating
bearing to be cleaned out. Doing this prevents wear in the plastic
bearing and maintains the right level of bearing friction, which in
turn helps maintains the preset declination.
Field information
Most of our walking is done off-track in rather complex country, and
continuous and accurate navigation is usually essential to
avoid 'geographical embarrassment'. The compass fits quite well in my
hand for those times when I need to follow a precise bearing. The
damping is sufficient that this is easy to do. While some people like
a heavy compass for this sort of work to help stabilise the unit in
one's hand, I have not found the light weight to present any problem -
and it is easier to carry for long periods than a heavy brass
military prismatic unit!
The flat base lets it rest on a map easily. I normally align the side
of the compass with the grid on the map and then rotate the assembly
until the needle is aligned with the red lines in the base. As
mentioned above, I can align the compass and the map to about one
degree in the field this way. I have yet to experience a practical
navigation problem which required anywhere near that accuracy, even
in the most difficult country. It is always sufficient to allow me to
locate nearby ridges and valleys by extrapolation from the map and to
determine our course. While there are many larger and more complex
compasses (and more expensive!) on the market, I do not believe any
of them would be of any greater utility to me.
On the other hand, I do have smaller compasses, but I have found they
are much more difficult to use in practice. Much care is needed with
the middle one to be sure of the bearing: it has to be 'very'
horizontal to avoid drag on the needle. The smallest one is not
really reliable: there is so little torque on the very short needle
that it jams far too easily. My conclusion is that the size of the DO
150 is about optimal for serious off-track navigation in our country.
Some more expensive compasses include a means for 'sighting' on a
distant point while reading the bearing. Taking several such readings
allows you to triangulate your position on a map (or to establish
where the enemy is so you can fire a cannon at them). However, for
several reasons we very seldom use triangulation. Australia is an old
country and the 'mountains' are usually eroded down to round lumps,
so there are few good points to take bearings off. The scrub is
frequently sufficiently thick that it blocks long distance views all
around. The terrain where we do a lot of walking tends to be more of
a dissected plateau, with no obvious peaks to mention, and often we
are in a narrow valley following a river rather than up on a ridge.
Anyhow, around here travelling for so long without careful navigation
that one needs to establish one's position by triangulation is
usually a recipe for disaster. Other users in other sorts of country
may find triangulation more useful.
The two holes and rounded corners work well. I hang the compass
around my neck on a loop of cord, and the fact that there are two
holes at the corners rather than one in the centre means the compass
always hangs flat against my chest, with the larger flat side against
my chest. I have never been conscious of the corners, so the rounding
might be of some use.
The capsule appears to be well sealed and that I have not seen any
air bubbles appear inside it. While such air bubbles do not affect
the accuracy of a compass, they don't look so good. Recta makes a
model which actually 'features' a bubble: it can be used as a spirit
level as well. However, sighting along the edge of the compass while
looking down at the bubble presents some anatomical difficulties.
The magnifying lens is of low power and I rarely use it. I never use
the scales along the sides, which is just as well since these lost
the pigment marking out of the engraved (or embossed) lines years
ago. I suspect that the pigment has been rubbed off by my skin and
sweat since the underside of the compass normally rests against my
chest. The N line for the rotating ring has also lost its pigment,
which makes setting the declination just a little more difficult.
However, the embossed line is still visible in transmission and the
capsule rotation is reasonable tight, so that I do not need to adjust
the declination setting more than about once every six months.
The absence of any fluorescent paint markings does not worry me at
all. For a start, experience shows the paint does not last more than
a few years. More importantly, I try very hard to be in my sleeping
bag before it gets that dark. On the rare occasions when I have had
to travel at night I have used the stars. (Here in Australia we have
a very convenient arrangement of stars called the Southern Cross and
Pointers which accurately point to the South Celestial Pole.)
International use
A common question is whether a compass bought south of the equator
can be used north of it, or vice versa. The reason for the question
is the tilt in the Earth's magnetic field. In Australia the field
points up at a significant angle, while in North America and Europe
it points down. I have often seen comments that the needle has to be
weighted at one end or on one side to overcome a tendency to align
with the tilt of the field, so that one needs a Northern hemisphere
compass and a Southern hemisphere compass. There are even some
comments like this on the Recta web site - in the section where they
are promoting a far more expensive 'global' version.
To put it politely, these comments are wrong. I bought this compass
in Australia, and I have have used it in Nepal, the UK and France
with complete success. I have also bought a similar compass in the UK
and used that one in Australia. So have many other people. Theory
gives way to experiment.
The reason for this lack of sensitivity to the tilt in the magnetic
field lies in the design of the pivot, as shown in the above drawing.
The centre of support is about 2 mm (0.07") above the plane of the
needle, at the tip of the pin, while the Centre of Gravity (CoG) of
the needle lies well below the plane of the needle. In effect, the
needle hangs 'down'. That is a major reason for the heavy metal ring
I mentioned before: it lowers the CoG. (Another reason for the
presence of the ring is to stop the needle tilting very far when
hanging around your neck, but that could be done with a far lighter
ring.) The torque due to the tilted magnetic field is actually very
small - and so of course is the torque aligning the needle in the N-S
direction. In practice the needle tilts maybe a degree or two before
the effect of gravity balances things out. (Yes, I have measured
this.) Given the normal use in the field, I doubt anyone would ever
be conscious of this.
Servicing
I have been using this compass intensively for many years. In that
time I have once separated the capsule from the base and cleaned the
capsule bearing. Otherwise I have done nothing to it. And it does not
need batteries.
Negative aspects
The loss of the pigment over time is the only negative aspect. I have
done nothing about it as it does not affect my use of it.
Likes:
Small
Cheap
Light
Accurate
Dislikes:
Loss of pigment (minor)
Would we buy another?
Certainly I would buy another compass of this size. I would not waste
money on a more complex unit, but I would also hesitate to go much
smaller. As many other companies sell compasses very similar to this
model, I see no reason to be especially loyal to this brand. But
then, it has worked well.
Biographical information
Name:Roger Caffin
Age:57
Gender:M
Height:1.66 m (5' 5")
Weight:63 kg (138 lb)
Email address:r dot caffin at acm dot org
City, State, Country: Sydney, NSW, Australia
Date:2-July-03
Backpacking Background:
I started bushwalking (the Australian term) when I was about 14 yrs
old, took up rock climbing and remote exploration walking at
University, later on took up ski touring and canyoning. These days I
do all my trips with just my wife. Our preferred walking trips in
Australia are long ones: about a week in the general Blue Mts (east
coast of Australia) and Snowy Mts (alpine) regions, and up to two
months long in Europe and the UK. We favour fairly hard technical
trips in remote country and prefer to travel fast and light. Our ski
touring trips are usually 5-7 days long as well, with full packs and
tents. In between we still do fairly long day trips: it's a form of
relaxation. Having discovered that 20 kg (44 lb) packs are no longer
fun, we have become believers in ultra-lightweight walking. Typically
we carry an ultra-lightweight tent (we need full insect proofing
here), Therm-a-rest mattresses, lightweight sleeping bags,
lightweight packs, a lightweight butane/propane stove, light climbing
rope (frequently used) and very light parkas. I would carry about 12-
14 kg (26-31 lb) total for a week, my wife would carry a bit less
(more when skiing of course).
I am also the maintainer of the Australian aus.bushwalking FAQ web
site www.bushwalking.org.au/FAQ/.
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a prize to the first person to find it. :-)
------
Owner Review - Recta Compass DO 150
Roger Caffin
Product Information
Manufacturer: Recta (Switzerland)
Year of manufacture: early-mid 1990s
Manufacturer URL: www.recta.ch
Listed weight (2003): 23 gm (0.9 oz)
Weight in use: 26 gm ( 0.9 oz) with cord loop
Dimensions: 52 x 95 x 12 mm (2" x 3.75" x 0.5")
Product description - general
This is a small oil-filled compass with an rotating capsule, set in a
small rectangular plastic base. The base includes a low-power 22 mm
(~5/8") plano-convex magnifying lens and engraved scales on the
underneath along the two sides - one metric, one imperial. (The
current model shown on the web site has a third scale across the
front edge, and they may be slightly different scales.) There are
holes in the two rear corners for a loop of string, and those corners
are rounded and curved up slightly to minimise any tendency to dig
into your body when the compass is hung around your neck. The DO 110
unit is identical except it does not have the moulded-in lens.
The outer ring of the capsule is black with white graduations in one
degree increments. It rotates in the base and the base has a North
mark, so the capsule may be set to compensate for the local magnetic
declination. (The North mark is invisible in the image here having
lost its pigment years ago.) There is a form of coarse knurling
around the capsule which allows a good grip for ease of rotation. The
base of the capsule is transparent with parallel red lines aligned N-
S relative to the outer scale. There are two red bands on the lines
closest to the pivot, one on each side, which allow me to align the
compass needle parallel to the lines with about one degree accuracy.
The needle is marked red at the N end and white at the S end. The
pivot appears to consist of a hardened steel pin set in the base and
a jewel (sapphire) watch bearing set in the needle. (The Swiss have a
lot of experience with such watch bearings.) There is a slight recess
in the plastic lid which forms the top of the capsule, and this
matches the top of the pivot boss on the needle. It serves to limit
the movement of the needle off the pin when tilted, and is shown in
the diagram below. There is no fluorescent paint on the needle.
Product description - technical
The needle is about 29 mm (1.1") in length, 2 mm (0.7") wide and
about 0.5 mm (0.025") thick. The length appears to be quite
sufficient to give it adequate magnetic torque to overcome any
friction at the pivot. The low thickness lets the needle rotate
fairly quickly through the oil, but there is enough drag that the
needle is only slightly under-damped at typical room temperatures.
The oscillation dies in about two full cycles. Under very cold
conditions the oil becomes a little more viscous and the damping
increases slightly, but since I normally hang my compass around my
neck inside my clothing it doesn't normally get that cold.
The pivot boss is of medium size, about 4 mm (0.15") in diameter. It
is hard to measure the height of the pivot point above the plane of
the needle: I estimate it to be about 2 mm (0.07"). There is a solid
ring of metal below the needle around the pivot, shown in the diagram
as the 'Lower weight'. This is quite important for the usability of
the compass in different countries around the world.
The capsule is retained in the base by a small wire spring right
around it. This spring can be removed (with care and some difficulty)
to separate the capsule from the base. This allows the rotating
bearing to be cleaned out. Doing this prevents wear in the plastic
bearing and maintains the right level of bearing friction, which in
turn helps maintains the preset declination.
Field information
Most of our walking is done off-track in rather complex country, and
continuous and accurate navigation is usually essential to
avoid 'geographical embarrassment'. The compass fits quite well in my
hand for those times when I need to follow a precise bearing. The
damping is sufficient that this is easy to do. While some people like
a heavy compass for this sort of work to help stabilise the unit in
one's hand, I have not found the light weight to present any problem -
and it is easier to carry for long periods than a heavy brass
military prismatic unit!
The flat base lets it rest on a map easily. I normally align the side
of the compass with the grid on the map and then rotate the assembly
until the needle is aligned with the red lines in the base. As
mentioned above, I can align the compass and the map to about one
degree in the field this way. I have yet to experience a practical
navigation problem which required anywhere near that accuracy, even
in the most difficult country. It is always sufficient to allow me to
locate nearby ridges and valleys by extrapolation from the map and to
determine our course. While there are many larger and more complex
compasses (and more expensive!) on the market, I do not believe any
of them would be of any greater utility to me.
On the other hand, I do have smaller compasses, but I have found they
are much more difficult to use in practice. Much care is needed with
the middle one to be sure of the bearing: it has to be 'very'
horizontal to avoid drag on the needle. The smallest one is not
really reliable: there is so little torque on the very short needle
that it jams far too easily. My conclusion is that the size of the DO
150 is about optimal for serious off-track navigation in our country.
Some more expensive compasses include a means for 'sighting' on a
distant point while reading the bearing. Taking several such readings
allows you to triangulate your position on a map (or to establish
where the enemy is so you can fire a cannon at them). However, for
several reasons we very seldom use triangulation. Australia is an old
country and the 'mountains' are usually eroded down to round lumps,
so there are few good points to take bearings off. The scrub is
frequently sufficiently thick that it blocks long distance views all
around. The terrain where we do a lot of walking tends to be more of
a dissected plateau, with no obvious peaks to mention, and often we
are in a narrow valley following a river rather than up on a ridge.
Anyhow, around here travelling for so long without careful navigation
that one needs to establish one's position by triangulation is
usually a recipe for disaster. Other users in other sorts of country
may find triangulation more useful.
The two holes and rounded corners work well. I hang the compass
around my neck on a loop of cord, and the fact that there are two
holes at the corners rather than one in the centre means the compass
always hangs flat against my chest, with the larger flat side against
my chest. I have never been conscious of the corners, so the rounding
might be of some use.
The capsule appears to be well sealed and that I have not seen any
air bubbles appear inside it. While such air bubbles do not affect
the accuracy of a compass, they don't look so good. Recta makes a
model which actually 'features' a bubble: it can be used as a spirit
level as well. However, sighting along the edge of the compass while
looking down at the bubble presents some anatomical difficulties.
The magnifying lens is of low power and I rarely use it. I never use
the scales along the sides, which is just as well since these lost
the pigment marking out of the engraved (or embossed) lines years
ago. I suspect that the pigment has been rubbed off by my skin and
sweat since the underside of the compass normally rests against my
chest. The N line for the rotating ring has also lost its pigment,
which makes setting the declination just a little more difficult.
However, the embossed line is still visible in transmission and the
capsule rotation is reasonable tight, so that I do not need to adjust
the declination setting more than about once every six months.
The absence of any fluorescent paint markings does not worry me at
all. For a start, experience shows the paint does not last more than
a few years. More importantly, I try very hard to be in my sleeping
bag before it gets that dark. On the rare occasions when I have had
to travel at night I have used the stars. (Here in Australia we have
a very convenient arrangement of stars called the Southern Cross and
Pointers which accurately point to the South Celestial Pole.)
International use
A common question is whether a compass bought south of the equator
can be used north of it, or vice versa. The reason for the question
is the tilt in the Earth's magnetic field. In Australia the field
points up at a significant angle, while in North America and Europe
it points down. I have often seen comments that the needle has to be
weighted at one end or on one side to overcome a tendency to align
with the tilt of the field, so that one needs a Northern hemisphere
compass and a Southern hemisphere compass. There are even some
comments like this on the Recta web site - in the section where they
are promoting a far more expensive 'global' version.
To put it politely, these comments are wrong. I bought this compass
in Australia, and I have have used it in Nepal, the UK and France
with complete success. I have also bought a similar compass in the UK
and used that one in Australia. So have many other people. Theory
gives way to experiment.
The reason for this lack of sensitivity to the tilt in the magnetic
field lies in the design of the pivot, as shown in the above drawing.
The centre of support is about 2 mm (0.07") above the plane of the
needle, at the tip of the pin, while the Centre of Gravity (CoG) of
the needle lies well below the plane of the needle. In effect, the
needle hangs 'down'. That is a major reason for the heavy metal ring
I mentioned before: it lowers the CoG. (Another reason for the
presence of the ring is to stop the needle tilting very far when
hanging around your neck, but that could be done with a far lighter
ring.) The torque due to the tilted magnetic field is actually very
small - and so of course is the torque aligning the needle in the N-S
direction. In practice the needle tilts maybe a degree or two before
the effect of gravity balances things out. (Yes, I have measured
this.) Given the normal use in the field, I doubt anyone would ever
be conscious of this.
Servicing
I have been using this compass intensively for many years. In that
time I have once separated the capsule from the base and cleaned the
capsule bearing. Otherwise I have done nothing to it. And it does not
need batteries.
Negative aspects
The loss of the pigment over time is the only negative aspect. I have
done nothing about it as it does not affect my use of it.
Likes:
Small
Cheap
Light
Accurate
Dislikes:
Loss of pigment (minor)
Would we buy another?
Certainly I would buy another compass of this size. I would not waste
money on a more complex unit, but I would also hesitate to go much
smaller. As many other companies sell compasses very similar to this
model, I see no reason to be especially loyal to this brand. But
then, it has worked well.
Biographical information
Name:Roger Caffin
Age:57
Gender:M
Height:1.66 m (5' 5")
Weight:63 kg (138 lb)
Email address:r dot caffin at acm dot org
City, State, Country: Sydney, NSW, Australia
Date:2-July-03
Backpacking Background:
I started bushwalking (the Australian term) when I was about 14 yrs
old, took up rock climbing and remote exploration walking at
University, later on took up ski touring and canyoning. These days I
do all my trips with just my wife. Our preferred walking trips in
Australia are long ones: about a week in the general Blue Mts (east
coast of Australia) and Snowy Mts (alpine) regions, and up to two
months long in Europe and the UK. We favour fairly hard technical
trips in remote country and prefer to travel fast and light. Our ski
touring trips are usually 5-7 days long as well, with full packs and
tents. In between we still do fairly long day trips: it's a form of
relaxation. Having discovered that 20 kg (44 lb) packs are no longer
fun, we have become believers in ultra-lightweight walking. Typically
we carry an ultra-lightweight tent (we need full insect proofing
here), Therm-a-rest mattresses, lightweight sleeping bags,
lightweight packs, a lightweight butane/propane stove, light climbing
rope (frequently used) and very light parkas. I would carry about 12-
14 kg (26-31 lb) total for a week, my wife would carry a bit less
(more when skiing of course).
I am also the maintainer of the Australian aus.bushwalking FAQ web
site www.bushwalking.org.au/FAQ/.
------------------------ Yahoo! Groups Sponsor ---------------------~-->
Inkjet cartridges up to 80% off. HP, Epson, Lexmark--we have your brand.
Free shipping on every order to the U.S. and Canada! Excellent service.
http://www.c1tracking.com/l.asp?cid=5510
http://us.click.yahoo.com/QWB0QC/.eUGAA/ySSFAA/V4TolB/TM
---------------------------------------------------------------------~->
To unsubscribe from this group, send an email to:
BackpackGearTest-unsubscribe-***@public.gmane.org
Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/