Magnetic Compass
Magnetic Compass
I am looking for a decently accurate compass/needle (and reasonably long) for rough polar alignment. Can anyone suggest which shops in Singapore to look for?
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timatworksg
- Posts: 767
- Joined: Mon Feb 01, 2010 9:42 pm
- Location: Pasir Ris
Hey bharat,
I use a mapping compass which I bought at a Beach Road Army Surplus store. It's made by Suunto and I have had it for many years. Used to Topo when I helped my friend and the scouts go hiking in Malaysia (that was then...lol)
I have a line drawn on the top of my Mount head so I can use that to line up with the compasses line. The Topo compass has an arrow for directional use, which helps in aligning this line. But most of all, find a way your comfortable with. Remember that Polar North/South isn't exactly where the mount is supposed to point. Polar and celestial are a little apart.
But as long as your just visual and simple planetary AP, that's no prob. Perhaps later you can dive into drift alignment, where up is down and down is up, left is right and right is left, and left can be up, etc etc....HAHA!
I use a mapping compass which I bought at a Beach Road Army Surplus store. It's made by Suunto and I have had it for many years. Used to Topo when I helped my friend and the scouts go hiking in Malaysia (that was then...lol)
I have a line drawn on the top of my Mount head so I can use that to line up with the compasses line. The Topo compass has an arrow for directional use, which helps in aligning this line. But most of all, find a way your comfortable with. Remember that Polar North/South isn't exactly where the mount is supposed to point. Polar and celestial are a little apart.
But as long as your just visual and simple planetary AP, that's no prob. Perhaps later you can dive into drift alignment, where up is down and down is up, left is right and right is left, and left can be up, etc etc....HAHA!
My wife never complained about how much time, effort & money I spent on my Astronomy hobby!................suddenly I met her!!!
Thanks, Tim. Luckily, the MSCP close to my house is oriented NS-EW (verified my measurements against Google Earth grid) so I simply use the parking lot markings to align my tripod & mount. However, I do need some N-S reference when I go elsewhere like ECP site.timatworksg wrote:Hey bharat,
I use a mapping compass which I bought at a Beach Road Army Surplus store. It's made by Suunto and I have had it for many years. Used to Topo when I helped my friend and the scouts go hiking in Malaysia (that was then...lol)
I have a line drawn on the top of my Mount head so I can use that to line up with the compasses line. The Topo compass has an arrow for directional use, which helps in aligning this line. But most of all, find a way your comfortable with. Remember that Polar North/South isn't exactly where the mount is supposed to point. Polar and celestial are a little apart.
But as long as your just visual and simple planetary AP, that's no prob. Perhaps later you can dive into drift alignment, where up is down and down is up, left is right and right is left, and left can be up, etc etc....HAHA!
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timatworksg
- Posts: 767
- Joined: Mon Feb 01, 2010 9:42 pm
- Location: Pasir Ris
I mark the balcony too! That way I'm pretty much aligned with minor corrections. ECP....where we ob you can't miss the southern Cross...lol! But a compass does help whenever you need one. If you get an Iphone with the compass then thats a snap!
Just don't get the compass to near the mount, especially when you have motors. Throws the needle off!
I also have a wood strip that has a compass right angled and stuck to it. Line that up with 2 legs of the tripod and point the North leg aligned with the compass reading.
As Croy mentioned, the tape is a good way to ensure the mount head and pier are always aligned before you start. At least some straight line thru the mount head so you know your pointed visually where you want to!
I also have tape marked on my counterweight bar so I know where to slide it for different set ups!
Just don't get the compass to near the mount, especially when you have motors. Throws the needle off!
I also have a wood strip that has a compass right angled and stuck to it. Line that up with 2 legs of the tripod and point the North leg aligned with the compass reading.
As Croy mentioned, the tape is a good way to ensure the mount head and pier are always aligned before you start. At least some straight line thru the mount head so you know your pointed visually where you want to!
I also have tape marked on my counterweight bar so I know where to slide it for different set ups!
My wife never complained about how much time, effort & money I spent on my Astronomy hobby!................suddenly I met her!!!
Hi Stuart,croys wrote:Hi,
The magnetic deflection here is pretty strong, so magnetic North is quite far off from true North. Good maps will have magnetic North and true North. You can also work it out from google maps or any map. In fact you don't even really need a compass, just find a landmark due North (or in fact any cardinal direction).
If you have somewhere you observe from regularly, mark the ground with tape near each leg, so that you can reposition the tripod. You can also use tape to mark the alignment of the tripod, half-pier and mount itself. Tape between two parts (e.g. mount and half-pier), then cut the tape. Next time line up the edges of tape. I do this on my balcony. It is repeatable enough for visual use, and it speeds up drift alignment for imaging.
I ckecked Singapore's magnetic declination on today's date on Geological Survey of Canada's website and it shows the decination as 0 deg 15 min E with an annual change of 1.1min W per year. I am not quite sure how this is to be interpreted but does it mean that the magnetic north is 15min to the east of true north?
Hi Bharat,
since you are just doing a rough alignment only, any simple compass design available on the market should do the trick. A roughly aligned scope at low power will have the object in the FOV for at least a few minutes, good enough for your entire family to look at it. I have seen decent compasses sold at DIY-Homeware shops that are around $30. But of course if you want higher end stuffs, you can check up the Silva compass and in case you want a super high end compass, you can get a prismatic compass. Anyway, they more or less work the same. Just buy a velcro to fix the compass on the tripod head and align accordingly, then remove the compass; it is more or less like that.
since you are just doing a rough alignment only, any simple compass design available on the market should do the trick. A roughly aligned scope at low power will have the object in the FOV for at least a few minutes, good enough for your entire family to look at it. I have seen decent compasses sold at DIY-Homeware shops that are around $30. But of course if you want higher end stuffs, you can check up the Silva compass and in case you want a super high end compass, you can get a prismatic compass. Anyway, they more or less work the same. Just buy a velcro to fix the compass on the tripod head and align accordingly, then remove the compass; it is more or less like that.