First alignment step, point it North :)

[starguest]

Here's a simple method for setting up the initial conditions for a mount's polar alignment - ensuring it's facing North. Also, for those who might not have Polaris visible, it provides a more exact north facing alignment.

The following may seem obvious and for some who have fixed tripod points in your garden you may have done this. Nevertheless, I haven't seen or read about this method anywhere.

Basically, the idea is to make a giant ' T ' shape, from some suitable length(s) of wood, which fits inside the tripod feet. Then, with the wooden ' T ' alone on the ground, place a rectangular shape, transparent plastic type of compass on the vertical part ' | ' flush with the edge, its open end pointing North, and move the ' T ' until the needle and vertical part is aligned to north.

I'm sure many have used a compass to make a rough tripod align but this allows a more exact setup as well as making permanent tripod marks and being portable.

Another thing is, I've found with a couple of different compasses, there may be some interaction with the metal legs and the reading is flawed, so just using the T alone helps.

I haven't seen all the commercial mounts/tripods but there should be an ' N ' or mark at the leg meant to point towards north/Polaris. If some, bizarrely, have a mark in the gap between legs then the method still applies, though inverted 180deg.

With the T in place, the tripod feet can be placed appropriately at each end.

Or first, in a garden or backyard, dig a small hole at each end and insert a short length of tube - some old spare 15mm plumbing pipe or sized to hold the tripod foot securely. I actually battered into the earth some broken off wine bottle tops! Those with a tiled, decking or other hard surface could make some painted marks.

Now to making the ' T ' shape.

In a suitable space, spread out the tripod legs to the widest you use them. If you have undulating or sloping ground where you normally observe from, it may be better to do this in situ because you need to raise 1 or more legs to have the mount base horizontal - according to its bubble level - and this means the feet points are wider apart.

The foot of the N pointing tripod leg is the apex of a triangle and the base is formed by the other 2 legs.

Measure the distance along the base where the feet meet the ground plus a few cm and place a coin or such halfway along. Measure the distance from the N apex foot to the coin plus a few cm. These are the lengths of wood needed and should fit within a standard 1.8m or 2.1m length of softwood 38x12mm from the diy shop, unless you have some spare pieces around.

The ' T ' shape horizontal part '--' will be the base and the vertical part ' | ' open end meets the N apex. I said above to measure distance plus a few cm. This is to allow a ' V ' notch in the wood at each foot point for a snug fit. Where the pieces meet, the vertical part should overlap the base and obviously meet it at 90deg.

I won't go into actual sawing and construction but just mention these points.

It helps if the V is made in one end of the base first, and with the tripod foot snug in the V the other end can be marked and cut. Note that the 12mm thick suggested may be too much for where the foot spike emerges. I had to cut a Eurostar train nose style slope over the notch area to allow the wood base to slide in easily; like this looking sideways on at the base, the slope being much less steep:

_

/ \

NB the forum editor won't allow the above to look the way I wanted, like a forward slash at left, a long line, a backslash at right. I'm sure you know what I mean though.

With the base done, do the notch/slope at one end of the apex part and with the foot snugly in the notch there should be enough wood to overlap the base. Carefully align it at 90deg and drill a hole through both parts. A long bolt with washers and a nut is used to keep the pieces together and allow swiveling to have a uniform, easily manageable length of wood you can carry to wherever you might want to set up.

Maybe paint it white and then mark on it things like lat/long coordinates for observing sites.

The process of polar alignment for an equatorial mount can be done now and there are a few guides around if your manual isn't that helpful. Here are Astro-baby's, both simple and more complex:

Astro-Baby Telescope Help

Astro-Baby Telescope Help

[msinclairinork]

Cheers for that!

Could you maybe attach some pictures?

Thanks,

Michael

[runoffshed]

I really like the wooden tee idea and also the fixed feet locators but can I just mention that for a bit more accuracy you should find out from an OS map how much your local magnetic north varies from true north. If you know this you can take it into account when using the compass and offset your alignment from the compass reading.

John

[Digz]

A really useful idea to get accurate North alignment and to create a reference for those without permanent setups.

I feel you just cant simply use a compass next the mount (especially the more sturdier ones like the EQ5 or 6) as there is so much metal it distorts the reading.

Thanks for taking the time to share.

[davew]

If you want to know magnetic off set try - Grid Magnetic Angle Calculator

It says 2*36 for me but by eye I got it to 4*. They are a tad more accurate I think

Dave.

[runoffshed]

If you want to know magnetic off set try - Grid Magnetic Angle Calculator

It says 2*36 for me but by eye I got it to 4*. They are a tad more accurate I think

Dave.

Very useful, Dave. I hadn't come across this before.

Many thanks

John

[Makron]

Very useful,

Thanks