Busy reading but missing the explanation

[happy-kat]

This jolly Rubbish weather has lead me now to look at building a barn door mount.

I am fairly up to grips with a basic barn door design (ha ha not the maths particularily though but the gist is undestood), but why do some have a latitude wedge in the design?

If the camera is mounted using a ball joint then the camera angle can be moved freely so does this not wipe out anything that the latitude wedge points the board at?

Any help on understanding to wedge or not greatfully received.

[Ags]

The axis of rotation has to point at the pole. The ball joint doesn't help.

[happy-kat]

If I have already lined the hinge up to the celestial pole why would a wedge give anything more as they all have the camera on a form of ball joint so it can point where ever?

[bambuko]

I always thought it was to do with ability to use it in different locations (i.e. different latitude).

So if you only going to use it in one location than you do not need to adjust, just set it for that latitude?

On the other hand ... I have been known to talk out of my rear orifice   so perhaps I am wrong?

[happy-kat]

If the thread does not change per rpm I can see a test coming on but this is a project for in a while I need to collect bits to make it cheaply first.

Still don't get why a wedge as images on googling have the contraption without a wedge mounted flat on the tripod.

[Ags]

Can you link to one of these images, I'm missing something...

[Lonestar70]

Hi Happy- Kat,

The camera ball head has nothing to do with the way the mount works.

If the whole barn door unit is mounted flat on the top af a tripod then you will get field rotation in your pictures... regardless of which way the camera is pointed

When you say if you lined the hinge up to the pole... it is not just a question of pointing it North.

The whole unit must be mounted at an angle equal to your latitude... this is where the wedge comes into play when the tripod is not equiped with any means of angling the top fixing.

Simply make a wedge with an angle the same as your latitude and glue it to the bottom of you barn door baseplate.

Now when it is fitted to the tripod and pointed North the hinge axis will be aligned to the earths axis and thus give you true right ascension rotation.

When setting up make sure the hinge of the Barn door assembly is on the Left hand side when pointing North.

It is the same thing as aligning the right ascension axis of an EQ mount with the rotational axis of the earth.

If the tripod is fitted with a tilting head assembly, then a wedge would not be required.

Why do you think the thread RPM would change?... if it did, then you would be in trouble... the speed (rpm) must be set such that the mount rotates at exactly the same speed as the earth... and that does not change.

I hope that helps.

Best regards.

Sandy.

[happy-kat]

Image here of an example I was looking at showing a wedge.

Thank you.

OK my tripod head is such that to angle it right would be tricky so a wedge it is then.

[Lonestar70]

Hi Happy-kat,

You are welcome, pleased I could be of some help.

I wish you luck with your build.

Best regards.

Sandy.

[happy-kat]

Getting there I now have a mini head for the camera, a hinge and a carriage bolt, I will have to order the T nuts after I work out the sizes I need for the bolt and a camera tripod mount thread.

[happy-kat]

Slow progress, now also have the T nuts and other fixing bits.

Thinking my ball head is too small it is very tiny.

Might get this one but is it too heavy does anyone think please?

It weights about 500 grams. I was thinking of it also for general use ball head.

http://www.amazon.co.uk/dp/B006O8E062/ref=wl_it_dp_o_pC_nS_ttl?_encoding=UTF8&colid=CPP32I3OI1GS&coliid=I1FF84CVKLR7H8

[happy-kat]

I bought a ball head from Astroboot when I got the weights for my home made counter weight bar.

The two locations I will want to use it in have latitude of 50.9535° and 49.4350° with this being so close (and what we can cut with a meitre saw) would 50° be close enough to use at both locations please?

[happy-kat]

Going to make one wedge of 50 degrees.

[Atreta]

You could make a variable latitude wedge too.

Once i was reading about and found a page teaching how to build it.

The wedge was made in such a way that the angle could be altered just by loosing a bolt and moving up or down and then tightening it again

just like with a satellite dish.

gonna post here if i find it again.

[happy-kat]

Yes maybe for a Mark II I could look at an adjustable altitude jobby.

Been thinking.

I use a wegde 50° and mount the barndoor onto that.

I have a small finderscope I can use for the hinge end.

I mount the wedge/barndoor onto the tripod which will be an AZ3 and hopefully on level gound.

So I gues I use the finderscope to be able to turn the tripod head on the azumith axis to locate polaris because the wedge at 50° is giving me the correct altitude?

Sorry for such rudementary questions just getting to understand why rather than just do the how.

So far I have two boards cut and then found I hadn't got the screws to mount the hinge lol, so off to hardware store tomorrow.

[Davey-T]

If your wedge is a fixed angle you can adjust the front tripod leg, the one pointing north, for polar aligning.

Dave

[happy-kat]

Thanks you for the replies

I think I need to go read more about polar aligning in general as I didn't get the leg thing as the legs are all the same rather than one is more lead than the other and the tripod head spins on the legs.

[Davey-T]

Like this

Dave

[happy-kat]

Thank you

I guess I can use the alt slo mo control to do that too rather than adjust a leg.

[Davey-T]

Thank you

I guess I can use the alt slo mo control to do that too rather than adjust a leg.

NO 

Dave

[happy-kat]

Oh ok

That is a very clear no then :-)

Just set me a challenge to work out why now lol

[happy-kat]

Just wanted to say my head is sure frazzled.

Currently researching which side the hinge goes on my barn door as my sight scope mount is one sided so I must get this right.

I have my wedge cut for mounting onto.

I have an AZ3 tripod.

So one leg will point north.

The wedge will be on the camera adatptor base that will effectively be facing north as well but in order to do that I will have the slanted face at the back on south otherwise the barn door when mounted would be facing the wrong way.

I am now working out (google) which side the hinge will need to be for my northern hemisphere.

I may get to use it one day lol