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Chubs, do you have a permanently mounted equatorial head. I would think you must have to be doing drift alignment.

As Gaz told you, Azimth is the movement in a horizontal plane. Altitude is the height of the polar axis up or down.

You must ensure that the head is perfectly base level and perpendicular.

You likely already know this, I said it just in case.

Ron. :D

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"Chubs, do you have a permanently mounted equatorial head". Does this mean that Chubs walks around with his head at an angle of

55 degrees? You could get a crick in your neck doing that Chubs. :D

Tom

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You must ensure that the head is perfectly base level and perpendicular.

No you dont.

You can start wherever you like with drift alignment. You end up with the RA axis of the scope pointing at the celestial north pole when you have finished, the tripod bit is adjusted for, so you can have that as wonky as you like. If you start with a level mount it takes less time, but not much, but you will always end up with a good alignment this way.

If you have a portable tripod mount, you need to put it back where it was the last time you did an alignment to speed things up, but you can do it with the wonkiest setup going and the drift alignment will compensate for it. It takes longer if you are a long way off initially, but it still doesn't take a long time to do it if you have a webcam.

Captain Chaos

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You must ensure that the head is perfectly base level and perpendicular.

Sorry CC, I am still living in the past when polar alignment was more critical because the only way to get a decent shot of a deep sky object was to track on a guide star manually for at least 15 minutes, so unless you wanted comets surrounding your target, you needed to have a more precise polar alignment.

Ron. :D

No you dont.

You can start wherever you like with drift alignment. You end up with the RA axis of the scope pointing at the celestial north pole when you have finished, the tripod bit is adjusted for, so you can have that as wonky as you like. If you start with a level mount it takes less time, but not much, but you will always end up with a good alignment this way.

If you have a portable tripod mount, you need to put it back where it was the last time you did an alignment to speed things up, but you can do it with the wonkiest setup going and the drift alignment will compensate for it. It takes longer if you are a long way off initially, but it still doesn't take a long time to do it if you have a webcam.

Captain Chaos

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My point is that starting with a perfectly level base, you then go on to adjust the angle between the base and the axis to get the axis pointed north accurately. Well why does the base have to be level to start with? The end result of drift (or any other kind of ) alignment is that the RA axis of your mount is exactly in line with the rotational axis ofthe earth. Once that is done you are polar aligned, end of.

A perfectly level base would be a good thing if you had to set the altitude by measuring the angle and thats all you had for alignment, but its just not necessary when you have alt-az adjustment on the mount head. You have to keep within the range of adjustment of the head, granted, but thats quite a wide tolerance.

Captain Chaos

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Well why does the base have to be level to start with

Been thinking about this CC..

If you start with a non level base then does each adjustment (south and east)

affect the one you just did to some extent so you you need to take more steps to get to alignment?

With a level base, is each adjustment then independent of the other?

:D

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My point is that starting with a perfectly level base, you then go on to adjust the angle between the base and the axis to get the axis pointed north accurately. Well why does the base have to be level to start with? The end result of drift (or any other kind of ) alignment is that the RA axis of your mount is exactly in line with the rotational axis ofthe earth. Once that is done you are polar aligned, end of.

A perfectly level base would be a good thing if you had to set the altitude by measuring the angle and thats all you had for alignment, but its just not necessary when you have alt-az adjustment on the mount head. You have to keep within the range of adjustment of the head, granted, but thats quite a wide tolerance.

Captain Chaos

When I said base, I meant the structure on which the mount is built, not the floor on which it stands,For example Rog. has put in a pillar in his new to be dome. That pillar is probably perpendicular to a degree of accuracy. The plate on the top that will support his mount will need to be level, and he has put machine studs there for that purpose. That is the level I am talking about.

If a polar shaft of any length is not perpendicular, ie at a pure 90 degrees to the horizontal, moving it in azimuth to point at the celestial pole, will not achieve accurate polar alignment. If you were able to project the plane of your polar axis onto the north south line of your local meridien, they must coincide exactly, or the afore mentioned is unachievable. I am totally aware that with todays technology, accurate polar pointing is not a prime requirement, The fact that most large observatories have Alt Azimuth mounted instruments cement that fact.

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Well yes Phil that will be the case, but unless the base is grossly unlevel (did I just invent another word?) the effect should be minimal.

A 5 degree misalignment would be very obvious but the interaction between the alt and az adjustments would be less than 10% (Tan 5 degrees = 0.0875). I think eyeball near enough level will always suffice.

For a polar alignment using the polar scope, you can have the tripod as wonky as you like, and it won't make any difference, unless the tripod sticks out on one side too much and hits the 'scope.

When I said base, I meant the structure on which the mount is built, not the floor on which it stands,For example Rog. has put in a pillar in his new to be dome. That pillar is probably perpendicular to a degree of accuracy. The plate on the top that will support his mount will need to be level, and he has put machine studs there for that purpose. That is the level I am talking about.

If a polar shaft of any length is not perpendicular, ie at a pure 90 degrees to the horizontal, moving it in azimuth to point at the celestial pole, will not achieve accurate polar alignment. If you were able to project the plane of your polar axis onto the north south line of your local meridien, they must coincide exactly, or the afore mentioned is unachievable. I am totally aware that with todays technology, accurate polar pointing is not a prime requirement, The fact that most large observatories have Alt Azimuth mounted instruments cement that fact.

Floor? Why mention the floor?

But if the polar shaft is perpendicular to the horizontal, it would be pointed straight up, wouldn't it? Why stress over getting the plate super level, then use the altitude adjustment screws to adjust it again?

If you had a super aligned setup, with the plate level, then made the plate unlevel by 5 degrees, then adjusted the altitude adjustment by 5 degrees the other way, would it not be aligned as before?

So long as there is a way of adjusting the polar axis such that it is parallel to the earth's rotational axis it will work. The only bit that matters is that the RA axis is aligned, the support structure could be anything at all, level or not.

Captain Chaos

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Well yes Phil that will be the case, but unless the base is grossly unlevel (did I just invent another word?) the effect should be minimal.

A 5 degree misalignment would be very obvious but the interaction between the alt and az adjustments would be less than 10% (Tan 5 degrees = 0.0875). I think eyeball near enough level will always suffice.

For a polar alignment using the polar scope, you can have the tripod as wonky as you like, and it won't make any difference, unless the tripod sticks out on one side too much and hits the 'scope.

When I said base, I meant the structure on which the mount is built, not the floor on which it stands,For example Rog. has put in a pillar in his new to be dome. That pillar is probably perpendicular to a degree of accuracy. The plate on the top that will support his mount will need to be level, and he has put machine studs there for that purpose. That is the level I am talking about.

If a polar shaft of any length is not perpendicular, ie at a pure 90 degrees to the horizontal, moving it in azimuth to point at the celestial pole, will not achieve accurate polar alignment. If you were able to project the plane of your polar axis onto the north south line of your local meridien, they must coincide exactly, or the afore mentioned is unachievable. I am totally aware that with todays technology, accurate polar pointing is not a prime requirement, The fact that most large observatories have Alt Azimuth mounted instruments cement that fact.

Floor? Why mention the floor?

But if the polar shaft is perpendicular to the horizontal, it would be pointed straight up, wouldn't it? Why stress over getting the plate super level, then use the altitude adjustment screws to adjust it again?

If you had a super aligned setup, with the plate level, then made the plate unlevel by 5 degrees, then adjusted the altitude adjustment by 5 degrees the other way, would it not be aligned as before?

So long as there is a way of adjusting the polar axis such that it is parallel to the earth's rotational axis it will work. The only bit that matters is that the RA axis is aligned, the support structure could be anything at all, level or not.

Captain Chaos

That is exactly what I am saying. i should have included the words "plane of the polar shaft, to suggest I meant straight up is just being plain silly. I think we should call a truce on this one, because word bandying is not going to achieve anything, and besides, we are both experienced enough to know what polar alignment requires.

Ron. :D

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Sorry Ron, wasn't having a go at you or anybody. Should have had a LOAD more smileys in there.

My sincere aplologies if anybody thought that I was being at all unpleasant towards them, that was never my intention.

Captain Chaos

No worries there my friend, I know from previous posts, you don't have mean bone in your body.

If we ever manage to meet I'll buy. :D

Ron. :D

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  • 6 months later...

Proof that running a search can provide great results! :D

I've neen reading up on 'drift alignment' and found the whole thing rather confusing....until I came across the site recommended in this thread. I've just purchased myself an eyepiece with an illuminated reticule so I can give it a go. Hopefuly i'll be able to take some serious astronomy photo's real soon!

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can one drift align using the crosshair screen in k3ccd using a CCD?

Wouldn't need to buy a reticule EP then...

Andrew

yes, actualy there's a tool in K3CCD......drift explorer which works quite well.

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can one drift align using the crosshair screen in k3ccd using a CCD?

Wouldn't need to buy a reticule EP then...

Andrew

yes, actualy there's a tool in K3CCD......drift explorer which works quite well.

That sound good...

Where's that setting? what sort of feedback does it give? Does it tell you what to adjust? Or do you still have to work that out for yourself?

Ant

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I have bought this http://wcs.ruthner.at/index-en.php

Not really used it but did have a quick play, loks very easy to use

I have used it and it almost completely demystifies the whole process. It's brilliant.

Just hook up a webcam to your scope and carefully follow the instructions. I won't say it's idiot proof, but it quantifies how much your alignment is out and shows you what to do to correct it.

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I have bought this http://wcs.ruthner.at/index-en.php

Not really used it but did have a quick play, loks very easy to use

I use this as well. You stick a web cam ( and barlow if you want) on the telescope , get the X wires visible , and watch the star to see which way it drifts. You can if you wish follow the procedure with the software which is a bit more involved. Its nice to sit and watch the laptop screen rather than squinting down an eyepiece.

John

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