Building a pier.

[simon84]

PICS Sly, pics !! we need pics

Ok Karlo, I'll get some pics sorted out tomorrow, now lets see what can I show you, a hole in the ground, some soil pipe cut to length and my plate with some holes in.....lol.

Its a great project, really enjoyed it so far. Cant wait for it to be fully operational although at this rate I think the Death Star will be completed before my pier.

[simon84]

Sorry for the delay in getting some pics on here. No camera at the moment.

Pier is all finished and is looking pretty snazzy all sprayed in black. Even the wife was quite pleased with the overall finish of it.

Performance wise, its very solid. Popped my NEQ6 on there with the ED80 and it looks the business. Hoping for a clear night soon so that I can get it polar aligned. Never done it before so going to have an evening of getting that sorted no doubt.

So hopefully I'll be imaging soon, built a new PC for the warm room which will be used for controlling the mount and the camera, the only thing I want to look into getting now is a method for focussing from the warm room.

[laser_jock99]

My 8 inch metal pier is taking shape. It's a two man job to lift and that's before I weld the base on. Will be a few months before I can install though as I need to get a mini digger on site to help with leveling the site. I don't fancy shifting all that earth by hand.

I'm intruiged though why people feel the need to have leveling adjusment facilites on permanent piers as there really is no requirment to have the top level. All you need to do is align the RA axis to the polar axis with the mount's adjustment. Having a perfectly level pier top has no effect.

[gary1968]

We NEED to have a method of levelling the top surface of the Pier Top after the Pier is built. This is required because if the Mount is not levelled correctly it will NEVER track / guide correctly for imaging. The guiding software will have to work really hard to keep the object in the same spot. You might even suffer field rotation if it is really bad.

For visual work you are correct, levelling it is not so important as most goto mounts will compensate for that with the 'sky model' they build duiring initial alignment.

I am sure that the above is correct, if not someone will be along soon to correct me. If it is basically correct then they might add more info to this.

HTH,

Gary

[laser_jock99]

The only reason I can think of for needing leveling on the pier head is if you use an ALT/AZ GOTO type driven mount or a 'wedge' type SCT mount- in either case it might make set up easier/quicker. So on field tripodI can see why a quick leveling before you drop a ALT/AZ GOTO mount is required. But such mounts are no good for long exposure astrophotography due to to the aforementioned field rotation effect. However, if using a more or less permanent set up with German Equatorial type mount then once properly polar aligned the levelness (or otherwise) of the pier head has no effect on the pointing or drive of the scope. If anyone can explain why it should then I'll happily be corrected.

[simon84]

I'm not totally sure on this but even an equatorial mount has to have its altitude set and if setting from a level plane it just makes everything easier.

If you pier head is out of level north to south then yes you can compensate using the altitude adjustment.

Am I right in saying that the software used for guiding goto mounts is designed to work from a level plane? If not then can someone tell me why my NEQ6 has a built in bubble level?

My only reason for including level adjustment on my pier is because every pier I've seen has it.

[gary1968]

I am not totally sure on this, but, if the Pier Top is not levelled it will cause problems with tracking / guiding for the following reason.....

You can point the polar axis at Polaris, even if the Pier Top is not level, and for visual it will be OK. However, even although it is 'pointing' at Polaris the polar axis will not be parallel to the earths axis. This, IMO, will cause the mount to track incorrectly, remember the a EQ mount only tracks in RA. When guiding, because the polar axis is not parallel to the earths axis, the guiding software will guide in RA and Dec.

If the mount is perfectly polar aligned then in theory the guiding software will have to do nothing in Dec.

IMO, this problem will be worse the more 'out of level' the Pier Top is.

But, bare in mind, that this 'out of level' problem will not show if the problem ONLY affects North / South as this WILL be corrected with the Altitude screws during Polar Alignment. Anything other that that out of level will cause problems detailed above.

I too could be off track with my thinking and I am sure if I am someone will be along sooner or later with another opinion.

HTH,

Gary

[Bizibilder]

Surely:

If the polar axis is aligned with the earth's axis (ie properly polar aligned) then the piece of metal that is the polar axis will rotate correctly NO MATTER what direction or angle the rest of the mounting is at. A correctly aligned polar axis simply ROTATES.

As long as the piece of metal that is the declination axis is at exactly 90 deg to the polar axis then that will be OK as well. (and once set it doesn't move anyway).

It is of no consequence at all where the rest of the mount is placed - except for convenience in operation.

(I think )

[laser_jock99]

I am not totally sure on this, but, if the Pier Top is not levelled it will cause problems with tracking / guiding for the following reason.....

You can point the polar axis at Polaris, even if the Pier Top is not level, and for visual it will be OK. However, even although it is 'pointing' at Polaris the polar axis will not be parallel to the earths axis. This, IMO, will cause the mount to track incorrectly, remember the a EQ mount only tracks in RA. When guiding, because the polar axis is not parallel to the earths axis, the guiding software will guide in RA and Dec.

If the mount is perfectly polar aligned then in theory the guiding software will have to do nothing in Dec.

IMO, this problem will be worse the more 'out of level' the Pier Top is.

But, bare in mind, that this 'out of level' problem will not show if the problem ONLY affects North / South as this WILL be corrected with the Altitude screws during Polar Alignment. Anything other that that out of level will cause problems detailed above.

I too could be off track with my thinking and I am sure if I am someone will be along sooner or later with another opinion.

HTH,

Gary

I don't have a GOTO mount so I can't check this out- but you could try an experiment by setting the tripod/pier top way off level. Polar align the EQ mount, set up the GOTO software- this usually involves taking positions of a few known reference stars. Then see how well the mount tracks. I think the accuracy of the polar alignment will have far more effect than the initial level of the scope. As you say the mount/software will have more work to do when correcting the tracking in two axis.

[gary1968]

mmmmm, you make good points there guys, I ain't so sure now. I think I'll do a wee experiment sometime. Not sure when, the weather is sooooo undependable that any cloudless night I have I try to use sensibley, but I will try at some point.

Gary

[Bizibilder]

Just a thought - Your fixed mount parts themselves rotate 360 deg a day because they are securely bolted to a planet!

[laser_jock99]

Just a thought - Your fixed mount parts themselves rotate 360 deg a day because they are securely bolted to a planet!

Yes....but we want our scopes to rotate in the counter direction! Thus (hopefully) remaining fixed, relative to the stars. One thing I never got to grips though- is why it is harder to track objects near the celestial pole than the celestial equator?