Knee joint flipless pier systems...

[ollypenrice]

While talking to Lucas Mesu I heard about an idea for delaying the flip on conventional mounts. It seems that ASA have got there already but, whatever, this does seem an interestng idea.

http://www.astrosysteme.at/eng/mount_ddm160.html

You need to order a latitude specific bend in the knee, but with modern fabrication methods that shouldn't cost the earth. I dare say it would be possible to build in a range of angles if the knee were given some articulation, too. Fine tuning of the Dec angle can be done at the ground attachment points. Letting the angled pier end in a small tripod base with one adustment available on the north foot would be all you'd need for fine tuning.

ASA are saying 'no flip' in their advert in the link, but surely that would depend on tube length? However, this system would clearly allow tracking far further past the meridian than pure GEMs on vertical piers.

I think this idea is veeery interesting! What do you reckon?

Olly

[Zakalwe]

yep...its.a.good idea. Theres nothing in the design that should cause a big issue for any fabricator. The bolting mechanism to the ground would need to be specified, as would the pier pad.

I would think that any GEM would be usable as long as the altitude adjustment has the necessary range and can take the forces working through the mount in a didderent way.

[nigelg]

I have seen these piers before but could not afford a pier and a Mesu 200. So just had the Mesu, maybe if the lottery give me a grant to fund it?

Thisis the one I considered. http://www.jtwastronomy.com/products/kneepier.html

Nigel

[JamesF]

I would think that any GEM would be usable as long as the altitude adjustment has the necessary range and can take the forces working through the mount in a didderent way.

If the top were made horizontal then perhaps you could use it without stressing the mount a different way?

James

[JamesF]

I have seen these piers before but could not afford a pier and a Mesu 200. So just had the Mesu, maybe if the lottery give me a grant to fund it?

Thisis the one I considered. http://www.jtwastronomy.com/products/kneepier.html

Nigel

Ah, that's what I meant in my previous comment.

James

[JamesF]

I have seen these piers before but could not afford a pier and a Mesu 200. So just had the Mesu, maybe if the lottery give me a grant to fund it?

Thisis the one I considered. http://www.jtwastronomy.com/products/kneepier.html

Nigel

Actually, with this design I'd have thought it would make sense to get rid of the top mounting plate and just make an "owl's nest" underneath the bottom plate.  It's not as though much material would even need removing because of the angle of the tube.

James

[ollypenrice]

The standard Mesu collides with itself eventually though; the limiting factor is the puck contacting a casing. No doubt it can be revamped to avoid this but the AWR wouldn't add much to the standard Mesu so far as I can see.

Olly

[JamesF]

How is polar alignment achieved?

James

[ollypenrice]

How is polar alignment achieved?

James

Don't know, regarding specific makes of knee pier. However, it would be naive to imagine that you could get a perfect alignement just be having a very accurate bend in the knee, I think. Life isn't like that. Some fine tuning is always going to be needed (kneeded??) so my feeling, as I said earlier, is that a little adjustment on the north foot of a three point attachment to the ground would be best. There would also be the issue of exactly polar aligning the knee bend. This might be a bit more tricky than meets the eye.

Olly

[Zakalwe]

If the top were made horizontal then perhaps you could use it without stressing the mount a different way?

James

Not much point really, as a long OTA could still hit the pier, unless the pier is custom made to sit the mount & scope combination. JTW say that they need to know what mount and OTA is being used before they make the pier. You might as well use a standard pier.

The idea behind the ASA one is that the supporting arm is along the RA axis so an OTA could track through a full 24 hours without colliding.

How is polar alignment achieved?

James

The ASA has a "levelling" plate at the bottom where it bolts to the ground. The azimuth adjustment is done at the pier base instead of at the mount.  See fig.10 here: http://www.astrosysteme.at/images/DDM160_ConstructionManual_E.pdf

Plus, I guess, the angle subtended by the pier would have to match the RA angle at your latitude.