... Lateral support CAN produce astigmatism. This is true for slings, whiffle tree, piano wires etc. For example, in case of piano wires, it is sufficient that...
but when placed at the COG it's fine correct? g. ... whiffle tree, piano wires etc. ... of action are displaced only a ... simlate it with FEM and to ... ...
Short answer is yes it is fine when placed on the COG and other conditions are correct like sling does not pinch mirror or pegs are exactly 90 deg apart. I...
... Dale: I was meaning exactly that: astigmatism might be caused by small misplacements of the restraint system; especially for 30 inches diameter (PS COG is...
... small misplacements of ... not exactly the optimal ... hmmm.... ok - I'll bite - why would the COG not be the best place!? We're talking the center of...
Mauro, The COG is not the center of the edge thickness. I have seen the following used to calculate it: The approximate formuala for the COG is Measured from...
Dale, Jim Burrows supplied me with this delightful formula for the COG (of a flat-backed mirror): Given E=edge thickness and C=center thickness, then the...
... Yes, the COG is where the gravity forces are balanced. As far as I recall (from FEM models) it is slightly different than the place that has "neutral"...
Mauro, ... I don't recall seeing this result in your posts, before. It would be nice to have more detail. In particular, - How far from the COG is the ideal...
Group, Sorry, I neglected to point to the graphic. It's in http://tech.groups.yahoo.com/group/bigdob/files/Koehler/ and is called test_stand.png. ... -- Steve...
... I mean that "thick" plates modelled in 3D of course reveals small differences wrt 2D models. The same concept of "neutral" effect is questionable. There is...
... I do not recall exactly. I recall the difference was very slight. Only a curiosity. I do not think it can have any practical effect. But rememebr, i made...
... I quickly reloaded one of the two-posts simulations (never published). I am not shure now what the were the baundary restraints. In my simulations the...
... PS the back restraints were similar: three points (on down and two high). PTV is about 12-15 nm on surface (1/18-1/23 waves on wavefront), including...
Hey: I just posted a couple of blems to our eBay store: A 15" F/4 with a chip and an 18" F/4.5 with some circumferential scratches. Both mirrors are brand new,...
... I have quickliy reworked th one-edge support (see http://autocostruttori.blogspot.com/ 2005/09/supporto-laterale-degli-specchi-parte.html and possibly use...
I have been struggling with getting my scope properly collimated. I use a laser to help the process, and noticed only recently that *after* I collimate to...
I'm with John, if the laser isn't collimated then collimation is a waste of time. Simply rotate the laser in the focuser, if the dot stays still then you are...
Hi there group. I´m looking for a 110-120 mm secondary mirror for my inminent 610 mm dobsonian. I contacted Reginato in Italy (I´m european) but they won´t ...
A half inch shift is very much for a racked in-out focuser, say over a distance of about 3 inches. If the cause is a not well collimated laser, the collimation...
As I do too. Think about it: The laser is fixed in the drawtube. Whether or not the laser is collimated makes no difference with respect to what the laser spot...
http://www.discovery-telescopes.com/optics.html http://website.lineone.net/~fmilsom/ATM%20page.html http://www.oldham-optical.co.uk/ has up to 30" optics sets,...
If the laser is off and the scope is collimated with the focuser racked in, then as the focuser is racked out the laser dot hits the secondary at a slightly...
It is likely that you are not collimating correctly, because the modern collimation protocol collimates to the focuser axis, i.e.the focuser axis is a given...
