Wedge Construction

[leon]

Hi All

Now this is just a general sort of discussion topic, and would like some thoughts from you good people out there.

I have my 12' SCT pearched on a peir, where the plate it sits on is dead level, in fact it is that level that if i pour a cup of water on it, the water just sits in the middle and dosn't run off.

Ok, thats fine you say, but i want to get a wedge for it for astrophotography.

Bintel sells the super wedge for 995.00, thats to much for me, so i got thinking, and figured i could make one myself.

So here is my theory.

The peir is flat, i know exactly where the pole is even during the day, with 100% accuracy, "Now thats no bull" (the tip of the very last rung of our extended antanna on the roof is exactly 37 degrees, and also dead south.)

I have taken images through a postal tube on the polar shaft of my camera platform, with a camera stuck in the back of the tube, and exposeed for thirty minutes, pretty well spot on. (check out attachment)

I figured if i made a steel plate construction, with an angle of 37degrees, and pointed it directly south, wouldnt that serve the purpose for an equatorialy mounted scope, and be polar alinged.

I maybe wrong here, and missing something, please correct me if that is the case, but what would be the thoughts on that idea.

Thanks Leon

[mick pinner]

you need to be able to make slight adjustments when drift aligning so a moveable wedge is very necessary, when imaging at very long focal lengths you will find constant tweaking of the wedge is needed to get it exact.
l've had mine wedge mounted for some time now and am still testing drift every now and then and minor adjustments still being made to get it perfect, this really is the most critical point of astrophotography even if autoguiding.

[ballaratdragons]

I can see what you are saying Leon, and I certainly believe an adjustable wedge can be made at home. Just make it adjustable in all axis. :thumbsup:

[leon]

Thanks guys,

Yes i agree that the wedge needs to have some sort of adjustments, and it will be mounted so that this can be done in both axis.
I probably forgot to mention that earlier.
Actually i found an alternative design called (The Mrttler Wedge) at this site.

http://members.aol.com/planclos/index/mettler.htm, reckon i might be able to follow this sort of design.

cheers Leon

[5ash]

Hi leon,
I have attached pics of a plywood wedge i made last year for my lx90. I ve made modifications since but only to enable controled adjustment. It works well and holds its alignment well.am able to take unguided photos for 2 to 3 minutes. plywood is made up of two 18mm sheets glued and nailed together to make 36mm ply.Cost me less than $30 to make using simple tools. It is also mounted on a pier . have not needed to make any adjustment to it yet. use one star alignment to adjust the alt and azimuth of the wedge . took 3 goes to get it spot on.
regards philip

ps ive seen a 12inch lx200 on a flimsier fixed plywood wedge!

[leon]

Thanks Phillip

Very impressive, and looks simple to construct, well now i'd better get to work on mine.

Cheers Leon