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Making a 6 inch Chief

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#1 Ed Jones

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Posted 25 June 2013 - 12:51 PM

I've been working on a 6 inch Chief. I'm trying Dave O's idea of mounting the upper OTA on a tripod in the corner. Shown here is the work in progress (two of the legs will be added later) to get a sense of what it will look like. Temporary Zip ties are holding the tube on the cradle.

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#2 kfrederick

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Posted 25 June 2013 - 01:33 PM

Looks nice! I had to use a green laser to find where mine was looking .It will not be centered an any axis . Setting circles will work but more setup is needed [I ask] There is a very large offaxis reflector mounted that way .See if I can find the link . over several meters diameter .

#3 Jeff Morgan

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Posted 25 June 2013 - 02:45 PM

Interesting, and probably a lot more approachable for a potential first time Chief builder. What are the ranges of focal ratios at that aperture?

#4 Ed Jones

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Posted 25 June 2013 - 03:41 PM

This one is F/12 and uses COTS lenses which I still need to order. I had made a couple of primaries a few years back and thought I go ahead an build it even though I already have another 6 inch Chief. An awesome performer I might add. I picked up a nice painted 80 mm telescope off Ebay although nobody makes a focuser for it. This one is a reflector focuser without the base.

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#5 Ed Jones

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Posted 26 June 2013 - 08:20 AM

The lens holder is PVC doughnut machined slightly smaller than the lenses and cut to a 15 degree wedge (the angle between the lenses) on a table saw. The delrin clips were made on a lathe to have a step equal to the edge thickness of the lenses then drilled off center. These can be rotated to center each lens in X and Y measuring with calipers from the edge. Brass pins were placed on the diameter as a rotation axis held in place by a tight fitting ring. This ring was cut from the left over tubing with a key filed into the ends to act as a solid ring. This allow the holder to be placed anywhere in the tube or rotation. Pretty slick.

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#6 Dave O

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Posted 26 June 2013 - 08:28 AM

"Pretty slick" is right! Wow! I particularly like your idea for adjusting the de-centers ... be sure to let us know how well that works (thinking it will be a bit of trial and error in adjusting these things?)!

I like 'simple' things, and this lens cell is getting simple enough to where even I may have to give it a go!
Cheers. Dave O

#7 kfrederick

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Posted 26 June 2013 - 10:43 AM

The thing you showed me about tipping the lens 90deg to the optical axis to see if the laser reflects back on its self Cannot be done with this? I like that on the 20. as it get the one axis of each lens nailed. Square Very nice Is there a baffle at the secondary? Are you going to Stellafane??

#8 Ed Jones

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Posted 26 June 2013 - 11:03 AM

The centration ought to be straightforward. In the X direction (axis of pins) the centration is zero and I can measure from the edge to make them equal with calipers. In the Y direction (wedge direction) the concave lens should be .027 inch farther than the convex lens from the thin edge. I can set the perpendicularity by checking with a laser, (rotating the holder). Finally if the holder rotation axis is off the holder can be rotated in the tube or the tube can be rotated in the cradle if I see any non-orthogonal astigmatism. That's the plan anyway.

#9 kfrederick

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Posted 26 June 2013 - 11:19 AM

Only the laser target and holder rotation need to be in correct rotaional axis with each other And the distance to focus from the last surface . Nice Should be simpler to setup . Move the whole top up till the moon focuses at the correct distance .

#10 Ed Jones

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Posted 26 June 2013 - 11:44 AM

Stellafane?


I doubt it.

#11 kfrederick

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Posted 27 June 2013 - 04:50 PM

Be nice some year For you and me to enter the 20 Chief as a joint build . Guess we should have done that 4 years back. Nice telescope .I guess you making a platform for it ?

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#12 Ed Jones

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Posted 27 June 2013 - 06:26 PM

I already have a platform for it. It should fit in my other 6 inch rocker box as well, at least temporarily. Here's the prescription BTW.

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#13 kfrederick

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Posted 28 June 2013 - 08:06 AM

http://www.toweropti...erOptical27.pdf

#14 kfrederick

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Posted 28 June 2013 - 08:08 AM

http://www.toweropti...erOptical25.pdf






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