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Odds and Ends
 













 

ODDS AND ENDS.

"Sky and Telescope" May 1994

Throughout the centuries, telescopes have had to cope with the atmosphere - so necessary for life but a hinderance to astronomers. In fact, while the largest telescopes in the world collect a lot of light. they typically cannot resolve double stars or the divisions in the rings of Saturn any better than a humble 6-inch reflector'.

"Sky and Telescope" August 1994

For large telescopes costing millions of dollars, the outcome is dissapointing; A 6' backyard telescope can achieve the same resolution"



It is my opinion that technically an optical system may be superior, but the average viewer cannot tell. Years ago when I had good eyesight I purchased an expensive orthoscopic eyepiece, but could not tell the difference from the Kellner eyepiece I was using. Perhaps if it was possible to look through both at the same time a difference might be noticed. I gave it to others to try in their telescopes and they could not tell the difference either.

Carborundurn Grits.

 
Grit Size
Inches
Microns
 
40
0.0258
684
 
60
0.0160
406
 
80
0.0105
266
 
120
0.0056
142
 
220
0.0026
66
 
320
0.0013
32
 
500
0.0007
16

Tropic Lap.

Quantity supplied to make an 8" dia. lap. ( Two Quantities)

Resin--------- 425 grams 460 grams
Woodflour---- 20 grams 65 grams
Castor Oil---- 40 ccs  

 

Above quantities make up 32.4 c.ins.

6" dia. x %<' thick lap 7 c.ins.
8" dia. x'/," thick lap 12.5 c.ins.





Instructions Supplied.

Preparation :-
(1) Empty the resin into an old sauspan or tin. This should be sufficiently large to avoid boiling over when the wood flour is added.
(2) Heat slowly until the resin liquifies.
(3) Pour in some castor oil and stir thoroughly.
(4) Gradually mix in the wood flour until the mixture is well and evenly saturated.

Forming the Lap :-
(1) Heat the tool by placing it in hot water for several minutes.
(2) Dry thoroughly and wrap a piece of masking tape or cardboard around it to dam up the lap. This strip should extend about 3/8" above the tool.
(3) Place the tool on sheets of newspaper on a flat surface. Carefully lades out the lap until it is at least 1/4." thick over the surface. It is wise to let the lap cool a little. If it is actually boiling it could crack the tool.
(4) To help the lap flow evenly, gently agitate the tool for several seconds.

Cutting the Facets :-
(1) When the lap cools remove the strip of tape and trim the edge with a sharp blade.
(2) Heat the lap in hot water for three to four minutes. Add detergent to stop sticking.
(3) Remove and press with the mirror on top until the lap conforms to the curve of the mirror. It is advisable to also warm the mirror.
(4) Cool the lap in water. Mark off the facets making sure they are off centre.
(5) Impress grouves with a heated metal strip or rule- Trim with a razor blade.
(6) Warm the lap slightly, coat with polishing solution and lightly press. If necessary re-trim the facets and the edge.

 

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