Quote:
Originally Posted by Lognic04
Unsure whether to do normal stroke or chordal?
|
Hi Logan
Use a centre over centre stroke to mate the tool and mirror. Use a 1/3 centre to get to and maintain a sphere during grinding and polishing. Chordal strokes are for hogging out the centre rapidly. They are normally used only in the early stages of rough grinding.
Can you post a picture of your ceramic tile tool? It might help us give you clearer suggestions on how to adapt it.
I noticed your exchange with Alex re a short focus telescope. I would suggest you avoid very short focal lengths on your first mirror. There are some amateurs getting amazing results with ultra fast scopes - Mel Bartels is the most obvious. However parabolising a short focus mirror is very challenging. If you were successful, you would then need to pay for a high quality coma corrector (paracorr 2), an excellent focuser and high quality (ethos or similar) wide field eyepieces to take advantage of the short focal length. I suspect these additions could easily chew up a couple of thousand dollars.
Your original design with an F5 to F6 10 inch mirror is challenging in itself but doable. You can then get away with no coma corrector, modest eyepieces and something like a GSO focuser.
Hope that makes sense, I'm really keen to follow your progress and hope to catch up one day at the ASV's Instrument Making meeting.
Regards
Rod.