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Just a note I was not trying to make you look foolish, lol.

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Only I can do that Andy...... I know you weren't..

Many of the issues I have been dealing with have been simply machine issues. I've never made a mirror by machine before....there is a learning curve..I am climbing. it's quite steap at present..but it isn't that high.

One thing is for sure.....once I get it down with your mirror....I'll have it down. Second the Porter machine definately hoggs out mirrors much faster then this machine does. it isn't a problem..really...just gives me time to focus and to make repairs to the Porter permanently.

I've also been giving my 10"f/15 refractor a lot of thought while *hogging* out your mirror. I have finally figured out my machining approach to attaching the tube adapter ring to the tube and making it collimated.

Plus.... old renters are out and we are getting ready for new ones....

Rob

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www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.

http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.

www.vimeo.com/6014031

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Might be a blessing in disguise, by hogging slower, maybe your able to avoid over shooting your depth, I dont know just looking for the silver lining

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Might be.....however...I check the hogging process often..the f/3.8 got that way because I had to rehog it out and in doing so I went deeper then intended.

Still....I'm taking this mirror from infancy to maturity....by way of extreme care and applied experience....gained from past failures.

Its hogging is nearly as smooth as fine grinding...too..since using the new diamond cutter.

Not much more to go.

Rob

--------------------
www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.

http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.

www.vimeo.com/6014031

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Diamond cutter..? like the ones I use to mill aluminum?...or something else entirely?

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A diamond stone cutting blade. A wet blade for cutting stone/glass/tile/cement.....

Rob

--------------------
www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.

http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.

www.vimeo.com/6014031

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Waiting for the new pitch? As I was reading about all your problems with the pitch I see there is actually a thread on the topic,lol. Dont know as it would help you though.

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Finished hogging the blank out...now I'm making the new grinding tool.....pouring die stone and epoxying pennies....

Fun stuff.

Soon we will be grinding.

Rob

--------------------
www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.

http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.

www.vimeo.com/6014031

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Spirograph???

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After fine grinding.....I think I'm ready to begin polishing.

Rob

--------------------
www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.

http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.

www.vimeo.com/6014031

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interesting photo...what am I looking at???? sorta looks like a donut ring raised with a low center and edge?????

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A parabaloid shadowgram is indicitive of this type of image. Kinda like a donut. Slower parabaloids such as an f/6~9 would show less of a pronounced central dip or bowl with a zone 7 hill around the mirror.

The shadowgram is taken within the caustic zone of the returning light rays. This is where the KE intersects the returning rays. It appears as if the center (being a shorter radius) is a depression while the marginal zone (which is of a longer radius) appears turned outward..so it looks convexed

Being this mirror is an f/3.8 the shadows between the zones is much more pronounced. This mirror still need further polishing and figuring to soften the zones and bring the center out a bit. This mirror is slightly hyperbolic. In My uneducated view.

Rob(I'm sure the experts will pipe in and correct me)

--------------------
www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.

http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.

www.vimeo.com/6014031

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Great job Rob that looks like a dramatic improvement!

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Thanks Johnny.....

I've worked hard to make it so. I've worked with making modified polishing tools to polish only the needed areas and I combined modified strokes to permit the tool to work only the areas I want to work.

Plus using the appropriate pitch for the temp of the shop is imperative to good contact(this I learned)

Droid's mirror is getting a bit more fine grinding so I can begin to see a slight polishing of the surface from the pennies. This method works well for me and then the polishing will continue with #55 Gugolz premium pitch.

Making mistakes is the best way to learn and grow....and I've made my share. No better way to become experienced....IMV

Again thanks.

Rob

--------------------
www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.

http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.

www.vimeo.com/6014031

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