140325 SBAU Telescope Workshop

140325 SBAU Telescope Workshop

Sam of Westmont, TomW, JerryW, TimC, JoeD, MikeChibnik (also member VenturaCoAS; SB Raytheon EE), ChrisU, EdK, TomT

MikeC showed his wooden stand for grinding or polishing.

TomW pouring 6" pitch lap tool for EdK into silicone mold sitting on the 12.5" mirror with Sam of Westmont observing work.








 Tom showing curvature of pitch lap tool since it is pre-formed while on top of mirror in perfect pitch lap mold.






Sam will take a 10" mirror from TomW and work it to F/4 with porcelain tool.

ChrisU donating some wood circular blanks for grinding / polishing tools and a mirror holder for Sam 10" mirror.



JoeD announced SBAU Messier Marathon this Saturday, March 29, but weather will be a question.  Also, talking paracorr optics with TimC and MikeK.



Some other odd stuff mentioned this evening: 
-Schmidt was a SBAU President. 
-At one time the Telescope workshop had over 10 people at one time. Tonight's nine is a new recent high number.
-Warren Bitters used to bring daughters to telescope workshop.

JoeD holding TimC's 8" pre-scratch; MikeC, TomW, Sam

TimC ground another 30 minutes on the donated 8", but after cleaning up he noticed a scary scratch on the surface.

The Crawford Comet

Update from TimC:

On 3/26/2014 10:53 PM, Tim Crawford wrote:

The top photo is of the original scratch from Tuesday's session. The second (sorry for the lack of focus) has been filtered to enhance it a bit. You can see I made a lot of progress in ridding the surface of this gouge. I agree with Jerry- this is the result of a small piece of tile that exfoliated from the tool during  5 micron grinding. Too bad- I was almost finished. Great lesson in this though. Suggestions from you were most helpful! Here's how it went:

I decided to put in about 10-15 minutes with 5 micron. Results were dismal. The same happened with 12 micron. So, reluctantly I went back to 500 silicon carbide. Here I had modest results and I realized in time I would get rid of most of the defect but not fast enough for my liking. So, I switched to 320 aluminum oxide. Total time with all grits was around 1 1/2 hour. The enhanced photo shows there are still traces of the gouge, but in reality it is diminished through a loupe. The main defects now are 2 main big chips (?) that are evident in the photo. The plan is to now resume with 500 silicon carbide for up to 2 hours. Following will be the subsequent steps from 12-5 micron. Total time could be 6 more hours but I may push it. I apologize for holding up the project. I am still learning so much here. As I said, I much appreciate the comments and support in this project. I am just not sure in the end if I will rid the surface of the entire defect. The defects in my estimation are around the 70 zone, so it can effect the image. After 6 hours plus polishing it will be minimal I believe. The greatest lessons here are to take care of the environment we are working in. It has become apparent keeping a clean environment is crucial to success, and even then there are just freak events like chipping of tile that may happen. (As a result of this I took the tool down to the lab and used a wheel to bevel the outside perimeter of the tile tool. ) The second lesson is to remember that no matter what we can always backtrack and redo any disasters that may happen on the journey to first light. Patience and good humor will be two tools we must include in our toolboxes. Well, enough for now- I'll try to keep you informed of progress, but for now it appears to be just a matter of time......and time heals just about everything.

T