Daily Archives: 6/6/2015

Gert’s 2015 Jupiter Campaign

I forgot to mention my chat with Gert, another telescope making regular up at the Chabot Telescope Maker’s Workshop. He’s a skilled astrophotographer and all around interesting guy, and has embarked on a campaign to do some high quality imaging of Jupiter. You can see some of his results here. Pretty nifty stuff. I copied (without permission, hope that’s okay Gert) one of his nicer images below as a tease, but you should surf over to his website for many more awesome results.

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He also suggested that this $300 webcam was especially well suited for astronomical images. Given his great results, I think I should pay attention to his recommendations.

Perhaps some time in the future I’ll get to doing some of this video/webcam astronomy.

Dusting off some old equipment…

If I am going to get going on this mirror again, I need to dust off and/or build some new test equipment. I never really did make an adequate Foucault/Ronchi tester, preferring to do all my testing at the workshop, but frankly, that seems a cowardly on my part. I suppose I’ll have to figure dummy one up. At it’s simplest, I really just need a light source (an LED, most likely dimmable) and a Ronchi grating. I also like the idea of setting up a small laser to serve as an alignment guide. That will probably be good enough to get started.

Then, I need to make some pitch laps. I think a full sized lap is probably a good idea, but I may want to make a smaller (8″ or even 6″) lap for figuring. I was getting pretty good at working subdiameter laps before I stopped, but I imagine I can get back to it quickly with a little project.

But one bit of old equipment that I have extracted from my garage is my mirror stand. Here it is with my 12.5″ mirror in place:

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Tomorrow I’ll spend some more time doing inventory on the parts and equipment I have. And maybe take the time to jury rig some Ronchi gratings.

Telescope Making: a new return to an old passion..

Even recent readers of this blog may not know of one of my old passions: building telescopes. Back when I was ten or eleven years old, I read an article in Popular Mechanics or some such that told how you could build a telescope from scratch, including grinding and polishing your own mirror (most amateurs build reflecting telescopes, where the primary optic is a mirror, rather than refracting telescopes which use lenses). Somehow, I conned my dad into beginning that as a project. We purchased a 6″ mirror kit from Edmund Scientific, and set to work.

Sadly, my dad was diagnosed with Hodgkin’s disease shortly after that, and passed away several years later. The telescope mirror sat unfinished in my mom’s closet for about fifteen years.

Until I moved to the SF Bay area in 1991, and learned of the Chabot Telescope Makers Workshop. They met up at the old Chabot Observatory every week, and under the leadership of mentor and friend Paul Zurakowski, hundreds of people learned about building and using telescope. I served as a volunteer instructor for a dozen or so years, helped hundreds of people on their projects, and did several of my own, until family commitments and such proved to be too much for me, and I stopped going, about five years ago.

And yet, I still am interested in it. Things are a bit smoother now than they were, so last night I decided to get up to the workshop and see what had changed. The answer is: not a heck of a lot. People are still showing up and building telescopes. A lot of the same people (Rich, Dave, Anthony, Mark, Alan) are showing up and carrying on in the same way they’ve been going on for years.

I brought in the project that I had going when I stopped: my 12.5″ f/5 telescope mirror. It was polished out, and I had begun figuring it, but it has sat on my shelf for more than five years untouched. I used the Ronchi tester that they have at the workshop to check out the general figure:

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(Pardon the bad cell phone picture, but it conveys the right information). Most of you won’t understand what you are staring at, but even though I’ve been away from this for a long time, I can see that the figure is a bit rough, with a broad center zone which is a little bit “flat”, and the overall correction is a little bit overdone. I think it’s time to make a new lap and get working on this scope.

I’m not sure that I’m going to get up to the workshop every week like I used to, but I am going to try to get up their at least once a week, and to do a little bit of work on my telescope every week. I’m sure you’ll be reading more about it here. Stay tuned.