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[ Mariner Home | Introduction | Optics | Plans | Final |
Construction I | Construction II | Construction III | Construction IV ]
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Deciding on the Aperture

I've always known I was going to have a large aperture reflector. I use my scopes until the point where I feel like I'm pushing the boundaries with the things I'm looking for, and then I start thinking about jumping up. It took about 6 years to make the leap from 8" to 12.5", and now it has been about 10 years since I built the 12.5". When I think about aperture jumps, I always think of it in terms of magnitude gain, and figure a reasonable criteria is that the jump in aperture should provide about a 1 step gain in limiting magnitude. From the 8" to 12.5", I went from just over m = 14 to just under m = 15. Using the same criteria here means I should be looking at scopes with limiting magnitudes of m ~ 16.

Using the m = 16 as a criterion, I end up in the 20"-24" aperture range. The figure on the left mapped out what I was talking about, but the figure on the right was the ultimate deciding factor.

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Of course the problem with using a magnitude gain of 1 is that the next time I have to step up (if there is a next time), I'll be looking at an aperture of ~32". Oh darn.


Acquiring Mirrors

I got into amateur astronomy originally because I was given a mirror kit. After working on the mirror for 6 weeks and then breaking it (I dropped the tool on it), I swore I would never make optics again. I love building telescopes, but I'll leave the mirror making to someone else. That being said, if I'm going to buy a mirror from someone else, then I want the best possible mirror my money can buy.

There are a lot of good mirror makers out there. Over the years, it seems it has become difficult to find suppliers of smaller mirrors, but in the large apertures lots of good names come up: Steve Swayze, Steve Kennedy, Mike Lockwood, Terry Ostahowski, and Carl Zambuto. When I finally started down the path toward the big scope, I sent some emails, talked to folks on the phone, and I eventually settled with Zambuto. There were other vendors (including some of the traditional optics companies like Pegasus, Galaxy, and OMI) that I could have gotten larger optics from for the money I had to spend, but Carl's reputation and his customer service completely convinced me to go with him, and I settled in on the 22" from Zambuto Optical Company. On 1 April 2010, I placed my order. Carl was gracious enough to send me some pictures during fabrication, and a Ronchigram when final figuring was being completed.

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Once I decided on the primary supplier, I also had to pick a secondary supplier. Conventional wisdom has been that Protostar provides excellent secondaries, but when I called on the size of interest, they were out of stock and didn't know when a new shipment would be ready. I asked for another recommendation, and they pointed me to Terry Ostahowski. I ordered a 3.5" secondary from Terry on 13 Dec 2010, and had him send it to Carl for evaluation along with my primary. The test results from Terry (left) and Carl (right) are shown below.

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Arrival

The optics arrived on 18 January 2011! I had to take a quick peek, but then I put it back in the box until the scope was done!

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[ Mariner Home | Introduction | Optics | Plans | Final |
Construction I | Construction II | Construction III | Construction IV ]
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Last Updated: 25 September 2012