ATM

Fear my mathematical prowess

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It took me awhile, but I finally figured out that the name of the figure that you get if you put a compass at each point of an equilateral triangle, and sweep […]

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ATM

Re: ASTROMART – Response to ad #562793

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I asked the original owner of the 13” mirror for some information so I could start working up a .. er.. “balance” sheet for the scope. I’m not doing cost analysis — […]

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Astro knowledge / ATM

Camera at the Newtonian focus

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My D70 is 5.5”x4.4”. That’s a coverage of 24.2in^2. A 13.1” mirror has an area of 134.78in^2. That’s a 17% obstruction. Even if I mounted the thing on a 5.5” disc, basically […]

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ATM

Blue CR-1

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Art asked if he could buy the blue CR-1 focuser that’s been sitting in my parts box. Until a day or two ago, I didn’t have a use for it. But now, […]

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ATM / Optics

Trixie's on the way

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I bought a 13.1” f/4.5 mirror and matched 3.1” secondary today for $400. It used to be a Coulter red-tube Dob, but I’m just getting the mirrors. They will turn into the […]

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Techniques

Polar Alignment Calculations

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Here’s a page that derives Polar Alignment Calculations. (update 5/2020: the original site is gone, so I found the text on Wayback and am inserting it below. This is by the original […]

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Gear / Observatory / Telescope

Special Guest Star takes the mount at Hilltop O

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The Astro Jedi needed somewhere to store his light sab—- I mean, bucket, and I was only too happy to accommodate him. I have decided that I need to come to a […]

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General / Maintenance / Observatory

Dome shutter is motorized again!

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I finally decided to bite the bullet and fix the shutter motor. Things went sideways last winter, and I’ve been opening the shutter manually (and tying it shut with rope, so we […]

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ATM

Trixie 2017 – tube mods

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I finally got around to cutting the MTA-UTA tubes to length; the only eyepiece that would come to focus with the focuser spacer in place is the Televue 55mm Plossl. If I […]

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