Post Atth8MUvNhIdXeFcJc by th@social.v.st
(DIR) More posts by th@social.v.st
(DIR) Post #Atth3G43sA3A8pFhZY by xdydx@mastodon.social
2025-05-07T21:28:25Z
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@RealGene @th I got that far, but I would have assumed that this was a problem solved centuries ago and accurate or even reasonable commercial products exist.But Trammell seems to building or tweaking one to address a challenge not yet encountered/solved to his satisfaction.
(DIR) Post #Atth3GkxIgMSHrJxQm by th@social.v.st
2025-05-08T08:08:03Z
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@xdydx @RealGene most people consult the tables in nautical almanacs and then do the math by hand or use a calculator, although I find the sexagesimal degree-minute-second arithmetic very error prone. My slide rule removes several of the table lookup and interpolations while also handling the base 60 computations.
(DIR) Post #Atth5oJnUMWAxNpV2G by th@social.v.st
2025-04-13T16:32:06Z
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Is anyone manufacturing custom slide rules?
(DIR) Post #Atth5pORUZpOI50ium by th@social.v.st
2025-04-14T11:18:20Z
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Now with solar declination and sine/cosine tables (in addition to height of eye correction, refraction, parallax, and upper/lower limb calendars)
(DIR) Post #Atth60pQyYxFkyiw0u by th@social.v.st
2025-04-14T15:44:44Z
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although this arrangement for the solar declination correction might be better, even though it makes low d changes less accurate.
(DIR) Post #Atth6F1IDGl7loNbRQ by th@social.v.st
2025-04-16T14:36:04Z
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No, that is not actually useful as a slide rule.
(DIR) Post #Atth6SbDj0Dpt0HykK by th@social.v.st
2025-04-16T15:15:26Z
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The slide rule's refraction adjustment is now temperature compensated.
(DIR) Post #Atth6sRtcIDE3c7tp2 by th@social.v.st
2025-04-19T09:44:35Z
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Paper prototyping reveals that the inner and outer rings of the circular slide rule should have a larger difference in their diameters.
(DIR) Post #Atth7DmAK7u6CYlspc by th@social.v.st
2025-04-27T18:02:45Z
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that's not quite right for the declination compensator.
(DIR) Post #Atth7UyUNYrXXhfSts by th@social.v.st
2025-04-27T18:19:10Z
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Better, although now I'm worried that instead of computing the elevation of the sun, this slide rule will summon a demon instead
(DIR) Post #Atth7fQrUvV3yb1GVs by th@social.v.st
2025-04-27T18:47:50Z
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That appears to correctly compute sin(declination)*sin(latitude) now
(DIR) Post #Atth7sszTeizhbHPf6 by th@social.v.st
2025-05-06T13:56:48Z
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Following up on the original question... Concise Products in Japan seems to still be producing circular slide rules https://www.sliderule.tokyo/products/detail.php?product_id=7
(DIR) Post #Atth83qYj2JdhFE7to by th@social.v.st
2025-05-06T14:33:12Z
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The combined Latitude, Declination, LHA grid didn't work, so instead I've added the normal S/ST, and T/T1/T2 scales to allow computation of Hc and Z from the corrected sextant height.
(DIR) Post #Atth8CygmBAO146FJw by th@social.v.st
2025-05-07T14:05:48Z
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Printed and laminated a prototype of my solar slide rule on 350g A3 at the local print shop and it works fairly well! Correcting sextant height for index error, temperature, refraction, height of eye and lower limb is fast, as is computing latitude from the noon sight. Computing Hc and Z is a bit more involved (using additional scales on the reverse side)
(DIR) Post #Atth8MUvNhIdXeFcJc by th@social.v.st
2025-05-07T14:33:58Z
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Lessons learned:* Definitely need a real clear pointer -- the temporary one is hard to read for the number of digits required for computing Hc and Z.* The two wheels need even more difference in diameter to make it possible to spin them independently.* The outer X scale needs to be more prominent.* The outer X^2 scale can be toned down.* A third scale could fit on the outside edge (maybe log or sine?)