#31
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46P, can't see
Mike Collins wrote:
StarDust wrote: On Sunday, December 9, 2018 at 9:13:17 PM UTC-8, Chris L Peterson wrote: On Sun, 9 Dec 2018 23:15:38 -0000 (UTC), Mike Collins I just found it again from my back yard. Not perfect seeing. I can just make out the Milky Way but only one star in the bowl of USA minor is visible. I make it out to about 8 seconds of arc. 8 _minutes_ of arc? That's very small? Few people here saying the comet is very large. Maybe the brightest part, the nucleus of the comet is 8 arc minutes? I went by the side of the comet I could see. I used the apparent distance between the nearby stars to estimate the size. It was exact where Luminos predicted. From the darker sky site I used for my first observation it might have been larger but you are observing from a city with light pollution maybe worse than my village. Getting in my car to observe the comet wasn’t an option last night due to early sampling of Christmas port. I went to a darker sky area a couple of miles away and the comet was easy in 10x50 binoculars but not visible with the naked eye. It was-1.5C and, as common at this time of year in Norfolk fog was beginning to form over the fields. I’m not good at estimating the brightness of extended objects like comets but it was less bright than the Orion Nebula and M31 and about 10 or 12 minutes of arc. The comet was also visible in the 8x40 binoculars I keep in the car for wildlife and bird watching. |
#32
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46P, can't see
Paul Schlyter wrote:
On Sun, 9 Dec 2018 23:15:38 -0000 (UTC), Mike Collins wrote: I just found it again from my back yard. Not perfect seeing. I can just make out the Milky Way but only one star in the bowl of USA minor is visible. Aren't you confusing seeing with transparency? Even with horrible seeing the Milky Way will be easily visible if only the transparency is good and the sky is dark. He might have meant the verb (colloquial), not the noun (technical) -- PointedEars Twitter: @PointedEars2 Please do not cc me. / Bitte keine Kopien per E-Mail. |
#33
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46P, can't see
On Monday, December 10, 2018 at 2:56:02 PM UTC-8, Thomas 'PointedEars' Lahn wrote:
StarDust wrote: I use C2A! http://www.astrosurf.com/c2a/english/ ACK. But to remind you, not every one is professor in math! This is a stupid reaction. I am not a professor in math either. I happen to study astrophysics (where this is repeated), but this is basic geometry (how to calculate the arc length on the circumference of a circle) that you learn in (high)school already. I took some of my *precious* *free time* to explain it to you *for free*, so that you can answer your question for an arbitrary celestial object for yourself next time, and you are *complaining* about that? And you still do not have the decency to introduce yourself to strangers with your real name? Tell me: Why should I read any of your postings again? -- PointedEars Twitter: @PointedEars2 Please do not cc me. / Bitte keine Kopien per E-Mail. I just asked a simple question, how big is comet? You answered with math calculations. I know what arc minutes and angles are, used it all my life, I use to be a Journey man machinist and later mfg. engineer. |
#34
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46P, can't see
On Mon, 10 Dec 2018 07:43:48 -0800 (PST), StarDust
wrote: In fraction one can use proximation, like the closest to .835 is 27/32 = 0.84375 or +1/32 away is 7/8 th! I think, a carpenter, cook or plummer don't care about 1/32 difference? LOL! Actually, 167/200 is even closer to 0.835 since it is exactly the same. You cannot get closer than that... If you care about a 1/32 difference depends on your demands of precision. A cook may not care, but a precision mechanic will care. If there's a mismatch of 1/32 cm between your eyepiece and your eyepiece holder on your scope, you may be unable to insert your eyepiece. |
#35
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46P, can't see
On Mon, 10 Dec 2018 19:11:54 -0000 (UTC), Mike Collins
wrote: Paul Schlyter wrote: On Mon, 10 Dec 2018 13:19:53 -0000 (UTC), Mike Collins wrote: I find it hard to format my brain in minutes and seconds of arc. I think of degrees and decimal degrees. Do you feel the same about time? So you use hours and decimals of hours instead of hours, minutes and seconds? "I'll see you at 9.835" - such a statement would be wilder most people... When I wrote planetarium software in the 80s I used decimals and only converted to minutes and seconds for the final display. That's natural. You want to use one unit instead of mixing different units internally in the software. For angles that unit could be degrees. Or radians, so the built-in trig functions work without any need for unit conversion. For time, hours could be that unit. Or, perhaps even better, days counted from some reference date. All with fractions to full machine precision of course. For display purposes you convert angles to whatever you want: degrees with decimals, or degrees and minutes with decimals, or degrees, minutes and seconds perhaps with decimals. The day count is converted to the calendar date followed by hours, minutes and seconds. If there's any input, the opposite conversion needs to be done. Ive grown up with time. But there arent 360 hours in a day. No, but there are 360 degrees per day where one degree is 4 minutes of time. You must distinguish minutes of time from minutes of arc here. One hour is 15 degrees, that's how you convert RA in hours from RA in degrees. As far as date goes I spent a decade working in an environment dominated by what they called, incorrectly, Julian Date. Actually it was a calendar with January 1st as day 001 and incremented by one every day. We needed to know the day number to identify the dates of barcoded samples. This would be as useful and easy as months but would never be adopted. That's the NASA variety of Julian Day Number, right? For each new year, they start again with 001 on 1 Jan. |
#36
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46P, can't see
On Monday, December 10, 2018 at 10:32:15 PM UTC-8, Paul Schlyter wrote:
On Mon, 10 Dec 2018 07:43:48 -0800 (PST), StarDust In fraction one can use proximation, like the closest to .835 is 27/32 = 0.84375 or +1/32 away is 7/8 th! I think, a carpenter, cook or plummer don't care about 1/32 difference? LOL! Actually, 167/200 is even closer to 0.835 since it is exactly the same. You cannot get closer than that... If you care about a 1/32 difference depends on your demands of precision. A cook may not care, but a precision mechanic will care. If there's a mismatch of 1/32 cm between your eyepiece and your eyepiece holder on your scope, you may be unable to insert your eyepiece. But can you visualize 167/200? That's what we talking about here! 1/32 cm is .012" it may be good enough to fit for an eyepiece! LOL! |
#37
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46P, can't see
On Tue, 11 Dec 2018 00:48:27 -0800 (PST), StarDust
wrote: On Monday, December 10, 2018 at 10:32:15 PM UTC-8, Paul Schlyter wrote: On Mon, 10 Dec 2018 07:43:48 -0800 (PST), StarDust In fraction one can use proximation, like the closest to .835 is 27/32 = 0.84375 or +1/32 away is 7/8 th! I think, a carpenter, cook or plummer don't care about 1/32 difference? LOL! Actually, 167/200 is even closer to 0.835 since it is exactly the same. You cannot get closer than that... If you care about a 1/32 difference depends on your demands of precision. A cook may not care, but a precision mechanic will care. If there's a mismatch of 1/32 cm between your eyepiece and your eyepiece holder on your scope, you may be unable to insert your eyepiece. But can you visualize 167/200? That's what we talking about here! 1/32 cm is .012" it may be good enough to fit for an eyepiece! LOL! I can draw a pie diagram showing 167/200 just as I can draw a pie diagram showing 0.835.and a diagram showing 83.5% - those tree diagrams will look exactly pthe same. But you talked about preferring common fractions over decimal fractions, however a decimal fraction can easily be converted into a common fraction. Perhaps you, by "common fraction" meant "a common fraction where the denominator is an even, and not a too large, power of two"? That's a small subset of all possible common fractions. |
#38
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46P, can't see
On Tuesday, December 11, 2018 at 10:46:48 PM UTC-8, Paul Schlyter wrote:
On Tue, 11 Dec 2018 00:48:27 -0800 (PST), On Monday, December 10, 2018 at 10:32:15 PM UTC-8, Paul Schlyter wrote: On Mon, 10 Dec 2018 07:43:48 -0800 (PST), StarDust In fraction one can use proximation, like the closest to .835 is 27/32 = 0.84375 or +1/32 away is 7/8 th! I think, a carpenter, cook or plummer don't care about 1/32 difference? LOL! Actually, 167/200 is even closer to 0.835 since it is exactly the same. You cannot get closer than that... If you care about a 1/32 difference depends on your demands of precision. A cook may not care, but a precision mechanic will care. If there's a mismatch of 1/32 cm between your eyepiece and your eyepiece holder on your scope, you may be unable to insert your eyepiece. But can you visualize 167/200? That's what we talking about here! 1/32 cm is .012" it may be good enough to fit for an eyepiece! LOL! I can draw a pie diagram showing 167/200 just as I can draw a pie diagram showing 0.835.and a diagram showing 83.5% - those tree diagrams will look exactly pthe same. But you talked about preferring common fractions over decimal fractions, however a decimal fraction can easily be converted into a common fraction. Perhaps you, by "common fraction" meant "a common fraction where the denominator is an even, and not a too large, power of two"? That's a small subset of all possible common fractions. I meant common fractions, what we use in daily life, 1/2, 1/4, 3/8 etc... Get it? Carpenter don't use 167/200? 1/16" is good enough to cut a 2x4! Try to measure 167/200" with a measuring tape from Home Depot, eh? Some how you have difficulty understanding things? Use to work as a machinist/tool maker for an optical shop, owner was a PhD chemist and sometime he had difficulty understanding simple layman terms. He's mined was up in the clouds all the time! Brain gets to complicated when receives too much education, different reality I guess? |
#39
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46P, can't see
On Tue, 11 Dec 2018 23:59:16 -0800 (PST), StarDust
wrote: I meant common fractions, what we use in daily life, 1/2, 1/4, 3/8 etc... Get it? Carpenter don't use 167/200? 1/16" is good enough to cut a 2x4! Try to measure 167/200" with a measuring tape from Home Depot, eh? Some how you have difficulty understanding things? I see. You are stuck with that outdated inefficient system of units of feet and inches. While the rest of the world has gone metric, the USA, Burma and Liberia prefer to stick to their outdated systems of measurements. No, I don't want to measure 167/200 inches with a measuring tape from Home Depot which probably only measures inches anyway. I'd much prefer to measure 0.835 cm with a **metric** ruler, measuring tape or other measuring device. That's what we who live in the modern part of the world do. On metric measuring devices the subdivisions are in powers of 10, not powers of 2, so decimal fractions are then very handy to use. Welcome to the world outside the USA! Yes, it does exist! For real!!! |
#40
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46P, can't see
On Wednesday, December 12, 2018 at 12:17:29 AM UTC-8, Paul Schlyter wrote:
On Tue, 11 Dec 2018 23:59:16 -0800 (PST), I meant common fractions, what we use in daily life, 1/2, 1/4, 3/8 etc... Get it? Carpenter don't use 167/200? 1/16" is good enough to cut a 2x4! Try to measure 167/200" with a measuring tape from Home Depot, eh? Some how you have difficulty understanding things? I see. You are stuck with that outdated inefficient system of units of feet and inches. While the rest of the world has gone metric, the USA, Burma and Liberia prefer to stick to their outdated systems of measurements. No, I don't want to measure 167/200 inches with a measuring tape from Home Depot which probably only measures inches anyway. I'd much prefer to measure 0.835 cm with a **metric** ruler, measuring tape or other measuring device. That's what we who live in the modern part of the world do. On metric measuring devices the subdivisions are in powers of 10, not powers of 2, so decimal fractions are then very handy to use. Welcome to the world outside the USA! Yes, it does exist! For real!!! Also England and Australia use the old system! They even drive in the left side of the road there too! LOL! Now days measuring tapes has both system of units, but still the inch is the mostly used, not metric! Progress , I guess! If you buy an American car and like to be a weekend mechanic, you have to buy tons of tools, in fractions units, 1/2" wrench or 1/4" drill bit or 16 oz. hammer etc... Crazy, but more profit in selling tools! |
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