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  #21  
Old December 10th 18, 04:09 PM posted to sci.astro.amateur
StarDust
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Posts: 732
Default 46P, can't see

On Monday, December 10, 2018 at 7:03:50 AM UTC-8, Paul Schlyter wrote:
On Mon, 10 Dec 2018 13:19:53 -0000 (UTC), Mike Collins


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.


That's why we never lost the fraction system, it's easier to think in fractions than decimals, like the 9.835 is not easy!
Most of the time, in every day life we don't need decimal precision!
  #22  
Old December 10th 18, 04:15 PM posted to sci.astro.amateur
Paul Schlyter[_3_]
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Posts: 1,344
Default 46P, can't see

On Mon, 10 Dec 2018 08:06:06 -0700, Chris L Peterson
wrote:
On Mon, 10 Dec 2018 05:23:56 -0800 (PST), 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?

What you can see with the naked eye is 5-10 arcminutes. The actual
coma is over a half a degree, but the outer part only shows up in
images. It's too dim for the eye.


I don't know that 8 arcmin is all that small. It's the size of large
maria on the Moon.


Useful naked eye test double stars a

Epsilon Lyrae - separation 3 arc minutes
Alpha Capricorni - separation 6.5 arc minutes
Mizar+Alcor - separation 12 arc minutes
  #23  
Old December 10th 18, 04:20 PM posted to sci.astro.amateur
Paul Schlyter[_3_]
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Posts: 1,344
Default 46P, can't see

On Mon, 10 Dec 2018 07:09:38 -0800 (PST), StarDust
wrote:
That's why we never lost the fraction system, it's easier to think

in fractions than decimals, like the 9.835 is not easy!

But 9.835 is the same as 9 and 835/1000

Or perhaps you'd prefer 9835/1000 ?
  #24  
Old December 10th 18, 04:20 PM posted to sci.astro.amateur
StarDust
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Posts: 732
Default 46P, can't see


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?

What you can see with the naked eye is 5-10 arcminutes. The actual
coma is over a half a degree, but the outer part only shows up in
images. It's too dim for the eye.


I don't know that 8 arcmin is all that small. It's the size of large
maria on the Moon.


Useful naked eye test double stars a

Epsilon Lyrae - separation 3 arc minutes
Alpha Capricorni - separation 6.5 arc minutes
Mizar+Alcor - separation 12 arc minutes


Good one!!!
  #25  
Old December 10th 18, 04:43 PM posted to sci.astro.amateur
StarDust
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Posts: 732
Default 46P, can't see

On Monday, December 10, 2018 at 7:20:04 AM UTC-8, Paul Schlyter wrote:
On Mon, 10 Dec 2018 07:09:38 -0800 (PST), StarDust


That's why we never lost the fraction system, it's easier to think

in fractions than decimals, like the 9.835 is not easy!

But 9.835 is the same as 9 and 835/1000

Or perhaps you'd prefer 9835/1000 ?


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!
  #26  
Old December 10th 18, 05:16 PM posted to sci.astro.amateur
Chris L Peterson
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Posts: 10,007
Default 46P, can't see

On Mon, 10 Dec 2018 07:43:48 -0800 (PST), StarDust
wrote:

On Monday, December 10, 2018 at 7:20:04 AM UTC-8, Paul Schlyter wrote:
On Mon, 10 Dec 2018 07:09:38 -0800 (PST), StarDust


That's why we never lost the fraction system, it's easier to think

in fractions than decimals, like the 9.835 is not easy!

But 9.835 is the same as 9 and 835/1000

Or perhaps you'd prefer 9835/1000 ?


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!


Your brain surgeon might!
  #27  
Old December 10th 18, 05:34 PM posted to sci.astro.amateur
StarDust
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Posts: 732
Default 46P, can't see

On Monday, December 10, 2018 at 8:16:48 AM UTC-8, Chris L Peterson wrote:
On Mon, 10 Dec 2018 07:43:48 -0800

On Monday, December 10, 2018 at 7:20:04 AM UTC-8, Paul Schlyter wrote:
On Mon, 10 Dec 2018 07:09:38 -0800 (PST), StarDust


That's why we never lost the fraction system, it's easier to think
in fractions than decimals, like the 9.835 is not easy!

But 9.835 is the same as 9 and 835/1000

Or perhaps you'd prefer 9835/1000 ?


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!


Your brain surgeon might!


Not until the 19th century?
  #28  
Old December 10th 18, 08:02 PM posted to sci.astro.amateur
Mike Collins[_4_]
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Posts: 2,824
Default 46P, can't see

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.


  #29  
Old December 10th 18, 08:11 PM posted to sci.astro.amateur
Mike Collins[_4_]
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Posts: 2,824
Default 46P, can't see

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.


I’ve grown up with time. But there aren’t 360 hours in a day.
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.


  #30  
Old December 10th 18, 11:56 PM posted to sci.astro.amateur
Thomas 'PointedEars' Lahn
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Posts: 76
Default 46P, can't see

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.
 




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