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Let's Photograph Comet 46P Wirtanen



 
 
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  #41  
Old December 25th 18, 09:37 AM posted to sci.astro.amateur
Paul Schlyter[_3_]
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Posts: 1,344
Default Let's Photograph Comet 46P Wirtanen

On Mon, 24 Dec 2018 22:54:55 -0600, hleopold
wrote:
On Dec 24, 2018, Paul Schlyter wrote
(in et):
On Sun, 23 Dec 2018 18:30:49 -0600,
wrote:
Way back in the late 70s early 80s I did, for a while, try

photography with
my scopes, but otherwise I have been strictly a visual

observer. I cant
believe the great stuff that we have these days. I am not

really a fan of
digital photography in many ways, I loved shooting film, and

that was how I
did astro photos back then.





You can still shoot film if that's what you enjoy to do.





The camera stores near me hardly carry any film anymore, except for

4x5 or
8x10. And I have gotten out of the habits I used to have. I love my

smart
phone for its ability to grab shots that pop up unexpectedly.


The camera in your smart phone is a digital camera so that makes you
a fan of digital photography.

The digital cameras are more than just DSLR cameras where a digital
sensor has replaced the film. Almost all digital cameras now also has
video capability. There are really small "adventure cameras" you can
bring along in conditions where you wouldn't bring your regular
camera. There are surround cameras which photograph in every possible
direction all over the 55000 square degrees over the entire sphere
around the camera. Some sky watchers set upp all-sky cameras (which
photograph only half the sphere) and run them all night long every
night and examine the time-lapse movies afterwards. A lot of this
would hardly have been possible with older film cameras.
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  #42  
Old December 25th 18, 09:42 AM posted to sci.astro.amateur
Paul Schlyter[_3_]
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Posts: 1,344
Default Let's Photograph Comet 46P Wirtanen

On Mon, 24 Dec 2018 22:04:24 -0600, hleopold
wrote:
If the numerator is always 20, what does this 20 mean? Is 20/20 in
some way different from, say, 25/25 or.30/30?


As I understand it, you should be able to see at 20 feet as the

average
person would see at 20 feet. (An average person with good eyesight

of
course.)


If you are shown to have a 20/30 in your right eye it means that

you see at
20 feet is like that average person would see at 30. In other

words,
your eyesight is not that great.


But what's the point of always having 20 as the numerator? Why not
instead perform the division and say 0.67 instead of 20/30? Or, if
you prefer common fractions, 2\3? After all 2/3 is equal to 20/30.
  #43  
Old December 25th 18, 09:46 AM posted to sci.astro.amateur
Paul Schlyter[_3_]
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Posts: 1,344
Default Let's Photograph Comet 46P Wirtanen

On Mon, 24 Dec 2018 14:47:15 -0700, Chris L Peterson
wrote:
On Mon, 24 Dec 2018 22:33:39 +0100, Paul Schlyter
wrote:


On Mon, 24 Dec 2018 09:26:32 -0500, Davoud wrote:
20/20, or metric 6/6 = 1. It's explained at
https://en.wikipedia.org/wiki/Visual_acuity#Measurement.


Ok, so it measures the visual acuity at a distance of 20 feet. But
wouldn't a measure of (practically) infinite distance be more
interesting to skywatchers? No stars are only 20 feet away.


The distance is largely irrelevant. It's measuring resolution... the
ability to detect close high contrast features as separate from one
another. The distance of 20 feet is simply a standard so that the

test
chart is always the same, and it's a distance that is practical in a
typical testing situation. Optically, 20 feet is pretty much the

same
as infinity for the human eye in terms of accommodation.


Modern refraction techniques project patterns on the back of the eye
and directly assess accommodation, focus, and astigmatism. But this

is
usually translated to the 20:X notation for simplicity.


But if the distance is irrelevant, why not perform the division and
say 0.67 instead of 20/30? Or at least 2/3 instead of 20/30? After
all it means that the person with 20/30 eyesight has 2/3 or 0.67 of
normal visual acuity.
  #44  
Old December 25th 18, 02:33 PM posted to sci.astro.amateur
Chris L Peterson
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Posts: 10,007
Default Let's Photograph Comet 46P Wirtanen

On Tue, 25 Dec 2018 10:46:25 +0100, Paul Schlyter
wrote:

But if the distance is irrelevant, why not perform the division and
say 0.67 instead of 20/30? Or at least 2/3 instead of 20/30? After
all it means that the person with 20/30 eyesight has 2/3 or 0.67 of
normal visual acuity.


It's just convention.
  #45  
Old December 26th 18, 06:48 AM posted to sci.astro.amateur
Paul Schlyter[_3_]
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Posts: 1,344
Default Let's Photograph Comet 46P Wirtanen

On Tue, 25 Dec 2018 07:33:29 -0700, Chris L Peterson
wrote:
On Tue, 25 Dec 2018 10:46:25 +0100, Paul Schlyter
wrote:


But if the distance is irrelevant, why not perform the division

and
say 0.67 instead of 20/30? Or at least 2/3 instead of 20/30? After
all it means that the person with 20/30 eyesight has 2/3 or 0.67

of
normal visual acuity.


It's just convention.


An unnecessary convention which should be removed.

Suppose that I, instead of saying "it's 5 degrees outside", suppose
I would say "it's 35/7 degrees outside". It's the same thing, but
you'd probably ask why I involved that 7 in the temperature, and then
I would reply "it's just convention"... See?
  #46  
Old December 26th 18, 08:39 AM posted to sci.astro.amateur
hleopold
external usenet poster
 
Posts: 20
Default Let's Photograph Comet 46P Wirtanen

On Dec 25, 2018, Paul Schlyter wrote
(in et):

On Mon, 24 Dec 2018 22:04:24 -0600,
wrote:
If the numerator is always 20, what does this 20 mean? Is 20/20 in
some way different from, say, 25/25 or.30/30?


As I understand it, you should be able to see at 20 feet as the average
person would see at 20 feet. (An average person with good eyesight of
course.)


If you are shown to have a 20/30 in your right eye it means that you see at
20 feet is like that average person would see at 30. In other words,
your eyesight is not that great.


But what's the point of always having 20 as the numerator? Why not
instead perform the division and say 0.67 instead of 20/30? Or, if
you prefer common fractions, 2\3? After all 2/3 is equal to 20/30.


I haven’t a clue. All I can say is that maybe your local eye doctor might
have an answer. The only thing I can think of is that like any other part of
human life eye doctors stick with some traditions. Nearly every organization
has traditions that are slow to change. As a former Navy person I ran into
lots of old traditions while in. Many did not really make any sense, now.
Maybe they did way back when. As a long time printer we had lots of
traditions on how we measured things, and even in the last ten years many of
those have slowly fallen to the wayside with the spread of digital printing.
We used to have many terms that were in use daily by printers back in 1969
when I first got into the business. When I reentered it about 32 years ago
most were still in daily use. But by the time I was retired a couple of years
ago most new printers had never heard of them even if they had been working
as printers for 10 years or so. The guy that trained me on the big web
presses was always mentioning things that we never dealt with anymore. And of
course when I started as a printer I started on one tower flat bed/flat sheet
presses before much later moving on to web multi-tower presses, again, a very
different kind of printing.

Printing used to be as they used to say: more art than science, same goes for
making eyeglasses. But these days not only are presses being replaced by
digital (laser) printers so are set up and pre-press, most of it is now done
by computers, as is mixing of inks (if you are still using a press that
actually using printers ink instead of pre-mixed cartridges from the
manufacture.)

Kerning, that used to be one of the most important parts of printing pages of
print, and one source of many traditions of how printers measure and move
things. Now nearly all of that is dealt with automatically by the software
long before the image ever leaves the set up computers. This was something
that I seldom had to deal with as I was an offset printer, not a linotype
printer. I have had some conversations with lino printers that have left both
of us scratching our heads even though the presses we both used are (almost)
identical, only the method is placing ink on paper is (vastly) different.
Both types of printing have very different current styles of training. Lino
is even further along towards being obsolete than off-set printing. These
days both types are becoming strictly boutique print shop use. Boutique Print
Shop, three words I never thought I would ever use in a sentence.

It used to be that a printer had to worry about things like what was the temp
and humidity at the time you were printing, and just for fun add in just how
old is that paper you are printing on. Paper that is less then six months old
prints very differently than a roll that is six years old and what kind of
paper, how thick, coated or uncoated, AND how had it been stored during that
time.

Most of the time nobody could tell you this kind of stuff, so you had to
learn by doing and by listening to older printers. This was one reason most
old printers did not really like training people who had gone through a tech
school, they had a lot of book training but very little practical training.
Now most of what we trained for is built into the software and hardware, or
completely ignored since the folks that build them expect the users to
actually use high quality paper, ink and not run them for 24 hours straight
or longer and never, ever cut corners. Things like how much, or little
fountain solution to use aren’t even a part of laser printed jobs. Or that
sometimes you need to add a little alcohol to that solution to fix a toning
problem that just won’t go away no matter what the makers of the machine
say.

The guy that trained me on my last press just retired, the press he had used
for most of his career was almost identical to the one he trained me on, but
the type of printing he did before coming to our shop was very different,
instead of one roll of paper going through the entire press, getting
different inks printed by anywhere from four to ten different printing
towers, he started off printing the old multi layered, multi-colored
forms.What we used to call business forms.

So his press that he learned on had up to six rolls of (basically) tissue
paper being fed into different towers to be printed, collated into a single
form, then it would be cut, glued into whatever form the customer needed.
Collectively these were known as “business forms,” they came in hundreds
of weird and wonderful forms, colors and styles. Having heard the tales that
I was told by my trainer, I am glad I missed that particular form of torture.
His favorite tale dealt with splicing tissue paper back together ten or
twelve feet in the air standing on top of the press or on a ladder using one
hand, the other was to prevent him from falling into the press.

Now years ago I had actually been to his former employer, I saw the presses
he worked on, in function they operated exactly as the one he trained me on,
but the reality was just as awful as he described, far worse really. Rolls of
paper being fed into the press at each tower, paper running above the press
from each tower before diving back into it to be collated and folded by the
bindery unit, I would have believed him if he said he had to do the splicing
while hanging by his toes doing a Tarzan scream. I was only there to pick up
some forms for my then employer, thank Bes. Too bad the family that owned the
company sold it, only to have it closed a year later. But I got a great
trainer out of it and a good friend.

Sorry about all that, but it is late at night and I am bored at the moment
and I guess I have the holiday blues. Why am I suddenly reminded of the old
detective from The Streets of San Francisco? I am not that bad, really.

--
Harry F. Leopold

The Prints of Darkness (remove gene to email)

"The line separating painfully bad analogies from weirdly good ones is as
thin as a soup made from the shadow of a chicken that was starved to death."
- Alydar2

  #47  
Old December 26th 18, 10:20 AM posted to sci.astro.amateur
hleopold
external usenet poster
 
Posts: 20
Default Let's Photograph Comet 46P Wirtanen

On Dec 25, 2018, Paul Schlyter wrote
(in t):

On Mon, 24 Dec 2018 22:54:55 -0600,
wrote:
On Dec 24, 2018, Paul Schlyter wrote
(in et):
On Sun, 23 Dec 2018 18:30:49 -0600,
wrote:
Way back in the late 70s early 80s I did, for a while, try

photography with
my scopes, but otherwise I have been strictly a visual

observer. I cant
believe the great stuff that we have these days. I am not

really a fan of
digital photography in many ways, I loved shooting film, and

that was how I
did astro photos back then.


You can still shoot film if that's what you enjoy to do.


The camera stores near me hardly carry any film anymore, except for

4x5 or
8x10. And I have gotten out of the habits I used to have. I love my

smart
phone for its ability to grab shots that pop up unexpectedly.


The camera in your smart phone is a digital camera so that makes you
a fan of digital photography.


Because it is at hand at all times. This I find a very good thing. But, like
the audio guys will argue about tube versus digital amps, the old stuff
“feels” better, or looks better. It is emotional, I know that.

When I pulled that old range-finder camera out with that large chunk of glass
on it I knew exactly what it would do from lots and lots of practice. I knew
how to manipulate the controls to get just the sort of shot I wanted. With
digital cameras you have to deal with some other persons decisions that are
built into the software and sometimes those decisions are so burned in you
can’t get around them. And, to be honest, shooting a dark street scene I
could adjust things to get what I wanted, which is a dark street scene with
real blacks, saturated color where there is color. I have never been able to
do anywhere as well with digital, it feels “flatter,” grayer instead of
real blacks.

It is all about the feels, emotions. I always found film, B&W or color
negative seemed to work with me. Daylight shots, digital is fine, but for
emotional “color” I love film and long shutter times, huge depth of
field, dark but not gloomy. “Bright Blackness” is an oxymoron but it
works, for me.

One of my favorite shots was taken at about 3 in the morning in SF, from the
top of a hill looking down a long street towards the bay, shortly after a
light rain, a dinner in the left distance with night owls having something to
eat before handing home, the dark streets glimmering from distant lights
reflecting from the water still on them, and a couple walking to their car,
crossing the street. This shot had the lens open for 6 full seconds,
basically hand-held, I had plastered myself against a brick wall not
breathing, braced myself as well as I possibly could as I counted the seconds
until I could close the shutter. I took that shot 10 times that night, one
came out perfect, in my opinion. The print was mostly black, little dots of
white, red, green and blue reflections off the wet streets and the people
that could be seen inside of the dinner and that couple, somewhat blurred,
but to me it said that they were in love and I think it came through. Even
the cat that sat there watching me make a fool out of myself remained quiet
while I got that shot. (No, the cat was not in the shot. He would have been
far too close and too bright, it would have been the center of attention, not
the couple in the distance.)

No, I was not trying to reproduce The Night Owls dinner painting though it is
a favorite of mine.

It’s all about the feels, man. ;-)

Oh, and about that video capability, I don’t do video, never have. It just
doesn’t feel right for me, more power to those that enjoy doing it. I like
trying to catch humanity in a moment, I may fail often but every once in a
while I would luck out, through practice and stubbornness, and get a good
shot that says what I want it to say. Which, strangely enough, is in the
middle of the night on near empty streets or beaches, sometimes after a light
rain. But mostly I want that photo to speak to me, not so much for me. If it
says something to me, I got it right, and I am happy.

Oh yes, I know I could have carried a tripod with me, but I liked having to
work for a shot without having to have half of an studio in a car. I wanted
something that did not scream “guy carrying a lot of expensive equipment
around in the dark.” Sometimes I carried a mono-pod, this had the advantage
of being useful in any number of ways, including being handy as a walking
stick if there were a lot of hills and SF had a lot of steep hills. I think I
went about photo equipment like I did with bicycling or camping, I liked to
keep it light and easy to carry anywhere, so I pretty much stuck with a total
of three lens on three cameras, Most times I carried two camera bodies, all
three lens, a mono-pod, a light meter and film, lots of film, a roll or two
of HP-5 or Tri-X, and three or four rolls of a good, fairly fast color
negative film. Maybe a roll of a slow ASA B&W film if I was going to be out
until dawn, I enjoyed taking shots of dew-covered flowers in the early light.
Oh yes, spare batteries for the light meter, just in case. I did learn my
lesson on that subject.

The nice thing about this setup is that it didn’t take up a lot of room in
my locker on my ship. On a Navy ship space is precious, you never have enough
that you actually can control. This is why I never got into developing color
film, took up too much room for the chemicals and equipment. I could develop
my B&W stuff, but I had them printed elsewhere. A good camera shop with a
really good print tech was a friend worth developing a friendship with, they
get to know what you shoot and how you like them to look and will actually
listen to you if you let them know you have made a change. You always
remember them at Christmas and their birthdays. Finding a print tech that
likes a challenge isn’t, or wasn’t, that hard back then. I am pretty sure
those are getting much harder to find these days.

The digital cameras are more than just DSLR cameras where a digital
sensor has replaced the film. Almost all digital cameras now also has
video capability. There are really small "adventure cameras" you can
bring along in conditions where you wouldn't bring your regular
camera. There are surround cameras which photograph in every possible
direction all over the 55000 square degrees over the entire sphere
around the camera. Some sky watchers set upp all-sky cameras (which
photograph only half the sphere) and run them all night long every
night and examine the time-lapse movies afterwards. A lot of this
would hardly have been possible with older film cameras.


But those are not the photos I was taking. (Gee, for some reason that line
sounds a bit overly familiar. ;-)

--
Harry F. Leopold
aa #2076
AA/Vet #4
The Prints of Darkness (remove gene to email)

“When I am stupid, that is when I am STRONG“ - Codebreaker

  #48  
Old December 26th 18, 02:43 PM posted to sci.astro.amateur
Chris L Peterson
external usenet poster
 
Posts: 10,007
Default Let's Photograph Comet 46P Wirtanen

On Wed, 26 Dec 2018 07:48:43 +0100, Paul Schlyter
wrote:

On Tue, 25 Dec 2018 07:33:29 -0700, Chris L Peterson
wrote:
On Tue, 25 Dec 2018 10:46:25 +0100, Paul Schlyter
wrote:


But if the distance is irrelevant, why not perform the division

and
say 0.67 instead of 20/30? Or at least 2/3 instead of 20/30? After
all it means that the person with 20/30 eyesight has 2/3 or 0.67

of
normal visual acuity.


It's just convention.


An unnecessary convention which should be removed.


Fine, take it up with the ophthalmological community. But it works,
people are comfortable with it, and I don't imagine it's likely to
change.

Suppose that I, instead of saying "it's 5 degrees outside", suppose
I would say "it's 35/7 degrees outside". It's the same thing, but
you'd probably ask why I involved that 7 in the temperature, and then
I would reply "it's just convention"... See?


If it were convention, it would sound normal to us and we'd use it
comfortably. That's pretty much what "convention" means.
  #49  
Old December 26th 18, 04:05 PM posted to sci.astro.amateur
Davoud[_1_]
external usenet poster
 
Posts: 1,989
Default Let's Photograph Comet 46P Wirtanen

Paul Schlyter:
But if the distance is irrelevant, why not perform the division
and say 0.67 instead of 20/30? Or at least 2/3 instead of 20/30?
After all it means that the person with 20/30 eyesight has 2/3 or 0.67
of normal visual acuity.


Chris L Peterson:
It's just convention.


Paul Schlyter:
An unnecessary convention which should be removed.

Suppose that I, instead of saying "it's 5 degrees outside", suppose
I would say "it's 35/7 degrees outside". It's the same thing, but
you'd probably ask why I involved that 7 in the temperature, and then
I would reply "it's just convention"... See?


Settle down! What happened? Father Christmas pass you by?

Once you know, as Mr. Peterson said, it's a convention, that's all you
need to know. It is used over practically the whole world and it works.
The world of measurement is full of conventions that, if being
originated today, might be done differently. But there is no need to
change them when everyone knows them. It explains why the general
public uses the English System of measures in the U.S. and some other
countriesincluding the U.K., frequentlyits a convention that serves
its purpose!

I was watching a British cooking show on TV the other day. "Add 250 g
of this or that, 500 g of the other and another 200 ml of milk. Roll it
up until it looks like this and cut into two-inch sections. Works.

--
I agree with almost everything that you have said and almost everything that
you will say in your entire life.

usenet *at* davidillig dawt cawm
  #50  
Old December 26th 18, 09:39 PM posted to sci.astro.amateur
Paul Schlyter[_3_]
external usenet poster
 
Posts: 1,344
Default Let's Photograph Comet 46P Wirtanen

On Wed, 26 Dec 2018 02:39:53 -0600, hleopold
wrote:
On Dec 25, 2018, Paul Schlyter wrote
(in et):
On Mon, 24 Dec 2018 22:04:24 -0600,
wrote:
If the numerator is always 20, what does this 20 mean? Is

20/20 in
some way different from, say, 25/25 or.30/30?


As I understand it, you should be able to see at 20 feet as the

average
person would see at 20 feet. (An average person with good

eyesight of
course.)


If you are shown to have a 20/30 in your right eye it means

that you see at
20 feet is like that average person would see at 30. In other

words,
your eyesight is not that great.


But what's the point of always having 20 as the numerator? Why not
instead perform the division and say 0.67 instead of 20/30? Or, if
you prefer common fractions, 2\3? After all 2/3 is equal to 20/30.


I havent a clue. All I can say is that maybe your local eye doctor

might
have an answer.


No he wouldn't. My local eye doctor wouldn't even say 20/30, she
would say 0.67 perhaps rounding it to 0.7 - as would most European
eye doctors. The 20/xx stuff is an American idiosyncracy.
 




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