Let's Photograph Comet 46P Wirtanen

On Sat, 22 Dec 2018 00:43:11 -0600, hleopold
wrote:

On Dec 21, 2018, Chris L Peterson wrote
Indeed, aperture is irrelevant. No amount of aperture can ever
increase the surface brightness of an extended object beyond what we
can see with our unaided eye. Given the size of this comet, it is best
viewed at low magnifications, and therefore there's no advantage to
more than just a few inches of aperture. (But aperture is critical to
good imaging, as it allows for shorter exposures and therefore a
better capture of this fast moving body.)

I agree. As for the speed of this comet, I had noticed that in David’s 4
shot stack where he pointed out that it was not a tail but movement between
the shots. I was really surprised to see that it had moved that far in, I
believe part of a night. I realize that when they are close comets are
normally moving quite quickly. Well depending on the geometry of course. But
so surprising to actually see it in the sky, where things seldom move fast.

Here's a quick and dirty animation (unprocessed raw frames) taken also
on 17 December. These were 60-second images acquired without any gap
between them, so we directly observe eight minutes of cometary motion
against the background stars. Yeah, it's moving pretty fast.

http://cloudbait.com/gallery/comet/2...7_46P_anim.gif

(Frame is 52.5 arcmin - nearly a degree- on each side.)

hleopold:
...Always a joy to see your photos, David, I look forward to more in the future.
I mostly read here, hardly ever comment. Not to mention I am jealous of your
set-up, though not of your location, as bad as our seeing is here you have it
worse.

Your words are kinder than I deserve! I have complained here about
Maryland sky conditions from time to time, but not too bitterly, I
hope. I try to take it with equanimity; I get what I get and I try to
make the best I can of it.

Same for my vision. I am 74 years old and I have macular degeneration.
My corrected vision in my left eye is 20/25, i.e., very good. But over
the past few months I have noted a deterioration in my right eye to the
point where I cannot read with my left eye covered. My ophthalmologist
referred me to an optometrist who specializes in low vision. My right
eye can't be "fixed," but a new pair of glasses, coming in about two
weeks, will help. Good that I'm not a visual observer; I can still
focus on a laptop display, but faint fuzzies don't work for me in an
eyepiece. I use a Bahtinov mask on my Tak 106
https://www.flickr.com/photos/primeval/30364292358.

--
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

On Sat, 22 Dec 2018 20:09:17 -0500, Davoud wrote:
My corrected vision in my left eye is 20/25, i.e., very good.

That's the same as 0.8 right? And full visual acuity would then be
25/25? Or 100/100 etc if you prefer that. Or just 1.0

On Dec 22, 2018, Davoud wrote
(in article ):

hleopold:
...Always a joy to see your photos, David, I look forward to more in the future.
I mostly read here, hardly ever comment. Not to mention I am jealous of your
set-up, though not of your location, as bad as our seeing is here you have
it worse.

Your words are kinder than I deserve! I have complained here about
Maryland sky conditions from time to time, but not too bitterly, I
hope. I try to take it with equanimity; I get what I get and I try to
make the best I can of it.

As, for the vast majority of us, we all must.

Same for my vision. I am 74 years old and I have macular degeneration.
My corrected vision in my left eye is 20/25, i.e., very good. But over
the past few months I have noted a deterioration in my right eye to the
point where I cannot read with my left eye covered. My ophthalmologist
referred me to an optometrist who specializes in low vision. My right
eye can't be "fixed," but a new pair of glasses, coming in about two
weeks, will help.

Age eventually gets us all, I am only 67, in 3 weeks to be 68, and my eyes
just ain’t what they used to be. Of course in my case I have to go back to
when I was 12 when my eyes went from practically perfect to very near-sighted
and very strong astigmatism in both eyes. Correctable but slowly getting
harder to focus as I age.

Good that I'm not a visual observer; I can still
focus on a laptop display, but faint fuzzies don't work for me in an
eyepiece. I use a Bahtinov mask on my Tak 106
https://www.flickr.com/photos/primeval/30364292358.

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 can’t
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. Used a home-brew camera and cut my 35mm film to
single frame. My camera was much like one that was described in Sky and
Telescope back about that time, starting with a short extension tube and
built up the body out of flat sheets of black opaque plastic glued together
to hold the film in place plus a dark slide to take the shot. If was fun, but
fairly frustrating at the same time. At that time I did most of my
photography using B&W film, so I was able to do my own processing. Not really
an easy thing to do on a Navy ship. About once a week I would take over the
head for our dept. berthing area to do processing. Even at night the light
leaks were ridiculous, I used a lot of black tape every time. And hoping like
everything that no one needed to use it for the few minutes while
transferring the exposed film to the tank. Yeah, I did used a changing bag
but you probably know how that works.

These days, though, I just mostly like to look at things through the scope.

--
Harry F. Leopold

The Prints of Darkness (remove gene to email)

On Dec 23, 2018, Paul Schlyter wrote
(in et):

On Sat, 22 Dec 2018 20:09:17 -0500, wrote:
My corrected vision in my left eye is 20/25, i.e., very good.

That's the same as 0.8 right? And full visual acuity would then be
25/25? Or 100/100 etc if you prefer that. Or just 1.0

20/20 is, as I understand it, “perfect� vision. Mine is 20/400 in the
right eye uncorrected, corrected to 20/15. left is somewhat worse, but
corrected to 20/15 also. Or it used to be, these days I am probably more
20/20 or slightly worse. Plus they have to correct for the bad astigmatism I
have in both eyes.

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

“I have an inferiority complex, but it's not a very good one.“ -
Vintagewheels

On Dec 22, 2018, Chris L Peterson wrote
(in ):

On Sat, 22 Dec 2018 00:43:11 -0600,
wrote:

On Dec 21, 2018, Chris L Peterson wrote
Indeed, aperture is irrelevant. No amount of aperture can ever
increase the surface brightness of an extended object beyond what we
can see with our unaided eye. Given the size of this comet, it is best
viewed at low magnifications, and therefore there's no advantage to
more than just a few inches of aperture. (But aperture is critical to
good imaging, as it allows for shorter exposures and therefore a
better capture of this fast moving body.)

I agree. As for the speed of this comet, I had noticed that in David’s 4
shot stack where he pointed out that it was not a tail but movement between
the shots. I was really surprised to see that it had moved that far in, I
believe part of a night. I realize that when they are close comets are
normally moving quite quickly. Well depending on the geometry of course. But
so surprising to actually see it in the sky, where things seldom move fast.

Here's a quick and dirty animation (unprocessed raw frames) taken also
on 17 December. These were 60-second images acquired without any gap
between them, so we directly observe eight minutes of cometary motion
against the background stars. Yeah, it's moving pretty fast.

http://cloudbait.com/gallery/comet/2...7_46P_anim.gif

(Frame is 52.5 arcmin - nearly a degree- on each side.)

Fast moving indeed. As I mentioned earlier, few things move fast in the sky,
other than meteors which move very fast. But this was surprising to me even
knowing that it is fast. Thanks for that. How far from the Earth was it at
the time you took those shots?

--
Harry F. Leopold
The Prints of Darkness (remove gene to email)

“People like me, who cannot think for themselves, are a dime a dozen.“ -
Pastor Dave

On Sunday, December 23, 2018 at 4:38:10 PM UTC-8, hleopold wrote:

“I have an inferiority complex, but it's not a very good one.“ -
Vintagewheels

'When my kleptomania gets bad, I take something for it"
- Ken Dodd

On Sun, 23 Dec 2018 18:38:19 -0600, hleopold
wrote:
On Dec 23, 2018, Paul Schlyter wrote
(in et):
On Sat, 22 Dec 2018 20:09:17 -0500, wrote:
My corrected vision in my left eye is 20/25, i.e., very good.

That's the same as 0.8 right? And full visual acuity would then be
25/25? Or 100/100 etc if you prefer that. Or just 1.0

20/20 is, as I understand it, perfect vision. Mine is 20/400 in
the
right eye uncorrected, corrected to 20/15. left is somewhat worse,
but
corrected to 20/15 also. Or it used to be, these days I am probably
more
20/20 or slightly worse. Plus they have to correct for the bad
astigmatism I
have in both eyes.

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?

On Sun, 23 Dec 2018 18:30:49 -0600, hleopold
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.

On Monday, December 24, 2018 at 8:09:24 AM UTC-5, Paul Schlyter wrote:
On Sun, 23 Dec 2018 18:38:19 -0600, hleopold
wrote:
On Dec 23, 2018, Paul Schlyter wrote
(in et):
On Sat, 22 Dec 2018 20:09:17 -0500, wrote:
My corrected vision in my left eye is 20/25, i.e., very good.

That's the same as 0.8 right? And full visual acuity would then be
25/25? Or 100/100 etc if you prefer that. Or just 1.0

20/20 is, as I understand it, perfect vision. Mine is 20/400 in
the
right eye uncorrected, corrected to 20/15. left is somewhat worse,
but
corrected to 20/15 also. Or it used to be, these days I am probably
more
20/20 or slightly worse. Plus they have to correct for the bad
astigmatism I
have in both eyes.

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?

The '20' in the numerator means a 20 foot distance. If you can read the 20/20 line on the chart from 20 feet then your vision is average/normal.

If you can read the 20/15 line then your acuity is better than average; others would have to be 15 feet away to read it.

If you can read the 20/100 line, and nothing smaller, then your acuity is worse than average; the average person could read that line at 100 feet.