APOD: A View from the Zone (2014 Mar 07)

Post a reply


This question is a means of preventing automated form submissions by spambots.
Smilies
:D :) :ssmile: :( :o :shock: :? 8-) :lol2: :x :P :oops: :cry: :evil: :roll: :wink: :!: :?: :idea: :arrow: :| :mrgreen:
View more smilies
BBCode is ON
[img] is ON
[url] is ON
Smilies are ON
Topic review
   

Expand view Topic review: APOD: A View from the Zone (2014 Mar 07)

Re: APOD: A View from the Zone (2014 Mar 07)

by Anthony Barreiro » Sat Mar 08, 2014 6:06 pm

Anthony Barreiro wrote:
Ron-Astro Pharmacist wrote:...Back to the light point question considering your responses, for collimating my reflector, do you think one light source better than another? (Not that I would likely choose Venus but it is a nice bright object)
You should collimate a telescope at the highest magnification atmospheric conditions allow. At high magnification planets are not point sources, they're disks, or crescent or gibbous. It's best to pick a star that's bright but not so bright that it's scintillating a lot. Stars that are higher in the sky will be steadier because you're looking through less atmosphere. If you're using a tracking mount, any star will do. If your mount doesn't track, Polaris is the best collimation star (in the northern hemisphere), because it's relatively bright and it's the slowest moving star in the sky.
You could also use a laser collimator.

Re: APOD: A View from the Zone (2014 Mar 07)

by LocalColor » Sat Mar 08, 2014 6:48 am

Lovely photo - for some reason the phrase 'Genetic Drift' comes to mind.

Re: APOD: A View from the Zone (2014 Mar 07)

by SouthEastAsia » Sat Mar 08, 2014 4:57 am

I'm liking this photo by Jack Fusco, very much...

Respects, from Nantucket Island, MA, Earth, current position.

Re: APOD: A View from the Zone (2014 Mar 07)

by Dick Shun'ry » Sat Mar 08, 2014 12:41 am

"Habitability is the conformance of a residence or abode to the implied warranty of habitability. A residence that complies is said to be "habitable". It is an implied warranty or contract, meaning it does not have to be an express contract, covenant, or provision of a contract. It is a common law right of a tenant or legal doctrine.[1]

In order to be habitable, such housing usually:
must provide shelter, with working locks
must be heated in the winter months (typically between October 1 and May 31 in the Northeastern United States)[2]
must not be infested with vermin, such as mice, roaches, termites, mold,[3] etc.
requires the landlord to stop other tenants from making too much noise (as measured by the decibel scale), second-hand smoke,[4] or from selling narcotics
must provide potable water"

I guess earth is not habitable.

Re: APOD: A View from the Zone (2014 Mar 07)

by Chris Peterson » Fri Mar 07, 2014 11:36 pm

Ron-Astro Pharmacist wrote:Back to the light point question considering your responses, for collimating my reflector, do you think one light source better than another? (Not that I would likely choose Venus but it is a nice bright object)
Collimation is best performed at high magnification, and through even a small aperture, Venus is not an optical point source. Use a bright star for collimation, high in the sky to minimize atmospheric effects. If you don't have a tracking mount, Polaris is pretty good if it's reasonably high for you.

Re: APOD: A View from the Zone (2014 Mar 07)

by Anthony Barreiro » Fri Mar 07, 2014 11:35 pm

Ron-Astro Pharmacist wrote:...Back to the light point question considering your responses, for collimating my reflector, do you think one light source better than another? (Not that I would likely choose Venus but it is a nice bright object)
You should collimate a telescope at the highest magnification atmospheric conditions allow. At high magnification planets are not point sources, they're disks, or crescent or gibbous. It's best to pick a star that's bright but not so bright that it's scintillating a lot. Stars that are higher in the sky will be steadier because you're looking through less atmosphere. If you're using a tracking mount, any star will do. If your mount doesn't track, Polaris is the best collimation star (in the northern hemisphere), because it's relatively bright and it's the slowest moving star in the sky.

Re: APOD: A View from the Zone (2014 Mar 07)

by Ron-Astro Pharmacist » Fri Mar 07, 2014 11:16 pm

Chris Peterson wrote:
neufer wrote:Each overexposed star becomes a saturated Airy disk diffraction pattern(; i.e., a bright circle surrounded by narrow rings).

Venus becomes a fat highly saturated Airy disk diffraction pattern convoluted with a tiny crescent(; i.e., basically just a very large bright circle).
Sounds good in theory, but that's not really what we're seeing.

The image scale is 3.3 arcmin/pixel. At f/4 (just guessing) the Airy disk will be about the size of a single pixel on the camera sensor (5 um). The image of Venus is saturated to about 10 pixels diameter, or a bit larger than the full Moon. Even allowing for the smearing of the Airy disk due to the fact that his is white light, there's no way that what we're seeing is primarily a diffraction effect. Venus is bloated by scatter and internal reflections from the optics.

Optically, Venus occupies less than 1/6 of a single pixel, so even with perfect optics and no diffraction it would never appear more than a point source, with no structure.
I've noticed the opposite can be true here on Earth. Light reflecting from my head does not indicate a h'airy' disc. :lol2: Today's photo shows much more favorable and interesting reflections.

Back to the light point question considering your responses, for collimating my reflector, do you think one light source better than another? (Not that I would likely choose Venus but it is a nice bright object)

Thanks, Art & Chris

Re: APOD: A View from the Zone (2014 Mar 07)

by orin stepanek » Fri Mar 07, 2014 10:00 pm

neufer wrote:
Ann wrote:
Orin, I can see that you have 4151 posts right now!

That reminds me of the interesting Seyfert galaxy NGC 4151
[which] has an active black hole at its center.
  • I, too, have always had my suspicions about Orin.
:oops: Oh Ann; now I messed it up! I added a couple of posts! :mrgreen: Art: How much do you know? :wink:

Re: APOD: A View from the Zone (2014 Mar 07)

by Chris Peterson » Fri Mar 07, 2014 9:48 pm

neufer wrote:Each overexposed star becomes a saturated Airy disk diffraction pattern(; i.e., a bright circle surrounded by narrow rings).

Venus becomes a fat highly saturated Airy disk diffraction pattern convoluted with a tiny crescent(; i.e., basically just a very large bright circle).
Sounds good in theory, but that's not really what we're seeing.

The image scale is 3.3 arcmin/pixel. At f/4 (just guessing) the Airy disk will be about the size of a single pixel on the camera sensor (5 um). The image of Venus is saturated to about 10 pixels diameter, or a bit larger than the full Moon. Even allowing for the smearing of the Airy disk due to the fact that his is white light, there's no way that what we're seeing is primarily a diffraction effect. Venus is bloated by scatter and internal reflections from the optics.

Optically, Venus occupies less than 1/6 of a single pixel, so even with perfect optics and no diffraction it would never appear more than a point source, with no structure.

Re: APOD: A View from the Zone (2014 Mar 07)

by neufer » Fri Mar 07, 2014 8:52 pm

Ron-Astro Pharmacist wrote:
Is Venus trying to tell us it will have the last word (or letter)?

It looks like an Omega Ω. Is that a cloud forming the underline?
  • Yes.
Ron-Astro Pharmacist wrote:
Even from behind the low cloud bank - it's showing off. Why doesn't it appear more crescent-like?
Each point star becomes a tiny Airy disk diffraction pattern. :arrow:

Each overexposed star becomes a saturated Airy disk diffraction pattern(; i.e., a bright circle surrounded by narrow rings).

Venus becomes a fat highly saturated Airy disk diffraction pattern convoluted with a tiny crescent(; i.e., basically just a very large bright circle).
http://en.wikipedia.org/wiki/Airy_disk wrote:
<<In optics, the Airy disk (or Airy disc) and Airy pattern are descriptions of the best focused spot of light that a perfect lens with a circular aperture can make, limited by the diffraction of light.>>

Re: APOD: A View from the Zone (2014 Mar 07)

by SamS » Fri Mar 07, 2014 8:10 pm

There's a streak in the top left corner. Satellite or meteor?

Re: APOD: A View from the Zone (2014 Mar 07)

by Anthony Barreiro » Fri Mar 07, 2014 7:08 pm

CURRAHEE CHRIS wrote:Beautiful shot!!! It is nice for me to see something relatively close to where I live. (Pennsylvania). I always feel like the horrible cloud cover blocks most decent shots here in Pa. It seems like I need to move out west (which im going to do when I retire :)) or live on the other side of the planet. Kudos to the photographer from Jersey!!! :) :)
At first I thought you were referring to Venus as relatively nearby, not New Jersey! It's all relative.

Re: APOD: A View from the Zone (2014 Mar 07)

by Ron-Astro Pharmacist » Fri Mar 07, 2014 7:07 pm

Is Venus trying to tell us it will have the last word (or letter)?

It looks like an Omega Ω. Is that a cloud forming the underline? Even from behind the low cloud bank - it's showing off. Why doesn't it appear more crescent-like?

Re: APOD: A View from the Zone (2014 Mar 07)

by neufer » Fri Mar 07, 2014 5:09 pm

Ann wrote:
Orin, I can see that you have 4151 posts right now!

That reminds me of the interesting Seyfert galaxy NGC 4151
[which] has an active black hole at its center.
  • I, too, have always had my suspicions about Orin.

Re: APOD: A View from the Zone (2014 Mar 07)

by Ann » Fri Mar 07, 2014 4:39 pm

Orin, I can see that you have 4151 posts right now! That reminds me of the interesting Seyfert galaxy NGC 4151!

The fact that NGC 4151 is a Seyfert galaxy means that it has an active black hole at its center.

Ann

SIC

by neufer » Fri Mar 07, 2014 4:10 pm

http://en.wikipedia.org/wiki/Sea_Isle_City,_New_Jersey wrote:
<<Sea Isle City's signature water tower always had "Welcome to Sea Isle City" painted on it until 2002 when the printed message was changed to "Smile! You're in Sea Isle City". "Sara the Turtle Day" is the city's local holiday, celebrating a fictional turtle named Sara who became the city's unofficial mascot. Sea Isle City became one of the first towns in New Jersey to receive LED streetlights powered solely by wind and solar energy.>>

Re: APOD: A View from the Zone (2014 Mar 07)

by Chris Peterson » Fri Mar 07, 2014 3:31 pm

Ann wrote:I think you are referring to open clusters M7 and M6.

There really are several globular clusters in this part of the sky, but they are too distant and therefore too faint to really show up in this kind of picture.
Actually, they are plenty bright. It's just that at this image scale, they appear very nearly stellar.

Re: APOD: A View from the Zone (2014 Mar 07)

by orin stepanek » Fri Mar 07, 2014 3:30 pm

It has been said: a picture is worth a thousand words; this one is! :thumb_up: :clap: :-D

Re: APOD: A View from the Zone (2014 Mar 07)

by Ann » Fri Mar 07, 2014 3:16 pm

Psnarf wrote:Thanks to reading APODs, I can now point out a couple of globular clusters right of center.
I think you are referring to open clusters M7 and M6.

There really are several globular clusters in this part of the sky, but they are too distant and therefore too faint to really show up in this kind of picture.

Ann

Re: APOD: A View from the Zone (2014 Mar 07)

by Psnarf » Fri Mar 07, 2014 3:00 pm

Thanks to reading APODs, I can now point out a couple of globular clusters right of center.

Re: APOD: A View from the Zone (2014 Mar 07)

by retrogalax » Fri Mar 07, 2014 2:41 pm

Very artistic , i like how the orange nuances of the sky and the sea shore are playing together in an subtle monochromatic effect.

Re: APOD: A View from the Zone (2014 Mar 07)

by CURRAHEE CHRIS » Fri Mar 07, 2014 1:39 pm

Beautiful shot!!! It is nice for me to see something relatively close to where I live. (Pennsylvania). I always feel like the horrible cloud cover blocks most decent shots here in Pa. It seems like I need to move out west (which im going to do when I retire :)) or live on the other side of the planet. Kudos to the photographer from Jersey!!! :) :)

Re: APOD: A View from the Zone (2014 Mar 07)

by epsztein » Fri Mar 07, 2014 9:07 am

To Parnessa: I respectfully disagree: the "cloud" that cuts Venus in two is simply a sea wave that is also not totally clear, as it did have some time to move. Furthermore there are lights of at leat two ships, possibly three, visible on either side on Venus and they are behind the horizon, unless there is some island out there.

Re: APOD: A View from the Zone (2014 Mar 07)

by Paressa » Fri Mar 07, 2014 8:10 am

Wonderful picture! I do not have a clear view of the east where I reside and these views are always welcome.
epsztein wrote:.... it is not a "low cloud" below Venus, but a high one... not that it is important, but since we all do love our guides...
There are actually two underlining clouds. One that is high just below Venus, and the other is the one that cuts Venus' reflection in two. That originally looked to me like a bright band in the water, perhaps created by Noctiluca scintillans, but after close inspection it is a "low cloud bank".

Re: APOD: A View from the Zone (2014 Mar 07)

by epsztein » Fri Mar 07, 2014 7:21 am

Ann, the answer is in your question: if you see the Milky so well, the bright one has to be Venus; as what we ignore is the angle of aperture of the picture, while time of exposure can be guessed by the receeding waters, and funny enough, an imperfection in APOD comments that can be spotted: a very rare observation, in this part of the galaxy at least: it is not a "low cloud" below Venus, but a high one... not that it is important, but since we all do love our guides...

Top