An image of Comet Ison or is it really a comet?

Originally posted by nataylor

Originally posted by filledcup
reply to post by nataylor

 

no no the green line i was refering to was for the photograph on the left showing earth. THAT line can be represented in any shape the presenter wants and claim that's how the planet is moving through space.

oh and thanks for telling me the name of the software. ill have a go at it. will go well with stellarium

edit on 20-8-2013 by filledcup because: (no reason given)

No the green line on the left won't be represented by any shape you want. That's the path Hubble takes when viewed from comet ISON. The path is as fixed as the green line on the right showing ISON's path is.

well that explains alot. i was reading that line as though it was meant to be a representation of Hubble's movement back/forth up/down in orbit at the 28 degree accent. which i would guess also moves up and down as in a gyroscope.

reply to post by filledcup


I really hope you are a troll.


Nevertheless there are plenty of posts explaining

Originally posted by Bilk22

Originally posted by alfa1

If people are going to get excited about pictures off the Hubble website, then they might as well also take the time to the read the blog post that describes the images.

These exposures were made while the telescope tracked the stars. Because of the motion of the comet and the motion of HST in its orbit around the Earth, the comet trailed slightly relative to the stars during and between these exposures. This is not the way comets are usually observed. Normally we would track on the comet to keep it stationary in the camera during the exposure. However, in this case we wanted to produce an image of the comet against a background clearly showing stars and galaxies.

And besides, this is just another example of NASA conspiracy paranoia, as if, once again, people delude themselves into thinking that somehow NASA gets to be the gatekeeper of all astronomical knowledge.
They're not.
Quite a lot of people have images comet ISON at this point, and yes, even from telescopes in their own back yard.

On face value the explanation seems reasonable. However, it then also seems somewhat contrived. Their explanation makes it seem as if the photography was being performed for some artistic purpose rather than scientific. Why did they need such a picture?

Start off by imagining there is a celestial sphere (or zodiac) around the earth. At some point on this sphere is the Sun. Comet Ison then travels along a plane that intersects the Sun, which will be appear as a thin line going all the way around on the celestial sphere and through the Sun. Next, the Hubble telescope is orbiting Earth, while all the time having to constantly point to the comet. As the Hubble telescope is on a near-circular orbit, travelling at 7500 metres/second it's view would move across the celestial sphere if not compensated for. For every micro-second, the telescope has to turn slightly (orbit = 360 degrees/90 minutes = 0.06 degrees/second). Add to that the fact that the telescope is zooming into a very small region of space, thousandths of a degree, there is going to be some "camera wobble".

Then again, that could be one of V shaped hotel UFO's with square windows that take space holidaymakers on tours around Earth. There was a UFO report of something triangular shaped with a row of large circular lights underneath. Maybe they're doing a holiday tour of Comet Ison going around the solar system.

www.uforth.com...

Originally posted by Deaf Alien
reply to post by filledcup

 

I really hope you are a troll.


Nevertheless there are plenty of posts explaining

well why would you hope that? that's what ive been asking for all along and they keep putting that image in my face. i wanted to see hubble's orbit around the earth so i can add it to my model and see this as tho i am standing in space accurately. not to see how the hubble orbit draws a line by mirroring the crescent of the observation. once i understand this.. ill understand alot more

Well, we should know soon enough, for if it truly is a comet, then it should have "ice on" it...

Originally posted by nataylor

ok i think i got it now.

hubble is changing angle as it's both revolving around the earth, and the earth is moving along it's orbit around the sun. in 43/48 minutes hubble covers the dark half/night side of the earth orbit. and as it enters the daytime side it starts moving away from the comet giving the appearance that the comet has made a sharp right turn from the photos taken during the period nightfall to daytime. that would also explain why there are gaps in the flight path due to long exposure. nasa decided to use this method to take full advantage of capturing the comet's flight path during the available time period. Hubble cannot observe the comet when it is on the daytime side of the earth simply because earth will be blocking it's line-of-sight until it comes back around the other side to night-time again.

so that would mean that the comet is traveling in this direction..

reply to post by filledcup


Thank you Filled cup.

Now I see, and get it. I needed the visual to wrap my mind around what was trying to be explained.

Cirque

Originally posted by CirqueDeTruth
reply to post by filledcup

 

Thank you Filled cup.

Now I see, and get it. I needed the visual to wrap my mind around what was trying to be explained.

Cirque

yeah.. but that angle is still too damn steep lol

id expect that comet to be moving fast enough against the Hubble's moving away to generate a curve rather than such a sharp angle. i guess maybe it isnt moving as fast as i thought.

reply to post by filledcup


You've got, basically. The comet is actually traveling from top to bottom, though. But I think you've got a handle on it.

for now im also going to retract this statement..

that would also explain why there are gaps in the flight path due to long exposure. nasa decided to use this method to take full advantage of capturing the comet's flight path during the available time period.

it doesnt explain this. this would apply if the photo was constructed of stacked layers over a period of days.. but not for one 43/48 minute session. the dark spots would have to be due to camera downtime.

reply to post by filledcup


I don't think it's as sharp as you think it is. You called the apparent turn the comet takes as 90°, but the angle is closer to 125°.

Originally posted by nataylor
reply to post by filledcup

 

You've got, basically. The comet is actually traveling from top to bottom, though. But I think you've got a handle on it.

right.. and that's because our camera is pointed down, observing the comet as it rises from under the sun. is that it?

reply to post by filledcup


Maybe you don't get it. No, in the animations I've provided, the camera is either pointing from the Hubble at the comet, or from the comet at Hubble.

Originally posted by nataylor
reply to post by filledcup

 

Maybe you don't get it. No, in the animations I've provided, the camera is either pointing from the Hubble at the comet, or from the comet at Hubble.

ok no not those. i get that. im refering to the nasa provided image from the hubble showing the 'winged disc' effect.

over a period of days would produce a zigzag like pattern i get it. it's actually a straight line or a line with a slight curve, but the hubble's moving away places the dot of light further because it IS further. the long exposure creates a chain of dots that appear as a line of light. creating the illusion that the comet has changed course..

i was giving the comet's flight path a 3d depth it didnt deserve due to that illusion. causing an exaggeration of the angle to much nearer 90-100 degrees. but i believe i have it fully visualized now.

Originally posted by nataylor
reply to post by filledcup

 

Here's an animation showing the HST's movement over 90 minutes. Each step is 5 minutes.

In 43 minutes, it travels about half of the indicated path.

Ok you got my vote on this one
Just that all the program I have use only let you chose from a point on earth
which one are you using
Thank

Originally posted by CoolStoryMan

Originally posted by CirqueDeTruth

That is so cool. It you can wrap your mind around it being a craft, even the wings are uniform. Amazing. I'm not surprised this was the last image!

What will be the 'logical' thing this turns out to be, I wonder? Lens effect, zoom effect? That is a really awesome find.

S n' F

Cirque

Probably the same logical thing that led to elinin and planet X destroying earth already

They didn't destroy it because they are busy gathering for the great war, they are waiting atm.

Originally posted by NeoParadigm
reply to post by abeverage

 

What is still a bit puzzling is why it does not show as one continuous line instead of three dashes of light? Wouldn't the object keep creating a continuous streak?

I was thinking the same thing. One would think they are 3 seperate long exposures with some time in between.

I think they did 3 exposures, but only with one filter maybe.( I don't know if that makes sense, just trying to make sense of their "single exposure" comment)

edit on 20-8-2013 by NeoParadigm because: (no reason given)

Anyone come up with any good explanation of this? To me an exposure is set and goes for how many seconds is requested and then a new image is created. Anyone who creates a long exposure with digital cameras does this I do this on my camera I would think they would do the same. Old film cameras you could do multiple exposure and I suppose some software could make the CCD create multiple exposures on one image but I doubt it.

Anything with multiple exposures would be done post effect. Unless I see some data suggesting otherwise one exposure means just that.

reply to post by abeverage


I posted this information earlier in the thread, but the three exposures with the F606W filter were combined into a single data set. Similarly, the two exposures with the F814W filter were combined into a single data set. You can see that in the first two lines of the table here: archive.stsci.edu...

The F606W data set has an exposure time of 1320 seconds, which is 3 exposures of 440 seconds. The F814W data set has an exposure time of 980 seconds, which is 2 exposures of 490 seconds.

And just to back up that it's not unusual to stack multiple exposures together, I point to the Wide Field Camera 3 Handbook: www.stsci.edu...

UVIS exposures can be split into multiple exposures. The Optional Parameter CR-SPLIT in the Phase II observing proposal can be used to equally divide the original exposure time into the specified number of subexposures.

Originally posted by abeverage
Anyone come up with any good explanation of this? To me an exposure is set and goes for how many seconds is requested and then a new image is created.

It is actually extraordinarily common in astronomical images to "stack" multiple frames on top of each other.
Actually more than normal, its standard practise.