A few questions about the tiny blue dot image

not sure if this is the right forum but, the tiny blue dot image.
If this image was taken from so far out. Shouldn't we be seeing other planets etc in this image? and what is the red band of light our planet is in and the other bands of light for that matter?

sorry, i would have posted the image but can't seem to figure out how to, not hard to find the image tho.

a reply to: dan121212

Its from Cassini I believe, thats Saturn's ring system. Not all planets line up for group portraits.

a reply to: pavil

Voyager 1 and i know planets dont do that but look at the vast space around us and nothing to be seen

a reply to: pavil

and it was taken when it was leaving the Solar System

a reply to: dan121212

a reply to: dan121212

Thinking of this one... Link

a reply to: BlueJacket

lol

a reply to: pavil

ah nice, never seen this one

originally posted by: BlueJacket
a reply to: dan121212

Check out what this astronaut has said about that topic:

briankoberlein.com...

I once did a thread about the 25th Anniversary of the original "Pale Blue Dot" image taken by Voyager in 1990

www.abovetopsecret.com...

Here is that image. I'm not sure if this is the same "Blue Dot" image you were talking about, because others have been taken since. In the picture below, Earth is the pale dot of light about half way up in the brownish band on the right. :

Earth's apparent size is less than a pixel; the bands are caused by sunlight scattered by the camera's optics.

As for the other planets, they may not have all been in the same part of the sky as the Earth was in that image. Consider when we look at our sky: The planets are usually spread about the ecliptic and only often near enough to each other to both be in the same image -- especially a magnified image.

In that same old thread I posted above, I also included a "family portrait" of the other planets that Voyager was able to see at around that same time:

From left to right, top to bottom: Venus, Earth, Jupiter, and Saturn, Uranus, Neptune. Mercury is too close to the sun to be seen. Mars was not detectable by the Voyager cameras due to scattered sunlight in the optics, and Pluto was not included in the mosaic because of its small size and distance from the sun.

a reply to: Soylent Green Is People

yeah, spot on, thanks for the info

I wonder, though, in the image that was composed of pixels in the first place, how did they determine than the Earth was "less than a pixel"?

a reply to: wildespace

The statement is based on the angular size that Earth would be from that difference. That would cover less than one pixel. However, at least one pixel will be affected by the light. You can't have half a pixel lighting up.

a reply to: wildespace

I guess it depends on how you define 'pixel' and where the image is viewed. The original image wasn't digital as such, as far as I can tell the camera was a vidicon tube similar to those used in early weather satellites. Modern digitial displays can have sub-pixels, with each pixel composed of three elements (RGB), though by the strict sense of the definition these are (as the smallest component of the display) actually pixels!

I suspect it's just a bit of "wow this is a really small dot" kind of description.

originally posted by: Phage
a reply to: wildespace

The statement is based on the angular size that Earth would be from that difference. That would cover less than one pixel. However, at least one pixel will be affected by the light. You can't have half a pixel lighting up.

And in addition to the discussion of the vidicon tech differences from modern CCDs, even if earth were a true point-light source it would still light up more than one pixel due to the point spread function determined by the optics.
www.zeiss.com...
It's one of the easiest ways of distinguishing cosmic ray strikes on CCDs from true detections of light; cosmic ray strikes do not form point spread functions, they have very sharp edges where they're inducing charge in a pixel but potentially leaving neighboring pixels completely unaffected.