Uranus from Voyager 2 in nearly identical processing as my Neptune image. The southern pole of Uranus faces the Sun almost exactly at this point in 1986. There isn't much to see going on. Still, there seems to be some subtle variation in color, which may or may not be real.
These days, the northern pole of Uranus is turning to face us. I find visible spectrum imagery of this planet to be nearly useless. Perhaps the only reason to look is to ensure that serenity remains. Current knowledge indicates Uranus is made of nearly the same stuff as Neptune.
Red: Voyager 2/ISS 585nm "Green" Filter (C2655615_RAW)
Green: Voyager 2/ISS 480nm "Blue" Filter (C2655639_RAW)
Blue: Voyager 2/ISS 400nm "Violet" Filter (C2655633_RAW)
Tags: Uranus Voyager 2 planet ISS img2png when will we return
Edit 2024 Jan 17: I uploaded a reprocessed version of this with less saturation and a bit better alignment of the planet and clouds. The pink isn't as obvious, but is still there.
And here's my take on a three-color visible light image of Neptune from Voyager 2. I was very interested to see the pink features in the clouds and northern pole come about with no effort whatsoever. The filter choices I think are a bit wider than the Hubble filters, so the image came out less saturated. I went ahead and enhanced the saturation of this image a bit after deciding it probably was a bit too pale.
What really surprises me about this is that I can't find any other images quite like it. Is Neptune really purplish/pink in its north pole and around its limb? Is it decorated with bright, pinkish clouds? I wish I could say for sure. It is different enough that I doubt myself significantly. Nonetheless, I wish to share it.
I have noted that most images utilize the Voyager "Orange" filter for red light, but when I looked at the filter plots I decided it would be more appropriate to use the "Green" filter, and the same pattern followed for the other two channels. I have made a note of the central wavelength of the filters in my list here. You can see if you agree with my choices. I used Photoshop's puppet warp feature to align the brighter clouds.
Red: Voyager 2/ISS 585nm "Green" Filter (C1115234_RAW)
Green: Voyager 2/ISS 480nm "Blue" Filter (C1115216_RAW)
Blue: Voyager 2/ISS 400nm "Violet" Filter (C1115210_RAW)
Tags: Neptune Voyager 2 ISS visible robot when will we return img2png planet
From Hubble in narrowband red, mediumband green and blue filters. I did not enhance the saturation for this image; the filter choices manage to separate the colors on their own with little processing effort required.
It is important to note that no one has seen a clear image of Neptune directly without the aid of a camera and various processing techniques. With that in mind, I have tried to modify my Hubble processing to match more closely with the Voyager 2 data. I have noted that the blue channel must be more emphasized, and the green channel less emphasized to approach what others have reported seeing regarding the human-perceived color of the planet. I have relied on the advice of H. B. Hammel and Björn Jónsson from short Twitter exchanges. Here and here.
I would guess that this is more saturated than Neptune may appear to a human eye, but it's hard for me to say. Based on this and the Voyager 2 data, I am intrigued by the possibility that the pinkish limb may be visible to a human eye, if a human was ever to travel there and bear intimate witness to such an elusive majesty.
The high clouds in the northern hemisphere have been evolving for the past few years. Previously, bright cloud formations have been noted nearer to the equator. They are large enough and bright enough that amateur astronomers have also been recording them and collaborating with pros. (Hat tip Björn Jónsson)
The easiest way to see the changes documented that I know if is via the OPAL website, by loading the various Neptune tables. archive.stsci.edu/prepds/opal/
Red: WFC3/UVIS F657N
Green: WFC3/UVIS F547M
Blue: WFC3/UVIS F467M
North is up.
Tags: Neptune visible Hubble HST UVIS clouds OPAL outer planet ice giant 14756
Here is cold, lonely Neptune floating in the distance seen in red and near-infrared light. I tried to process it similarly to my Uranus image, but without the rings to contend with, I could ease off the glow around the planet a lot more smoothly, so the planet doesn't look as much like it's floating in a haze. If you flip back and forth between this and the Uranus image, you can see how they compare in size to one another as they are presented in appropriate relative sizes as they appeared to the telescope. Both are scaled up 200%. This was imaged on 2017-10-07 at around 12:14 UTC
The OPAL project has a page containing several years' worth of data, including map-projected images. You can check it out or maybe make your own maps if you are into that sort of thing here:
archive.stsci.edu/prepds/opal/
Data from the following proposal were used to create this image:
Hubble 2020: Outer Planet Atmospheres Legacy (OPAL) Program
Red: WFC3/UVIS F845M
Green: WFC3/UVIS F763M
Blue: WFC3/UVIS F657N
North is up.
Tags: Neptune Hubble HST planet red near-infrared infrared OPAL Proteus 14756
Update 2017 Nov 21: There is a web page for the OPAL project here that I was unaware of when I posted this: archive.stsci.edu/prepds/opal/
Uranus imaged by Hubble on 2017-10-27 at 01:15 UCT (that's 9 days ago from the time of this posting). I believe the moon to the right is Miranda. A few smaller moons are also visible in the image, and several more still are detected in the raw data, but are too dim to see with this processing. The brightening in the longer wavelengths at the limb of the planet is real, though I do not understand exactly why it happens.
This proposal is on the Director's Discretionary budget, so there's no proprietary period. Also available are recent images of Neptune! If you enjoy planetary processing, now is a good chance to get your hands on some fresh, public data. You can head over to the MAST portal to find it. Use an advanced search to filter it down to only images of moving targets taken in the last couple of months, and then sort the list by start time. Alternatively, you can also filter it by Proposal ID to 15262 and look at all the data currently available from that proposal. Sometimes there are gems from other proposals, though.
The moons and a small bright spot appear multi-colored because they moved in the moments between each exposure. The blue channel is not infrared, but rather a narrowband filter typically used to capture Hα and [N II] emission. It seems to work ok here as a kind of shorter wavelength red filter, with the other two channels containing more red and near-infrared. I found the combination gave it a pleasing amount of color separation without going into ultra vivid, technicolor land as so many infrared images do.
A great thing about these wavelengths is that the rings and cloud bands are clearly visible at the same time with the right tweaks to the value curves. Most images of Uranus have had separate processing for the rings and the planet because the rings are so very dim. I gave them both the same processing instead of separating them.
Here, you can also see the "X" shaped light pattern emanating from the planet, which is just like a diffraction spike we see on bright stars. This pattern, and the faint, fuzzy, glowing halo are effects produced as light interacts with the telescope—not something that is actually there around the planet.
The image is scaled up 200% from its original form. The latest version of Photoshop introduced a new resampling algorithm which they have called "Preserve Details 2.0" which maintains some of the sharper edges better than previous methods.
Data from the following proposal were used to create this image:
Hubble 2020: Outer Planet Atmospheres Legacy (OPAL) Program
Red: WFC3/UVIS F845M
Green: WFC3/UVIS F763M
Blue: WFC3/UVIS F657N
North is up.
Tags: Uranus planet planetary infrared near-infrared visible red moons Hubble HST OPAL 15262