Animation of comets and a backwards rainbow

[furrysocks2]

This one had me going... looking E, sun's in the SW about 20 degrees alt.

 

For fun, I also had a play with comet orbital elements from the Minor Planet Center. Here is a quick animation of the known comets in elliptical orbit, projected RA/Dec each September-ish for the next 270-odd years:

• I didn't know so many comets orbited backwards.
• I note that there appears to be a great deal more "movement" in the fringes early on in the animation that slows down as the animation progresses, I guess that is due to them being identified when closer to the sun and therefore they slow down as they get further away.
• The jumble in the middle are likely to be mainly Jupiter-family comets, generally having orbital periods <20 years.
• There's one on a ~24 year orbit, you can see it periodically rising up under the word "ARG1" and shooting off to the right.. PK16S010.

Because the earth orbits the sun, our vantage point in space changes over the course of a year, the effect of which is greatest the closer a comet is to us. Here's an animation spanning two years where retrograde motion of comets can be seen:

I make no claims as to the accuracy of any of this, but it might interest someone.

 

 

[Ravenous]

2 hours ago, furrysocks2 said:

This one had me going... looking E, sun's in the SW about 20 degrees alt.

Interesting rainbow picture!

Note the red is on the inside of the curve - so this might be the secondary rainbow (which is outside the primary bow and usually  dimmer)

Secondly as it's centred above the horizon, maybe it's a reflected rainbow?  That is, the rain in that region is illuminated by light reflected off the water, from the sun that's approximately behind the camera.

That's my theory anyway!

[furrysocks2]

10 minutes ago, Ravenous said:

Interesting rainbow picture!

Note the red is on the inside of the curve - so this might be the secondary rainbow (which is outside the primary bow and usually  dimmer)

Secondly as it's centred above the horizon, maybe it's a reflected rainbow?  That is, the rain in that region is illuminated by light reflected off the water, from the sun that's approximately behind the camera.

That's my theory anyway!

Cool to get a theory. I'd not considered the second.

I think, though, you're looking for an explanation to something that's not actually there...

[furrysocks2]

Also, look at the second comet animation, there's one that appears to be orbiting the celestial pole. I had to find an explanation for that, too... C/2015 D4 (Borisov), currently in Ursa Minor.

You can see that declination is never below 80 degrees. The comet has a highly inclined orbit, 77.3 degrees to the ecliptic plane, and our tilted earth orbits the sun - I think all that must combine to produce the pattern of apparent position seen in the animation.

It's moving away just now, back in 600 years or so. Also looks like the variation in dec is slowing down, I guess due to it's increasing distance meaning our orbit around the sun effecting smaller and smaller changes to its declination.

[furrysocks2]

On 03/10/2017 at 10:13, furrysocks2 said:

This one had me going... looking E, sun's in the SW about 20 degrees alt.

Increase saturation, and the backwards curve is just an optical illusion.

[LukeSkywatcher]

I do believe that the rainbow is called a Solar Circum-horizontal Arc. Its caused by ice crystals reflecting sun light.

[furrysocks2]

2 minutes ago, LukeSkywatcher said:

I do believe that the rainbow is called a Solar Circum-horizontal Arc

Not this one I don't think - sun was indeed behind the photographer. It just looked concave due to the shaft of light coming through the clouds and a faint dark-ish nibble out of the red just above the level of the cliff.

I've seen those halos though, they're cool!

[LukeSkywatcher]

Ive seen Sun Halos before but they appeared round the Sun.......not in the complete opposite direction to where the sun was. 

[SilverAstro]

Why is the rainbow cut off by the distant sea horizon ? I thought rainbows always appeared in front of (distant) things ?

[furrysocks2]

On 06/10/2017 at 19:39, SilverAstro said:

Why is the rainbow cut off by the distant sea horizon ? I thought rainbows always appeared in front of (distant) things ?

I don't know... :/  dynamic range of camera? Maybe it was taken with HDR on or something.