Uranus' orbit / celestial path anomaly??

[Dennis]

Hello,

From the series of avi’s covering the recent occultation of Uranus by the Moon, I plotted, as faithfully as I could, the positions of Uranus against the lunar limb, to show the “path” of Uranus as it approached the limb.

Image inventory:
The disc of Uranus processed in Registax from an avi leading up to the occultation.
The normally exposed lunar limb from an avi immediately after the disc of Uranus disappeared behind the lunar limb.
A series of frames from several avi’s leading up to the occultation. These showed the position of Uranus relative to the grossly over exposed lunar limb.

The ‘scope was tracking on Uranus and the lunar limb crept up on the planet’s disc in each successive avi.

When I plot the disc of Uranus against the correctly exposed lunar limb, by overlaying frames from the approach avi’s, to match the lunar limb profile features, the resultant path of Uranus appears curved, getting steeper towards the point of contact.

I wasn’t expecting this? :confuse2:

EDIT: Added an image showing how I performed the registration.

Cheers

Dennis

[avandonk]

The Moon is moving more slowly with respect to the 'fixed' stars. Uranus on this time scale would do the same.

Bert

[[1ponders]]

That looks great Dennis.

I think what you are seeing is the result of the differences in proper motion between the two objects. It looks like Uranus is curving, but that is an optical illusion. I believe it due to the fact that the moons orbital radius is so much smaller than Uranus and it's obit is tilted differently to Uranus in respect to our viewpoint, that the moon is "dropping away" from the orbit of Uranus. Try overlaying you images with Uranus going straight, and moon will drop away.

Fantastic illustration

[Dennis]

Thanks for the explanations Bert & Paul - I initially thought my hand-eye coordination had gone awry.

I love the "dropping away" analogy Paul, it sums it up beautifully. :thumbsup:

Hmm, wish I were clever...:doh: :doh:

Cheers

Dennis

[beren]

Hm ere Paul beat me to it :P .....top work Dennis matching a fine image with an astronomical event is just great :thumbsup:

[jakob]

Fantastic images Dennis, I love the education I'm getting (for free).
I was wondering what the event looked like as from here I had a good cover of Clouds!
I wanted to look with Bino's, would I have seen Uranus?
Rgds J

[[1ponders]]

Uranus is normally easy to see with binoc jakob (no disk though) but it would have been difficult to see against the glare of the full moon.

[Tamtarn]

:clap: :clap: :clap: Fantastic image Dennis we're in awe of what you guys do

[sheeny]

Stunning photography there, Dennis!:eyepop: :thumbsup:

And an excellent explanation of the curved locus of Uranus, Paul! I noticed that from Dennis's other post. Like Dennis I didn't expect that, so I had it on my list of things to ponder when I finished browsing posts... then I found this:D .

It seems surprising to me though that the rate of curvature of the locus should appear to change so much so quickly as the conjunction approaches... I'm sure you're on the right track, it's just that the movement of the moon between the first and last images is not large (a few degrees only?)... hmm, just thinking out loud here really!;)

More mental wrestling to occur over this I feel!:P

Al.

[[1ponders]]

Hi Al.

I think you will find that if you were to accurately measure the change in position for each image the drift/time will be linear (or as close as over the imaging time to make little difference). It only looks curved due to the the change of frame time. ie time from frame 1 to 2 - 5 min, 2 to 3 - 2 min, 3 to 4 - 30 sec etc (these are only demonstration times to give you the picture/idea)

[[1ponders]]

Dennis can you supply the actual times of exposure?

[[1ponders]]

Well I just did that little line drawing exercise and I was way off beam. There is a continual change of angle. I still think I'm on the right path, I'll just have to think about it a bit more.

[[1ponders]]

There is another factor in this that I hadn't considered either. The "apparent" rotation of the moon. I have just run that morning through Starry Night and it is quite easy to see the effect with the moon moving at a different angle to Uranus (use the RA and DEC grid as a reference) and the "apparent" rotation of the moon as it moves from east to west. Due to this rotation the "top" reference mountain will be moving away from Uranus adding to the "dropping away" effect . Make sure you use the moon as your "center" point and not Uranus. If you use Uranus as the "center" point you get the "dropping away" effect.

[jakob]

Refraction or 'bending' of light rays?

Has the Moon an Atmosphere?

Please excuse my ignorance, I should keep quiet.
:screwy:

[[1ponders]]

Atmospheric refraction in the Earth's atmosphere, could be something to consider if the moon was closer to the horizon jacob, and their positions were right, but this image was taken around 00:45 in the morning so the moon and Uranus would have been about 12 degrees to the west of a line drawn north and south (meridian) so it's not likely.

No atmospheric refraction for the moon as it has no atmosphere to speak of.

[netwolf]

Great Job Dennis. :thumbsup:

Does the moon emit heat into space? Could that be causing refraction?
Just poking in the dark here.

Regars

[[1ponders]]

I've attached a screen dump of the relative angles of the Moon's and Uranus' orbits so you can see where part of the effect comes from. Another aspect of this, of course, is Dennis' alignment on the features of the moon. Because the moon is dropping away and "rotating" visually, then aligning features on the moon will have an additional effect of "pushing" Uranus higher (I'd be lost without " " :lol: , will someone please make me an " " smilie :P )

[Dennis]

Gee Paul - you missed your calling.....you should have been a planetary scientist. :thumbsup: :thumbsup: I've just returned from an outing so I'll dig up the avi's and post a composite image with the times on it.

Thanks to all the people who lent their brains to solving this "mystery" - a hard ask for a Sunday morning!

Cheers

Dennis

[[1ponders]]

Dennis could you do a composite image centered on Uranus moving in a straight line?

[[1ponders]]

Doesn't matter Dennis. I've just checked out your other post and it appears that features on the moon move in a downward direction as Uranus moves closer to the moon.

[Dennis]

Hi Paul

I have just completed a sub set where I used Registax to "lock on" to an (over exposed) profile feature on the lunar limb and the result was that the movement of Uranus was in what appears to be a straight line.

I'll see if I can do the same for another couple of avi's then use Registax to align on the Moon and see how the (discontinuous) path of Uranus comes out.

Cheers

Dennis

[Chrissyo]

Congrats Dennis, it looks your image has been featured on LPOD :thumbsup: :thumbsup:
http://www.lpod.org/

[Dennis]

Thanks for the heads up Chrissyo, I'll just pop over there and have a look.

Cheers

Dennis

[iceman]

Nice one Dennis! Well deserved, yet again.

[sheeny]

Good thinking, Paul! I thought there was a bit more to it... my apologies for letting you do all the thinking yourself - I got distracted with other projects around the house (and I'm writing an astro-timer program:P ).

Thanks,

Al.

[[1ponders]]

That's alright Al. I needed to give it a good revving. From some of the stuff ups I've made over the past couple of weeks it was pretty obvious my minds only been running on half its cylinders. I needed to get the gunk out. :lol:

[davidpretorius]

From David Arditti in the UK (one of the guys on Damian Peach's astro email list):

"Interesting discussion - I agree with the conclusion. The apparent curved path is due to the fact that the frames are registered on the features of the moon's limb. Those features are rotating round the moon's centre slightly with changing libration. This is not a uniform motion, but a sinusoidal oscillation - hence the apparent curved path of Uranus. The movement of Uranus with respect to the centre of the moon would be close to a straight line."

[[1ponders]]

:face:

[Dennis]

This post describes an error in the registration procedure used to generate the original image showing Uranus’ apparent path and now shows the corrected image.

To generate the apparent curved approach path of Uranus to the lunar limb, reference points on the profile of the over exposed limb of the moon were used to manually register the disc of Uranus on a master image of the correctly exposed lunar limb.

However, the reference images used for this technique were generated from short clips (cropped from longer avi’s) that had been stacked to make Uranus more visible for the alignment process. These short clips used Uranus as the alignment point so the resultant bmp produced a “smeared” lunar limb profile; that is, extending from the initial position on the 1st frame of the short clip to the last position on the final frame. Even though these clips were only a few seconds long, when inspected carefully it is possible to see distinct features on the profile of the lunar limb drifting downwards.

The Uranus registration errors crept in through choosing the most distinct profile of the limb in each bmp and then aligning Uranus by eye, on screen, using a straight edge. This method should have used the profile from either the 1st or last frame, not the most distinct profile. It is through this oversight that registration errors have crept in.

To remedy this error, single frames from avi’s were selected for the second attempt. Using layering and image enhancement techniques in Corel PhotoPaint 12, the disc of Uranus from several frames was superimposed on a master frame and this now shows a reasonably straight line for the occultation approach. See attached image.

Hmm, an important lesson in the value of peer reviews. Apologies to all our readers for the sleepless nights lost in pondering this non-existent anomaly.

Cheers

Dennis

PS - I have attached the ugly looking layered image for information purposes.

[iceman]

I love it Dennis, your work is very inspiring. You are always so humble and talk about how much you learnt off us... man, this type of work you do is just fantastic and speaking personally, I wish I could do this stuff you do!

Incredible capture of a rare event.

[iceman]

PS: Nice to see your name on it ;)

[[1ponders]]

That looks better Dennis ;)

Thanks for the exercise :thumbsup: :lol:

[sheeny]

Good on you, Dennis!:thumbsup: The locus of Uranus looks more like what I expected now! You did a great job of making the original look like something natural in an inexplicable way.:lol:

Don't worry about getting us to think about it - we enjoy a challenge. Besides... it was no trouble really... Paul did most of the thinking!:rofl:

Al.

[fringe_dweller]

:eyepop: your the man Dennis! mindblowing! how good is the colour in the planet!! if you were a band I would chanting more! more! more! along with the crowd :)

[ving]

like this?

[[1ponders]]

:lol: Thanks ving, that's exactly what I'm after :lol:

[[1ponders]]

So how do I use it now :shrug: :confuse2: :confuse3: :screwy:

[sheeny]

http://www.iceinspace.com.au/forum/attachment.php?attachmentid=16805&stc=1&d=1158037984cut and pastehttp://www.iceinspace.com.au/forum/attachment.php?attachmentid=16805&stc=1&d=1158037984 using http://www.iceinspace.com.au/forum/attachment.php?attachmentid=16805&stc=1&d=1158037984Ctrl Chttp://www.iceinspace.com.au/forum/attachment.php?attachmentid=16805&stc=1&d=1158037984 and http://www.iceinspace.com.au/forum/attachment.php?attachmentid=16805&stc=1&d=1158037984Ctrl Vhttp://www.iceinspace.com.au/forum/attachment.php?attachmentid=16805&stc=1&d=1158037984like this...;)

Al.

[sheeny]

That'd be a big "whoops" there on my part!:doh: :rolleyes:

It looked good on the edit screen!:lol:

Al.