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.
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.
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 ).
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.
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."
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.
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!
Good on you, Dennis! 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.
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!
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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 
