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Moon Tracking

Andrew*

By Andrew*
in Imaging - Discussion

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Andrew*

Andrew*

Posted
Posted

I have a query about tracking the moon while imaging. Watching the AVI I took of the moon, it moves quite quickly across the FOV. This much over 17 seconds:

2010_normal.jpeg

2011_normal.jpeg

I thought my alignment was pretty accurate, but didn't actually check on a star to see if the alignment was poor or if it was the moon's movement relative to the stars.

Is this level of movement acceptable for lunar imaging - that is, will the program align the images okay? Also, when it aligns, does it cut off the bits which aren't common to all the frames?

Andrew

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GazOC

GazOC

Posted
Posted

You'll want better accuracy if you start using barlows to get closeups...

When Registax aligns, parts round the edges that may not be in all the frames tend to blur, you can get around this by specifying how many pixels around the frame edge are not to be stacked on the 'stacking' page (or you can just crop the final image yourself obviously). :smiley:

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barkis

barkis

Posted
Posted

The moon orbits from west to east, and the earth rotates east to west, so sidereal drive rate is too fast for the moon, it need to be slowed slightly. Also at certain times during a lunation, the moon can change in declination pretty rapidly, up to 7 degrees a day, or 1 arc second in three seconds of real time, so if an exposure time exceeded three second, a declination drive is necessary.

This information was taken from Nortons Star Atlas.

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Andrew*

Andrew*

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Thats not an option on the HEQ5 without Skyscan.. :(

no :)

Ron, I don't think I can blame the moon's movement for this :smiley: - obviously my 3-minute alignment technique needs to be revised... to 5 minutes!

Cheers all. But don't think my questions are over :nono: :evil:

Andrew

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themos

themos

Posted
Posted

I've done hand-tracked (no motors, slow-mo controls of an EQ1) avis of the moon with an effective FL of 2700mm and I've found that Registax4 can be coaxed into aligning them (hundreds of frames). But I am finding that software frustrating. What I want to do is run a rough alignment first and have it remembered by the program in any subsequent run where I try to improve matters by going multi-region.

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trevboyd

trevboyd

Posted
Posted

I've found that roughly tracking by hand is good enough - registax will align and stack the images. You just end up with regions along each side of the resulting image that are fuzzy where some of the frames have been cropped. You also need to make sure that your alignment points don't creep off the edge on any of the frames, as that seems to mess up the alignment.

All my moon stacks on here using a webcam have used this technique.

HTH

Trev

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themos

themos

Posted
Posted

Isn't there an option to save a registered (as in aligned) AVI from Registax?

Yes there is. That might be worth trying out next time. I also have the problem that I (almost) invariably see, during the optimisation phase, that things are not going too well and I hit cancel and then the software gets into a muddle and you have to start again. Saving a half-registered movie might help.

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themos

themos

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Another frustrating couple of hours with Registax last night. Honestly, I am beginning to hate that software. There is just no indication which of the myriad settings are actually used in the calculation phases and everytime I re-visit the stackgraph to tweak it, the feedback on the sliders is nonsensical, and the cancel button doesn't really work (you never know what messed-up state you will end up in).

PS: the only good thing is I managed to save a half-registered movie...

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Vega

Vega

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Posted

The moon orbits from west to east, and the earth rotates east to west

:nono:

Nic picking here but doesn't the moons orbit follow in the same direction as the Earth's rotation? The Earth's rotation (from West to East) makes everything in the sky appear to move from East to West. The moons 28+ day orbit in the same direction as the earth's rotation makes the moon appear to move slower and stay up above the horizon for slightly longer than the rest of the background sky. If the moon orbited the Earth in 24 hours it would stay stationary in the sky all day and night.

Vega

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  • 3 weeks later...
Grant

Grant

Posted
Posted

How would I upload a 524 MB AVI for you chaps to play with?

Trevor, if you want to upload a file that size I can provide some web space for you to upload it to, let me know if you do and I will organise it and send you the details - it will take a long time to upload though! Alternatively, I can send you my details and you could post me it on CD and I can upload it for you?

The ability to upload large, raw files is a new feature coming to Stargazrs (now UK Astronomers) very soon! :D

Cheers,

Grant

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