Polar align - Poncet platforms and parallactic tables

Using SharpCap's Polar Alignment feature
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aquariusCZ
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Polar align - Poncet platforms and parallactic tables

Post by aquariusCZ »

Polar align is a great tool.
It would be very useful for us, but we can only rotate the RA axis by 15-20 degrees.
Please, for all owners of EQ platforms and tables, will the tool be modified?
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Re: Polar align - Poncet platforms and parallactic tables

Post by admin »

Hi,

I don't know how good the accuracy would be for such a small rotation angle – in some ways the problem of solving the polar alignment calculation is similar to finding the intersection between two lines. If the lines are only at a shallow angle to each other and there is some uncertainty in the position of each line then the area in which the intersection may occur is more uncertain than it would be if the lines were close to being at right angles to each other for the same uncertainty in the position of each line.

If you try rotating very slowly then you should find that dark red crosses start appearing on the image once the rotation reaches about 15° and then an extra one will appear for every 5° of rotation beyond that. These are actually tracked to help people who have problems with the alignment work out if the rotation centre is changing as the amount of rotation changes (usually a sign that something is fixed firmly and is moving as the mount is rotated). If you can see these crosses being shown (they represent SharpCap's estimate of the centre of rotation) and the ones that you see appear to be in the same place to within a pixel or two rather than being separated then there might be a chance of making this work with smaller rotations.


Cheers, Robin
aquariusCZ
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Joined: Wed Apr 15, 2020 1:02 pm

Re: Polar align - Poncet platforms and parallactic tables

Post by aquariusCZ »

Hi,
I think the algorithm will work accurately enough even with a small RA rotation.
POLAR ALIGN draws me a red cross with a parallactic table when turning the RA by 15 degrees.
However, 15 degrees is not enough to complete the whole process and POLAR ALIGN does not offer correction of the RA axis direction.

I think it is enough to reduce the condition of rotation of the RA axis to 15 degrees and POLAR ALIGN will work with EQ platforms and tables.
Any lower accuracy of the setting will not matter.

That will be a huge step forward for us. The drift method on devices with a virtual RA axis is not for humans. :evil: :D
 
Cheers, Tomas
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Re: Polar align - Poncet platforms and parallactic tables

Post by admin »

Hi,

Give the very latest version on the download page a try – there is a checkbox on the polar alignment UI to allow low rotation mode to be enabled which should allow you to move on if the rotation exceeds 15°. I must admit I haven't been able to test this as it is (a) cloudy and (b) not dark yet :)

Cheers, Robin
aquariusCZ
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Re: Polar align - Poncet platforms and parallactic tables

Post by aquariusCZ »

Hi,
I did not expect such a speed of solution. This is excellent.
I don't have my parallactic table here. I will bring the table tomorrow and try the new version. Big thanks.
Cheers, Tomas
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Re: Polar align - Poncet platforms and parallactic tables

Post by admin »

Hi,

It was one of those requests that is easy to do – the hardest part was making a checkbox so that the new behaviour can be turned on or off.

Cheers, Robin
aquariusCZ
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Re: Polar align - Poncet platforms and parallactic tables

Post by aquariusCZ »

Hi,
I tried the modified POLAR ALIGN function on the parallactic table using a f=200mm lens and QHYIII178C.
It works. :D In three minutes I set up a table with the result GOOD.
Image

Once I had the equipment outside and set up, I tried the NGC7000.
Image
table + photo tripod + Witty1, Jupiter 200/4, QHY5III290M, filter Optolong L-eNhance,
Mono16, 1280x960, bin 2x2, exposure 15s, gain 450, 100 shots,
composed in DSS and modified in PaintNet, reduced.
22.5.2020-00:08, Frydlant nad Ostravici -Czechia
Cheers, Tomas
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Re: Polar align - Poncet platforms and parallactic tables

Post by admin »

Hi,

Glad to hear that it works! Hope you get some more clear skies to keep imaging over the next few weeks :-)

Cheers, Robin
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