Polar alignment during the day

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Florin Andrei
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Polar alignment during the day

Post by Florin Andrei »

I figured this is the best place to ask this question. :)

I have a CGEM mount. What is the best way to do polar alignment when the only visible object in the sky is the Sun? Currently I try to gauge North as best as I can (using the smartphone, mostly, but I could use a magnetic compass with declination charts), point the mount that way, use the bubble level to make sure it's vertical, the latitude angle is already dialed in.

Using the hand control, I do the alignment procedure: Solar System alignment, select the Sun, all done. But there is always a residual tracking error after that.

Is drift alignment the only technique I could use to fine-tune alignment? I've done it before, but it's slow.

I do not always have the luxury to align the mount at night and leave it there ready for the next day.


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Re: Polar alignment during the day

Post by EGRAY_OBSERVATORY »

Ok, this is question previously answered with a recommendation.

1 The mount and tripod will need to be perfectly level/horizontal in all directions. This should/could be achieved by having three small pads on the ground (if available in a garden), which also could be horizontal. (small concrete pads, wooden/metal could do).

2 If no garden is available, but on hard-ground surface, then to make suitable markings (chalk/indelible-pen/paint for repeating the next session's setting-up in daylight.

3.. At (for say one-night) do your Polar alignment procedure as recommended by the mount-instructions (+ any star alignments too).

4. When satisfied that the scope is sufficiently aligned, point the scope to Polaris and then lower toward horizontal and North.

5. See what can be used as a marker for that position from the scope to North and either mark at the distant object/wall/fence etc., if possible.

6. Then if possible for daylight/Solar use, just repeat the setting-up (as above) but obviously without the stars !!

7a. That should be near enough for Solar-tracking rates which hopefully you can trial and possibly make any fine-adjustments..
7b. The CGEM mount may allow for some corrective input to keep alignment via its' hand-controller...

I don't know of, or think that "drift-alignment" really can apply for Solar or Lunar/planetary purposes, as is normally achieved using stars, which track at different rates than Solar etc.

Best wishes
Terry


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Re: Polar alignment during the day

Post by EGRAY_OBSERVATORY »

I meant to add Florin,
That for just viewing the Sun, accuracy is not mandatory for good tracking, so much as imaging for AVI type movies for stacking etc.,

Single frames with any camera are usually only requiring a small fraction of a second for Hydrogen-Alpha dependant on the camera type.

Movie files can cover many seconds through a few minutes (depending on preferences), so a fairly accurate Solar tracking is a better option, even though, if near enough accurate, some stacking may cater for the tracking error and align the Sun into a single frame.

I can set-up one of my Vixen mounts with just guessing the North and not too accurately levelled and with my nice SkySensor 2000PC HBX, slewed to the Sun with its' Solar Rate and just with a little adjustment, been able to track very well for short periods.
Some luck rather than extreme accuracy - may well get a good result...

I do of course have an observatory with a stand-mount and three-scopes with their own cameras, so once set-up, rarely needs any adjustment.
Polar-alignment having been acquired by a QHY PoleMaster camera to a computer-screen with its' special program.

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Re: Polar alignment during the day

Post by minhlead »

I use a small app called Polar Aligment pro which have a daytime PA feature. It's not very precise but bring you close enough for solar.


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Re: Polar alignment during the day

Post by Carbon60 »

I just use a compass and my eyeball. Place the compass on the ground under the mount, extend the rod that holds the counterweights and look down vertically, aligning your eye, the rod and the parallel lines on the compass housing with the needle pointing to magnetic north. Simply ensure that all are aligned and that the compass has been corrected for your local declination angle and the mount will be suitably aligned for solar imaging, which, as Terry says, doesn’t have to be perfect. Once aligned, then adjust the legs to achieve level.

Hope this helps.

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Re: Polar alignment during the day

Post by Merlin66 »

I have the HEQ5 mount set outside on the balcony. The initial set-up was achieved using the SharpCap PA method at night and the position of the feet marked. Setting to the marks gave a 90% repeatable positioning. OK for solar imaging.
The final set-up can be tweaked using the drift of the solar image in the camera FOV. Straightforward and works!

For the "portable mount" I used SunCalc ( https://www.suncalc.org/ ) to find the meridian and set the mount to that, then checked the altitude of the polar axis with the neat "Level Box" ($10 from eBay) accurate to 0.1 deg.


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Re: Polar alignment during the day

Post by Rusted »

A liquid damped, rectangular "protractor" compass, kept well away from ANY heavy metal.
I use a 2m long, square aluminium tube against the flat side of the mounting. Compass resting on the tube.
A small, magnetic, digital clinometer on the PA shaft. Or PA housing, if parallel with the shaft, to check PA altitude matches location.

Once roughly aligned I use SharpCap with the crosshairs graticule, the sun's image and drift.
It takes only seconds when the image is large enough BUT you MUST rotate the camera FIRST.
To ensure the sun's limb follows the crosshairs when driven up and down at slew speed on the paddle.

Lots of guide videos on drift alignment on YT these days.


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Re: Polar alignment during the day

Post by Montana »

We all do it differently, this is my method https://www.flickr.com/photos/alexandra ... 535593245/ just make sure you have your compass adjusted for true north!

It works fine every time for me even at 5x on the C11 tracking is pretty accurate :)

Alexandra


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