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03-11-2020, 02:51 PM   #31

QuoteOriginally posted by MossyRocks Quote
I get that fairly frequently. I find it mostly happens when the movements aren't restricted to one axis but also when there are things that have a large effect on the electronic compass . If I have a calibration that finishes before I have gone through all 3 motionsI assume it is bad. I also make sure to do a regular calibration and a precise calibration each time.

Not really. Where I am CNP is about 45 degrees from the horizon when facing towards true north (which for me happens to be well within 1 degree of magnetic north at the moment). The only time the CNP would be at the zenith is if you were actually at the north pole. For the purposes of human time scales stars all have a fixed position using equatorial celestial coordinates. The declenation portion is a measure of how far they are from the celestial equator and the closer to the celestial equator something is the higher linear speed it has. This linear speed is the same all the time regardless of the time of year or one's position on earth. Polaris or the north star is basically at +90 for declination (it is actually about 1 degree from it) and being right at the celestial north pole it;'s right ascension is basically meaningless. However the great Orion nebula (M42) has a declination of about -5.5 degrees or being 5.5 degrees south of the celestial equator so it is basically on the celestial equator and as such has a huge linear speed across the sky. While it's declination is fixed it's height in the nigh sky varies over the course of a day and for me with my approximate 45N latitude it would get to about 40 degrees above my physical horizon but is will always be that 5.5 degrees below the celestial equator.

Nope. The O-GPS1 talks about declination not latitude or zenith so a 90 degree declination means point it at the celestial north pole, a 0 degree declination means pointing it at the celestial equator, and -90 degree declination means pointing it at the celestial south pole.

If you really want to get a handle on where things are and get your bearings when looking at the night sky I suggest getting a cellphone planetarium app. For free ones I like Sky Safari as it has a more complete catalog of objects than others and if you want to pay you can go ad free. You can have it show the equatorial celestial coordinate grid and also make use of the compass and tilt features in your phone to show you what you are looking at. If you want a program to use on your computer a really good one is Stellarium which has tons of objects in various catalogs you can load.

Everyone has to start somewhere, I was a beginner at one point as was everyone else.
I installed Sky Safari on my phone, very nice app will hep me a lot when looking for targets, thanks. StellariumI have on the house computer.

03-13-2020, 03:59 AM   #32

QuoteOriginally posted by AstroDave Quote
The satellite orbits are continuously monitored and accounted for in the GPS broadcasts.

At the level we are concerned with, humidity has NO effect on astrotracer operations. It might cause your apparent camera position to be off by a few centimeters but that will have no effect on astrotracer operation. You would have to be mislocated by 10 to hundreds of meters before the sensor motion would not be adequate to stop star trails (assuming everything else was set up correctly - which seems to be the achilles heel of astrotracer operation!).
As an ending discovery, Rather than go through the motions they suggest to do a calibration, I racalled my phone has a compass, that requires me to do a figure eight held up to calibrate.
I did this with the k-3 for a few moments and got an OK. Not only that, I was able to track stars for 90 seconds with the 28mm, longest before that was 50 seconds.

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