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INDI Library v2.0.6 is Released (02 Feb 2024)

Bi-monthly release with minor bug fixes and improvements

Polaris Hour Angle & GPSD

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Hello

I have a just setup an USB GPS module for my Pi4.
GPSD is working and VirtualGPS is disabled.

Do you know why "Polaris Hour Angle" is different between Ekos panel and INDI panel?
And which one should I use?


Thanks
Nico
Last edit: 3 years 9 months ago by Nicolas MONNEINS.
3 years 9 months ago #56153
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Hello,

Location is in multiple places within AstroBerry. A quick check is to open GPSPANEL. The default location is Warsaw, Poland. If that is your location, then the clock of the PI has drifted. The PI does not come with an RTC. RPI cases are not RTC friendly. Look at PI time. Adding an RTC is doable with planning.

If GPSD is working, INDI Device Manager should accept GPSD when selected to do so. If not selected or not working, INDI takes the System.

This leaves us with the multiple places of location. KSTARS and PI have a GEOGRAPHICAL LOCATION. In PI and KSTARS, the default location is Warsaw, Poland. Change both locations to your geographical area. Then look at Polaris angle.

Synchronization of location is a manual effort. KSTARS is dependent on the OS for many time and location stores. INDI logs will show the clock difference between its time and the system.

It is an aesthetics issue. I like harmony. So, I normalized my AstroBerry. It should make smaller log sizes.
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3 years 9 months ago #56161

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Thanks.
"GPSPANEL" and "INDI-KSTARS-EKOS" both give my current location, retrieved from my GPS module, so I think that my GPS module & GPSD are working properly.

But I still don't understand why the "Polaris Hour Angle" is different between Ekos panel and INDI panel? There is more than 20minutes difference.

However, the HA value given by the left GPSPANEL seems closer to the correct one (the one I get with SynscanInit).
3 years 9 months ago #56166

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Replied by Andrew on topic Polaris Hour Angle & GPSD

I have seen this before. Often different polar finder apps calculate a different PHA. Without understanding what they are doing under the hood I can only guess as to why. But I've always suspected some do not factor in the Time Zone Meridian offset correctly.

Edit: Here are the results from various tools.
GPSD 2:03
KStars 1:37
SynscanInit 1:46
Stellarium: 1:37
Cartes Du Ciel 1:38
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Last edit: 3 years 9 months ago by Andrew.
3 years 9 months ago #56167

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Hello,

The big take away from this is that each solution says to believe their story on where they think we are. In the meantime, our scope and its location are tied to a system. Each system must sync the mount to its internal clock. Therefore the polar pole has a million differences depending on where each system calculates its PHA.

The true test comes when the first GOTO and SYNC command goes to M81 and you see nothing by space. What is interesting is that KSTARS, Stellirium, and Cartes Du Ciel have very similar solutions. 1 sec difference is insignificant. No mention was given of syncronized clocks in these findings. The other are significantly different. Who does everyone believe?

I just recently added RTC to my RPI4B and RPI3B+. GPSD was nice but Raspbian and NTP don't mix. As proof, my RPI4B clock time was 1 hour behind the GPSD time in EKOS. I was puzzled. Then I remember the Raspbian and PI caviat about no RTC. Ok, the geographical location profile needs to be changed. Yes, I am not in Warsaw Poland.
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Last edit: 3 years 9 months ago by John Robison. Reason: syntax
3 years 9 months ago #56172

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Replied by Andrew on topic Polaris Hour Angle & GPSD


I had each application open at once with common location and time settings. Then quickly noted their figures to within the minute.
Last edit: 3 years 9 months ago by Andrew.
3 years 9 months ago #56180

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Hello,

Fantastic. Then the difference between is pretty significant. GPDSD +29 secs and SynscanInit +9 seconds is pretty big swag calculations.
3 years 9 months ago #56182

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Replied by Andrew on topic Polaris Hour Angle & GPSD

It's worse than you think. The smallest significant figure I provided was Minutes, not Seconds.
GPSD 2:03:ss
KStars 1:37:ss
SynscanInit 1:46:ss
Stellarium: 1:37:ss
Cartes Du Ciel 1:38:ss

Also I live at Longitude 75°W, just a few kilometers from the Eastern Time Zone Meridian. So Time Zone offset is not a factor at play here.
3 years 9 months ago #56186

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Hello,

Thank you for the correction. Minute deviations are pretty dramatic. Even in minutes, KSTARS, Stellarim, and Cartes Du Ceil are more aligned than GPSD and Synscaninit. NTPD GPSD is supposed to not be working with Raspbian INDI. No hooks are in the process. This would explain its drift faster. Then again, NTPD requires configuration. That would make it a guess.

It should not matter the location of Polaris in one sense. We are looking at establishing the Celestial Pole. After that, time becomes critical. If not, deep space is all the view we will get. If we wait 8 minutes, the object will be in the view eventually.
3 years 8 months ago #56226

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Note that GPSD calculates Polaris Hour Angle for the time of last fix (the clock does not tick after), whereas sliding GPS Panel provides ticking clock synchronized with GPS (or system if you use Virtual GPS).
As the result Polaris Hour Angle displayed in sliding GPS Panel is current (and constantly changing), which is not the case for GPSD.
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3 years 7 months ago #57762

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Replied by Joaquin on topic Polaris Hour Angle & GPSD

“RPI cases are not RTC friendly”
Which problems they have ?
Stellarmate gadget comes with a RTC...
3 years 7 months ago #57802

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Hello,

Cases with heatsinks and fans around the big chip IC. Usually the RTC wants Pins 1,3,5, and 7 for the 3V device needs. This is where the conflict happens.
3 years 7 months ago #57810

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