Mach1 Park 3 curiosity


Nick Iversen
 

This isn't a problem but I'm curious about what is going on here. I do a polar alignment (1 arc min accuracy according to PHD2) then unpark from Park 3 as shown in the photo at left. I do a night's observing using plate solving and mount synching in Sequence Generator Pro. Then at the end of the session I park to position 3 and the mount goes to the position in the second photo. It doesn't line up. The angular distance is quite large.

What does this mean? Why doesn't it go back to where it started? The real question is - for the next night should I start from this position? Is this my true Park 3?



Roland Christen
 


What does this mean?
Whenever you do mount sync you shift both axes from the star point and establish a new start point according to the time that is entered into your mount at initialization. For every second of time error the mount will change the RA angle by 15 arc seconds. For every hour of error you get 15 degrees of offset. From your images it looks like your controlling software (keypad or whatever you use for initialization) has a time error of a few minutes for your location. Remember, local time in a time zone is not very accurate. Next time you do this sequence, change the time in the mount by +- 5 minutes and then park. Watch what happens to the RA position.

Bottom line, don't worry about the exact park position when parking the mount. When re-initializing, simply use Autostart YES in the keypad, and it will go to the correct place in the sky. Don't "Resume from Park3". If you are not using the keypad, then "Resume from Present position" in your software.

Rolando


-----Original Message-----
From: Nick Iversen <inoddy@...>
To: main@ap-gto.groups.io
Sent: Thu, Feb 4, 2021 4:13 pm
Subject: [ap-gto] Mach1 Park 3 curiosity

This isn't a problem but I'm curious about what is going on here. I do a polar alignment (1 arc min accuracy according to PHD2) then unpark from Park 3 as shown in the photo at left. I do a night's observing using plate solving and mount synching in Sequence Generator Pro. Then at the end of the session I park to position 3 and the mount goes to the position in the second photo. It doesn't line up. The angular distance is quite large.

What does this mean? Why doesn't it go back to where it started? The real question is - for the next night should I start from this position? Is this my true Park 3?



--
Roland Christen
Astro-Physics


Roland Christen
 


Whenever you do mount sync you shift both axes from the star point
That should say start point.

Rolando


-----Original Message-----
From: Roland Christen via groups.io <chris1011@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Thu, Feb 4, 2021 4:52 pm
Subject: Re: [ap-gto] Mach1 Park 3 curiosity


What does this mean?
Whenever you do mount sync you shift both axes from the star point and establish a new start point according to the time that is entered into your mount at initialization. For every second of time error the mount will change the RA angle by 15 arc seconds. For every hour of error you get 15 degrees of offset. From your images it looks like your controlling software (keypad or whatever you use for initialization) has a time error of a few minutes for your location. Remember, local time in a time zone is not very accurate. Next time you do this sequence, change the time in the mount by +- 5 minutes and then park. Watch what happens to the RA position.

Bottom line, don't worry about the exact park position when parking the mount. When re-initializing, simply use Autostart YES in the keypad, and it will go to the correct place in the sky. Don't "Resume from Park3". If you are not using the keypad, then "Resume from Present position" in your software.

Rolando


-----Original Message-----
From: Nick Iversen <inoddy@...>
To: main@ap-gto.groups.io
Sent: Thu, Feb 4, 2021 4:13 pm
Subject: [ap-gto] Mach1 Park 3 curiosity

This isn't a problem but I'm curious about what is going on here. I do a polar alignment (1 arc min accuracy according to PHD2) then unpark from Park 3 as shown in the photo at left. I do a night's observing using plate solving and mount synching in Sequence Generator Pro. Then at the end of the session I park to position 3 and the mount goes to the position in the second photo. It doesn't line up. The angular distance is quite large.

What does this mean? Why doesn't it go back to where it started? The real question is - for the next night should I start from this position? Is this my true Park 3?



--
Roland Christen
Astro-Physics

--
Roland Christen
Astro-Physics


Nick Iversen
 

Thanks. That's what I wanted to know regarding the next unpark.

I start from a iPad app. The time is accurate to under a second. What does "local time in a time zone is not very accurate" mean?


Nick Iversen
 

OK I may have figured it out. I start from the iPad which sends an accurate time and location to the mount. Then I start APCC from the laptop which isn't connected to the internet and so has an inaccurate time. Presumably it updates the mount with the wrong time.

It would be useful to have a "Get time from mount" option in APCC.


Roland Christen
 

If time is accurate, then it might be that your last recal or sync was so low on the horizon that the plate solved position is off by many minutes of arc from the ideal point in the sky due simply to atmospheric refraction. In that case you have repositioned the mount to a bogus reference point and the next slew to any object (or park) will be off by that distance. In any GoTo mount all subsequent slews are always referenced to the previous synced position. And that can lead to errors depending on where that last sync was done.

Rolando

-----Original Message-----
From: Nick Iversen <inoddy@...>
To: main@ap-gto.groups.io
Sent: Thu, Feb 4, 2021 7:26 pm
Subject: Re: [ap-gto] Mach1 Park 3 curiosity

Thanks. That's what I wanted to know regarding the next unpark.

I start from a iPad app. The time is accurate to under a second. What does "local time in a time zone is not very accurate" mean?


--
Roland Christen
Astro-Physics


Jeff B
 

Curious.  A time zone spans a distance in longitude.  If I place identical cell phones, Ipads, GPS modules or what ever, at both sides of the time zone, will they read the same time or will they roll over to say, the next minute, at the same or different times?  Does universal time take care of that?

Ignorant Jeff

On Thu, Feb 4, 2021 at 8:50 PM Roland Christen via groups.io <chris1011=aol.com@groups.io> wrote:
If time is accurate, then it might be that your last recal or sync was so low on the horizon that the plate solved position is off by many minutes of arc from the ideal point in the sky due simply to atmospheric refraction. In that case you have repositioned the mount to a bogus reference point and the next slew to any object (or park) will be off by that distance. In any GoTo mount all subsequent slews are always referenced to the previous synced position. And that can lead to errors depending on where that last sync was done.

Rolando

-----Original Message-----
From: Nick Iversen <inoddy@...>
To: main@ap-gto.groups.io
Sent: Thu, Feb 4, 2021 7:26 pm
Subject: Re: [ap-gto] Mach1 Park 3 curiosity

Thanks. That's what I wanted to know regarding the next unpark.

I start from a iPad app. The time is accurate to under a second. What does "local time in a time zone is not very accurate" mean?


--
Roland Christen
Astro-Physics


Roland Christen
 

Universal time is calculated in the mount by using the local time and the longitude that you enter. If your longitude is off, then the calculated universal time will also be off. The mount runs internally on universal time.

Rolando



-----Original Message-----
From: Jeff B <mnebula946@...>
To: main@ap-gto.groups.io
Sent: Fri, Feb 5, 2021 9:11 am
Subject: Re: [ap-gto] Mach1 Park 3 curiosity

Curious.  A time zone spans a distance in longitude.  If I place identical cell phones, Ipads, GPS modules or what ever, at both sides of the time zone, will they read the same time or will they roll over to say, the next minute, at the same or different times?  Does universal time take care of that?

Ignorant Jeff

On Thu, Feb 4, 2021 at 8:50 PM Roland Christen via groups.io <chris1011=aol.com@groups.io> wrote:
If time is accurate, then it might be that your last recal or sync was so low on the horizon that the plate solved position is off by many minutes of arc from the ideal point in the sky due simply to atmospheric refraction. In that case you have repositioned the mount to a bogus reference point and the next slew to any object (or park) will be off by that distance. In any GoTo mount all subsequent slews are always referenced to the previous synced position. And that can lead to errors depending on where that last sync was done.

Rolando

-----Original Message-----
From: Nick Iversen <inoddy@...>
To: main@ap-gto.groups.io
Sent: Thu, Feb 4, 2021 7:26 pm
Subject: Re: [ap-gto] Mach1 Park 3 curiosity

Thanks. That's what I wanted to know regarding the next unpark.

I start from a iPad app. The time is accurate to under a second. What does "local time in a time zone is not very accurate" mean?


--
Roland Christen
Astro-Physics

--
Roland Christen
Astro-Physics


Jeff B
 

Thanks! 👍🔭


On Fri, Feb 5, 2021 at 11:18 AM Roland Christen via groups.io <chris1011=aol.com@groups.io> wrote:
Universal time is calculated in the mount by using the local time and the longitude that you enter. If your longitude is off, then the calculated universal time will also be off. The mount runs internally on universal time.

Rolando



-----Original Message-----
From: Jeff B <mnebula946@...>
To: main@ap-gto.groups.io
Sent: Fri, Feb 5, 2021 9:11 am
Subject: Re: [ap-gto] Mach1 Park 3 curiosity

Curious.  A time zone spans a distance in longitude.  If I place identical cell phones, Ipads, GPS modules or what ever, at both sides of the time zone, will they read the same time or will they roll over to say, the next minute, at the same or different times?  Does universal time take care of that?

Ignorant Jeff

On Thu, Feb 4, 2021 at 8:50 PM Roland Christen via groups.io <chris1011=aol.com@groups.io> wrote:
If time is accurate, then it might be that your last recal or sync was so low on the horizon that the plate solved position is off by many minutes of arc from the ideal point in the sky due simply to atmospheric refraction. In that case you have repositioned the mount to a bogus reference point and the next slew to any object (or park) will be off by that distance. In any GoTo mount all subsequent slews are always referenced to the previous synced position. And that can lead to errors depending on where that last sync was done.

Rolando

-----Original Message-----
From: Nick Iversen <inoddy@...>
To: main@ap-gto.groups.io
Sent: Thu, Feb 4, 2021 7:26 pm
Subject: Re: [ap-gto] Mach1 Park 3 curiosity

Thanks. That's what I wanted to know regarding the next unpark.

I start from a iPad app. The time is accurate to under a second. What does "local time in a time zone is not very accurate" mean?


--
Roland Christen
Astro-Physics

--
Roland Christen
Astro-Physics