Re: AP 1600, Universal Time and Connecting to Auxiliary Astronomy Programs for Control

Dale Ghent

I have no idea what "Auto DST" in SkyTools means. Generally a planetarium app should make issues surrounding time transparent to the user and not have to present these time conversion options that can be confusing.

One thing that can be happening here is that the keypad is still initializing the mount and its time upon power-on. This will happen if the "Auto-Connect" setting in the keypad is set to the default of "Yes". If you want to not have the keypad initialize the mount upon power-on, then you must set Auto-Connect to "EXT", for External. This allows the mount to be initialized by the A-P ASCOM driver on the connected PC.

This is important because once the mount is initialized after a power-on, it cannot be reinitialized - ie you cannot turn on the mount with the keypad connected and its Auto-Connect set to Yes, and then connect to the mount using the ASCOM driver and have it reinitialize. That is not possible.

This stuff is covered on pages 16 and 17 of the Keypad manual:

On Mar 16, 2021, at 20:44, Jack Huerkamp <> wrote:

Dale and the Others Who Responded,

I tried leaving the AP keypad set to UT and setting the PC to my local time (CDT) and added a second UT Clock. I got a similar view to what you sent to me. I tried setting my location in SkyTools to Central Time with Auto DST enabled in SkyTools. I tried to slew to the Sun at about 5PM CDT and from the Park 3 position, the mount started moving to the eastern side of the meridian. The Sun was setting in the WSW. I stopped the slew, parked the mount in the Park 3 position and shut down SkyTools and APCC.

I powered the mount down, waited 30 seconds and powered it back up. I set the keypad to Central Time and Summer. I set the computer time to Central Time, eliminated the second time zone (UT) and started SkyTools. I set my location to Central and enabled auto DST rules. I connected the mount to Sky Tools, did a slew to the Sun, it did so with the Sun centered.

I give up on trying to use UT in the keypad and will have to bite the bullet and change the keypad twice a year to conform to either winter or summer. Using this technique for 6 years has worked. I just wanted to eliminate the semi-annual change the keypad time routine. But I am finding the doing so is easier and less stressful than trying to use UT.

Yours truly,


Jack Huerkamp
Jack's Astro Accessories, LLC
38388 Pine Street
Pearl River, LA 70452-5192
30.37N 89.76W

All of us get lost in the darkness.
Dreamers learn to steer by the stars.
………………………………….Neil Peart

From: <> On Behalf Of Dale Ghent
Sent: Tuesday, March 16, 2021 11:24 AM
Subject: Re: [ap-gto] AP 1600, Universal Time and Connecting to Auxiliary Astronomy Programs for Control

As the document implies, confusion can be lessened by just running all the things in UTC, especially if the person is unaccustomed to operating in multiple time zones. By having your PC and keypad display in UTC, you won't have to change the GMT offset on the keypad twice each year and the time on the keypad will always match the time displayed on your PC. In that sense, such consistency might be attractive to some people.

But it isn't an absolute must for proper operation of the mount. You can still run your PC and keypad in any combination of UTC and local time, you just need to be aware of what the keypad is set to regardless, and if it is set to something other than GMT/UTC, then you will need to manually adjust the timezone offset twice a year if you are in a locale that observes some form of DST.

In Windows (and, at least Windows 10, I'm not sure about previous versions) you can configure the clock in the system tray to display the time in multiple timezones. For example, my imaging PC's clock's main display is my local time zone (US/Eastern), but I added UTC as well if you mouse over it. You add time zones to display under the system time settings in Windows.


On Mar 16, 2021, at 11:29, Jack Huerkamp <> wrote:


I got this link from George at Astro-Physics in which it says for a
dedicated observatory PC, to set its clock to UT along with the hand
controller being set to UT:

But it sounds like you are saying to set the observatory PC to local time
and the hand controller to UT, since SkyTools in my case is looking to the
computer time to locate targets.

If so, I will go to the observatory today and set the computer back to local
time, set SkyTools as well and see what happens.

Yours truly,


Jack Huerkamp
Jack's Astro Accessories, LLC
38388 Pine Street
Pearl River, LA 70452-5192
30.37N 89.76W

All of us get lost in the darkness.
Dreamers learn to steer by the stars.
..............Neil Peart

-----Original Message-----
From: <> On Behalf Of Dale Ghent
Sent: Tuesday, March 16, 2021 8:58 AM
Subject: Re: [ap-gto] AP 1600, Universal Time and Connecting to Auxiliary
Astronomy Programs for Control

So here's the deal: the mount CP deals only in UTC. All calculations
involving positions of objects in the sky are done UTC. For the purposes of
a mount's internal operations, UTC is the only thing that matters.

When you set the timezone on the keypad, you are essentially just
configuring the keypad's display and input of UTC time as local time. The
mount itself doesn't care that your offset from GMT is now -5 instead of -6.
That factors into none of its operations and calculations. What it does
factor into is how your keypad displays time, and how it converts time that
you input to and from UTC. The former - displaying the same time as your
local time - is just for convenience. The latter - inputting your local time
- is critical for the mount to derive the proper UTC time if you were to
program the mount's clock using the keypad. So if your local time is
18:45:00 and you were to program your mount's clock using the keypad today,
it would definitely need to know your current offset from GMT so that the
proper conversion to UTC can take place (that it would be 23:45:00 UTC).

The reason why you have to manually set the GMT offset in your keypad every
time DST begins or ends (or if you move to a different timezone altogether)
is because the keypad lacks its own timezone database that it can use to do
this automatically. You might ask "well how hard would it be for the keypad
to have one so that I don't need to do this". It's a valid question, but the
reasons are fairly basic. The timezone database is large and would occupy a
non-trivial amount of the keypad's very finite amount of static memory. It
also changes quite often as various countries and locales change their DST
observances or, in rare cases, which timezone(s) they are in. This would
demand that A-P issue several firmware updates a year in order to keep up
with these changes.

As for the computer and accessing the mount through the ASCOM driver, this
changes the situation in terms of mount time management. In this case, it is
presumed that your computer's clock is reasonably accurate as any modern OS
will automatically sync the computer's clock to an internet time source at
least once a week or more often, assuming it has internet access. There is a
setting in the A-P ASCOM driver to sync the computer's clock to the mount.
This should always be on if your computer's clock is reasonably accurate.
The ASCOM driver itself will then program the mount in UTC time directly in
this case. Despite your computer's timezone being set to US/Central, the OS
itself still operates in UTC internally. Because your OS does have a
maintained timezone database, it can do the display and input conversions
between your timezone and its internal clock, which runs in UTC.

So, the only reason why you would want to run your computer in UTC is if you
prefer viewing time that way. Even if you set the display of time on your PC
to be in your local timezone, the mount is still going to get programmed
with the proper time in UTC. It makes no difference to the mount.

As for the keypad, you can also just leave it with a timezone offset of 0 so
that it displays and takes input in UTC. However if you want it do display
and take time input in terms of your local time, you will need to manually
set the proper GMT offset whenever DST starts and ends.

On Mar 16, 2021, at 09:13, Jack Huerkamp <> wrote:

I use SkyTools 3 and SkyTools 4 to control my AP1600 mount using the ASCOM
driver. But every 6 months, I was having to switch the AP keypad from
standard time to daylight savings time and then back again 6 months later.
It was suggested to me to set the AP keypad to UT and also setting the
computer to UT to avoid have to mess with keypad settings every 6 months. I
did so and can control the mount using the keypad.

I then tried configuring my observatory location, but when I connected the
mount to SkyTools and did a slew to the Sun this afternoon, the scope tried
to aim into the ground on the southwest side of the pier. I need to know
how to set my location in SkyTools now that the mount and computer are set
to UT. I am in the Central US time zone.

I would appreciate feedback on this as I would hate to have to go back to
setting the computer and AP keypad to the current local time.

Yours truly,

Jack Huerkamp

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