Assistance with ASIAIR and DST

MattyV

Good Morning,

Last night is the first opportunity I had to get out and shoot since we here in Colorado turned our clocks back. I use a Amazon Fire HD10 to control the ASIAIR. Last night I was able to set the mount up (HEQ5-PRO) and started polar aligning. The first issue and I'm not sure if this is a bug with the new firmware:

I would place the camera on auto refresh with a 10 second exposure (narrowband filter). It would take the picture and show where my RA axis was in relation to NCP. I would make adjustments to the mount but the RA axis wouldn't reflect that on the next two pictures. I even intentionally made drastic movements on the mount to get it to show. For some reason it will only show changes I make after the third exposure where as before it should changes after every exposure. I can replicate this issue even with auto refresh off.
The next issue is once it was polar aligned it struggled locating actual targets. I choose the M45 which was high in the eastern sky at the time and the mount pointed the camera below the horizon and toward the ground. I saw the DST post and was wondering how to manually set the time on a tablet without it trying to correct automatically? Also does that sound like the issue? I connected my hand controller to the mount only one time ever and that was after the Rowan Mod to make sure it slewed so not sure if that threw the mount off either?

If you're still here thank you for your time.

-Matt

w7ay

MattyV

Matt,

If you do not have an absolute encoder, your mount could have switched pier side after the polar alignment's 60 degree slew, and got confused whether to reverse the directions of the motors. Recall that slews don't change pier side -- only GOTOs do.

I recommend that right after finishing polar alignment, to use the Home button in Mount Settings to first home the mount, and only perform GOTO after that recalibration of home position.

If the Home button itself has a problem, disconnect your mount from ASIAIR's mount settings, move the mount manually to home position, then reboot the mount and do the needed star alignments (mount with encoders normally don't need that last step), and then reconnect the mount in ASIAIR's mount settings. If you are careful not to jog the tripod/mount, your polar alignment should stay good after the manual homing -- just be gentle.

If you are in North America, Daylight Saving Time is over. So, you needed to tell the mount, using the hand controller, that you are out of DST -- this ensures that Meridian Flips occur when a star crosses the Meridian. With ASIAIR, you need to tell the most mounts with GPS that you are not using DST even in Summer.

Chen

MattyV

w7ay

Hi Chen,

Thank you for responding. I've never had an issue with the mount before in the summer. So it's probably a DST issue like you mentioned. I don't have the GPS add on for my mount so I think the issue might be with the ASIAIR and the time it's getting from the tablet?

w7ay

MattyV I don't have the GPS add on for my mount so I think the issue might be with the ASIAIR and the time it's getting from the tablet?

I am lucky that my mount's GPS is on the hand controller and I never connect the hand controller except to set up defaults once in a year or two (usually to recalibrate the relative encoder's index). So I have been able to just let ASIAIR sync the mount's time and longitude over from the tablet.

Some mounts with GPS refuse to let ASIAIR change override is own GPS time and location, and that is where you need to make sure DST is off, and all times are based on Winter ("Standard") time offset from UTC. The best is to check the Local Sidereal Time of your mount (hand controller should read it out) -- if LST is correct, your mount and the ASIAIR should be in agreement. There are a number of Apple App Store apps that will give LST. If you have to set the time on the mount manually, try to set your mount to within 15 seconds of LST, since that determines the auto meridian flip time, if you want to use that function in ASIAIR.

If you have a tablet that does not have GPS, and your tablet is connected to the ASIAIR's hotspot, it would not be able to get the correct location and time; double check to make sure time and location in the ASIAIR Mount Settings are correct. If not, correct the number(s) at the first window when you initially launch the ASIAIR app.

Chen

MattyV

w7ay

Hi Chen,

Thank you for you response. I downloaded an app and now I can see my local time and my sidereal time. So I need to make sure my mount matches my sidereal time right?

My tablet does have GPS on it but the time adjusts automatically with DST. So do I need to adjust the time on the tablet?

Thanks

w7ay

MattyV So I need to make sure my mount matches my sidereal time right?

Correct, Matt. As long as LST agrees, or both UTC and Longitude agree, you should be good to go.

Another way to do a quick sanity check is first use a carpenter's level to level your mount/tripod in the east-west and north-south directions. Then look up a planetarium program (like Sky Safari) and use the mount's hand controller to move to an RA that is within a degree or so of the Meridian, and with a declination that is equal to your local Latitude. The same carpenter's level should show that the optical tube is pointed almost perfectly vertically at Zenith. If there is an east-west tilt, you have a time or longitude error, otherwise, you are again good to go.

Basically, the RA of a star is a fixed number, but the earth rotates and revolves around the Sun. 24 hours of sidereal duration (about 23 hrs 56 mins of wall clock time) is the time it takes for the star move to the same point that your mount is pointed at the next day. LST determines when the star crosses the Meridian -- a star transits across the Meridian when the LST precisely equal to the star's RA. So, that is the way the mount knows how far a star is east or west of the Meridian. If the LST of the mount is wrong, then the mount would move to the wrong place.

My tablet does have GPS on it but the time adjusts automatically with DST.

GPS chips output UTC. It then converts to Local Time using the UTC offset, and that offset is different by 1 hour between Summer (DST on) and Winter (DST off). If ZWO would just stop using local time and reference only to UTC, we wouldn't have all this confusion. It is a self inflicted wound by the programmers at ZWO.

So do I need to adjust the time on the tablet?

You should not have to touch the Location or Time services of your tablet's OS. Just turning off DST in the Mount should be sufficient to make the mount agree with ASIAIR's time.

Chen