Strange Longitude/Latitude for Mount

johnpd

Several times ASIAir shows strange longitude/latitude numbers for my mount. "Mount Info" shows for Longitude "E 488dg 04m 59s" while for latitude shows "S 00dg 00s 00m". The "Phone Info" numbers (I am using an iPad) show the correct coordinates. When this happens, the AISAir goto's do not function properly. Any possible cause for this? My mount is a Rainbow Astro RST-135. I have it set initially in Alt-Az mode pointing South (180 dg AZ) and level (0 dg ALT) which is its standard ALT/AZ parking position.

JohnD

w7ay

johnpd "Mount Info" shows for Longitude "E 488dg 04m 59s" while for latitude shows "S 00dg 00s 00m". ... I have it set initially in Alt-Az mode pointing South (180 dg AZ) and level (0 dg ALT) which is its standard ALT/AZ parking position.

When that happened, did you try to force the Latitude and Longitude data to be uploaded to the mount from the tablet by tapping Sync To Mount in the Telescope Setup window of the ASIAIR?

The Latitude and Longitude settings in the Mount have nothing to do with the parking position.

Next time you see a wrong latitude, check the Hubo-i local Latitude and Longitude in the hand controller. It is possible that GPS has not yet acquired, or you did not go into the GPS menu of the hand controller to long press ENT button to register the GPS location to your mount's internal memory. When you use location from the Hubo-i's GPS, you should see an "A" on the hand controller's window (see documentation). (The GPS unit is not in the RST-135 mount; both WiFi and GPS radios are in the Hubo-i.)

That being said, I never myself use the RST-135's hand controller. I leave the hand controllers out of both of my two RST-135 mounts, and let the GPS in my cellular enabled iPads be the ones to set mount data. This way, there is zero conflict. Except for calibrating mount offsets and 5 star alignments for the mount to model itself (which you don't need with plate solving), the ASIAIR can do all the controls of the RST-135 without using the hand controller.

Except for indoor lab experiments (with my AZ-GTi, for example), I do not use Alt-Az mode. Both of my RST-135 mounts are set to Equatorial since I have not done any visual work in twenty years now -- I have been exclusively doing instrumentation, where Equatorial is essential.

One of my RST-135 is left outdoors semi-permanently (no grease in an RST-135 to gunk up) on a Mortar tri-pier (reduces the work to polar align nightly), and the second mount is on top of a Gitzo carbon fiber tripod, and primarily used as a standby for the first mount.

When set to Equatorial mode, the RST-135 has worked flawlessly with ASIAIR since ASIAIR v1.4.

ASIAIR v1.3 was a disaster until RainbowAstro loaned an RST-150h to ZWO (and I believe ZWO still has the 150h in their office). But, be sure to use a cable with a high quality USB Type B connector; I also use copious amounts of Gaffer tape to solidly hold the connector to the body of the RST-135 itself and also to strain relive the cable. If you find flakey mount readings, or the mount disconnects when slewing (especially during a Meridian flip or Homing), that connector is the first place to check.

By the way, displaying angles above 360º is a common bug with the ASIAIR. the 488º East is simply 128º W. They simply did not account for the modulo 360 in many places. You will get used to it. It has been mentioned uncountable times on this forum and ZWO has ignored it, so I don't expect they will ever fix it.

Chen

johnpd

Hi Chen,

Thanks for your reply. I have tried the "Sync to mount" which under my understanding should sync the coordinates of my iPad (which are correct) to the mount. When I execute that option, it says that the sync completed successfully. However nothing changes. I still have the weird coordinates displayed in the ASIAir for the mount. There are times when my mount cannot get a GPS signal. I don't know why. It does populate the proper time though. I don't know if there is some kind of temporary gap in the GPS satellites at that point or what, but I know it is useless to continue when this happens. After a while the mount does pick up a satellite and the GPS coordinates are properly populated in it. I then set the coordinates by pressing and holding {ENT} key until the "A" appears on the GPS screen. However even then the ASIAir may not reflect the GPS numbers from the mount. And the secondary screen on the RST-135 that should reflect the current GPS location (at the main screen, press and hold the {ENT} button and bring up the "Location" then "GPS Base" option) still shows the weird coordinates which makes no sense. How can the two screens be different? I am at a loss at to what is going on.

JohnD

w7ay

johnpd There are times when my mount cannot get a GPS signal. I don't know why.

The GPS in the Hubo-i is poor, to say the least.

In general, you really need more than 3 satellites to get a good fix. If you remove the hand controller, and use a cellular equipped iPad, you will have assisted GPS to pinpoint your coordinate.

A single satellite will get you time information, but you need a swam of them for good PPOP of your location. That is where assisted GPS comes in, since the cell tower data will correct for the small errors (the tower knows where it is from historical data, so it computes a small correction term based on what the GPS data -- this correction term is then sent to a cell equipped device).

The cheaper tablet models do not come with cell chips, and an iPhone may be better than an iPad for setting up the mount. However, if you have set up Location Services properly and have access to WiFi, I believe assisted GPS also functions in iPadOS.

Just leave the handcontroller disconnected when you are doing instrumentation work.

And by the way, it is known, although not widely known -- the best position (and often, only position) of the Hubo-i GPS antenna is with the hand controoler's keyboard facing down towards ground (i.e., back of the unit faces the sky), and preferably with no metal surfaces nearby.

Remember too that while you are in the Telescope Setup window, the ASIAIR does not consistently update the numbers in it. You need to switch the Telescope Setup window to another window and then back to the Telescope Setup for ASIAIR to properly update everything (very poor UX execution).

Ditch the alt-az mode, ditch the handcontroller, and an RST-135 will pair perfectly with the ASIAIR for instrumented astronomy.

Add an iPad Pro with cell chips, and you are off to the races. I use a larger 12.9" iPad in the house and take an old 9.7 inch iPad Pro outdoors when I need to do polar alignment.

Chen

johnpd

Thanks Chen,

I have an iPad Mini with cell connection. I have set up Location Services enabled for the ASIAir "while using" and enabled cellular data for it. I am considering getting a full iPad or iPad Pro. The Mini is very easy to handle but a bigger screen would be nice. I was wondering were the GPS module was in the RST-135. I will play with the hand controller more to see if I can get better results.

I am also considering switching to EQU mode. I was worried about cables getting messed up with that but the only external cable I now have is the power cable from the battery to the ASIAir so that is probably no longer an issue. EQU mode will allow longer exposures. I will need to get a guide scope and camera as well.

I have ordered the TP-Link travel router as I am being eaten alive by mosquitoes now. It would be great to do everything from inside (except for alignment) to escape those hungry little buggers.

Once you do polar alignment do you need to do any further alignments? The RST-135 normally requires alignment to a certain number of stars (they say 5) to get its internal model straight. Can this be eliminated and you can just use plate solving to go to objects? I tried doing plate solve after just doing a {Home} in Alt-Az mode and that did not work very well. Right now aligning with multiple stars is rather time consuming.

JohnD

w7ay

johnpd Once you do polar alignment do you need to do any further alignments?

Only if you want the mount to model itself, in which case, you need to perform a star alignment with at least 5 stars (see manual). After star alignment, the accuracy of blind goto would be more accurate -- but that is for people who don't have plate solve ability (for example, visual types). If you have plate solving, there is not need for the mount to model itself. It can't model away field rotation either, so in either case, you will need to do polar alignment.

Anyhow, this is the wrong forum to discuss the pro and cons of the RST-135.

Can this be eliminated and you can just use plate solving to go to objects?

Plate solving gets you to an object but does not solve field rotation. You need good polar alignment for that. Or buy a Praxis or ARCO.

Chen

johnpd

Well I tried one more time. It took 3 shots to get the RST-135 GPS and the ASIAir to agree on coordinates. It was running fine but then after a while, the ASIAir reported the latitude as "S zeros", but the longitude was correct. Soon thereafter the longitude change to the wild "E 489....". Don't know what is going on. I guess my next step is to jump into EQU. By the way the TP-Link 750 worked great. You did not have to do any configuring. Just set the switch to Extender mode, use an Ethernet cable to connect it to the ASIAir, set the Air to "Wired Ethernet", and TP-Link picked up whatever WiFi setting the Air was using (2.4G or 5G). Also the Air does a halfway decent job of stacking in Alt-AZ and adjusting for field rotation.

JohnD

mjb87

So did this ever get sorted out? I have a new ASIAIR Plus and I am having the exact same issue trying to use it with my RST-135. Longitude is reported as 492 degrees. The GOTOs are in the opposite meridian of the target. I almost had a mount crash. "Sync to Mount" (which is ambiguous -- it should say "Sync Mount to Phone") does absolutely nothing. The mount works OK when the hand controller is used and ASIAIR is not in the loop. As soon as I put ASIAIR in the loop it goes crazy. At that point, even if I turn off the ASIAIR and go back to the hand controller, it still doesn't work. The ASIAIR seems to be sending bad location information to the mount. BTW, I tried two different ASIAIR Plus units and several different iPhones and iPad. Same result. Location services are operating and ASIAIR has access to the location information.

johnpd

What communication protocol did you set on the RST-135? You need to use the Rainbow protocol, not the LX-200 one otherwise you get strange results.

JohnD