Takahashi EM -11 mount and ASIAir

SteveZ

My mount is a Takahashi EM-11 with a Temma-2z controller. I connect it to the ASIAir Pro through an ST-4 cable. I think that is my only option, but I don’t know for sure. I use 0 minute for "Stop tracking x min before Meridian” and 1 minute for “Do AMF x min after Meridian.” The ASIAir and the mount behave oddly during an AMF. While the mount is slewing during the flip, the ASIAir will start to take images and attempt to solve them. Of course, this won’t work while the mount is moving. The ASIAir ultimately times out, tries again with another image to solve, times out again, etc. Eventually when the mount has completed the flip, the ASIAir will finally solve, auto-center, and wait for the guider to settle. Typically, the first frame after the AMF is bad due to streaked stars. Subsequent frames are fine. It takes about 13 minutes for the mount to flip, then after the bad first exposure, its about 18 minutes of downtime at the peak of imaging. I’m not sure there is much I can do to improve this, but I wanted to share. You don’t hear much about Tak mounts and the ASIAir. Also open to any ideas. Thanks for any suggestions you can share!

SteveZ

SteveZ sorry, I should have said that the controller on the mount is connected to the ASIAir with a serial cable. The ST-4 cable connects the autoguide camera to the controller on the mount.

w7ay

SteveZ My mount is a Takahashi EM-11 with a Temma-2z controller. I connect it to the ASIAir Pro through an ST-4 cable.

No, when I used my EM-11 with ASIAIR, I could do pulse guiding with it. No need for ST-4 guiding. Just select the EM-11 in Mount Setup -- don't choose On-Camera ST-4 as your mount.

If you prefer to use ST-4 Guiding, the other functions on the mount will not work.

ASIAir will start to take images and attempt to solve them

Before v1.8, ASIAIR will not auto center accurately enough, so I have not used auto-Meridian flip. Just manually stop the mount before the target reaches zero hour angle, wait until the target has definitely moved across the meridian, and send a GOTO to the same target from ASIAIR to the mount. The EM-11 will then execute the Meridian flip for you. You can then repeatedly plate solve and do a sync-and-goto to recenter the object after it finished flipping.

Make sure your mount is completely level, especially in the East-West direction, to get a good Transit (time a target crosses the Meridian) timing. Remember that every degree you are not level in the east-west direction is 4 minutes of extra time that your mount will not execute a meridian flip. You can use the "align to zenith" method described in the EM-11 mount manual to get a good accurate level. Only Takahashi gives that reliable old method of aligning the mount; all the other mounts make you do star alignment, forgetting that one of the best pointing method relies on the earth's gravity -- but you need an accurate bubble level, or a digital inclinometer that can read better than 0.1 degrees (lot of cheap ones at Amazon -- they are much easier to read in the dark than bubble levels).

Subsequent frames are fine. It takes about 13 minutes for the mount to flip.

Yeah, that is an indication that your mount is about 13/4 degrees (about 3 degrees) off level in the east-west direction.

Remember that ASIAIR does not actually perform any flipping. Once it reaches the time to flip, the ASIAIR keeps blindly sending a GOTO to the mount (once every minute or so). The mount then executes a Meridian flip once its hour angle is past 0 degrees. If the target has not yet gone past meridian, that GOTO command will simply cause the mount to do a non-flip GOTO (i.e., very small movement). ASIAIR will discover (through a plate solve) that a flip has not occurred, and try another GOTO a minute later.

That being said, it has been two years since I used my EM-11. But I don't thing anything as changed.

Chen

SteveZ

w7ay

Hi Chen,

First, thanks for the prompt reply and the useful information. I appreciate it very much!

w7ay No, when I used my EM-11 with ASIAIR, I could do pulse guiding with it. No need for ST-4 guiding. Just select the EM-11 in Mount Setup -- don't choose On-Camera ST-4 as your mount.

If you prefer to use ST-4 Guiding, the other functions on the mount will not work.

After reading your response I realize that I have made a big mistake. I’m very new at this and the ASIAir is the first controller I’ve used. I have no previous experience with NINA, PHD2, etc. so thanks for your patience with me. 🙂

Here is my mistake: I simultaneously connected the RJ cable from the guide camera to the Temma controller AND a serial cable from the Temma controller to the ASIAir using a serial-to-USB adapter. I don’t know the effect of trying to simultaneously perform both ST-4 and pulse guiding, but maybe that is causing the problem. For what it's worth, I use the “Takahashi Temma 2” option on the Mount Settings page and the total guide error is typically between 1" and 2".

w7ay Before v1.8, ASIAIR will not auto center accurately enough, so I have not used auto-Meridian flip.

I am using version 1.8(8.83) and it seems to accurately identify the meridian.

w7ay Make sure your mount is completely level, especially in the East-West direction

I check the level of my mount with each session and it seems level in both N-S and E-W. I also think the polar alignment is pretty good. Last night, I checked the PA with the reticle in the mount and with the PA function on the ASIAir (which said the alignment error was 0.00”). All that said, I use a bubble level, so I'll get a precision digital unit to improve on my leveling process. Thanks for the suggestion.

w7ay Remember that ASIAIR does not actually perform any flipping.

Understood. Thanks for that. I read this in previous responses you've made on the forum. It is nice to know that the GOTO command is sent about once every minute.

Thanks again!

Steve

w7ay

SteveZ For what it's worth, I use the “Takahashi Temma 2” option on the Mount Settings page and the total guide error is typically between 1" and 2".

Hi Steve,

I had been able to get 0.7" with the EM-11, with the very poor autoguiding in the old ASIAIR. With the current state of guiding in ASIAIR, I would be surprised if you can't do at least 0.5". With a little patience, perhaps.

I have the pretty old EM-11 that took both 12V and 24V supply, and even with a 24V supply, I still needed to balance the mount really well. Make sure you do that. (I got lazy in my old age, and bought myself a RainbowAstro mount with strain wave gears that don't need balancing, or even a counterweight).

If you are new to all this, be sure to check the web on the topic "third axis balance." If you look down your OTA from the eyepiece end, the left and right sides of the telescope needs to be perfectly balanced -- otherwise the mount balance will change as your telescope tracks a target through the night. A finder of guide scope that is not mounted in the vertical plane could cause this imbalance. And electronic focuser that stick out on one side of the OTA can cause this "third axis" imbalance. A Electronic filter wheel that is not perfectly symmetrically mounted can cause the imbalance, etc, etc.

Here is a YouTube video on what 3rd axis balance is all about:

https://www.youtube.com/watch?v=zmla32ksH_I

I simultaneously connected the RJ cable from the guide camera to the Temma controller AND a serial cable from the Temma controller to the ASIAir using a serial-to-USB adapter.

Yeah, lose that RJ-11 cable (strictly speaking an RJ-12, but most people call it RJ-11). I don't think any signal flows down the ST-4 port when you choose the Temma 2 mount. But at best, it is still extra cable to imbalance your system. At worst, ZWO actually sends pulses down that cable and it will really screw things up. The only time you really need ST-4 nowadays is if you use something like the Hinode solar guider in the daytime. Most software today will handle "pulse guiding" (i.e., guiding using the mount's command protocol), so you won't need ST-4.

I checked the PA with the reticle in the mount and with the PA function on the ASIAir (which said the alignment error was 0.00”)

First of all, you cannot trust the ASIAIR polar alignment to more than 15". Worse if you are aliging with declination angles away from 90º declination. And also worse if you are located at lower latitudes, where the polar region is closer to the horizon (atmospheric refraction).

Next, polar alignment only points the polar axis of the mount to the North (or South) celestial pole. It does not assure that the angle with respect to horizon is correct.

As an experiment, go out one night and look at Polaris (moderately close to the celestial pole for the current epoch). Pan your head sideways (azimuth) and up and down (altitude) until Polaris is "centered" in your view. You have now polar aligned your head :-). Now... tilt you head, while keeping Polaris centered in your view. Notice that you are still "polar aligned" (i.e., Polaris is in the center of your view). But, the top of your head is no longer pointed at Meridian! This is like a mount that is not leveled in the east-west direction.

I.e., polar alignment is not the same as having the zero hour angle of your mount pointed at the Meridian. They are different parameters.

The ST-4 cable connects the autoguide camera to the controller on the mount.

Understood. The ASIAIR sends commands to a camera that has an ST-4 interface.

Chen

SteveZ

w7ay I would be surprised if you can't do at least 0.5

That will be my goal!

w7ay (I got lazy in my old age, and bought myself a RainbowAstro mount with strain wave gears that don't need balancing, or even a counterweight)

That mount is a new technology for me. I'm looking at upgrading in the near future, so I need to consider this. I'm already old, so I have that going for me!

w7ay be sure to check the web on the topic "third axis balance."

I've already done this to some extent. I didn't know what to call it, but I have some lead ballast tied to the side of my OTA opposite the EAF. It can be fine tuned I'm sure, but the balance is pretty close. I decided to get the side-mounted counter weight shown in the videos to help fine tune it. Thanks for that tip!

w7ay Yeah, lose that RJ-11 cable

Done. Tonight will be clear so I'll get a chance to see how the guiding goes without the RJ-12 cable and with a more careful level and balancing of the mount. Wish me luck and thanks soooo much!!!

SteveZ

Hi Chen,

So here is my update from last night. The short story is that things went well thanks to your help. Here are some details.

First, I removed the extraneous RJ-12 cable. 😅

Then, I carefully re-balanced the OTA in RA, Dec, and the third axis. It was close before, but now is perfect. It's actually beautiful to see it remain stationary no matter where I place it and let go. 😀

Next, I fine turned the level of the mount with an optical bubble level. I did this in both N-S and E-W. I extended two of the tripod legs by about a mm to achieve a more perfect level. Then I polar aligned using the mount's reticle.

Once dark, I refocused the guide camera and recalibrated the guiding. I used exposures of 2 sec with a gain of 300 on an ASI290MM mini. Binning was 2x. I use an OAG on a 757 mm telescope. The guiding results were definitely improved. I had 0.5" or less for short periods of time. Looking at the logs in PHD2LogViewer this morning, I had a total RMS of about 1" over a 3 1/2 hour window. The seeing conditions were "average" last night according to Astrospherics. PHD2LogViewer said that, over a 2 hr window, the RA Drift was +6.85"/min, the Dec Drift was -0.44"/min, the Polar Alignment Error was 1.7". I don't have a sense for how good or bad those values are. I can provide the guiding parameters that I had on the ASIAir if that is helpful.

All that seems pretty good to me, but of course if I can make it better, I'll try. Overall, it was a very good night, again, thanks to your previous help. I have a couple of questions.

First, when the ASIAir issues a GOTO command, a window pops up for "GoTo Target." Here is one from last night.

As you can see, the mount is actively slewing while this window is open. The camera has taken an image and the ASIAir is trying to solve it, but since the mount is slewing, this is not possible. After a while (usually between 2 and 3 minutes) the solve fails. What controls this timeout period for the solving? Can I change it? It's not a huge deal because the mount eventually stops slewing and the ASIAir gets a successful solve. The problem is that this can waste up to three minutes of precious imaging time at the meridian.

My second question is more simple. Do I need to re-calibrate the guiding after an automated meridian flip or does the ASIAir know to flip the calibration data automatically? I've looked for an answer on line, but so far it has eluded me and I don't want to experiment in the middle of an imaging session.

Thanks as always and best,
Steve

w7ay

SteveZ As you can see, the mount is actively slewing while this window is open. The camera has taken an image and the ASIAir is trying to solve it, but since the mount is slewing, this is not possible.

First, very good on the success you are getting, and how satisfying it is to achieve third axis balance.

As to the plate solving while slewing, it is yet one of the myriads of bugs you get with each ASIAIR release. They do not properly regression test their software before releasing them.

The best you can do for now is to turn off Auto Centering. The toggle is called "GoTo Auto Center" in Mount Settings.

I never let ASIAIR do anything automatically. I do my own centering after a GOTO, I do my own focusing (I wrote my own V-curve program on my Mac, or best yet, use a Bahtinov mask when it is not freezing outside), I do my own autoguiding calibrations, I do my own meridian flips, I set my own flat exposure times, etc, etc.

Auto-anything in ASIAIR is fraught with bugs. The basic stuff in ASIAIR do work (not cutting edge, but basically works), but let it try to replace a human, it falls apart, like you have seen.

Do I need to re-calibrate the guiding after an automated meridian flip or does the ASIAir know to flip the calibration data automatically?

No, if memory serves, the EM-11 is one of the more common Fraunhofer style mount ("German mount") that only requires the RA axis pulses to be reversed after a meridian flip. Some computer controlled mounts also require a declination reversal. From what I remember, EM-11 is not one of those odd-ball mounts (Takahashi is always very traditional, all the way to their color scheme and stamped brass plates for serial numbers.)

After doing a meridian flip, all you need to do is to open the little Calibration Data window in the Guide Window (tap on that icon with "i" in a circle) and turn on flip, if you are autoguiding with the telescope on a different side of the pier as when the calibration was done. If you use ASIAIR's "auto Meridian flip," then this toggle is done automatically for you. Just make a note of which side of the pier you last calibrated at, and just toggle the Flip button when guiding on a star on the opposite side of the pier. Remember that there are two Meridian flips per day. one between the pole and the Meridian that contains the Zenith, and the other on the Meridian that contains the nadir.

By the way, you might find this old program of mine a hoot. I wrote it back in the 2005-2006 timeframe when literally nothing was available on a Mac to control a Takahashi mount:

http://www.w7ay.net/site/Applications/cocoaTemma/Users%20Manual/index.html

It uses Apple's Cocoa framework, thus the name cocoaTemma. It even has a polar clock to show where Polaris should be in the polar scope at the time you are setting it up :-).

Chen