P.Keller

During installation of a telescope in Greece I was able to make some test exposures with this telescope. We where lucky and the seeing, though the telescope is installed near sea level, reached 0.8" in 200s subs. Was also a great test of MLPT, all exposures where unguided. Since with this seeing, even 0.2" will show up as elongated, the MLPT on AltAz was really given a hard test but it worked well (after sorting out some final bugs) Sucess rate was around 90%, even up to 85 degree altitude. Rotator also worked well. But of course, the Canon 5D we used is still not comparible to a standard CCD as it has quite large readout noise. Very good for bright objects, but still a problem with dim.

the influence of temperature dependency for refraction correction is minor and neglegible compared to other errror sources like hysteresis etc. Also, the temperature gradient in the atmosphere is something that cannot be measured anyway, even if you measure the temperature at the altitude you are observing, you can have a temperature inversion above etc. So there is no real sense in doing this.

thats easy. You have to select the right dome in the dome settings and check the box "active control by sequence". We do all our exposures in Chile with the ascom scope dome driver.

Point Grey Video Cam

I made some images with our 80cm Chile telescope and made a video: https://www.youtube.com/watch?v=QXXLA94mTSY

Hi Christian, although this may seem a lame excuse, the main problem with trailed stars is in 90% of the cases a timeflex problem. MLPT cannot correct a problem where the pier is sinking into the ground while the exposures are made. But you can measure this with timeflex procedure in Sequence. The first reflex after getting elongated stars is to think its the pointing file or some software bug or some MLPT problem but the truth is that in most cases its just bad luck with some time flex problem. We even have this problem on fixed installations, where a complete building is bending by 10 arc seconds due to temperature changes in the night and causing tracking problems. We have not ordered a tip/tilt sensor with A lot of thought in mobile telescope setups should be put in the way the pier/tripod is fixed to the earth. To check wether MLPT is working or not, one way is to make a bad polar alignment and clear the configuration.

Hi Kazuo, I don't think that other programs will be able to manage pier flip etc. with MLPT so I work further to optimize Sequence. I also have your wish list and we are continuing to make sequence better. Antonio, Ascom Cloud Sensor has been added and you can try for a test version. Mail me at p.keller@astrosysteme.at. What happens is that when it receives a nonsafe condition, it will park the telescope, close the cover and close the dome. Philipp

Hi Evgeny, we have developed an Ascom Driver which uses Soap TCP/IP as communication base. The easiest thing would be to use the TCP/IP and make a simple wrapper for your indi protocoll. I assume its not to much work. Currently, one customer is already controlling the mount with a MAC. But please give us 2 more month before we officially release this.

my experience is that a truss tube is MUCH better than a closed tube if it comes to wind problems. But if you have a truss newtonian with a big light shield opposite to the focuser and a long tube it can also be bad. Small truss tube Cassegrains should perform best. But if you have more than 4BFT I would consider a dome.

the power of the motors is indeed another limitation to correct very strong gusts because you would need a very fast acceleration which needs more power than the mount can apply. Of course this depends on telescope weight. But as I said, the problem with tube flex comes first and will limit your ability to work in strong wind conditions anyway.

Hello Hector, the wind speed is not the important factor, its how gusty the wind will be. The reason is, that the mount can handle a constant load very well (it will push against the wind torque until the measured encoder position is according to the calculated target position. The mount does 1000 measurements per second but if it gets really gusty it won't be able to correct it fast enough. Also, I think that the flexure of the tube caused by the windload will be a dominant factor.

Hi there, 0.0.9 can't make MLPT through the Meridian. Also, there is a bug when the MLPT is going through the Meridian so you have to try to either have the full MLPT on East side or on West side. We are working on a new Version which Robert mentioned and where MLPT even with flippling between the exposures will be possible.

you have to connet through the POTH or Ascom Hub. Don't connect directly to AstrooptikServerTelescope but select first the Hub and then inside the Hub, select AstrooptikServerTelescope

Ascom knows only one homefind method. This will always slew to Park1. There is no option to slew to Park2 by Ascom. A new Sequence Version is beeing tested by some users which allowe entering multiple targets, autofocusing etc. with MLPT. When everything is error free, it will be released. I am using it on my 80cm telescope since 100 nights now (www.chart32.de)

the automatic tuning does not always work well if the mount is heavy loaded and you might try to tune it manually. A low frequency shaking is always a to high P+I or to low D. A noisy high frequency is a to high D. What you observe is low frequency, so you have to reduce P and I (if you move the I slider a little down it will work). Philipp

I think the rotation of the assymetric filter wheel by the rotator should be managable by the mount. +-1A is OK. But during sensorlessfind the balance should be quite well because otherwise the back and forth motion keeps the mount also to travel in one direction during this measurement and this spoils the result. It is very important that the focuser, CCD and filterwheel is balanced. This is a lot of weight. Maybe you have to add a counterweight to the tube. Regarding the ACC device errors, this is caused when the USB port is lost. Can you try to connect it to another USB outlet of your computer or another Hub or try another cable ?

you said that you have perfect balance but did you check the balance http://www.astrooptik.com/asa/Balance.pdf ? You can easily have balance in one position but have problems in another position, especially with heavy CCD or filterwheel you need to add a counterweight opposite to the CCD on the tube. The sensorless find looks like the tube is moving a little in one direction while you make it. The velicity limit in the servolog means you moved the mount by hand to fast. It then looses the encoder position and thus the right magnetic angle. The movement in DEC during sensorless find is a little small. Use higher current here. The magnetiv angle it writes in the LOG can be different each time because it depends where you have your mount when you power up. Having different values here each time is not a problem. A problem however is, when this angle is corrected by a huge amount after homefind. This means the magnetic angle is found wrong. It should be between 340 (=-20) and +20 degree, not more. So right now I would guess its a balance problem (this is the problem in 90% of all support cases we have) or it could as well be a tuning problem. If you like, I can take a look via teamviewer. Please then contact me via p.keller@astrosysteme.at P.S. Did you change something on USB when you added the camera ? 08:44:27.556: readInt16 read error 2x. Received error# from ftdxx.dll was 3072 08:44:27.571: Now trying ResetDevice, this returned 0 08:44:27.587: readInt16 after ResetDevice still not working, returned error# 3072 this does not look nice, there seems to be a USB problem.

you will probably notice, that the most error of the 10 arc sec happens in the first part of the flex time. This is something that will help you in real exposures. Also if you have 1.5" trailing and you have 2" seeing the image will not look so bad. Have you ever measured the real trailing by making short 5s exposures every minute and then determine the pixel localtion of a certain star ? Your result is not unusual. You can be sure the result is real because the mount stays exactly in place and always slews back to the same encoder reading, removing any pointing error the mount could make. Therefore, also polar alignment is completely irrelevant in this test. Maybe you cannot optimize this with a SC telescope. I am not experienced with them.

I checked and can conform this behaviour. Maybe it did not show because tracking is usually turned off in Park. We will correct this with the next release.