For some time now I have been experiencing this serious type of problem to which I have not found a solution for now. Photographing at long exposure although the guide maintains acceptable values (RMS tot: 0.58 -0.70) at a certain point the stars are moved. I noticed that this happens when the DSO approaches the meridian (even an hour before and in any case when the tele points very high). I checked that there are no pushups, pulling cables and whatnot, but everything is fine! The pole alignment has also been redone and we should be precise enough. What I can still point out is that a short time ago I had redone the registration of the worm and gear wheel coupling on the two axes, bringing the driving graph to definitely lower values. Furthermore, I believe that if this registration had been incorrect, the guide would not have been so efficient. Technical data: NEQ6 pro mount, Apo triplet Astroprofessional 102/714 reduced to mm. 570. Driving with Skywatcher 70/500 and Orion Starshoot and Atik 383 L + CCD. Any advice and suggestions welcome. Clear Skies.
The unknown problem
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Is that something that occurs only once in a session or is it periodic? If the former then there is some slop in the system that is getting flipped once the assembly reaches a certain point and then everything settles down. In the other case there might be issues with balancing. Do you have a tracking graph? if not make one to understand what is going on here.
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He has already done this to me several times, even on different subjects, always near the meridian. Even before performing the meridian flip (it also occurs an hour before it). Tonight around 00.15 while the meridian was reported to me by APT at 01.38. I photographed the driving chart at the time of the problem and the magnified stars on the captured frame.
It looks like you got a loose element in the imaging train but to be sure you'd also want a tracking PE curve to be certain it isn't the mount that is the problem. The tracking correction curve as reported by PHD2 isn't good enough. To create one PE curve move the mount in azimuth by several degrees off from precise polar alignment, point the scope to a star 30 minutes before crossing the meridian and around the celestial equator. Keep imaging at around 60-300s intervals depending on image scale untill you reach the meridian. Do not perform a meridian flip and keep tracking/imaging after crossing the meridian for few other minutes. Process the light frames as you would normally do, taking care to apply flats. Then we'll see how the mount is actually performing on its own. And we'll take it from there.
Obviously you should NOT be guiding when doing the above.
Obviously you should NOT be guiding when doing the above.
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What do you use for guiding? The 1h before meridian flip is suspicious. There appears to be in some circumstances a hickup when the Starwatcher mount had been set on daylight saving time, then bad things can happen when connected to a computer. I have had some issues (guiding/tracking(don‘t exactly remember) basically stopped 1h before the MF. Since I put the handheld computer on (usually it is in my closet, as I am using an ASIAR directly connected to the mount via USB), and disabled DST. But I never could reproducibly track down exactly what happens, there are also some related reports in various news groups, again related to DST but not fully to the point.
If tracking continues much the same and the stars have jumped / moved then differential movement between the scope and guide scope seems to be the problem, my guess is something like the tightness of a rotation ring, ( I have a flt132 and it has Teflon or similar plastic ring in the rotation behind the focuser, being plastic the locking screws embedded itself and no longer employed sufficient pressure, pulled it apart and remedied)
simplest test is to wiggle the camera and see where the play is….. my guess it’s NOT the mount.
simplest test is to wiggle the camera and see where the play is….. my guess it’s NOT the mount.
I photograph and shoot remotely, and the PC in the Observatory is updated and accurate in daylight saving time. As for the set-up slips and rotations, I will do a thorough check in the next few days, especially fearing the telescope in the position where it starts to have problems, which is this in the photo.
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