MarkS

Hi Stephen, I am not quite sure what you are asking, but if you are trying to make and use a pointing file or get a polar alignment, instructions are in the Autoslew guides which you can download from the ASA drive. Sequence is a convenient way to make and save a PointingError.pox file; then you solve it and save it with Autoslew. Hope this helps. Mark

This may or may not be much help, but I have been using a DDM60 in mobile systems for some years, and I evolved by trial and error a start up procedure which guarantees a clean start up. I transferred the procedure to my DDM85A rollabout system and it also works every time. An important feature is that once everything is connected together, the mount power is turned on BEFORE the computer power is turned on. This always seemed to guarantee clean a start up, whereas failure to do this could cause problems....... I never found out why, and I just did what worked. Mark

Hi Stephan, I don't have a TCF-s focuser, but I use a FLI Atlas with Sequence. You need to find by experiment how Sequence interprets the number of steps in mm. With the Atlas, I found that Sequence 'thinks' 1000 steps is 1mm. In fact 1000 steps of the Atlas is 0.083mm. I then had to enter appropriate Coarse and fine AF steps in Sequence settings. These were 24mm and 12mm respectively. The actual movements of focus are 2mm and 1mm. These amounts gave good AF results. Also, because the Atlas is so slow, I had to increase the focuser time-out to 100sec to prevent overflow error messages. I also increased the Maximum Way from Startpoint to 10mm. (ie actual 0.83mm). You will need to find the right numbers for your focuser - but I hope this helps as a guide. Mark

9.2 and 4.6 kg Mark

With a heavy load, balance is very critical on both axes, particularly RA. The total load (OTA plus camera etc) should not exceed 28 kg for the DDM60. Overloading these mounts must be avoided!!! Read the recent discussion on balancing - I think it's the 'DDM85 position crash'. It is definitely a case of near enough is NOT good enough! Balance is critical. Tuning the motor parameters is well covered in the manuals. Always worth a read, even if one knows what one is doing, but I suggest you don't try to push the PID numbers too hard - the system will tell you that you have gone too far by going into oscillation. I'm not sure, but I suspect that very high PID settings may exacerbate motor current increases over time. Relaxation slews at intervals during a run is good practice. I'm not sure what you mean when you say that the problem mostly occurs close to the horizon. Why would you image there? If you try to send the mount too close the lowest altitude limit, it will get into trouble. In any case, for good imaging it is best to limit altitude to above 40 degrees or so. I set the limit in Autoslew to 25 degrees, but never image below 40 degrees. Hope this helps. Mark

Recently I had to go through commissioning a new laptop. I thought I knew what I was doing as I had been using two ASA systems for years. It turned out that I had forgotten about some critical but simple steps, and after the mount heading off for the wrong hemisphere and refusing do what it was told, I gave up and called Wolfgang at ASA for a Teamviewer session. He sorted it in about 2 minutes - much to my shame! The basic problem was, that in spite of having all the software and program data properly installed, it is critical that you 'Set new Homeposition' after having done the Homefind and then pointing the scope at the zenith or some star. This may or may not be your problem, but the erratic behaviour points something of this sort. Others may have better ideas, but in any case it won't hurt go through the manual and check that the fundamental first set-up steps have been followed. Only then should you start looking for subtlties🙂 Mark

Try setting park1 as your horizontal OTA position, and set Park2 to the zenith Mark

You could leave Park1 at the zenith, as it is useful for testing, and use Park2 as your parking position. Mark

PS: Read the thread on DDM85 position error crashes. Cheers, Mark

What load is the mount carrying? These currents look high to me on both axes. My DDM 85A carries an OTA and camera with a total weight of about 28kg - which is a relatively light load. Current on the DE axis is usually below 0.3A, and on the RA axis usually below 1.2A. The currents are dependent on load, however I do not know what the current vs. load curve is. Mark

I have an ASA 0.73 Reducer, and its dimensions are exactly as per the ASA drawing. Are you sure what you have is an ASA reducer? Mark

Robert, I definitely get best long term performance if I finalise RA balance by running the system for an hour or so on each side of the meridian, and adjusting counterweights until I get the most equal current draw over time on each side. I find that in the Southern Hemisphere the optimum current occurs when the counterweight slightly favours the East side. See my above post also. Mark

I did not want to suggest bearing problems until you tried everything else. I hope you can resolve the problem even if it means the mount must go back to ASA. I can understand your frustration with lockdowns - here we have a 5km limit on travel, so I have not been able to get to either of my sites for 3 months.....they are not remotely operated Mark

It is very unlikely from my experience that small DE imbalance will cause RA tracking failure. Your Clservo log shows that the Axis 2 currents generally remain <2amps. You could probably refine the DE balance - concentrate on the OTA horizontal position. Your on-site assistants need to realise how critical the balance is. Adjusting DE balance by moving the OTA is tedious and tricky. 1mm can make a significant difference. RA Balance definitely needs refining. It also needs very fine adjustments to the counterweight position. My procedure - which is not done remotely - is to use the Balance Tool with the counter weight bar pointing east and then west. The best position of the counterweight is different for each side. I set it between the two positions, and then let the mount track for a long time. I have a 0-5amp digital ammeter in the 12V power line to the mount, and I watch and record the current over time. If the current starts to run away, I move the counterweight accordingly. I then do the same on the other side of the meridian. This enables me to refine the counterweight position better than the Balance Tool does In my case the final optimum favours the east side (I'm in the Southern Hemisphere) slightly. In regards to 'relaxing' the mount, there are two important issues. Firstly, it is vital not to set the tuning parameters too tight (PID numbers too high). I have found it better to set the tuning manually. Generally the heavier the load, the tighter the tuning needs to be. But I would always try to set the lowest tuning numbers I can while still obtaining good tracking for up to 15 minute subs. The load on my DDM85 is approximately 29kg, whereas your is at least 42 or so (OTA + FW + Camera + bits and pieces) so I don't require as tight tuning as you. But I suggest you experiment with lower numbers. (Incidentally, the sensitivity slider on my set-up is 1 degree for both axes.) There is another important setting, particularly for heavy loads. In Sequence you can program periodic 'Stick/Slip' slews, which are designed to relieve excess current build-up during long runs. You can program intervals between the slews and the distance in degrees for the slew. Then during the run every,say 40min, the mount will slew 5 degrees, or whatever you set, and back again. I include the routine on both my DDM mounts, one which is relatively heavily loaded (DDM60), and the other, (DDM85) which is lightly loaded. If you are not using Sequence, I strongly advise you to program such a feature into your routine. Mark

The log shows that every instance of a position error is associated with the RA motor current increasing to 5Amps. In normal slewing or tracking this level of current should not be reached by either motor. It also appears from the error log that the slew to -38.2 degrees stops at ~-42. This raises several questions: 1. Is the mount running into an obstruction during the slew? Are there trailing wires which could snag? (this may seem a silly question, but it has happened before) 2. Does this behaviour occur at other positions? 3. Does it ever happen while tracking, or only during a slew? Current running away during a slew is most likely due to an obstruction. The logs support this possibility, as the mount seems unable to get past -42 degrees when it is trying to get to -38. This sudden behaviour occurring during a slew is almost certainly not due to imbalance unless that imbalance is seriously high. RA current running away during a long tracking period is usually due to imbalance, but it happens gradually until the mount mistracks. This can occur even if the balance is only a little off. With a heavy payload this type of failure is more likely than if the mount is not heavily loaded. Check that the payload is within the mount specification. The problem is unlikely to be software. If you have not already done so, I suggest you test the system during the day by slewing and tracking at varying positions and obtaining Clservo logs for the whole time you are doing the tests. You need to see what the logs show when the system is working properly as well as when it fails. Do you have a camera in the observatory so you can see what the system is doing? Hope this helps

Mike, The Moravian camera fans are internally connected to the 12V power supply in the camera. That is, they are NOT externally controlable. The camera must run on FIXED 12V. It should never be connected via the ASA fan port, which is intended to run telescope fans only. Mark

Gerald, I can't answer you directly, as I don't have a DDM60 pro, but I do have a DDM85. I imagine that the fan control works the same. There are only the two connections on the 3-pin fan plug. The fan is controlled by voltage variation (I don't know if it is done by mark-space ratio or DC voltage adjustment, and I can't get to my gear to check). In any event the variation occurs within Autoslew. Have you tried re-installing Autoslew? If that doesn't fix it send an email to ASA Support - response is usually prompt. Mark

I assume you are using CCDInspector to analyse for curvature. This may seem heretical, but I do not take a lot of notice of CCDInspector. I find it can give highly variable results - even within a single run. Having said that, there is always going to be some field curvature, and the FWHM of stars will deteriorate as you move out from the centre of the image. The deterioration may or may not have a curvature component. I find the most reliable - if very tedious - way to assess the image is by eye! (I produce my images primarily for printed display, so it's very important that the stars in the corners can stand up to very close inspection.) The sort of typical figures that CCDI gives for curvature of subframes from my ASA10/G3-16200 system are between 16 and 25 degrees, and these numbers bear little relationship to the visual result in the corners of the finished image. Even my Custom Officina Stellare RiDK/G4-9000 set-up yields 10-15 degree measurements in CCDI when all corner stars are spectacularly tight. So I assess collimation and alignment using Pixinsight Script>Image Analysis>Aberration Inspector and FWHM Eccentricity. These give good visual and numerical indications of image quality. As I say, it's tedious, but I find it worthwhile. Hope this helps. Mark

The Cats Eye will give excellent on-axis collimation, even if the secondary mirror is not at the correct distance from the primary. So there may still be tilt. Only adjust two secondary screws at a time, and don't touch the centre screw. This will ensure that the secondary is only being tilted, and stay in the correct axial position. If the secondary has never been moved along the optical axis of the OTA, you should not have tilt problems (Unless the camera itself needs correcting. This can happen!) If the secondary needs re-positioning, there is an ASA document on how to get it right. Mark

I have not used my G4 with my ASA10N/ASA3" Wynne/AAF3, but I use a G3EC with external filter wheel with absolutely no problem. This camera weighs 2.9kg, whereas the G4EC plus L FW weighs 3 kg. So you shouldn't have any trouble. However, the ASA 10 alignment and collimation will be critical to minimising tilt. The dof for a f/3.6 scope is only ~+/-17micron. Therefore focal plane curvature plus tilt plus focus inaccuracy must be within a 35 micron band across the sensor dimensions. The axial position of the OTA secondary mirror must be spot on to take tilt out of the equation - it isn't good enough to just have axial collimation! The G4 Mkll of course has a tilt corrector, but it still pays to ensure the OTA alignment is as good as possible. Hope this helps. Mark

I can't answer your question directly because I have no experience with 10 Micron mounts. However, I offer the following comments: 1. The ASA learning curve is perhaps steep, as the direct drive system is very different from others. I just threw away the old rulebook and started again! Balance and motor tuning are super-critical. 2. Some users seem to find the software difficult to deal with, particularly when trying to use it in conjunction with other observatory management software. Again I have no personal experience here. 3. There have been many software updates over the 7 years I have been using the ASA gear, but this has slowed recently. 4. A look through this forum will reveal quite a bit of frustration with Sequence, and there is rumoured to be a major update some time in the future. However, Sequence has some overwhelmingly valuable features. For me, the most critical of them is MLPT. This sets ASA apart from the rest, and is one of the keys to accurate tracking of the DDM mounts. I believe it to be vital. I currently have a 2400mm f.l. system which has no difficulty at all with 20min subs. (DDM85A) My 'standard' subframe exposures are 5min or less for LRGB, and 10 - 15min for NB. (The optical/CCD train is fairly fast - f/8 and 12micron pixels.) 5. The only DDM system failures I know of have been due to attempts to push beyond their weight carrying capacity. I did have bearing problems with one of my DDM mounts - a DDM60 - but this was corrected very promptly. 6. I have always had valuable assistance from ASA Support when needed - often via Teamviewer hook-up. Hope this helps. Mark

So you need a 14mm spacer to increase the backfocus distance. Then there is the matter of the axial position of the Parracor in the focuser to ensure you can reach focus. The ASA Wynne barrel design ensures this happens - you may need to experiment to find to right position for the Parracor. Mark

Chris, Don't worry about collimation for the moment. The three images you present do not all show the same characteristics: I guess that the focus settings were not the same for each shot. However, the aberrations are roughly symmetric in each, and the CCDI image of curvature is symmetric. But the curvature is awful! I am not familiar with the Parracor, but I suspect that the backfocus distance of 57.3mm, which is correct for the ASA 3" Wynne (measured from the front face of the Wynne to the image plane) is not correct for the Parracor. I don't know what information is available for the Parracor, but I suggest you start there, unless you can get a ASA Corrector.... Perhaps others may be able help more than I? Regards, Mark

The ASA10N/3"Wynne does not vignette noticeably with a KAF8300 size sensor. I see no vignetting with a similar set-up, but I use 36mm filters. The adapter is 42mm i.d. When checking for ray path obstructions remember that the rays are converging. I suspect the filters may be too small. Mark

Hi Nick, You have opened a thorny subject! Newtonian type astrographs are very difficult to collimate AND achieve coplanarity on the image plane and the sensor plane. All collimation tutorials that I've seen achieve collimation of the central ray, which is generally fine for observing, but the problem is that there are any number of configurations that will give central ray collimation, BUT ONLY ONE that results in coplanarity of image and sensor planes. The faster the optics the more critical the problem is because the focus depth becomes extremely shallow. In your case it is about as critical as it gets! I have checked this by obtaining "perfect" axial collimation on my ASA10N for a range of secondary axial positions encompassing several millimetres. Many of these alignments yield disastrously misshapen stars in the image corners when using a 16200 class camera with an image diagonal of about 34mm. The ASA method does get to the correct distance, but I would recommend that you ensure you get the same positioning with the mirror turned 90degrees in BOTH directions. I found this tedious but doable. Note that when both the setting and the axial collimation are correct the image seen looking down the focuser barrel with Cat's Eye or similar tools will not exhibit concentricity. Again, the faster the optics, the more pronounced the effect is. I am assuming here that the ASA8H behaves similarly to the ASA10N. Hope this helps. Mark