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Some nights my guiding goes perfect for 6 hours, I don't lose any subs. Tonight, it's not windy at all, and the Clear Sky Chart shows the seeing is good, transparency is excellent and no moon or clouds. Tonight my guiding numbers are acceptable, .35"-43" RA and .38"-.45" DEC. Suddenly the DEC jumps up to over 2.5". I press the "Clear" button on the guiding graph and the numbers return to acceptable. Why does this happen? Doesn't "Clear" merely clear the graph, and not change anything with the actual guiding? I've checked for cable snags, all cables OK, both before and after the meridian flip. I'm also seeing sometimes after dithering, the guiding gets totally lost and, again, if I press the "Clear" button on the left side of the guiding graph, the guiding returns to an acceptable range. Why does dithering mess with the guiding? Is there anything I can do about that? And why does pressing "Clear" return the guiding numbers to within acceptable limits? I'm finding autoguiding the most challenging part of imaging. I hate losing subs. My PA is spot on, < 1' error on alt and az. When imaging, I stay away from the telescope at least 15 feet to avoid any vibration messing with the guiding. Still, it behaves erratically and I don't know why. My AM5 strain-wave mount isn't supposed to have any backlash, but maybe it does?? Thanks, Jerry |
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Are the spikes happening during the dithering between subs? The display shows you the average over the visible graph so a large spike can throw off the average until the spike moves off to the left. Pressing clear just clears the graph so the average starts to recalculate. I think you can get the guiding log off the ASIAIR (perhaps by plugging it in to the USB C port)? You can then look at what was going on in more detail. |
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Hi Jerry, What's your guide rate and sub exposure time? I'm using Rainbow Astro strain wave mount and have periodic spikes. Strain wave drives require fast guide rates 0.5s (in bad seeing I'm sometimes switching to 1s). At this rate even if there is a spike, it's corrected very fast, so I never end up with rejected subs. It's worth noting (although some will disagree with me) that AsiAir has very questionable PA routine. Even if it's spot on, by the time you tighten all bolts it WILL be off to a degree (you can easily test it by re-running PA routine without re-adjusting the knobs - you will see that the final result will be different from what you achieved initially, and if it's way off that would be the answer to your problem). So if your spikes are lengthy, i.e. recovery takes several seconds, I would suggest to re-do PA and re-calibrate PHD. Strain drives are very powerful and can handle poor PA quite well, however you may also end up with irregular guiding. With regards to "Clear", it just clears the graph. To reset guiding, you need to disable and re-enable it. As I mentioned above, re-calibrating PHD tends to help. |
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I press the "Clear" button on the guiding graph and the numbers return to acceptable. Why does this happen? Doesn't "Clear" merely clear the graph, and not change anything with the actual guiding? Because the guiding numbers shown are an average of whats visible on the graph. So for example, some big spikes will affect your RMS until those spikes disappear off the left side of the graph. When you clear the graph, you wipe out the spikes and it starts averaging out from that point. Hope that makes sense? |
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I have had something similar happen to me as well. I have an overloaded SWSA GTI that guides under .7 arch sec most of the time (which is completely fine for my optics as I run at 1.8 arch sec/pixel, so I never have any noticable blur) On some nights however, I get these huge guiding spikes out of nowhere, and lose an entire sub. It's completely random as to when it happens, on some nights it doesn't even happen at all. It's just a 15-20 arch sec jump in one axis, straight in one direction. I've checked for cable snags, I've checked if maybe the guide camera slipped a bit, but nothing. After I lose that sub, everything either goes back to normal and it doesn't happen again for a few nights or it happens in the next sub... Completely no pattern to it. My point is that before I bought the asi Air plus, I was using phd2 guiding and never had any issues. Granted, I only used it for about 5 nights but if it was the mount or guiding setup I think it would have happened in that amount of time. Any ideas on what this could be? |
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Filip Lebeda: Possibly the guiding tuning parameters need to be adjusted to make it less aggressive. I found a guide about this online but I don’t have the link to it now. You might be able to find it. |
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Thanks everyone for sharing your experience with me! Jerry |
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Hi Jerry, No guide rate with the AM5/ASIAIR Plus. It's set to .5s and can't be changed. Guide exposure time is 1". The way to stop the PA routine from slipping is to tighten a little both the az and alt axis levers but not too much. Then do PA and tighten them up a bit more. The azi axis levers don't have to be that tight, the knobs are tight enough. |
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Hi Jerry, I've started doing PA with the ASIair and then immediately do PA with PoleMaster. Only one night so far and it was a night with poor seeing. My intent is to see the difference between them and record the values over time. |
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| I have had the same intermittent issue. I solve it by shutting down guiding, clearing the calibration, then recalibrating. My best current guess is that when I get the warning that guiding calibration should be done between 20 degrees and 30 degrees rather than at a higher or lower level it means it. My issues so far have come when I do calibration too close to either the North Pole or the equator. |
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It happens to me from time to time and I am not sure why. I have better guiding now that I calibrate toward the celestial equator and meridian. I also start with my aggression around 60 and later into the night, I have it adjusted down to 35-40. "Some ASIAIR Guiding Tips: You can use the (i) button at the very top right of the Guide controls to clear the stored calibration.In the Guide Settings you can choose whether or not to auto-restore a stored calibration.If there is no stored calibration then initiating guiding will automatically perform a calibration. In the Guide Settings, you can define the Calibration Step (I believe the default step is 2000msThis calibration duration is used to make sure the star moves enough to detect axis orientation.You can experiment, but I think a star movement of 24" in about 5 steps works well. A calibration step duration that is too small will result in the star not moving enough, and one too high can result in the star being lost or moving 24" in too few steps. The most important factor here is your guide focal length. Wider field (shorter focal length) requires larger value.For example, the ZWO Mini Guide Scope is probably around 8000ms, a typical 50 or 60mm guide scope is probably around 2000, while an OAG might be only 500 (depending on focal length of main tube)I use the ZWO ASI290MM MIni in an OAG on the Redcat 51, at 250mm focal length, i find that anywhere between 1500 and 2000 works fine.A good calibration should only take 4 or 5 steps. There are ways to use ASAIR Guiding to determine the best Guide Rate (0.25, 0.5, 0.75, 0.9) for your mount, and the best Aggression, and Exposure, but first you need to get good calibration. Once you have a good calibration, you generally don't need to re-do it, unless you are rotating your guide cam relative to the mount axis (such as an OAG rotating with image train) As far as Gain is concerned, I use 300 with my ASI290, again, on my particular setup/focal length. I would recommend using the highest gain wherein you can see stars without any (or very little) noise. All of this, of course, doesn't account for any bugs or known software glitches that ZWO may have introduced. EDIT:Just a bit more about the GAIN, I would use a higher gain in order to use smaller exposure... say 1 second, while doing calibration, and for figuring out the best guide rate/aggression. Once you've dialed in aggression, I would change the exposure to around 4 seconds so your not "chasing the seeing", which should smooth out your graph. With the longer exposure you could lower gain if the image is too noisy." https://www.cloudynights.com/topic/772521-asiair-pro-guiding-calibration-issue/ |
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| Found this on Cloudy Nights .comMore ASIAIR Pro Guiding Tips: There are so many variables that will influence the actual setting/numbers that I think the best way to help would be to outline the process of discovering the best setting for your particular setup. Guide Rate: A "guide pulse" is the pulse used to keep the mount moving at Sidereal rate (presumably). Guiding Rate is the (major)multiplier of this pulse used for guiding corrections, and Aggressiveness is the (minor)multiplier. The easiest way to "dial-in" ASIAIR guide settings is to first start with Guiding Rate, found in the Guide Camera Settings. Pick a star and start guiding (single star guiding). Set the Aggressiveness for both DEC and RA to 50%, and change through each of the Guide Rate settings (0.25, 0.5, 0.75, 0.9). Many mounts do well with 0.5 and many default to this. What we are trying to do here is to correct for PA alignment and PE, so we are just looking at the trend. You can use a faster exposure time, say 1 second, so the graph fills the complete width of the screen faster, but wait for a full screen to see what the RMS error is. Cycle through each Guide Rate Setting, and watch for a full screen. The setting that has the best RMS error (lowest number) after a full screen will be the best Guide Rate for your Mount and tonight's Polar Alignment. For Aggressiveness, start with DEC first, and lower the setting to 5%. Watch the DEC graph (Red), it should trend away from center, either North or South depending on your Polar Alignment. You can then set your direction, North or South, depending on which makes your DEC line come back towards center (you can increase your aggressiveness to see the effect quicker). Auto may work for you, but you don't want your mount "bouncing" back and forth because of over-corrections, so it may be best to set the correct direction. Now slowly increase your DEC Aggressiveness until corrections bring your DEC line back to center in 1 or 2 pulses without over correcting. A little cross-over (over correcting) is fine now and then, but your just trying to keep the DEC nudging back to center as needed. As you increase DEC aggression, you may get to a point where the pulses will over-correct, this is where you want to back it back down a step. The actual DEC RMS Error will be as good as it will probably get for tonight, with your current PA accuracy, seeing conditions, etc. If you know your PA is pretty good (and it should be with ASIAIR PA) then the RMS Error should mostly be about seeing, and you can shoot for/expect a similar RMS Error in RA due to the same seeing, however, PE will also effect this number. Follow a similar process for RA (Blue), to where the Aggressiveness keeps the RA error close to the DEC error without "bouncing" back and forth. You want your guide pulses to be "nudging" your corrections, not playing "patty cake" back and forth, or "speed up, slow down, speed up, slow down" because they are too strong. Once you get the RMS error as low as you can (it will vary from night to night), then you can use a longer exposure, say 3 or 4 seconds, to smooth it out even more, so your not chasing the seeing conditions. This is just a general description of how you can "tweak" guide settings in ASIAIR Pro, and will work for many mounts, however, there are some mounts that behave a bit differently. For example, I don't increase my guide exposures for my RST-135, using 0.5 second exposures, or sometimes 1 second max with multi-star guidingthis |
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Jerry Gerber: I don't know about CSC, but I do know that my local weather can't get it right, ever. Clear no longer means clear. I use ASIair on two scopes running simultaneously, side by side and when little wisps of cloud blow in on 'clear' nights, the guide numbers go up on both machines at the same time. |
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DavesView:Jerry Gerber: I think climate change is impacting weather prediction. We can't pump 10s of billions of tons of CO2 gases into the atmosphere every year and expect no consequences. Over the summer I planned a dark sky outing about 4 hours north of where I live. I looked at several weather reports, all said it was going to be clear, and 100F. I got up there, a densely forested area of Mendocino California and it was definitely 100F. But it was also raining, lightning, very cloudy and the fire danger was extreme. I turned around and drove all the way home. |
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| I was having the weird intermittent guiding issue as well so I stayed up and watched the guidescope view. indeed a wisp of cloud came along and obscured the guide star for a moment. ASIAIR likes faint stars, probably because they are smaller, but they are also the easiest obscured when a bit of cirrus cloud drifts by. |
