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I've been upgrading my gear recently to a ASI air and a guide Setup. It has times in which it works really well but looking at the data over a night, I can confidently throw away over half of my data because the guiding just wouldn't work properly. My Gear: Sky watcher star adventurer GTI Zenithstar 61 - 360mm f/5.9 Canon EOS 600D Full Spectrum mod ZWO Asi 120mm mini guidecam ZWO Asi mini guidescope ZWO Asi air mini I recently had a really beautifull clear sky without a moon. So the guiding should've worked really well. It constantly lost it's guiding stars and sometimes completely went off the charts to try to correct the tracking. Sometimes it couldn't settle at all and took ages until it was in the right position again it's very unpredictable. Here are my dither settings: Stability 2.0" - Time 10s to settle - 50s Timeout if settling doesn't work right away I dither 30 Pixels every frame I calibrate the guiding every night and Polar align with the asi air to a 5 and close to a 4 (don't yet know what that exatly means) My stars look mostly like this. sometimes with a straight streak, sometimes round etc. (it's very creative if that's what you're going for.)  This is is an example where it had stars to track but it still went off the charts. (I get that the stars do look out of focus, I fixed that, same problem)  I tried to play with the aggression as well, bumping it up to 50 and 70 but sometimes id would just make it even worse. This is a small part of that clear night :  I stumbled across this thread: https://www.cloudynights.com/topic/773176-asiair-pro-guiding-issues/ Where he had to install a new Firmware update to the ASI guide scope and it worked out for him. out of some reason the files that are needed for the update are not included in the download anymore, so that doesn't work either. Here is my setup  What do I do to make the guiding better and more reliable? I really can't trust it. before I bought the guidescope I sometimes had better success without guiding at all managing to get 2 up to 3 min exposures. I'm mostly taking 3 min exposures. |
4.21
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I haven't used the ASIAir in a long time but from your screenshot it look like you've moved the guiding aggressiveness all the way down to 5% and 10% which sounds like it'll barely be able to correct anything. If I remember correctly, they are usually 100% for DEC and 70% for RA by default and I never changed them back when I was using ASIAir. That was giving me between 0.2" and 0.5" of error depending on sky quality. EDIT: Sorry I just saw the part where you've tried moving the aggressiveness up. My next guess is the amount of pixel you use for dithering. 30px sounds like a lot and the graph seems to show that you're losing track of the stars after a dither. Keep your aggressiveness up to the default and try 5px dithering or lower for a start. Jens: It would be important to understand this metric as a bad polar alignment can throw your guiding off. Was it 5 degrees, 5 arcminutes or 5 arcseconds? Try to get us a screenshot of your polar alignment results. |
1.91
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I had a GTI for 6 months too, and I know the pain of guiding problems with it. To be able to help, we need a bit more information:
In your Screenshot, the guide stars in the background look very dim, maybe your exposure time for it is to short, so you either lose the stars or the stars "jump" around due to being affected by the air. With that mount your polar alignment has to be better to get better guiding, you should aim for something below 2' and see if the guiding improves. |
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3.61
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So with the polar alignment, since I don't have a view to Polaris, I'm using the all sky polar alignment feature of the asi air. I can't tell you right now how big the total error was, but I'd argue I was really close. I think those numbers mean 0.5 degrees This isn't mine. in the center it's a 5' insead of a 2' so one level more precise than this example  I played around with a exposure time from 0.5 seconds to 2 seconds. I mostly stayed with 2 seconds though. and I put the gain all the way up to 100 to make the image as bright as possible for the guidescope to see the stars. I also feel like when I start guiding, the Asi air always chooses very dim stars to guide with. even if there are much brighter and more visible stars in the frame, it won't choose those. I tried selecting one manually but it would automatically go back to the multi star guiding. How can I reduce the drag of the cables? they need to be a certain length in order to not get tangled up when moving the mount, but I do get your point. and it's balance really well, I made sure of that |
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Jens: I've had this happen to me before when my gain or exposure time was too high. It'll always prefer a dimmer star over the ones that are clipping in the center. Clipped values are no good for precise guiding. If by 100 you actually mean 100% you may want to go much lower than that. With the ASI174MM as guiding cam, I was running 2 seconds exposure / 240 gain (the medium gain setting in ASIAir) which translates to 60% of the maximum gain of this camera. And that is while using a OAG which most likely receive less light than your guidescope. For your polar alignment, the circle indicating 2' means 2 arcminutes and you're still a bit outside that. It should not be that hard to get it at least under 1'. For reference, I always get my polar alignment under 0.2' |
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1.91
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Jens: 5' is worse than 2'. Next time, try to get it even below the 2' and check if it improves the guiding. The Guide log has information about Polar alignment of the night, check if it is good there. I always got the PA spot on before the session, but the GTI is just so lightweight and the knobs so wobbly, I often got very bad PA reported by the Log after the night, due to some shifting. I played around with a exposure time from 0.5 seconds to 2 seconds. I mostly stayed with 2 seconds though. 100 gain and 2s should be fine. I also feel like when I start guiding, the Asi air always chooses very dim stars to guide with. even if there are much brighter and more visible stars in the frame, it won't choose those. I tried selecting one manually but it would automatically go back to the multi star guiding. Oh my god you just gave me some horrible flashbacks of the countless nights I've tried to improve these problems with the AIR and the GTI. The AIR is just not perfect, it's useful for us amateurs and makes things easy, but overall it's just a heavily tuned down PC with basic features, and often kinda bugged. How can I reduce the drag of the cables? they need to be a certain length in order to not get tangled up when moving the mount, but I do get your point. If it is balanced with the cables, it should be fine. |
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That's great, I found my error in the log software to be 18.6' (arcminutes?) I still haven't developed a understanding of that term haha. I'll try to be more precise next time, I've also heard that the All sky polar alignment isn't as precise as a real polar alignment. but I don't really have another option. I was actually contemplating going to a Raspberry pi with Stellar mate installed, that's for sure still an option. Since my astrokit has to be portable, using a laptop isn't really favorable. So I now have two different opinions about the Gain settings 240 gain with 2 sec or 100 gain. what's the better option? |
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Jens: 100 gain seems fine if you actually meant 100 as an absolute value. What made me believe that you maybe meant 100% is : "all the way up to 100" In any case, you must not over-saturate the stars or it'll always insist on picking dimmer stars, even if it look better to your eye. ASIAir is a perfectly fine little box for deep sky. The only reason I moved out of it is for things such as the writing speed for planetary on the disk, access to many tools to calibrate things such as sensor tilt, connecting other cameras on top of the telescope to monitor the sky etc... I can't comment on the All-sky polar alignment, never used it and last time I checked it was an experimental feature. Here's a little compilation of what I and Johannes noticed so far: - Get the aggressiveness back to default (100% for DEC and 70% for RA), they work extremely well as a starting point. - Don't dither so much, 5px max should be fine at your focal. - Try to improve the polar alignment, under 1'. - Perform guiding calibration while not pointing at Polaris. - Make sure your cable are not pulling too much on the mount/scope. - Make sure the weight is well balanced on the mount. - Do not over-saturate the stars on your guiding camera, adjust exposure time if gain is already low, adjust gain if it is too high. Too high gain will also introduce noise. - Make sure you take new dark frames on the guiding camera for the gain that you're using. |
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Jens: Well 18' is not good. But it's great that you found the error there, so you know where the problem is. I'll upgrade to a mini PC eventually, but for now I'm happy with the AIR. Regarding the gain, you can just try which works better, I think in the AIR you can set "low" and "medium", start there. |
1.91
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I second what @Miguel T. mentioned. Your cables look a bit messy and they may cause some hikes in one or both axes. Get the RA aggressiveness high as you are getting a runaway in RA probably due to an unbalanced mount in RA, a cable pulling in one direction, or less than ideal polar alignment. I do not own that mount but as it is intended to perform great as a portable rig, I would be happy to get the RMS down to 1'' and probably not any lower than that. Considering, your image would be rendering something larger than 2'' per pixel (given your camera sensor size and f ratio), stars would look round nonetheless. |
3.87
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| Most of the points have been hit already but I prefer to not dither every frame for a few reasons. I realize you are using a Canon and they are a bit more sensitive to dithering but try dithering every other frame or even less depending on how long your subs are. I dither every 10-15 minutes no matter how long the subs. 10 minutes for shorter projects, 15 minutes for multi night projects. With my lower end mount I am always trying to dither as little as necessary to avoid the inevitable slow settle and DEC backlash. I lose about 30% of the frames right after a dither but less than 10% of the other frames this way. Plus every dither costs you some time, as much as a minute. You save a lot of imaging time if you dither as little as possible. |
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Hello Jens, Much more information in this post about all your gear. The photo and other images are helpful too. I will first mention that I do not use ASI Air so I won't be able to provide much help with that. The first thing I notice is your small image of a star. This is looks quite similar to what I would get before I started guiding. Since you are guiding it makes me think that either your mount is not properly responding to guiding inputs or something is happening in your setup to cause vibration. The "trail" looks fairly straight so I'm suspecting it may be vibration related. From that perspective, I did some googling and added up all the listed weights for your gear and got 7.3 lb. The Star Adventurer GTI is rated at 11 lb. Typically, the recommendation for astrophotography, is that the gear is appox 1/2 the mounts rated capacity. So, while your setup may not be the ideal weight, it is certainly not overloaded. Indeed, other similar setups work fine. One thing I do notice is that your counter weight is nearly at the end of the shaft. This could be problematic. The further away from the rotation center, the higher the moment of inertia. I'll not go into the full physics explanation and formulas here, but basically moment of inertia is the amount of effort required to start or stop a rating mass. So, while your mount may be balanced, because the balancing mass is further away, more effort is required. Increasing the balancing mass and moving it closer to the mount will result in a lower moment of inertia. One thing I would recommend is adding more balance weight so that you are about 1/4-1/2 way on the shaft. Moment of inertia creeps into all sorts of area on mount system. I see you are dithering. This could very well be related to your problem too. If the moment of inertia is too large, this could be inducing oscillations that simply don't have time to dampen when you dither. A very quick and easy test is to turn off the dithering. I started with an EOS-60D and have used 1600MM, 294MC and 2600MC and I have never dithered any of my images. Since I started guiding, I honestly never had an image with walking noise or anything else that indicated the need for dithering. It's my opinion that good guiding is far superior to dithering when it comes to good images. If you do need/want to dither it is fine, but for troubleshooting purposes you need to simplify you setup so that you can see what is causing the issue. In fact I would keep the dithering off until you have resolved the guiding issue. Another area that needs some serious attention is you cable management. One of the great advantages of the ASI Air is that everything can be mounted on the scope and the only cable required is power. You have cables dangling and hanging all over the place. Each adds the possibility for snags and vibration. Spend some time using cable ties and get the cables bundled so that you don't have such a rats nest and spider web of cables. I can see that most of your cables have long lengths, it will be to your advantage to purchase shorter cables that are more appropriately sized. Using a 2m cable when a 0.5m cable would be far more preferable. I do realize that not all cables come in shorter lengths, but whenever possible, use the shortest cable possible. Your guiding graphs also tell a story. Your first images shows the RA starting to make corrections, but the smaller chart is showing what appears to be fairly periodic Dec error. As I mentioned before, I don't dither so perhaps this is your dithering movements, if it is, then this is a good indicator that turning off the dithering for troubleshooting is a good idea. If it is not from dithering then you may want to take a look at your mount and make sure there is nothing in the Dec movement that could be causing this. The ASI Air uses a version of PHD2 that they (ZWO) have modified, as such the ASI Air guiding is not supported by PHD2, but most to the PHD2 information that you can find on the web will be useful. One thing that PHD2 recommends for troubleshooting (and indeed for some mounts that have Dec issues) is to disable the Dec guiding. IIRC the setting is something like "guide in one axis only". I'm not sure is ZWO has this option in their setting, if you can turn off Dec guiding it may provide some good troubleshooting. The Star Adventurer GTI is a lightweight mount and the the periodic error is fairly high. I feel that if you get some of the basics such as balance and cable management better optimized that your guiding results will improve. There are also some basic software/configurations such as turning off dithering and disabling Dec guiding that should help in troubleshooting. John Schnupp, N3CNL 2007 R1200RT +73,100 1995 XLH 1200 106,495 (retired) Georgia, VT 44.7675°N, 73.1592 |
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Wow thank you so much for your extensive answer, I really appreciate that. So the main reason I upgraded my gear in the way I have, is to actually be able to dither. Walking noise has been a thing that has been plaguing me since the beginning of my astrophotography journey and has ruined tons of nights. Guiding in that aspect is pretty much secondary. But since I have it, it'd be stupid not to use it properly. I tried dithering with the new setup only every 4th frame or so, and again the image wasn't turning out right. So I will stay with dithering for sure since it removes my biggest headache I've had in astrophotography. To your weight suggestion. that does make sense, I think it's weird that this could happen by just using the mount as intended, but especially with small movements I can imagine that it's hard for the mount to move and stop all the weight. That's definitely something I'll consider upgrading. The Cable management is something I'll definitely have to figure out. I just couldn't figure out what the best way is to keep the cables flexible enough to move the mount freely but not let the dangle like they do now. I've only just learned today that cable drag is actually a thing, so that needs to be addressed for sure. I have to take a look but I think only guiding in one axis should be possible. that's definitely worth a try. What I have found is that whenever the mount dithers, it of course needs time to settle, and yes that periodic correction in the graph is the dithering. But it seems like, through the dithering, the guiding gets confused and sometimes can't settle in a reasonable time to start the next exposure. Now the max settling time I set to 50 seconds, which should be plenty, it doesn't seem to be enough though. sadly in this way I'm loosing so much time which I could use imaging. I could try a less aggressive dither though, that might help to resolve that issue as well. What confuses me the most is the times it just works flawlessly, I have periods of over 15 to half an hour without any issues and out of some reason it starts again. Anyway it really sounds like, you get what you pay for, and these are all the shortcomings of this rather cheap mount. I have the money together to upgrade to a new camera, the asi 2600 duo (since that's cheaper than the pro) but I also thought about maybe upgrading the mount to the zwo AM3 which would probably resolve a lot of the issues I'm having. But I feel like I'm chasing a tail here, by hoping new equipment won't have any problems, but since it's astrophotography that's probably not the case. Thank you again so much for your time to write such a in depth answer to my problem, I really love this community, just for that it's awesome to be an astrophotgrapher. |
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Hi Jens, I'm using the GTi with two scopes, a FMA230 and a 76EDPH, and same ZWO gears like you, except the guidescope. There is some points you should pay attention to : Calibration axis of the guiding camera : try to be lined up with the RA/DEC axis of the mount by turning the camera body in the miniguide scope. Blue and red lines from the calibration graph should be very close to the white axis lines of the mount. The more angle you have between calibration/mount axis, the more compensation will be needed in both direction. Look at the diagram in the guiding screen after calibration and correct it if needed. Add IR/UV-cut filter in front of the 120MM to improve star shape, Get the guiding star size between 2.0 and 4.0, peak between 100-200. And here are my other setting : Dithering every 3 frames is enough, 5 px max, stability 2'' or 3'', 3'' to settle, 90'' timeout, Calibration steps 1200ms, RA/DEC duration 500ms, Guiding rate 0.5x Aggr. settings depend on sky quality, but normally RA = 55-75%, DEC = 45-65% Regarding the guidescope, I found mine a very poor optical quality and switched for the SVbony 30/120. Cheaper and better to my opinion. With both setups, I'm having pretty good guiding, from 0.4 to 0.9 RMS, and "trow" away only 5-10% of my 300'' lights, especially right after meridian flip... I get sometimes 1.5 ''/px but that's fine because it's still under the image's resolution I have with the 76EDPH (2.2 ''/px) and the FMA230 (3.3 ''/px). Here is a sample of a 300'' taking with the FMA230 + ASI533MC Pro.  Tying the cables together will probably reduce vibration ;-) Hope my two cents will help. Christophe |
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Calibration axis of the guiding camera : try to be lined up with the RA/DEC axis of the mount by turning the camera body in the miniguide scope. Blue and red lines from the calibration graph should be very close to the white axis lines of the mount. The more angle you have between calibration/mount axis, the more compensation will be needed in both direction. Look at the diagram in the guiding screen after calibration and correct it if needed. The rotation of the guide cam inside the guide scope doesn’t matter. That’s why we calibrate it. The red and blue lines are just telling which way is which in relation to the image on screen. It would be a complete waste of time to do this. |
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Quinn Groessl:Calibration axis of the guiding camera : try to be lined up with the RA/DEC axis of the mount by turning the camera body in the miniguide scope. Blue and red lines from the calibration graph should be very close to the white axis lines of the mount. The more angle you have between calibration/mount axis, the more compensation will be needed in both direction. Look at the diagram in the guiding screen after calibration and correct it if needed. Trying to improve guiding accuracy isn't wasting time at all... Saying that, I've read several threads across the web explaining this feature and found itself pretty reliable for my setup. |
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| The walking noise is very much a known canon issue, so is banding. The Sony sensors used in almost every Astro camera are much more resistant to walking noise. That’s why many of us can get away with so little dithering. So either buying a new camera and dithering much less often or aggressively or upgrading your mount should solve the issue. I have no experience with the ZWO mounts but my EQ6R settles from a dither very fast and has no issues. My EQM-35 is a constant struggle with dither recovery due to DEC backlash, like your GTI. IMHO, an upgrade to a 2600 pro would vastly improve your imaging, likely more than the AM3 at this point. But that’s just an opinion. |
