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So been looking into the ZWO EAF running with an ASIAIR, Do you need to set a backlash value while running it with the ASIAIR, some people say yes some say no? If so how do you know what number to enter e.g Z73 Scope? Thanks Chris |
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No need to set the value.
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I've used the ZWO EAF with a ASIAIR for about 18 months. I've never set a backlash and it works just fine…
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I will be the 3rd. I never set a backlash.
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I set the backlash for it just so that when I am taking flats, if the EAF went to zero and I need to go back manually to the right focus without access to stars, I am relatively confident that it will go back to the right position. They say you don't need a proper backlash to get AF routine right. But I find that odd because the EAF performs autofocus in two stages. The first stage it runs through the different focal positions and creates a curve to roughly predict where the best focus is, and then it rewinds the focus back close to the trough of the curve and does fine advances depending on where it is on the curve. I would imaging that rewind motion would have been affected by backlash. Perhaps because it will have a forward then a backward back lash, it will cancel out even on the second run. |
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I've never set the backlash and have yet to see any issues with doing it this way, flats also seem fine. I never set the EAF back to zero though, I leave everything as is between sessions. I suppose the EAF/AA+ combo is smart enough to bypass the need for backlash adjustment as it acts on readings from the exposures it takes, not just relying on simple movements of the focuser. So I don't really see how backlash would be relevant for the end result, as I would assume it would fine tune until the desired readings are met. I'm not that into the whole "how it functions" tech wise, but at least that's what I've believed so far, I might be wrong though. |
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I'm not going to say you do or don't have to, but it's so easy to do there's no reason not to. Run the focus in or out a couple turns in coarse adjust mode, which ever one. I'm going to assume you went in first. Then set the adjustment for the fine step to something like 5. In fine adjust, tap it, and count how many times you need tap it to see the focuser move. Let's just say you had to tap it 4 times. 4 times with the fine step set to 5, means you put 20 in for the backlash. (step size x steps to move focuser) = backlash It literally takes a minute to do, and it's not like you're going to be disconnecting the EAF from the telescope every night. |
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You might be fine without setting a backlash, but that doesn't mean there's no backlash. On the EAF, if you run the focuser in one direction, then reverse directions and watch the number of steps until the focuser actually engages and moves (the collar set screw is a good indicator of motion), you'll likely notice that your EAF has between 80 - 100 counts of backlash. Do this in both directions, and average the value you get each way. I paid no attention to backlash until I tested and found my EAF has what others had posted….about 90 counts. So, again, you can probably get by without, but if you want it to be correct, you can easily test the backlash yourself and set it. Good luck & CS, Doug S.
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I am not an ASI AIR user, but I assume by the comments given, that ASI AIR does not support backlash overshoot? I use backlash overshoot with my EAF in N.I.N.A. and it works flawlessly. If ASI AIR doesn’t support backlash overshoot, they should! Jim |
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Chris Addison: *** I suspect every ZWO EAF has some backlash so you really should measure it and input a backlash value. *** |
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I had to set the backlash value. ASIair was unable to find focus without it. It's easy to set up, takes 2 minutes. My value is 40 for example.
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Hi, I have set backlash on my EAF. It's better if you use AsiAir, but not only. This is the link to the EAF manual in which you can find the correct backlash setting method. EAF_Manual_EN_V2.4.pdf (zwoastro.com) |
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When I used the EAF first with Astroberry (EKOS-based, like Stellarmate) I measured and entered a backlash value of 31 which worked pretty well (I used the pencil & elastic band method). When I switched to the ASIAIR, my value of 31 was already automatically entered into the config. I didn't enter it, I have no idea how it got there unless the ASIAIR somehow measured it when I did my first autofocus, or if there is some onboard memory on the EAF that retained my backlash value between devices in the same way that we are able to upload firmware. The two-step autofocus makes a lot of sense, though - run through enough positions to create the curve, clear the backlash and advance until it meets the bottom of the curve. Works a lot better on the ASIAIR than it did on the Astroberry… |