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I can't find where to set the guiding to auto re-calibrate after the flip. I'm using NINA and PHD2 with an OnStep mount (WarpAstron WD-20). Assuming there is a setting and if so, is the setting in PHD2 or NINA and where specifically? Thanks!
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8.11
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You can force that by using the advanced sequencer in NINA and I believe the option is in PHD2. I am wondering though why you want to do this. You shouldn't have to just because of a meridian flip.
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2.39
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Tony Gondola: I have searched everywhere (except the correct location) in both NINA and PHD2, hence the 'where specifically'. In NINA sequencer, there is not an option that I can find to deal with this after the flip. There is the option to force calibration during the initial startup at Start Guiding. As to why, I'm not sure that I want to, but I want to try it. Others such as ASIair offer the option after flip. Several subs after the flip, the guiding has totally failed 2 nights in a row, that I have to shut everything associated down and start over. I'm told that calibrating at meridian is a must component for accurate guiding on the WD-20. After flip, it's looking at meridian, so... Yeah, I know. Sounds wonky and even PHD2 balks at it when I do it manually. That info came from the WarpAstron forum. |
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Yeah, that's weird. I use NINA with Green swamp Server to control the mount and of course PHD2 and it just works. In NINA if you want to force a calibration you have to be using the advanced sequencer, not legacy. In advanced it's available in the start guiding command. That instruction will give you the option to force calibration. |
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2.39
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I'm stuck with ASCOM hub on the OnStep platform. I use the Advanced Sequencer. NINA allows me to put 'Start Guiding' in the main 'Instructions' area of the sequencer, but doesn't allow me to put it in the 'Triggers' area. Probably because that would trigger a start guiding command after every image. Just a guess. The sequencer no longer operates on the 'Instructions' area after the initial startup, so it doesn't cover flip.
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8.79
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You want to do your guiding calibration close to 0 declination and the meridian, not at your target location (unless it happens to be close to 0 dec). When you state "several subs after the flip the guiding has totally failed", that implies the guiding worked for some X subs after the flip, but then fails. How does it fail? What does the PHD guide log show? Not sure if you've seen this post on CN, but it mentions something about AEB getting triggered. Might be worth checking out? WarpAstron WD20/OnStep- what am I doing wrong? - Mounts - Cloudy Nights |
0.00
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DavesView: *** in phd2 it's called meridian flip calibration tool, it's a wizard that will create two calibration s for both sides of the pier *** |
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Jonny Bravo: Looking at the subs, it looks as if the mount just stopped moving. Could be AEB freezing the mount. I have encountered that and had changed the setting from 2 to 5 several sessions ago. So is it correct that I should calibrate at meridian? |
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8.79
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DavesView: You should only have to calibrate once - at the beginning of the session. That calibration should be done at, or near, declination of 0 and close to the meridian. As @Jordan Morley mentioned, PHD2 has the meridian flip calibration tool, but it only determines whether you need to enable the "Reverse Dec output after flip" flag for your mount. If it looks like your mount isn't tracking after the flip, then definitely check out the AEB settings. I don't own a WD20, so not sure if there are some kind of limits set around the meridian (i.e. need to be more than 5 minutes). |
12.25
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You should not have to calibrate after the meridian.. I have not calibrated my guiding in nearly a month, despite my rig moving inside every morning after I use it… I do not rotate my camera/telescope/guide camera in the OAG at all… so provided my polar alignment is as close as possible to where it was last time, the calibration should remain the same (and it does) my guiding has not been above 0.6" RMS in all that time, and frequently as low as 0.35". I do not calibrate after flips either, and have never found the need to. My mount is the Emcan Astro EM31 Pro, which is also an OnStep mount - so you should find your WD20 to perform much the same. I would however look at your mounts meridian limits to ensure its not having some sort of issue with limits being hit. |
1.20
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Can I ask what is wrong with calibrating on Target ? I use EKOS on Mac and it defaults to calibrating on target, regardless of if I use the Ekos internal guider or PHD2. it seems to work just fine calibrating on target for me , and after meridian flip I normally reverse the Dec guiding direction. this is because I prefer to use one direction guiding, mainly to eliminate Dec backlash. |
6.06
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David Russell: Wrong is a strong word, but the issue is the DEC angle plus altitude. The accuracy of calibration measurement varies roughly as the sine of the DEC angle. So best at zero, at 30 degrees it's 50%, 14% at 60 degrees. So if your target is in the 0-30 degree range it's not bad to calibrate on target, but if your target is at 75 degrees -- not great. It may still calibrate, it doesn't necessarily give grossly wrong answers, but it is not as accurate. Altitude is also relevant. I typically start imaging when a target hits about 25 degrees altitude, so I want to calibrate even sooner. Calibrating at low altitude is significantly worse than at high altitude due to going through twice as much atmosphere (+/-). But all that said, PHD2's guiding algorithms are pretty robust, and adjust themselves, so if it calibrates in a "bad" location, it will not work quite as well, but it may not be awful in terms of results. But lots of really smart people who contributed to that program (I am not one) say it's best to calibrate high and near DEC zero, at least within (I think their recommendation is) 30 degrees. |
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6.06
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David Russell: Consider doing a couple things.... get your polar alignment a bit incorrect, like 3-4 arc minutes. Not awaful, and play with it depending on results. Set your DEC algorithm to 'resist switch'. Let it guide with DEC also. Having polar alignment a bit off causes (in particular) DEC drift, which means you will be chasing small DEC drift all the time, which means it won't need to do a DEC reversal which is when backlash appears. This way you get the general benefit of RA only guiding but it can still do a bit of DEC refinement if needed for whatever reason. Note you want the minimum PA error that allows it not to reverse much, too much and it's chasing it rather than just occasionally putting it back. This all presumes of course you have tried backlash compensation, and it didn't help. |
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Thank You Linwood. Great reply. I generally only image about an hour and 1/2 before and after meridian, so I guess I would be around the zero to 30% area. This might explain why the PHD2 calibration on target has been working successfully here for me. Thanks for the help. Dave |
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6.06
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David Russell: No, that's distance from meridian. The 30% suggestion is the DEC angle (look at the target RA/DEC), it doesn't change with time. You want the DEC angle to be -30 to +30, and the altitude to be somewhat high, like over 50 degrees or so. Depending on latitude this may mean you have to get a blend of the two if you are in very high latitude. |
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2.39
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Jonny Bravo:DavesView: Went through several mount limits. I calibrated the meridian and then calibrated guiding. After putting together all the info here and reading the recommended threads, I probably did have an AEB instance in both failures. I've set my AEB to be less aggressive. I'll have to do some searching and find the secret to recovering from AEB without having to power cycle the mount, then use the hand controller to get to home. I'll see if it works tonight. Thanks to everyone for taking a look. |
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Not sure if this covers your OnStep issue....Jordan said this above... This is from Openguididng.org: Meridian flip calibration ToolThe meridian flip calibration tool (wizard) is used to automatically determine the correct value for the setting Reverse Dec output after meridian flip. Running the wizard involves two calibrations -- one with the telescope on the East side of the pier, and one on the West. You will be instructed to slew (meridian flip) the telescope when needed. This only needs to be done once for each type of mount you use. You must carefully follow all the instructions shown in the wizard's dialogs - failing to do so or taking short-cuts will invalidate the results and will siimply waste time. I ran this after my guiding left the graph a couple of years ago after my first meridian flip. I have had no issues since. |
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One issue that causes the need to recalibrate is you have one of the ASI2600 Duo. The guider chip is next to the image chip. So when you rotate the camera the guide chip rotates also. Some what annoying.
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6.22
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I have done OAG and it does not require recalibration after the flip. Some mounts want the Reverse Dec after Flip enabled, other mountings do not. If your mounting messes up after the flip then toggle the Reverse of Dec Flip box to the other value in the PHD setup. Since every sensor on your rig is rotated 180 degrees after a meridian flip, the only thing that needs to be checked is Reverse of DEC output value in PHD2. Its on or off… BTW, if I need to run the calibration tool. I only run it one side of the meridian, not both…
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3.10
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Regards calibrating near Dec 0 or calibrating at the target declination. Assuming you have a mount connection via ASCOM, PHD2 has information on where the mount is pointed and can recalculate the RA versus Dec gude rates as you change declination. It will throw a warning if you try to calibrate too far from Dec 0 as any calibration errors may be multiplied when you change declination for a new target. Calibrating at your target dec will work perfectly well as long as you are at that declination, it can arguably be a better calibration but only for that declination. Calibrating near Dec 0 and retaining the cal while you point all over the sky is convenient but that is really the biggest advantage. Without a mount connection, PHD2 can't determine the declination to calculate the rates (I know it is getting to be a pretty rare thing to have a mount without an ASCOM connection to feed pointing information to PHD2) and in that case you have to calibrate at the target Dec anyway, target by target as well as pre and post meridian for most mounts. It has been pointed out in this thread, the purpose of the meridian flip assistant is purely to work out if you need to tick the "Reverse Dec" box for post meridian guiding. It is fairly easy to tell anyway. If you calibrate on one side of the meridian and it is guiding well then immediately post flip the star shoots off the screen faster and faster as the dec corrections get bigger and bigger, you almost certainly need to make that setting the opposite of whatever it is. |
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Blue: Well, I'll argue the other way. Calibration is about measurement, how far the mount moves the view at pulse guiding speed, and relative direction of the axes to guide star motion. Those measurements' accuracy is a basic trigonometry problem. It's not like polar alignment or something impacted by refraction (at least not to a degree that's relevant), so I argue there is no benefit in calibration near the target UNLESS your mount has such poor tracking that it behaves differently in different areas of the sky. So yes, I agree it's "arguable".  |
2.41
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With Asiair, you can activate an antomatic recalibration after meridian flip. My experience shows that it works fine. Asiair uses an adaptation of PHD2. As to guiding in general, Asiair sarts guding 10 seconds after taking the first image. So relaxing ! |
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Linwood Ferguson: I will perhaps re-word that differently. No matter what, there will be some errors in calibration (The same as in any other measurement) it is not to do with mount performance at different dec. The length of guide pulse required to move the sensor a given number of arc seconds in RA is shorter near dec 90 (Plus or minus, does not matter) than at dec 0. PHD2 calculates the correct length pulse to move a given distance based on the dec that you calibrated at, and the dec that you are currently at. If you calibrate well away from dec 0 and then move closer to 0, the dec pulse time is multiplied and so are any measurement errors. If you calibrate at the target dec there is no recalculation of the rate so no multiplication (Or division if you go up in dec) of the measurement error. As I wrote, the calibration can arguably be better at the target dec. You probably won't improve in guiding at higher declinations but if you were to calibrate around dec 20 either side then image right on dec 0, that would have the error multiplication effect to some degree. |
