Chris,
You’re getting a lot of good advice here but have you been able to tell if this ‘excursion’ is tied directly to either RA directional motion or Dec motion of the mount?
I have an AM5 (new to me) and the chart of PEC that came with it was not all that impressive it seemed. Is it possible that your main camera exposure lengths are long enough that there is now exposure to some kind of hiccup in the PE scheme?
The fact that it’s on one side of the pier only is strange but does (weakly) point to an issue with balance or tension on the mount on that side where a ‘rough spot’ might be getting exposed and have more effect than it should have. Are you using the counterweight? It’s hard to assess actual balance on these things because you can get them to swing freely like a worm gear style EQ mount. Maybe just changing the balance point would have an effect.
Also I don’t know how to myself but there are people aroound that (very generously) will look at your PHD2 guiding logs and analyze them for you and that would be good information as well.
Tough problem, I feel for you…
Bill
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I still convinced itsl is not tracking error.
i would be very curious to see if you get this star shape without the reducer.
It look more like an optical issue to me.
When your scope is in meridian flip position, any chance something could be creeping in fron of the optic (let say a cable ?)
It truly look like sometype of aberration.
rratid a WO optic that gave me wierd stars in given position because the optic would "deform" or "move" on their own weight…
Also WO have some crappy reducer that would induce bloating.
Anyway just my 2 cents, im far from being a expert. But like I say I doubt it is mount releated
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Esa Viitala:
Do you use a Pier Extension (like the PE-200)? Previously, I had some worse elongated stars when using my Askar 120APO just before the meridian flip. I never seen it at the time but my suspicion was that the scope (or something on the scope) was touching the tripod. I now have the extension pier and no issue around the MF anymore.
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Esa Viitala:
What is the clearance between your camera/cables/EAF thermometer probe/or whatever else might be hanging down from the lower end of your telescope just before the meridian? If one of these starts touching the tripod, it can cause all kinds of interference with tracking and guiding. This woud be more so just before the meridian than after because afterwards the tension is getting less and less whereas on the opposite side it gets worse.
Do you use a Pier Extension (like the PE-200)?
Also the nubbins are all reddish (the other part of a star is bluish), which is a sign of chromatic aberration, and then maybe the proximity to the meridian plays some role in causing the reddish "nubbins" to appear.
I'm just guessing here. So my 2 cents. Thanks to all for the responses…I’m going to check out the scope when it’s near Meridian…while I thought my cables were decent…I have one that occasionally snags on some of the AM5s knobs…I do have the pier extension. having said that…all of these comments are making me wonder if it’s not that one cable…will check and report back.
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Chris:
Esa Viitala:
What is the clearance between your camera/cables/EAF thermometer probe/or whatever else might be hanging down from the lower end of your telescope just before the meridian? If one of these starts touching the tripod, it can cause all kinds of interference with tracking and guiding. This woud be more so just before the meridian than after because afterwards the tension is getting less and less whereas on the opposite side it gets worse.
Do you use a Pier Extension (like the PE-200)?
Also the nubbins are all reddish (the other part of a star is bluish), which is a sign of chromatic aberration, and then maybe the proximity to the meridian plays some role in causing the reddish "nubbins" to appear.
I'm just guessing here. So my 2 cents.
Thanks to all for the responses…I’m going to check out the scope when it’s near Meridian…while I thought my cables were decent…I have one that occasionally snags on some of the AM5s knobs…I do have the pier extension.
having said that…all of these comments are making me wonder if it’s not that one cable…will check and report back. In my scenario, one cable was hanging in a strange way, new the meridian, that was, in my scenario enough. I completely rearranged my cabling, moving it closer to the center of my mount and then strapping the cables on to the scope, so nothing would be hanging or dangling in strange ways 🥴
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Chris:
Guiding with 2 second exposures. Try with 0.5sec if you can. That works best. I'm usually around 0.3-0.4 total RMS with 0.5sec exposures on FRA500 with reducer and off-axis guider. Check this thread out.
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Certainly looks like a snag/dragging cable to me… The only other thing I would be pretty confident to blame would be differential flexture between the guider and the imaging scope. I have seen VERY similar behavior from my old rig, and I discovered that the focuser in the guide scope had a little bit of wobble in it. I locked it down really tight, that wobble went away, and so did my guiding issues.
I would be surprised if it turns out to be anything other than cabling issues, or differential flexture, purely because of how the issue is manifesting only near, and predominantly before meridian flip… It seems VERY unusual that you'd see this sort of behavior without there being some sort of tension on something from a cable dragging or snagging somewhere, or the guider having a bit of movement that is exacerbated by the telescope pointing straight upwards…
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Here: DEC & AR aggr 40% exposure 1.5s calibration step 500ms focal lenght 1624 mm (RC8) with OAG (ASI174mm)  |
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Alex Nicholas:
Certainly looks like a snag/dragging cable to me... The only other thing I would be pretty confident to blame would be differential flexture between the guider and the imaging scope. I have seen VERY similar behavior from my old rig, and I discovered that the focuser in the guide scope had a little bit of wobble in it. I locked it down really tight, that wobble went away, and so did my guiding issues.
I would be surprised if it turns out to be anything other than cabling issues, or differential flexture, purely because of how the issue is manifesting only near, and predominantly before meridian flip... It seems VERY unusual that you'd see this sort of behavior without there being some sort of tension on something from a cable dragging or snagging somewhere, or the guider having a bit of movement that is exacerbated by the telescope pointing straight upwards... Alright now this may be more of a culprit…was uncertain what flexture was until your detailed post (thabk you). I have noticed a slight wobble in the guide camera in the ORION 60mm…now you’ve got me wondering if this isn’t it. the problem I have believing it’s cabling is that the error will manifest for a few subs then go away then come back again…all before the flip. Given the slight movement of the mount while tracking I’m struggling to see how cabling would cause an on/off/on issue for the subs pre flip. (NOTE: that said I did tighten up the one cable in question just to be sure) for my next outing: tighter cable organization 1s exposures on the guide cam (or less) Ensure guide cam is tight in guide scope
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Chris:
Hi All,
I've been imaging for a year now and noticed a weird tracking error on most nights...usually before the Meridian flip.
It self corrects either frame to frame or sometimes after a few frames. It manifests as a small nodule, nubbin or bubble next to the imaged stars...tried to take a pic of it below (sorry for the bad iPhone picture).
AM5 tracking error?
I've been deleting these frames but was curious if it was correctable.
Mount AM5
Cam 2600MC
Guide scope Orion 60mm
Guide cam: ZWO 224
 I have the same error! I tried an EQ8 and the AM5n and the control is ASIAIR, and I have the same error!
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I have the same error! I tried an EQ8 and the AM5n and the control is ASIAIR, and I have the same error!
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I have the same error! I tried an EQ8 and the AM5n and the control is ASIAIR, and I have the same error! Pre Meridian flip only? How many subs (roughly) per session are you experiencing it? Couple nights ago I lost about 10-12 pre flip
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Chris:
I have the same error! I tried an EQ8 and the AM5n and the control is ASIAIR, and I have the same error!
Pre Meridian flip only? How many subs (roughly) per session are you experiencing it? Couple nights ago I lost about 10-12 pre flip
befor Flip
After Flip:
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I have the same error! I tried an EQ8 and the AM5n and the control is ASIAIR, and I have the same error! Probably some bug in how the air decides to pause shooting, wait for the meridian, then flip. I've encountered other weird bugs during flips. Last one I saw was guiding wasn't stopped and I happened to look as the telescope began to slew while still taking guide exposures. I kept trying different flip settings til all that stopped. Currently at 1 minute before and 1 minute after. Not seeing issues.
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Looks a lot like starting the image before the guiding is settled.
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I have the same error! I tried an EQ8 and the AM5n and the control is ASIAIR, and I have the same error!
Probably some bug in how the air decides to pause shooting, wait for the meridian, then flip. I've encountered other weird bugs during flips. Last one I saw was guiding wasn't stopped and I happened to look as the telescope began to slew while still taking guide exposures.
I kept trying different flip settings til all that stopped. Currently at 1 minute before and 1 minute after. Not seeing issues.
Appreciate the comment but at least in my instance the bug happens an hour or two pre flip...its not just butting right up against the ASIAIR's plans steps of stop shooting X mins out...wait...flip...settle etc.
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Kevin Morefield:
Looks a lot like starting the image before the guiding is settled. Hmm...possible. Will see if my three changes (lowering guide exposures, tighter cabling and minimizing scope flexure) have any effect on tonight's test!
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Chris:
Kevin Morefield:
Looks a lot like starting the image before the guiding is settled.
Hmm...possible.
Will see if my three changes (lowering guide exposures, tighter cabling and minimizing scope flexure) have any effect on tonight's test! I would first look at how guider settling is defined and what your guider and imager to see if it is still centering the star when the exposure begins.
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Chris:
I have the same error! I tried an EQ8 and the AM5n and the control is ASIAIR, and I have the same error!
Pre Meridian flip only? How many subs (roughly) per session are you experiencing it? Couple nights ago I lost about 10-12 pre flip
befor Flip
After Flip:
Interesting...yours are manifesting the opposite side of mine...but also appear to correct after the flip.
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I've seen this on a few AM5 mounts… I work in support for Telescopes Canada. Take a look at your guide logs and see if you notice a periodic blip… a blip every couple of minutes won't affect your rms but it can definitely affect your images.
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I was going to say that looks like exposures starting before settling after a dither. Are you dithering? If so, watch to make certain the image doesn't start too soon. Also, I finally started using a counterweight with my AM5, and it's overall behavior has improved.
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Kevin Galka:
I've seen this on a few AM5 mounts... I work in support for Telescopes Canada. Take a look at your guide logs and see if you notice a periodic blip... a blip every couple of minutes won't affect your rms but it can definitely affect your images. Good to know thank you and will do!
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Andrew Fryhover:
I was going to say that looks like exposures starting before settling after a dither. Are you dithering? If so, watch to make certain the image doesn't start too soon. Also, I finally started using a counterweight with my AM5, and its overall behavior has improved. Excellent suggestion...will look to see if I can change the dither rate in the ASI Air
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I have something similar, only since the latest ASIAir update. I think mine is actually dithering during the exposure once every 5-10 minutes. If it dithers in the middle of exposure time I get double stars. If it happens toward the end of the exposure, I get shapes like yours. It doesn’t matter if I have dithering set on or off.
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Hi, I have not been through all the thread but I share my experience.
I have an AM5 without counterweight carrying a TS CFAPO 90F6 and a guiding scope SW EV0guide50.
In my opinion if you have a good guiding log (PHD2 log viewer), a stable one, without jerky period, the only reason why you could get some elliptic stars is differential flexure.
Differential flexure can be assessed with a simple method: you setup your scope, polar aligned, and you choose a target. Once you are tracking and guiding properly you capture some pictures from you camera and from your guiding camera (easy with PHD2), then you slew in RA only the equivalent of 30mn to 1H (7.5 to 15°) you capture both from the main camera and from the guiding camera and you repeat 2 to 3 times.
Then you platesolve the images you captured and you plot in an excel file the result and you compute the angular distance between images between main and guiding cameras. You will see if the angular distance moves as you imitate the tracking of your setup across several hours. If there is some you can computre what will be the effect on a capture of 3, 4, 5mn according to your main camera exposure time.
On the other hand, if you have only a few frames showing this kind of stars from time to time, or just after the meridian (I had it) it is a question of transient effect, some wind burst, some settling time after meridian. And you most probably have to live with it.
Hope this helps, Frédéric
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