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David Whelan: All tails pointing at the center indicates a spacing or coma corrector issue. Unless of course you are not using a coma corrector, and then this is likely coma that you are seeing. |
3.01
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@jewzaam Maybe focuser sag. I've seen it with Esprit scopes before. Wouldn't this show as sensor tilt? I will take a look though. I am running the scope with the focuser rotated 180 degrees, so it's upside down. I'll see if there is any adjustment to tighten it up and see if I have clearance to rotate the focuser back to right side up. |
2.71
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@jewzaam Maybe focuser sag. I've seen it with Esprit scopes before. I missed when you noted that it happens regardless of where the scope is pointed, sorry. In that case I don't think it's sag, although when I saw it on an Esprit 100 the errors were across the frame. |
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3.01
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I missed when you noted that it happens regardless of where the scope is pointed, sorry. In that case I don't think it's sag, although when I saw it on an Esprit 100 the errors were across the frame. Fair enough, worth looking into! As far as I can tell the focuser is rock solid. And the Esprit 120 has a rail on the top (now on the bottom with my rotation) of the focuser. I will still give rotating things 180* a try, I believe I will have clearance with the EAF.. enough to make it work for a test at least. |
1.81
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I see thsi also from time to time with my 130 mm TS Triplet, almost sure this is due to bad seing or even maybe a thin layer of clouds. https://skyandtelescope.org/astronomy-equipment/beating-the-seeing/ |
1.20
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Hans Kelgtermans: You can see significant camera fan vibration issues by looking at satellite trails in your existing data. They will show wiggles instead of being straight. |
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3.01
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Richard Carande:Hans Kelgtermans: Not sure about the fan theory but there is something going on. Image with satellite in-line with the tails. I do not see wiggling.  But at 90* from this, cutting across the tails, I do see a wiggle.  Close up of one particular bit that happened to be brighter and I feel shows an obvious wiggle. It's near the top left of the field above.  Just to talk through it, would this be something the mount could introduce? My RA guiding is kind of meh but I would expect elongation side to side, not at a roughly 45* angle. Camera orientation is 90*, so long edge ("down" on all these images) is towards the mount. |
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1.20
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This wiggling is not as bad as I had a while back, but it does seem to be there. I think it's too fast to be the mount doing corrections, unless there is something vibrating on it. Here is the wiggling I was seeing, and some basic analysis. This gets worse with increased focal length. This was at 1960mm focal length. I didn't see it with the same camera at 650mm. |
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| Thinking more about my RA comment before, that makes no sense. Would see elongation left/right only if pointed at a celestial pole. If it's RA guiding then it would show up at an angle relative to the declination. Looking back at old data (almost 2 years) there are tails but less so. Orientation changes depending on the declination. And looking at older data where I have a meridian flip, the orientation of the tail is the same before and after flip. But I could be looking at a data set that isn't great. Will have to think about this some more and find something that can better show some correlation if it exists. |
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3.01
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Richard Carande: Wow, that's quite interesting and clearly periodic. Thank you. From what I see it's not uniform which _could_ maybe be the mount. But given the star tails show up in very short exposures when not guiding it's an unrelated problem. I've been reviewing some data with a C8 with 0.63x reducer/flattener and I do not see same star tails and I don't see any periodic wobbles to satellite trails in any direction across the field. The C8 is on the same mount and I've been using the same camera as on the Esprit 120. |
