michael8554

Examine the belts for damage, if you fitted them. There are strategies for guiding with backlash. RA can be slightly unbalanced east heavy to take up the backlash. A PA Error will cause Dec to drift either north or south, gentle guiding in the opposite direction can keep Dec at one end of the backlash. If you get PHD2 to Calibrate, following the instructions to clear backlash first, you can run the PHD2 Guide Assistant for a worm period. That will show how the RA worm drive is behaving. Michael

Hi Daz The ST102 has 500mm FL, so the ASI183MC sensor has to be 500mm from the objective lenses. The ASI 183MC has 17.5mm Flange Distance. 500 - 17.5 = 482.5mm Take off the diagonal and put the focuser in mid range. Roughly measure 482mm from the scope objective. That's where the end of the camera's M42 flange needs to be. Measure from there back to the end of the focuser. That's how much spacer you need. Buy the nearest stock spacer, the focuser will take up the difference. Michael

Putting collimation to one side for the moment, look at the star shapes of an in-focus image. Progressively more teardrop-shaped stars toward the edges of the frame are a sign of coma, inherent in the basic SCT design. Michael

I'd say that's due to coma, which is not unusual for an uncorrected SCT. Michael

Yes I did notice that the ZWO ASI 224MC has a tiny 1/3" sensor, so maybe tilt won't be an issue. Michael

Hi Ian From what I understand, the 2" Optical Back can be unscrewed from the end of the focuser, revealing a M48 thread. The ZWO ASI 224MC has M42 threads. So you need a suitable length Female M48 to Male M48 extension, plus a Female M48 to Male M42 adapter at the camera end.

Okay, I already got the message 😆 Michael

Yes in Alt, but not necessarily in Dec - which do you mean ? Dec 45d pointing south would be 85d above horizontal. Dec 45d pointing north would be almost horizontal. Michael

Envious, edge-on Galaxies with my 8" SCT are just white streaks. Michael

Have you got the order wrong ? Image 3, Polaris, is pointing roughly 20 degrees above horizontal, but Polaris is currently roughly 50 degrees above the horizon when pointing north. However Image 2, 5degrees, is pointing 50 degrees above horizontal. Image 1 isn't pointing north or south so impossible to tell if it's pointing anywhere near 45 degrees. Those were Dec not Alt figures ? Michael

Well if Reid say the optics aren't pinched, and 106mm is the right spacing. Then who am I to contradict them........... 😆 Michael

Centre of image seems okay, apart from the hint of diffraction spikes. Edges show coma, needs more spacing. Michael

Okay, thanks to whomever said it first ! Michael

Gorann to the rescue ! I hadn't registerd that the RA and Dec deviations were smaller than the 1.6arcsec/pixel image scale. Now I know 😆 Michael

Nicholas's analysis is compelling. But it makes no sense to me, if RA is deviating twice as much as Dec, that the stars can be round. Is DSS (or whatever) only stacking the subs with round stars ? Michael

There is a degree of coma, but centre is elongated too, so primary problem is guiding. RA error is twice that of Dec, which means elongated stars. Michael

Sorry Tony, If it's not the setting in the mount menus, then I guess it's in NINA, which I know zero about. Michael

I'm with you now. You want something like DitherMaster or PHD2Max, that tells PHD2 to Dither when it detects an image being downloaded into a named folder in your PC. Michael

Hi Tony Doesn't matter how big or small your Total Guide Error is if RA and Dec figures are very different. Your PHD2 screenshot shows RA = 0.79arcsecs, Dec = 0.37arcsecs. So RA error is twice that of Dec . That means elongated stars. The elongation in the NINA shots hopefully suggest that the imaging camera is rotated 90 degrees, so that RA is up/down ? Also the guide rate is only 1.5arcsec/sec due to Guide Speed being set to only 0.10x, as shown in the Review Calibration shot. Needs to be at least 7.5arcsec/sec. Michael

Maybe I'm confused by the description of the problem. Guide with PHD2 and the Lodestar. Dither PHD2 with Maxim. Capture images with Altair Capture. You don't Dither the Altair 294C Pro, you Dither the mount. Michael

1. I see that they have their own knob type focuser on them that i am guessing adjusts the primary mirror to get focus? Yes But by doing this, wouldn't it always be putting the scope out of collimation? Maybe, if your OTA has a lot of mirror flop. 2. By adding a Crayford focuser, would this only be for very minor adjustments? Yes 3. There is talk of mirror flop as the scope moves around, I take that is why the scope apparently get shipped with the mirror locked down with bolts? So are they designed to say collimate or focus on a star, then re install the bolts to stop the mirror moving? The mirror is locked during shipping to prevent the heavy primary mirror coming free of the somewhat lightweight focusing arrangement during the usual rough handling. If you were imaging with just one setup, ideally you'd collimate and lock the mirror, and from then on only use the Crayford, to make fine focus. Visual use involves changes of eyepieces which may not all focus with the limited Crayford range. Michael

With no Dec drive your PA needs to be very good for long exposures. And RA may well be suffering from Periodic Error. Michael

There seems to be a hint of diffraction spikes ? But a screengrab is not good enough, post a jpg of one sub. What exposure was that ? To judge star shape, eliminate guide errors by taking a short exposure, stretched if necessary. Guiding at 0.19 Total is no help either. If RA and Dec errors are very different then you will have elongated stars. What camera ? Any filters ? OAG or guidescope ? Michael

22:46, no change, still "clear to 05:00" Many years ago I was working at Television Centre, in a windowless environment. We'd surface for an evening meal in the airy canteen. The weatherman appeared, he'd just recorded the late night weather report. He looked out of the windows, put down his tray, and headed back downstairs. It was snowing outside.......... Michael

21:46, still "clear", still 100% cloud Michael