michael8554
Members-
Posts
4,992 -
Joined
-
Last visited
Content Type
Profiles
Forums
Gallery
Events
Blogs
Everything posted by michael8554
-
What's wrong with my telescope?
michael8554 replied to StuartT's topic in Getting Started With Imaging
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 -
What's wrong with my telescope?
michael8554 replied to StuartT's topic in Getting Started With Imaging
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.
-
Odd star shape.
michael8554 replied to Perrywarburton's topic in Getting Started Equipment Help and Advice
Okay, I already got the message 😆 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
-
Odd star shape.
michael8554 replied to Perrywarburton's topic in Getting Started Equipment Help and Advice
Well if Reid say the optics aren't pinched, and 106mm is the right spacing. Then who am I to contradict them........... 😆 Michael -
Odd star shape.
michael8554 replied to Perrywarburton's topic in Getting Started Equipment Help and Advice
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
-
Help understanding Celestron Cassergrains
michael8554 replied to bluesilver's topic in Discussions - Scopes / Whole setups
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 -
Odd star shape.
michael8554 replied to Perrywarburton's topic in Getting Started Equipment Help and Advice
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
-
Predicting uninterrupted clear skies 1800 to 0500. Looked out at 19:45. 100% Clouds....... Michael