Re: OK, First light worth sharing...
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Hi gang, I can understand why some people might be leery of using Gemini-calculated planet positions, and a Gemini GoTo, for making a Gemini sky model.?? Yet I also find that my own use of the small planets and deep sky objects works just fine for me, when using a PC based sky chart to send Gemini the coordinates of the object.?? So here are some thoughts on why it might be working well for me, but not for those using a Gemini alone.?? I am not using the Gemini-1 programmed planetary positions for the GoTo.? I am instead using Stellarium (see links below) as my PC based Sky Chart.?
Stellarium
"knows" its coordinates of each deep sky object very accurately.? ?I center that object/planet in Stellarium, then press the CTL-1 to issue the GoTo that position.? And that works just fine.? I center my object then press CTL-3 to Synch or press the Gemini.net Add Align Point to align Gemini to those coordinates.?? I am NOT using the built-in Gemini-1 list of deep sky objects alone.? I think the predicted object positions have be calculated from numerical models from some known earlier position and some time prediction equations.? The model parameters were entered many years ago ago, maybe over a decade ago, so the predictions might have some slight error today for fast moving planetary positions.?? The deep sky objects positions can be looked up, and would not change sky location over our lifetime as they are very far away.? But the Earth's polar axis position is always changing, so that stars like Polaris change their RA and DEC position over the years (also why the polar scope reticule Polaris position changes over they years too, so you need an updated reticule from time to time.)? ?Stellarium on the PC knows these object and planet positions very accurately. So I should revise my advice to say: if using a PC based sky chart, try choosing any star, or deep sky object, or planet in the sky chart, issuing a GoTo from the sky chart (sends the RA and DEC position to Gemini), then center that object/star with the Gemini and your camera or eyepiece, then issue Add Align Point to the Gemini.? Give it a try and see if your Model building becomes faster and easier. _______________________ Related issue for imaging small faint deep-sky objects with tight field-of-view systems: I find this issue when I have aligned my Gemini to nearby bright stars, then try to GoTo a very faint object for imaging, using PC based Stellarium to show where the mount is pointing: If I issue a GoTo, say to M1 Crab Nebula.? The mount will slew to M1 then stop... Gemini thinks it is done.? In my light polluted area, M1 is invisible.?? In my camera image using a 12 inch f/10 SCT, M1 usually will not be in the image.?? But on the PC, expanding the location shown by the Gemini, I can see that the Gemini shows the mount is slightly off of M1.?? Then I manually slew to dead center the "Scope" icon to the center of M1.?? In my camera image: M1 is usually dead centered in the image frame. So I think the Gemini knows very accurately where it is pointing.?? But somehow the Gemini has a "GoTo
tolerance" of some closeness to the object target and it is programmed to stop if the mount gets within that tolerance.?? If you are doing wide-angle shooting like with a refractor, you probably see the target well centered,? but with a very tight field of view like an SCT, you might not find the target in the image field (might be in a wide field eyepiece though!).?? Anyway, try my trick of manually centering the object using your sky chart... see if that solves the problem.?? Best of luck, Michael _____________ For those interested: ?Stellarium??also has add-ins (plug-ins) for asteroids, comets, eyepiece fields of view, camera image chip fields of view, so that you can really "see" what to expect in your camera or image.? It's all free and excellently done.? I am connecting the Gemini-1 using ASCOM, a 4 pin Gemini-1 serial port cable through a ATEN UC232A USB to Serial port device, and the Gemini.net software driver, and the separate program Stellarium-Scope provided freely by??? On Thu, Feb 13, 2020 at 11:58 AM Brian Valente <bvalente@...> wrote:
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Michael Herman