TPoint vs. APPM -- Translation Possible?
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mjb87
I use APPM with great results on my Mach2 with the 130mm refractor. I have been unable, after a year of effort, to build a APPM model on my 1100 with the 300mm f/15 Cassegrain. The FOV and the pixel size is just too small to get plate-solving to work reliably. Yes, I've tried focal reducers, different databases, different cameras, etc., etc. When I do get solutions they don't make sense,e.g., 7 degree orthogonality difference whereas ConeSharp says it is about 10 arc-minutes.
I can easily build a TPoint model using TSX for that setup by visually aligning the stars selected. Took me 40 minutes last night to build a 24-point model. However, that locks me into using TSX, with the tracking/pointing in APCC turned off. There are time I may want to taker TSX out of the loop. Note: I am looking primarily for pointing accuracy as opposed to tracking accuracy with this setup since I do not do long-duration unguided imaging. It is mainly planetary and visual work. So the question: is there any way to translate the TPoint results into an APPM model? I suspect not, but had to ask. Alternatively, is there any way to to manual star alignments in APPM instead of using plate-solving? Thanks, Marty |
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George
T-point cannot provide dual-axis tracking with AP mounts…only APCC can do that.
Regards,
George
George Whitney Astro-Physics, Inc. Phone: 815-222-6538 (direct line) Phone: 815-282-1513 (office) Email: george@...
From: main@ap-gto.groups.io <main@ap-gto.groups.io>
On Behalf Of mjb87 via groups.io
Sent: Tuesday, November 2, 2021 8:28 AM To: main@ap-gto.groups.io Subject: [ap-gto] TPoint vs. APPM -- Translation Possible?
I use APPM with great results on my Mach2 with the 130mm refractor. I have been unable, after a year of effort, to build a APPM model on my 1100 with the 300mm f/15 Cassegrain. The FOV and the pixel size is just too small to get plate-solving
to work reliably. Yes, I've tried focal reducers, different databases, different cameras, etc., etc. When I do get solutions they don't make sense,e.g., 7 degree orthogonality difference whereas ConeSharp says it is about 10 arc-minutes. |
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Ray Gralak
Hi Marty,
So the question: is there any way to translate the TPoint results into an APPM model? I suspect not, but hadUnfortunately, there is not a TPoint translator nor a way to manually select stars at this time. What is the field of view of your setup and pixel dimensions of the sensor? -Ray |
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mjb87
I've tried four cameras, all coupled to a focal reducer. I've tried binning from 1x1 to 3x3.
Sensor data (microns and arcminutes): Sensor 1: Pixel = 5.9 and FOV = 1.4x0.9; unbinned image scale = 0.40 (Mono) Sensor 2: Pixel = 3.8 and FOV = 3.5x2.6; unbinned image scale = 0.26 (OSC) Sensor 3: Pixel = 3.8 and FOV = 4.7x3.1; unbinned image scale = 0.26 (OSC) Sensor 4: Pixel = 2.4 and FOV = 2.3x1.6; unbinned image scale = 0.16 (OSC) I am targeting scale at about 0.9 to 2.1 and binning appropriately. However, my seeing isn't great and I'm probably at 1.5 arcsec FWHM. I can easily manually align a star (e.g., using TPoint) and I can do lucky imaging but I'm having a problem with platesolving. Again -- my primary concern is pointing, not unquided tracking, so the dual-axis tracking is a "nice to have" for this installation. I'm mainly interested in pointing accuracy. |
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Ray Gralak
Hi Marty,
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Since you mention TPoint, does that mean you have SkyX? If so, have you tried plate-solving any of your images with SkyX's image link? If needed, there is a much deeper stellar database available: https://www.bisque.com/product/theskyx-pro-database-add-on/ -Ray -----Original Message----- |
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mjb87
Hi Ray... I have not tried the automatic TPoint modeling methodology yet.
To my uneducated eyes, it seems the problem is that the platesolving routines, given the very low FoV, cannot identify enough stars above the underlying noise caused by mediocre seeing. So I get failed solutions or erroneous solutions. Not sure denser data is the solution. Marty |
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Ray Gralak
Marty,
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Can you expose a little longer, say 10 seconds, to get a deeper image? -Ray -----Original Message----- |
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mjb87
i'll give that a try. May be a week or two before I can.
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