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Showing results for tags 'platesolving'.
Found 5 results
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Celestron's EdgeHD product line features an integrated field flattener. As with all flatteners, these produce optimal results when the imaging plane is a specific distance from the flattener. In the EdgeHD whitepaper Celestron describe the optimal backfocus of 133.35mm (5.25") for the 8" model, and 146.05 (5.75") for the 9.25", 11" and 14" models. They suggest that the image plane should be placed within 0.5mm of this distance. When putting together an imaging train it can be quite hard to determine the actual backfocus. You could add together all the optical lengths quoted by manufacturers, you could get calipers and actually measure each part or even try to measure the entire thing (although it can be quite hard to figure out where to measure from. At some point, you have to trust some manufacturer spec (unless you fancy risking your sensor). Once all this is done you might, however, find that things vary ever so slightly; everything from the tightness of threads to the T-ring not quite giving exactly 55mm. How do you work out if you've done it all correctly? In a table in the whitepaper (page 13), focal lengths are given for each OTA (for example 2125mm for the 8" model). Hypothetically then, it should be possible to measure whether or not you're at optimal backfocus by plate solving for your image scale. In the same table, an image scale is given for a sensor with pixel size 6.4 micron but you can use a calculator (such at the astronomy.tools one) to work out the expected image scale for your particular sensor. This does require that your image is as close to perfect focus as possible. Putting all this into practice. I used my calipers to try to get the image train as close to 133.35mm as I could and then plate solved some resulting data taken with a DSLR with 5 micron pixels. From my calculations, if I'm in focus at the correct spacing, I should have an image scale of 0.485"/pixel. However, my astrometry.net solves gave an image scale of 0.495"/pixel. Working backwards, this indicates that I was at a focal length of 2083mm, quite a way inside 2125mm. Although I can't find a reference I've read that, for an SCT, the focal length changes by approximately 3mm for each 1mm of backfocus, this implies that my sensor is 14mm too close! Now, I'm no expert with calipers but I feel like I couldn't have been more than a few mm out, and if anything I thought I was too far. I suppose I could have been a bit out of focus but surely not ~10mm. Is there a mistake in my logic of aiming for 2125mm focal length? -
The other night, I got a rather weird thing happen using Sharpcap. In live-stacking, the first image arrived and it was full of stars. So, without changing any settings, I did a "platesolve" (which also realigns the scope) to centralise my target. It did its single frame capture and I got a practically blank screen and a message saying it could only detect 3 stars. I tried reducing the "sigma" setting, as advised by the on-screen message, with little effect. What gets me is that the same settings produced a whole mass of stars in each of the subs that were being live-stacked. Never had this happen to me before, and no, of course I didn't do anything intelligent like saving the log file! I can always try to replicate this next time (although I always find trying to replicate something that isn't working to be a weird activity in itself!), but on the off-chance that anyone can see what was happening without the log file, I thought I would ask. Thanks. -
I have been very busy beavering away in my new obsy so I haven't had much time to come onto to Stargazers Lounge, but when I need help I know somebody on SGL has already encountered the same problems so I'm hoping to be helped with an Idiot's guide to Astrotortilla. I don't think it's the setup as I have downloaded all of the index files I need to run it, I also have setup my camera/telescope combination and everything is running okay - except it won't platesolve. I even gave it a photo of M51, used telescope simulator and even upped the search area to 180deg - still nothing. Can anybody help me -
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I don't have a goto mount and I wondered if there was just a simple way of showing where the scope is pointing on (for example) stellarium or kstars. I try and star hop to where I want to go and in the depths of the garden (or remote) I don't have any wifi to run nova.astrometry. so Im looking for a platesolving app that can run standalone on a windows laptop. Usually I get to where I want to see, but sometimes I just get lost so Im looking for something that will help confirm or show where I have ended up so that I can manually adjust the scope to get where I want. A typical use case would be.... Locate bright star near target. Check collimation of camera, finder, telephoto (with dslr or gpcam + startcap) Move/starhop to target. … check whats supposed to be in the finder … mhh its not there. -- reverse steps and try again. … mhh its still not there check Im at the right start, double check target position and and try again … mmmh still not there Then what I want to do is * take a photo and platesolve to find out where Im actually looking at this time * correct manually using slow mo or some more star hopping * hopefully get to the target, and enjoy the view. Ive tried loading up 'all sky platesolver' which I can get to solve and give me location RA and DEC, but then I cant see how to get that location just to show on a star map. Also I cant get any images to show on the screen from allskyplatesolver (although it says it should - image get not-found type error) I don't really care what star map I use. I don't really want to start copying and pasting ra and dec into scripts at 3am. The details of the platesolving apps seem to be mainly focussed on driving a mount to a location, whereas I just want to confirm where I've ended up pointing on a map so I can do the correction myself. Any help please ? PS - I might be trying to do this at 3am in a grassy field with the laptop balanced on an upturned crate whilst doing this ? -
I had wanted to get plate solving working in APT , after getting a bit puzzled by it downloading both plate solving applications ASPS -all sky plate solver and platesolver2, finally deleted PS2 and managed to configure ASPS and solve an image posted on APT forum ,so in theory this is ready to use within APT ,i found this article on APT forum which you may find useful if you fancy giving it a try http://astropetros.eu/wp/?p=669 just tried solving an image i had ,didn`t have correct path for ASPS so sorted that ,retried and success it solved .
