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larryh

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About larryh

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    Marriottsville, MD
  1. Robin, you're a genius! I finally had success with polar alignment last night. With my images sized to 640x480 it worked quite nicely and had no problem with solving. It is a terrific capability. I apologize that you were actually troubleshooting my setup rather than any issue with your software. Thanks again for all your help. -Larry
  2. Yes, I just checked (indoors, not through the scope yet) and I can select a 640x480 resolution instead of 720x480 in Sharpcap and the image changes shape as desired. I will test polar alignment again next time I'm out. I have very high hopes! The embarrassing thing is that I've been recording images with a bad aspect ratio all this time. I'm wondering if this might also improve the "roundness" of my stars. I'll find out soon. Thanks for all your help Robin!
  3. A little more info...the specs on my chip are that it has a pixel size of 5x7.4 um and a resolution of 976x494, therefore an aspect ratio of 4880x3655.6 which is very close to 4:3 (I guess standard NTSC format?). If I am indeed using the framegrabber to convert that to 720x480 (will check tonight), that is a 3:2 aspect ratio and so would distort the frame as you said (not tall enough, or too wide depending on how you want to look at it). It looks like it should be more like 720x540 or 800x600. I do recall that there were other choices for the framegrabber resolution but I don't remember what they were (not sure how I ended up picking 720x480). I will report back when I know more.
  4. Robin, Thanks for the research. I did realize that my pixels were not square, but I thought that the image was still proportionally correct. But now I'm scratching my head as to how that could be so. Perhaps when the analog signal is created in the camera the non-square pixels are taken into account to produce a proportionally correct image. I'll have to check next time I'm out, but I think my framegrabber makes a 720x480 image from the analog signal. If the image is not proportionally correct, then why would the Astrometry site be able to solve? There is a parameter on that site that allows for star misalignment that I've been setting at 5 pixels, but that's quite a bit less than the 9% adjustment you needed to make. Does your solution match the Astrometry solution when you get it to work? Anyway, I will look into what my options are in the frame grabber. thanks, Larry
  5. Robin, here's a couple more examples taken last night. These are raw frames from video. Sharpcap seemed to be finding a reasonable number of stars, usually more than 10, but could not solve. http://nova.astrometry.net/status/1202593 http://nova.astrometry.net/status/1202595
  6. Robin, I found the astrometry site very interesting. I didn't realize something like that was available. I've played around with my images some and I've gotten a solution off of that site with a modified image. Here are two examples of ones that it was able to solve. The key, as you said, was mainly reducing noise. It did not seem to be affected by the hot pixels. For both solutions I restricted the parameters to 20-60' FOV, RA 24hr, Dec 90 radius 5 deg and 5 pixels star movement. Solution page: http://nova.astrometry.net/status/1196556 I also tried reducing a frame to black and white. It seemed easier to adjust levels and reduce noise. Solution page: http://nova.astrometry.net/status/1196620 So, I've got a few ideas of what to try next time, including using in camera stacking to reduce noise and possibly setting the camera to black and white. I'd be interested to know if these frames are solvable by your polar align routine, but I will be trying it again regardless. Thanks again for the help and tips.
  7. Thanks for the attempt Robin. I will try to improve the quality of the frames I'm feeding to the algorithm. I think if I turn on the in camera stacking that will clean up the noise a good bit. Since someone has gotten it to work with a smaller FOV than mine, I figure there is hope. Thanks again. - Larry
  8. FYI, someone on Cloudy Nights is reporting success with polar alignment using an FOV of 35'x27'. I must have other problems...
  9. Hi Robin, I had a chance to try the polar alignment again and it was still not able to solve. This time I captured a few frames before the clouds closed in. I polar aligned using the ZEQ25 polar scope first, so these should be fairly close to the pole. Here are two representative ones, along with a dark so you can see which are the hot pixels. For whatever reason it did not seem to be picking the hot pixels this time, so that may not be the problem. The frames are short live stacks but the dark is a single frame from a dark video (was not created using "capture dark", which crashes for me). By the way, it seems like sometimes Sharpcap might be vertically flipping the image when it saves the stack. I had to flip the dark to get it to match the stack. I estimate the FOV of these frames to be 44'x32'. Thank you so much for your program. With or without the polar alignment it's a great tool. Remember, as a software person I can tell you, you'll find the last bug when you stop looking!
  10. I was kicking myself today that I didn't save some images. You are right that I have an analog camera and frame grabber. I will capture some images next time I have a chance. Thanks! -Larry
  11. Hi Robin. I had a chance to try out the polar alignment with my setup last night. It was not able to solve any frames (always said "not solved" and latest frame status was "not solved"). It's hard to tell what the problem might have been. It was definitely finding stars, and usually over 10 but less than 20. I have two theories. First, the simple one is that my FOV is too narrow and the algorithm does not consider an image scale that small when trying to plate solve. My other theory is that I noticed it would often pick a (to me) known hot pixel(s) as stars which may be causing it to have a problem. I increased the minimum star width up to 3 pixels which seemed to mostly get rid of the hot pixel selection, but then the real star count often was below 10. I restarted the routine several times and would give it a few minutes each time before giving up. I'm wondering if you are stacking and trying to plate solve on the stack, or whether it is an entirely new attempt on each "frame". The hot pixels would be more of a problem if you are using a stack. I think I saw frames come up with no hot pixels selected and more than 10 stars. Anyway, my thought is that if a dark frame could be subtracted just like in live stack, that would help with the hot pixels. I suppose another method would be to allow the user to select areas to ignore due to hot pixels. I figure your dark frame subtraction code already exists from live stack though. Since we don't know if that's really the problem I'm not sure it's worth spending time on. If you have any thoughts on other things I could try, I'll give it another shot next time I get clear skies. Thanks! Larry
  12. Thanks Robin, I will report back with results when I get a clear night.
  13. Hello. Quick question about polar alignment. I see on the website that the FOV requirement is 1 - 2.5 degrees however, with my setup, I can't quite get to 1 degree even with a 0.5x focal reducer (I have a small chip camera and 750mm FL). Is it possible the polar alignment will work with a smaller FOV? I think I'm around 0.5x0.75 degrees with the 0.5x FR. Has anyone tried it with less than 1 degree FOV? Thanks!
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