开云体育

Digest Number 3526

Rick Thurmond All Messages By This Member #14708 开云体育 I’ve started a page on my website at? Not very complete yet, but keep checking back. ?I’ll put the mechanical, electrical, and software there over time. Thanks for your interest! Rick toggle quoted message Show quoted text On Sep 7, 2015, at 2:33 10AM, Alexei Pace <alexei.pace@...> wrote: Dear Mr Thurmond, I would be very interested in seeing more details of your self built focuser for Hyperstar! I too have a C14 with Hyperstar which I have just bought to use with my DSLR (6D). Best regards, Alexei Pace Malta
wecwell All Messages By This Member #14709 开云体育 Rick, ? ?Maybe you could look for spatial frequencies, e.g. do a spatial Fourier transform and find a spatial frequency peak that corresponds to stars. That would be pretty processor intensive. JPEG files are already encoded as Discrete Cosine Transform. You may be able to get spatial frequencies by examining the file. (Possibly helpful article here: <>) The JPEG will only give you spatial frequencies over 8x8 pixel blocks but that may be sufficient. -Charlie Lasnier toggle quoted message Show quoted text On Sep 7, 2015, at 2:16 AM, C14_EdgeHD@... wrote: Remote Focuser for C14 Sun Sep?6,?2015 1:43?pm (PDT) . Posted by: "yahoogroups@..." rick.thurmond A while ago I got a HyperStar for my C14, which converts it to f/2 using the primary mirror and some optics. It replaces the secondary mirror. I use it with my Nikon D600 SLR with great results. I needed a way to focus while looking at the camera, but all the motorized focusers I could find were way out of my budget, so I decided to design my own. It uses an Arduino to control everything, running software I wrote. A stepper motor drives the focus knob, and I have a hand controller with a rotary knob and display. The Arduino is in its own box attached to the pier, so that motion of the telescope doesn’t drag the hand controller around. I designed the plastic parts and had them 3D printed, the rest of the parts came from Adafruit. If anyone is interested, I’d be happy to share the design. Now the question is, how to determine when the focus is optimal. I can drive the Nikon using gphoto on a raspberry pi (I’d rather not take a laptop out to the telescope but if I have to, I will use a MacBook). With that software I can capture jpg or nef files onto the raspberry pi. Can anyone suggest software that can read a jpg and either do fwhm or some other measure of sharpness? I’d really like it to report sharpness of the whole photo as a single number. Rick
Rick Thurmond All Messages By This Member #14712 开云体育 I’m debating whether I should look at one star, using FWHM or Half Flux Diameter or a similar measure, or whether there is a way to have the software look at a larger subset of the whole image. ?If I use a Raspberry Pi I don’t have a whole lot of processor power. ?It will be a good software challenge for me. ?Wavelet analysis might be faster than FFT and give good results. ?Wolfram and Mathematica are installed on the Pi. ?Jpeg file size is another possibility, as it might measure how much entropy is in the image. Rick toggle quoted message Show quoted text On Sep 9, 2015, at 12:47 51AM, Charles Lasnier clasnie1@... [C14_EdgeHD] <C14_EdgeHD@...> wrote: Rick, ? ?Maybe you could look for spatial frequencies, e.g. do a spatial Fourier transform and find a spatial frequency peak that corresponds to stars. That would be pretty processor intensive. JPEG files are already encoded as Discrete Cosine Transform. You may be able to get spatial frequencies by examining the file. (Possibly helpful article here: <>) The JPEG will only give you spatial frequencies over 8x8 pixel blocks but that may be sufficient. -Charlie Lasnier On Sep 7, 2015, at 2:16 AM,?C14_EdgeHD@...?wrote:

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