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Astrofriend

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About Astrofriend

  • Rank
    Star Forming

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  • Website URL
    http://astrofriend.eu/

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  • Gender
    Male
  • Interests
    Astronomy, Cars, old stuff
  • Location
    Sweden
  1. I use Hugin to find the lens distortion parameters, it works with a testpattern I have made. Lars
  2. Astrofriend

    DIY Equipment test at Comet 123P/West-Hartley

    Yes, when living close to a city you can't have to big expectatoins. But this was fun. Objects along the eclipta I just have two capture between they leave the horizon and get hide behind the building in front of our balcony. Lars
  3. Astrofriend

    Mount gear ratio calculator

    Hi Gina, I tested your figures in my gear ratio calculator. With a standard 180:1 worm drive and two 3:1 belt reducers (I have modified it to take two reducers), 400 step stepper motor and 16 bit micro step I get 0.125" / step. Good to not use 64 bit micro step, gives poor torque and not so good precision. What kind of timing belt are you plan to use, glasfibre, steel inforced, kevlar etc ? I have a nylon belt with steel inforce in my belt reducer to my focuser. Maybe I can get i better with smaller teeth pitch and kevlar, but I don't have that experience today yet to judge. And I think my focuser is good and no need to improve it today. A lot of people rebuilt their EQ6 mount to timing belt drive. But it looks to be very difficult to set the tension of the belt because of the incluser. The tension is important to get low backlash. I have read at other threads you started, you build a lot of equipment your self I understand. Background from the industry, or? /Lars
  4. Astrofriend

    Mount gear ratio calculator

    Hi Gina, Stepper motors makes it easier to find driver bord. My EQ6 mount is fine but I want something little bit better. A true directdrive system had been nice, but too expensive today. Maybe cheaper in future because of the lack of mechanical gears. /Lars
  5. Astrofriend

    Mount gear ratio calculator

    Hi Gina, Do you plan to use stepper motors or DC motors with encoders? /Lars
  6. Astrofriend

    Mount gear ratio calculator

    Have you ever had thoughts to build your own motor driven mount? Then you need to know how to get the gear ratios you need. You also need to know what angular resolution your motor works with, what does one step from your motor correspond to in arc seconds. I have made a Mount Gear Ratios calculator on my homepage. It's new for today and there can be some mathematical erros in the calculation so double check everything before you buy any expensive parts! Here it is: http://www.astrofriend.eu/astronomy/astronomy-calculations/mount-gearbox-ratio/mount-gearbox-ratio.html Let me know if you find anything wrong with it. /Lars
  7. I added an illustration of how it goes with the bits when doubling the values: http://www.astrofriend.eu/astronomy/astronomy-calculations/bit-resolution/bit-resolution.html Maybe easier to follow? There are situations that are not correctly handled, see it like a development project. /Lars
  8. Dealing with bits can be confusing, I always thought that when I have 32-bit floating point I was on the safe side with margins. Maybe not the case when stackning lot of images and doing HDR. I made a bit-resolution calculator to do some theoretical test: http://www.astrofriend.eu/astronomy/astronomy-calculations/bit-resolution/bit-resolution.html From that you have a theoretical calculation of your need of bit-resolution without rounding errors. Noise and other things will hidden the last digits in your number, but still if you stacking a lot of images or doing HDR you get interesting results. The calculation is of course simplified, there are in theory lot of cases when you need infinite number of bits, When saying 32-bit in image processing it's normally 32-bit floating point format. From that you can only use 23 bit to store the your pixel value in. The others are used for signs and exponent. /Lars
  9. Hi, I normally using the AstroImageJ software when doing the first steps in my preparing of astrophotos. My camera is a Canon EOS 6D, it has a normal singel color sensor with Bayer pattern filter. There are a lot of different Bayerpattern, Canon normally has the filter order RGGB. In my case I read out the overscan region of sensor and then maybe the start pixel position can be at another color filter. Sometimes I feel it's a bit hard to bring out the color in the following steps. So I had to test that I didn't mixed up the Bayer pattern when I created the macro that do the demosaicing. To test this I made a RGB color test pattern image and took photos of it. Then demosaicing the CFA image to get 4 new images Red, Green1, Grenn2 and Blue, each 1/4 of the original size. From these images I easy see if the demosaicing is done correct. If it's interesting read about more details I have put together a page over what I do when testing the demosaicing function: http://www.astrofriend.eu/astronomy/tutorials/tutorial-raw-demosaic-combine/tutorial-raw-demosaic-combine.html What result did I get? It was correct so I don't have to worry about that as long I keep my Canon camera. /Lars
  10. Hi Vlaiv, Yes of course, the last 24 bit is for the sign. But if you have +/-32000 or 0 to 64000 it stills is the same total range. Used the 16 bit example here. Thanks about info division, have not gone that deep into that, yet. I will change this part in the Bit Calculator later when I have think it over. There are always some deeper things to take care of. But must limit it to be useful. /Lars
  11. Hi, Thanks for the comments, about the flat calibration I did it simple, just say it need at least one more bit, maybe I shall increase this to 2 or 3 bit as you suggest, that's more realistic. All the other I think I already have in the text. It's in an early stage now, lot of updates will come when tested out. There is a choice if bias should be included or not depending of the situation, if you suspect it cancel out, just omit the bias. If you have separate bis for dark and flat it doesn't cancel out, I see now that I forgot the flat bias. Myself I do dithering and meadian stack with flat calibration only which work ok with my Canon 6D camera which have low static pattern. One more thing is that all cameras are not linear, to correct for that you need more precision also, often second degree correction or more. I have done some correction for that when workning in Matlab, but that was more just a test. Lens distosion is another part that ad more demand on the precision if you want to correct for that. About the 32-bit format. What I know the exponent of 8 bit use 7 bit for exponent and the last bit for the sign. Like this +/- 127. Altogether they make 8 bits. But in some system they only use 23 of the 24 bit to store data in. I don't why and when this differ. Thanks again for the comments and good feedback! /Lars
  12. When talking 32-bit files I normally feels that I'm safe with big margin to not clip any information in my astro image files when workning with them. But is it really so? After some discussing I feel, why not try to make a Bit Resolution Calculator? Here is my new Bit Resolution Calculator: http://www.astrofriend.eu/astronomy/astronomy-calculations/bit-resolution/bit-resolution.html For sure there will be some mistakes in it. I correct it when I found something. The calculations are also simplified. I'm a little bit surprised over the result, but still in the safe area when not doing something extrem. Note this is a theoretical simulation and in real life there are a lot of noise that mask the rounding errors. But still interesting to test what happens in different situations. /Lars
  13. Astrofriend

    SGPro Dither Setting

    It could be a bit confusing how big the move of dithering really is. I sometimes use DSS (Deep Sky Stacker) tool to aligne the images. From there you have a table how much it has moved each image relative each other in X and Y-axis. From that you get an idea about the dithering in average. I use other software, APT, PHD2 and EQMOD when I use my equipment for dithering setup. Maybe you can fins something useful from what I have written here: http://www.astrofriend.eu/astronomy/tutorials/tutorial-dithering/tutorial-dithering.html /Lars
  14. Astrofriend

    EQMod Setup Impulse buy.

    Hi, Most common problem is that when you have CdC running and EQ6 connected to the USB port it have wrong port adress. What happens is when you try to connect to EQ6 from CdC the EQMOD window just flash for a short moment. You can find the port number EQ6 use in the Windows system. And then set that port number in the setup for EQMOD, you find that too in the menu in CdC. If you later change the USB port you get a new number and then must redo the setup. I'm very satisfaid with EQMOD and it's well worth the time to have it working. I have looked around in my projectpages and if there is anything that I have written about the stup. But didn't find anything direct about setup. I have ATP (camera controll), EQ6 USB-focus (motorfocus), PHD2 (autoguiding), AstroTortilla (plate solving) connected to ASCOM and most of them also controll the mount over EQMOD direct. You can have a look at my project page if you get in problem with something belonging to that: http://www.astrofriend.eu/astronomy/projects/astronomy-projects.html Earlier I got a lot of problem when moving from Windows Vista to Windows 8. The EQMOD's USB to serial driver was incompatible, I think all that kind of problems are solved today. /Lars
  15. Hi, I must be stupid man who spend so much time and money on astro equipment when there are no clear sky. But the January 19 there was a clear sky, not perfect but good enoguh to take out the telescope on the balcony. I live close to a city, it's not only the clouds that is the problem, nasty light pollution also. My Telescope is a TS130 APO with a 3" field flattener and the camera is a Canon 6D full frame. Work very good together with very low vignetting and sharp all the way out to the corners. Control it from an astroserver that is built around a mini PC. Nowadays I can have it setup in just one hour. I have the mount stationary on the balcony at the winter and normally there is no need to polar aligne it. From that I mount the telescope on the mount and until it had cold down I have everything started up, focused, pointing correct and tracking with auto guidning. Not bad, earlier it could take three hours until I could start taking photos. But the comet, did I get anything? The comet 123P/West-Hartley was at this time weak with a magnitude at 12.9. I was not sure if it was possiblie to get anything. But after I had staked my 40 x 30 seconds images I could clearly see the comet. I have it here at my homepage with some more information: http://www.astrofriend.eu/astronomy/my-astronomy-photo/comets/123p-west-hartley.html I also tried to make a time lapse movie of it, but the move of the comet was too small to see anything. But first I had to make a monochrome images of the RGB imges to get the noise down, with out that it wasn't possiblie to align the comet. The process goes like these: Dithering taken images Subtract constant Demosaic (no interpolation debayering) Flat calibration Aligne at one point at a star close to the comet Recombine RGB images to mono (second time I keept the RGB version) Aligne at comet (second try I skiped this) Stack Adjust color gains crop out borders Subtract backgrund To do the RGB to Mono combine I had to make a new macro for the AstroImageJ software I use. It just took me 12 hours to have a noisy comet image and I'm happy with that /Lars
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