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Found 8 results

  1. Had an interesting chat by email with the SAM app devs. I suggested to them that incorporating dithering (obviously only in one axis though) in the app would be a nice feature. They emailed back saying nice idea they will try to implement it .
  2. wimvb


    In order to minimize noise in my data, I've gone the Tony Hallas way and started dithering between exposures. My setup is a simple one (EQ3 Pro with Pentax K20D, no guiding), and I try to keep everything as much standalone as possible, since I don't want to take my computer out in freezing cold or wet grass. Unfortunately this also means I have to do dithering by hand, i.e. pushing the Dec/RA buttons on the Synscan hand controller between exposures. Doing this for a few hours in a stretch at -10 C or colder, is definitely not my idea of having fun. So I started thinking of automating the dithering procedure. Searching the internet, I found no solutions for unguided dithering compatible with my setup, so I decided to build my own. The idea was quite simple: The RJ12 port of my Synscan hand controller controls the camera, working as an intervalometer. The Synscan mount controller has a guiding port, so all I had to do is find a way to send signals to the guider port in between exposures. So, I built a simple circuit around an Atmel ATtiny84 which takes the Synscan camera control as an input. It senses when an exposure ends and sends a signal to the guiding port. A counter keeps track of which command to send from a simple string: 214488222111444488..., where 2 means Dec+, 1 means RA+, 4 means Dec- and 8 means RA-. So here is a pictures of my solution. The ditherbox is the black box below the mount controller. It has three connections: input from the hand controller (RJ12), output to the camera (phono plug type) and output to the mount (ST4, RJ12) FYI, I put the code and a more detailed description on my Github page: https://github.com/wberlo/AutoDither I've tested it and it works like a charm. Unfortunately I have no images yet with this setup, because when I tested it, clouds moved in after just 5 exposures. I do have 20 dithered exposures of clouds.
  3. Hello to all Can anyone give me the right settings for using Dithering as I tried it last night and its dithering alright to the point after 20 exposures the picture is almost off the screen! A wasted evening. I had it on the setting APT Dithering with distance on 1! I'm assuming if I choose 2 or more it will move more right? There is also a setting for APT pulse but I can't hear it moving on that setting. I'm using a eq6 with EQMOD and Cart du Ciel which all are running fine. I'm connected to the scope also via APT as that is the only way Dithering will work as I do not have a autoguider. Any ideas? I'd be very glad to hear how others have it working. Thanks so much! Gerry
  4. Hi again, I've started on DSLR AP recently and I am doing it on an EQ3-2 mount with the RA+DEC motor upgrade and the enhanced handset with an ST-4 port. Im capturing using Backyard Nikon on my laptop and I would like to dither between light frames, but I am doing it unguided. Reading up on the Backyard... forums it seems BYN does indeed support unguided Dithering, so that should be possible. What is unclear to me is if I can do it with the handset: enhanced-dual-axis-dc-motor-drive-for-eq3-2 My next question is, how would i connect my laptop to the ST-4 guider port? Using something like this: zwo-usb-to-st4-guider-adapter ?? Hope you can help me out, been searching forums for a good while now, and no clear answer to be found.. Clear skies!
  5. Now that imaging season has come to an end, I have the time to do some reprocessing of old data, and I thought I'd share some of my processing methods. I gathered much of that data before I started doing dithering, and the usual background I am fighting looks like this: This is an extreme crop of a wide field image of the area around NGC 1499 (the whole frame covers the area from M45 to Mirfak), taken with my unmodified DSLR. The stars show trailing, but this is not a problem in the final image. Process details: 12 subs, integrated using AVERAGE integration with sigma clipping; no other method for hot pixel removal was used. As you can see, despite pixel rejection during stacking, there is a streaking pattern. This is due to hot pixels which weren't removed during the calibration/stacking process. In my case, it never made a difference if I used darks or not, some of this pattern always remained. The next image shows the stacking result for the same subs, but this time with MEDIAN integration with aggressive percentile clipping (20 % high values) and hot pixel removal during calibration (cosmetic correction using the Auto Detect option in PixInsight): As you can see, the streaks are gone, and it will be much easier to process this image further. Since I can't control my cameras temperature, and it's difficult to match dark frames to light frames, I don't take dark frames anymore. Instead I rely on bias frames and cosmetic correction to remove read noise patterns and hot pixels. During this past season, I started using dithering, and found this to be the best way to remove stacking artefacts and large scale noise (what Tony Hallas calls "mottle"). I typically dither 15 pixels between frames in a spiraling pattern. After star alignment, the dithering pattern looks like this: M45_dithered.mp4 This is a crop of debayerd and aligned raw files. No calibration process or cosmetic correction was used. As you can see, the stars are aligned, but the hot pixels move around and will be effectively removed during image integration. If these were calibrated files, I would also have used cosmetic correction, and the number of hot pixels would have been much lower. I hope this information can be of use to anyone fighting the same problems. Cheers,
  6. Hi, I am using the SA with a Canon 650D and a 300/4.0 L USM for some months now. In order to get longer exposure times (>30 sec) I just got a little guiding cam (TSGM120M: https://www.teleskop-express.de/shop/product_info.php/language/en/info/p8963_TS-Optics-Mono-Planetenkamera-und-Guidingkamera-mit-Aptina-CMOS-Chip.html). Stand alone guiding like the M-GEN II is way to expensive from my point of view, so I decided to use PHD(2) on a laptop to do the guiding. I use the Orion 50 mm Guide-Scope mounted on the second port of the L-Mount. But I don't know how to set up PHD2 to work with the SA. The guider-cam will be connected over USB to the laptop and over the ST-4 cable to the ST-4 port of the SA - now question about that. There are some users in the forum, who already work with PHD and the SA as far, as I have seen. So maybe someone could help me about what "Mount" and "Aux Mount" do I have to choose in the connection dialogue of PHD? How do I switch off DEC-guiding, as the SA doesn't provide it? Any experience with the dither function BackyardEOS provides with PHD2 connectivity? Many thanks in advance! Chris
  7. Hi, I am at the moment trying to set up "Dithering" on my APT. I am presently using a Canon 600D, with Orion ED80 Refractor, mounted on my NEQ6PRO. Please note, I have not yet progressed to Guiding - NO GUIDING Do I basically select "APT Dithering" and maybe leave all the other settings at Default? Most grateful if anyone can let be know which settings I might need to adjust, and to what values. Finding it all a little bit confusing ! Many Thanks Steve
  8. Hallo! I have written earlier about using dithering technic instead of traditional dark and bias calibration. I have updated my tutorial with a calculation of the noise from Dark/Bias vs Dithering calibration: http://astrofriend.eu/astronomy/tutorials/tutorial-dithering/tutorial-dithering.html#part06 Of course it's simplified but still show you what to expect, it depend very much on the camera and your site's darkness. This is a way to reduce the static pattern (column defects, hot pixel etc) in image. I hope you find it interesting! /Lars
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