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About Jessun

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    Lyon France
  1. Dual ED80 setup

    That Geoptic bar looks familiar ;-) I used three to run three OTAs bolted to the bar. I settled for shimmies but it was never perfectly aligned. I bought two adjustment saddles from FLO and then the project was decommissioned.... Never got to try them out. For me the problem was always the focuser. Even Moonlites weren't up to the task. Cool build you have there now! /Jesper
  2. Hi! I used to be a great fan of the RC design but have had much more use of refractors over the years. Setting the spikes/no spikes and halos/no halos issues aside I nowadays think a good quality refractor is the all around winner. Easy to use, handle, clean, transport, store etc. Hubble and all other big ones would be refractors no doubt if it wasn't for weight and engineering drawbacks. Luckily today we have such a wide range of CCDs/CMOSs to choose from that it's easy to match scopes/cameras vs the seeing you can expect. What a delightful problem to have on ones hand! /Jesper
  3. Help with a OSC ccd

    I'm sure you have found this box, but it's easiest to use on a daylight image first time. Block of the scope with cardboard or something leaving just a smallish hole helps if you can't get exposures short enough not to flood the CCD. Only a few options the matrix can be set at. You'll find it!
  4. Help with a OSC ccd

    Don't toss the camera or indeed the images in the bin just yet. There are just a few de-bayer options to choose from. Try them all, perhaps best to try without the IR block since it you test it out in daylight the filter can cause a confusing tint on the finished debayered image. But no problem in keeping it there for astrophotography. I always had one in. Keep trying. Both AstroArt and Nebulosity can do the job. /Jesper
  5. I see this effect with my OIII filter in particular. I have to deal with it separately in processing. I almost think it's a CCD cover glass artefact, just because no other part of the imaging train is rectangular. It looks like you may want to experiment with different flats too for vignetting. /Jesper
  6. Guide Scope Mounting

    Hehe, calm as a cucumber. The two biggest myths I've come across regarding astrophotography concerns f-ratio and field rotation. Guiding is tricky enough as it is, with finding a guide star, getting software to work, avoiding oag prism artefacts etc etc, that it's only right to point out the single thing budding photographers don't need to worry about. /Jesper
  7. Guide Scope Mounting

    Your typical gem can rotate in ra and dec. Assuming pa is spot on, what part of the metal structure on the mount warps itself along this third axis? /Jesper
  8. Guide Scope Mounting

    I for one don't think that you can introduce field rotation by pointing the guide scope in a different direction. Only polar misalignment can cause this. But it's useful for sure to aim at the same general direction to permit the scope to track at the correct speed. Atmospheric diffraction plays tricks as you go close to the horizon. I agree that the complexity of various mounting systems add nothing really to the final result - often quite the opposite. Might as well just superglue the thing on :-D /Jesper
  9. An improved Crayford or not?

    I like the thinking. (Not knowing what I'm talking about really since I'm no engineer) My Feathertouches are in storage at the moment so I can't examine them. They work. I used to have Moonlite's but pretty much threw them away in anger. There were bearings all over the place and the draw tube wobbled like crazy from the get go. /Jesper
  10. January 29, 2018: Full disks as single stack and 13-pane mosaic

    Superb! I have no knowledge of lunar imaging but this sure looks splendid! /Jesper
  11. Dedicated DSO camera confusion!!!!

    Hi, I would start with this site: http://www.newastro.com/book_new/camera_app.html Download the CCD Calculator. It's similar to the one in the advice above, but personally I like this better. Three quick questions to answer: - What is the resolution that is useful at your location? Measured in arcsec/pixel, this is determined by the quality of your sky. In this context it has nothing to do with the number of pixels on a given CCD, it's just a figure that applies to your location and perhaps your ambition. At this stage you will need to match the pixel size of a CCD you consider with a certain focal length to achieve this ballpark number. - What area do you wish to cover in one frame? Narrow for planets or large for nebulas? The actual CCD size determines this. Costs typically go up as they increase in size. - How fast would you like to expose? Having found the resolution you'd be happy with and the focal length of a scope matching this, it's time to look at f-ratio, in other words as you maintain the focal length you open up the aperture of the imaginary scope. Each inch adds a lot of money. As to cooling, it's not as simple as cooler is better. It depends on how one particular CCD handles heat. Some CCDs are more forgiving than others and manufacturers match the cooling needed to the CCD. They can only cool a certain number of degrees below ambient temperature so your location might be a factor. In a hot country with warm nights it's worth looking at cooling specs. Astrophotography is complicated and most rigs you'll see are slightly different to suit the user - or the user's budget. Part of the hobby is to learn enough to find your perfect rig, and this is time consuming. I have spend days looking at the CCD calculator alone... Good luck! /Jessun
  12. Mount Stops Slewing

    Shot in the dark: does the handset have a battery? /Jesper
  13. Looks superb and very innovative to me! /Jesper
  14. The future for mounts?

    Amazing how such wobbly and thin looking cogs can be so strong. Always wondered what an industrial robot would be capable of carrying a scope. It would be quite a sight. /Jesper
  15. Interesting thread. Did anyone run a CMOS with at least 5 or 10 min subs? Would amp glow or something else destroy the image? /Jesper