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About Chriske

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  1. Chriske

    Advice On Dob Mirror Cells Please...

    Looking at these pictures again, I would add more cooling fans. This is to speed up things but most of all to spread cooling more evenly over the back of that mirror.
  2. Chriske

    Advice On Dob Mirror Cells Please...

    Hi, missed this on, sorry for the late reply. A conical mirror normally does not have these ribs. In fact the mirror will perform sooner without these ribs. I had a similar experience in the past. Using high magnifications these ribs will be visible until the mirror is at ambient temp. Depending on your mirror-cooling-system it will be visible for a long time or not. The deformation in the mirror looks like spikes around a star. Looking at the diffraction pattern of a star you'll be surprised.Very slowly it will disappear. But again it all depends on what type of mirror-cooling you'll be using.
  3. Chriske

    Easy PCBs

  4. Chriske

    Easy PCBs

    My pal Guy also uses Eagle to make his layouts. But instead of etching himself he does send his files and a company does make our PCB's for a very low price. And they’re really good. Last set of 10 PCB's we've ordered (credit card size) costed 4.90$
  5. Chriske

    3D Printers

    If people would not buy that ultra cheap stuff this wouldn't happen in the first place. A few days ago I found a 179€(!) printer on the net. Build volume 220x220x250 + heated bed. In the add they even mention : all parts are precision made....! This is a heap of nonsense..! Oh, and they also mentioned : beside the manual(there's no support from the shop were it was bought)
  6. Chriske

    3D printed Foucault tester - V2

    On hold... We've decided to (maybe) install a cam combined with a zoom-lens to capture the focograms. That zoomlens is needed to cover the entire area of the chip. The bigger the image the smaller details can be seen . An example of a very detailed focogram is posted higher up in this thread. Using a regular webcam(even with the lens)the image is WAY to small. So I need another solution. A disadvantage of using my camera(as I always did in the past) is that I can not go 'live'. Meaning after the focogram is taken I need to connect my camera to the PC to have a look at the images on screen. I have no experience with cams and other stuff. So my question : is there a good quality webcam(or other USB device) I can use to view 'live' images. I do not need the lens, I would use an old zoom-lens instead. Or maybe there is some other good device with a zoom-lens to do the job...? Preferably not to expensive...
  7. Chriske

    A Cheap Huge Worm Gear

    rotate the mount 360° around we never do, and most of us don't do that. That is a calculated disadvantage we can live with. And indeed it's not meant to be used to do some accurate work. For more accurate work we had another solution. But I can't post it here because it would be off topic and most of all I do not want to hijack this thread.
  8. Chriske

    Fixed post mirror grinder advice

    We did join that group too Gina, but decided to go our own way. I completely redesigned the inner structure (drive system.) The original MoM did run on bronze bushings. Well I replaced that all with large ball bearings + very sturdy holders for them. That's one of the changes I made. If I would have had my 3Dprinters back then, I would have printed these holders. Now they’re made of 15 mm thick aluminium. Way to thick, but that's what I had at hand at the time.
  9. Chriske

    A Cheap Huge Worm Gear

    In the past we did use hose clamps, like this one. We bought these things by the meter so we could cut the required length. Each package contained 20 meter of the stuff + 20 worms. These worms were very easy to attach. If you only need to track for observing it's more then adequate.
  10. Chriske

    Fixed post mirror grinder advice

    Me and my pal Marc have a M-o-M each. It can handle mirrors up to 20". One is now loaded with a 20" mirror. It'll be a f/4.5. To feed the carbo we work with peristaltic pumps. Fully automated. When the container runs out of slurry the M-o-M stops. Containers completely filled with carbo the M-o-M will run for about 1.5 hours. The peristaltic pump/ units(partly printed) are interchangeable, so no need to clean these units at all. For every grade of carbo it takes us under a minute to install the nexy peristaltic unit. The only carbo we still do manually is while hogging out (#120). It takes me 2 hours or so to clean up a 20" mirror. That 'cleaning up' has all to do with this ugly looking machine... For smaller mirrors I use this one.
  11. Chriske

    3D printed Foucault tester - V2

    Damian there's a never ending discussion here whether Ronchi or Foucault is best. As a matter of fact I never use Ronchi. Reason : the only value is that Ronchi will give you only an estimate how the curve of your mirror looks like. In the end when that spherical mirror is ready to 'go' to a parabola you absolutely need a Foucaulttester. What's more all de very small and 'delicate' roughness visible in a FT is not visible at all in the RT. Look at the focogram higher up in this thread. That mirror has severe zones and on top of it it has scratches and microrippel. Again, there's no way you'll be able to see all that in a RT. And a another thing, when a mirror is not completely polished out, it'll be clearly visible in the FT, not in the RT.
  12. Chriske

    Rebuilding 18" dobsonian

    John, To have a very smooth azimuth action (especially with these large scopes) you need to add a central teflon pad, around that central bolt. Even with teflon pads and formica you'll end up with a bit backlash. You also end up with a little bit to much friction.(again --> large scope). What I do is sanding the central teflon pad a bit down, just a little bit, the thickness a of a sheet of paper, maybe even less. Then I install all options on the scope, including eyepiece and place rocker on the base. I try and move in azimuth. I do that while the scope is almost pointing in the zenith. If there's (to) much friction or backlash then remove scope and add some thin sheet of plastic and place it UNDER the teflon pad, try again. If there still some backlash or to much fiction, again add some thin plastic and try again. Continue doing so until the scope moves with butterly smoothness. Purpose of this procedure is to take away ALL(!!) the weight from the outer pads. All the weight of the scope and rocker should rest on that central pad. The outer pads should only guide that rocker and also hold it level.
  13. Chriske

    3D printed 130P focuser

    Correct, that's why I use thin sheets of metal(or brass) to have planes to allow smooth action while focusing. Tested it without these planes but that was 'No go..!' at all..!! This is an example of these planes. Using these planes there is no difference compared with any other focuser at all. Perfect and very smooth action. The sheet brass parts are only 0.4 mm thick This is a reversed Crayford btw.
  14. Chriske

    3D printed 130P focuser

    Nice one...!!!!! But there is a drawback using these linear slides. You loose lots of focusing travel. The concept of these slides limits you to use maximum travel of the focuserbody itself. Therefore it would be better to use ball bearings to do the guiding work. You still loose travel but far less compared to these slides. I was planning to do the same in the past, but a 50mm long (expensive!)slide only gave me 25mm travel.
  15. Chriske

    Artificial Star from a led light torch

    kbrown, Pinholes for testing optics should be as small as possible, but most of all it needs to be absolutely round. Another important point is using a thin object to allow light to pass through. I always use a (very)thin sheet of brass and make a hole in it with a needle. Then I carefully sand it to remove all burrs that are made by the needle. Next I gently push the burrs that are forced into the hole(during sanding) outside and sand again. I repeat all this until the hole is completely clean and absolutely round. During this operation I take care not to push the needle deeper every time the hole is 'cleaned up' by the needle. Do not make that little hole to small of course. Checking is done with a magnifying glass. Lots of info is found on the net. This is one of the many. It does not tell how to make that hole, but gives lots of info about that hole and what to expect from it. Info 'how to make' I got from Ingalls's books a very long time ago... A printed pinhole is not a good idea. Because that hole is not 100% round and it is made out relative thick material it will result in extra and unnecessary diffraction.

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