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  1. DanC.Licks

    Introduction and question to the aperture of scopes

    I just used two little magnets out of cheap bit holders. You can get stronger ones though, and it wouldn't hurt. I would keep the one inside as small as possible. Careful! They are surprisingly easy to lose! I would keep the outside one on the inside of a band of some sort, something that moves...
  2. DanC.Licks

    Introduction and question to the aperture of scopes

    I just had a long chat with my telescope expert friend, and it seems that I have misunderstood a couple of things about resolution etc. This is the gist of our conversation: If a lens is diffraction limited, as our scopes normally are, and as are high quality camera lenses, it means that they...
  3. DanC.Licks

    Introduction and question to the aperture of scopes

    This one would work perhaps... http://www.ebay.co.uk/itm/Microscope-Parts-Variable-Range-1-5-36mm-14-Blades-Variable-Iris-Diaphragm-1PC-/252101022818?hash=item3ab2645462:g:-0oAAOSwiLdWAlXf
  4. DanC.Licks

    Introduction and question to the aperture of scopes

    Here "wide" open, stopped down one stop, and then two stops. I had it placed just in front of the focus tube at infinity. That comes to about 320mm in front of the focal plane. There is no vignetting on the 4/3 sensor. Shots of the gray sky are clean. The BAD news is that "wide" open it is...
  5. DanC.Licks

    Introduction and question to the aperture of scopes

    Well, the good news is it works! The magnet idea was brilliant! Here is what I came up with: Should be pretty much self explanatory. It is placed just inside the lip of the tube so you can see how it works.
  6. DanC.Licks

    Introduction and question to the aperture of scopes

    Tord, You forgot that the image gets flipped before it reaches the sensor. How far in front of the sensor that happens I do not know. I would just go to some photo second hand shop and pick up a couple of junk lenses. The one I will use was out of one I tore apart for the telenegative. Don't...
  7. DanC.Licks

    Introduction and question to the aperture of scopes

    Not sure, but I found one that has an opening of about 28mm. I will give it a try. I envision a light weight lever with a small magnet attached to the end, hanging straight down with the scope mounted in the gimgal. On the outside I will make a band of neoprene with a hole punched in it for a...
  8. DanC.Licks

    Introduction and question to the aperture of scopes

    Good idea! Keep trying. You might consider mounting the diaphragm on a piece of thin plywood of plastic or aluminium that could be fit inside the scope tube a little in front of the focus tube so that it would always be in the same position. A lever with a small magnet on the end could then be...
  9. DanC.Licks

    Introduction and question to the aperture of scopes

    Lens cap definitely better than the iris so far back!
  10. DanC.Licks

    Introduction and question to the aperture of scopes

    Actually, the best placement of the diaphragm is not the node, but about half way in between the front element and the focal plane, which would put it well within the tube of the scope. The one pictured is out of some throw away lens, can't even remember what it was, something I found somewhere...
  11. DanC.Licks

    Introduction and question to the aperture of scopes

    Servus Jörg, Welcome! Your English is fine! A diaphragm SHOULD be as close to the optical node* as possible, which is difficult to do. I have had some luck with putting one on the end of the focus tube, inside the scope. Hard to do and not easy to adjust! ;) The dew cap solution is simple, but...
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