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marcus_z

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Posts posted by marcus_z

  1. Ken, if the 71FL is an option for you, I can offer you an objective lens assembly. For reference, you can find professional measurements of a 71FL here: Wellenform - Zertifizierte Fernoptik - Objektive - Angebot. Their conclusion is: "When focusing on green (546nm), blue (486nm) is very well diffraction-limited, and yellow (589nm) almost diffraction-limited. Red (656nm) is defocused and is therefore below the diffraction limit of 0.80 strehlpoints. Because perception of red is weak in the dark, the red color fringes (resulting from the defocusing of red) can only be seen very faintly, if at all." I think that conclusion is right and resembles my experience at the eyepiece.

    The 71FL is shorter and lighter than the FC-76D. If deep-sky is your priority, the 71FL/72FL might be more interesting for you, for shallow-sky the 76D might be more interesting. One thing is sure, the 71FL offers more aperture and less weight than the FS-60CB (at a higher price).

  2. 58 minutes ago, JeremyS said:

    Are you planning to fit a finderscope, @marcus_z?

    No, I don't think I need one. For planets I just use the tube as orientation. For deep sky I might just use the lowest magnification eyepiece as a finder. A Panoptic 41 gives a 4.6 degree TFOV and 14x Magnification. That is almost like a finder, but with much better aberration control and eye relief. But I'm not 100% sure about the low mag eyepieces which I should use for travel...

     

    I'm thinking about a Masuyama 45mm, which gives a 6mm pupil and should work good with filters. Maybe a 16mm Nagler for open clusters, but then I don't know which eyepiece to take between the two...

    • Like 2
  3. Recently I acquired a second-hand FC-100DC with MEF-3. I don't think that the MEF-3 is the optimum, because there is some flex in the sheetmetal plate that attaches to the housing. I expect the FTF micro pinon to be more precise due to less backlash. But certainly since Tak focusers vary quite a bit one might be equally satisfied with his/her copy.

  4. 37 minutes ago, 25585 said:

    How are your uses of the 2 going to differ?

    That I don't really know :-) They are quite redundant.

    I wanted to have the DL first and then changed my mind to get the DC. Now at the second production run I could not resist and ordered a DL. In the long run, I want to build a binoscope with two DCs. And then I have the DL as a single.

    • Like 4
    • Thanks 1
  5. 1 hour ago, 25585 said:

    What Moonlite flange fits the FC range?

    The OTAs have a M95x1 male thread. If you take the DC, then you can remove just the focuser, with or without the extension tube, and use an adapter with a male M77.5X1 thread. If you go the Starlight Intruments route, you can use:

    A20-304 for DC, DF, and DL

    A20-302 for DC

    A30-1903-85 for DC, DF, and DL

    • Like 1
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  6. 2 hours ago, pystab said:

    I understand you can push it where you want or turn the slo-mo knobs, and when you let go the clock drive just takes over, no hunting for clamps or clutches. marcus_z, any comments?

    Hi Tim, that's it exactly. You can use it like a porta and move the scope freely without clutches. For fine movements you either turn the knobs or, on the motorized axes, you press buttons on the Starbook One.

    I just want to make clear, that the FC-100D is at the limit of this mount. With the tripod legs not fully extended it definitely helps. Focusing at 200x needs a fine focus, because of vibrations. I usually sit on an astro-chair to reduce jitter. When you change from a lighter to a larger eyepiece you'll notice that it sags (e.g. when swithing from Tak LE5 to an Ethos 4.7). However, I have had really good observing sessions with this setup, but some of us could be disappointed. An ED81S/SD81S might be a far better match. Before the Tak I had an 80/480 triplet on the mount which was a perfect match. I recently acquired a 150/600 Newton which seems to be a good match for the AP as well. A 4" long focus refractor is definitely not recommended.

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