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About Piero

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    Amateur astronomy, biological signalling networks, bioinformatics, software engineering, mathematics, languages.
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    Cambridge, UK

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  1. oh okay, now I got a contest when this can be used. Thanks a lot!
  2. What a man! I'm watching this documentary right now.. Thank you John for sharing this. ------- Could someone explain me what he means at 32.28 when he says "In this class there is no bubu that can be followed by a life of sorrow", please? I've never heard this idiom.. Does it mean that whatever mistake one makes [in mirror making], there is always a remedy / way around [e.g. doing it again with another mirror]?
  3. I quickly checked those threads I posted before, and they don't contain the post I was referring to. Apologise for this. Here some reference: "The FC100DF handles my Baader Mark V with 2x Panoptic 24mm without any issues." https://www.cloudynights.com/topic/507650-question-on-tak-fc100-dc/#entry6725143 , https://www.cloudynights.com/topic/507650-question-on-tak-fc100-dc/#entry6725501 https://www.cloudynights.com/topic/459189-help-with-bino-configuration/ (using Tak-fc100)
  4. I remember I read a post from a gentleman on CN who stated how much travel was needed for binoviewing using the DF. According to those measures, the 2" diagonal was not suitable (at least with the 2" clamp), but the T2 diagonal (that you have if I remember correctly) works fine. I think this post is in one of these threads (.. haven't double checked!): https://www.cloudynights.com/topic/535739-takahashi-fc-100-dc-basic-questions/ https://www.cloudynights.com/topic/513141-takahashi-fc-100dc-vs-takahashi-fc-100df/ https://www.cloudynights.com/topic/507650-question-on-tak-fc100-dc/ https://www.cloudynights.com/topic/511658-takahashi-fc-100df-first-light-report/
  5. A nice photo here of the two siblings (DF and DC) here: https://www.cloudynights.com/topic/535739-takahashi-fc-100-dc-basic-questions/#entry7193389
  6. This might be even more helpful: https://docs.google.com/spreadsheets/d/1KtV9Hl0XRQ-IGLiCjxIGSzss-b9TJ_j8ssk0lhh5UpI/edit?usp=sharing . It's a spreadsheet I did for computing the necessary information I need regarding the telescope - eyepiece system. You should be able to download and adjust it with your telescope - eyepiece set. Let me know if you have problems, please. The following is off-topic, but I preferred to say it anyway just for clarity. In the spreadsheet the magnification factor of a tele-extender / barlow is applied to the eyepiece. For instance, a 10mm eyepiece used in combination with a 2x barlow becomes a 5mm eyepiece. Whilst this is handy for quick mental calculation as well as for a spreadsheet (because it makes clear which shorter focal length eyepiece you might not need to buy!), it is not really correct optically. The multiplication factor of a barlow / tele-extender is actually applied to the focal length of the telescope. For instance, a 600mm f.l. telescope becomes 1200mm using a 2x barlow. The computation of magnification, exit pupil, and fov remain the same (using the updated focal length). The difference is that in the first (wrong) interpretation, the eyepiece always sees the same light cone, whereas in the latter (correct) interpretation, the eyepiece sees a much longer light cone (e.g. 2 times longer if a 2x barlow is used). Increasing the light cone can have positive effects, but this is not taken into account in the spreadsheet. NOTE that you don't need a barlow / tele-extender with your current telescope because it is already slow (focal ratio > 7), because you can already achieve small exit pupils with common eyepiece focal lengths.
  7. I'd have expected the FT to be around 8cm and I went rather close. Your focuser is essentially 30mm shorter than the DF. I haven't measured but from what I read it seems to me that the DF drawtube is 2.5".
  8. I believe so. They are both f7.4, so the focal point of the DF + 2" diagonal path should be the same as the focal point of the DC + 1.25" diagonal path. EDIT: My measurement doesn't include the 2" extension tube. I didn't include this as the telescope doesn't reach focus with it using a diagonal, but only in straight through mode.
  9. Favourite summer DSO?

    There are so many lovely targets in the summer that is difficult to select just one! I love to sail from Cepheus/Cygnus down to Scutum / Sagittarius / Scorpio and stopping for a while on every beautiful island I encounter!
  10. I just measured the distance for my FC-100DF. 15cm, from the beginning of the focuser to the 1.25" adapter. 10.5cm if used in 2" mode. Edit: measures taken with drawtube completely retracted.
  11. That's very short indeed! I have to say that so far I haven't had any inward issue with my DF + 2" BBHS. I don't binoview though.
  12. A lovely set of scopes you got there! Super review and a very interesting thread!
  13. Thank you John! Getting a thick handle like that in the eye must not be pleasant! If I remember correctly from one of your posts, you observe with your left eye, right? If so, at least you didn't hit the good one! I'll pay extra care! Thinking about it , I always hold the handle. Dunno.. This gives me certainty about the telescope angle and slow motion accuracy.