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Zermelo

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Posts posted by Zermelo

  1. New or second hand? If the latter, make sure it hasn't been activated on too many other phones. I think it allows up to four.

    There are several members who have bought AZ70s solely to cannibalise the Starsense for other scopes, and they seem to think it was worth it. There's a thread somewhere on their efforts.

  2. 1 hour ago, Louis D said:

    I thought the Sky Watcher Freedom Find mounts use encoders to keep track of alignment regardless of the clutches.

     

    1 hour ago, malc-c said:

    Some mounts are fitted with encoders, which mean drive clutches can be released and the scope manually moved without the handset loosing positioning.  However these will need calibrating from a known starting point first time used 

    Yes, the SW Freedom Find feature uses dual encoders, and you can move the mount manually (provided you remember to switch on the dual encoder feature in Synscan each time you set up - the default is "off"). However, once you do that, the gotos for the remainder of the session are generally less accurate, because the second set of encoders are located on the coarse side of the gearing. I've found that it is still accurate enough to locate objects within an optical finder, unless it's having a hissy fit.

    But I believe that the Star Adventurer doesn't have FreedomFind in any case.

    • Like 1
  3. On 13/03/2024 at 17:06, Brian O said:

    Faster than light inflation at the birth of the universe has always been a great problem.

    The constraint of the speed of light applies to inertial frames of reference within the theory of special relativity. The expansion of space itself is described in the theory of general relativity, and is not constrained in the same way.

  4. 7 minutes ago, Captain Scarlet said:

    I have a collection, mostly TeleVue, including some very high-end eyepieces. They are almost all very good indeed, to my reckoning, but only one has totally blown me away with its capability, showing me one particular object one night that others could not. It was my Baader BCO 10, showing Mimas easily at only 94x through my 140mm refractor. Barlowing with a Celestron Ultima 2x continued to show it, but I could not see it at all through my TV Delos 6 or Tak LE 5. Returning to the BCO again, there it was. In that test, the best eyepiece I own, and the cheapest! I have a BCO 6 in transit, it’ll be interesting see if it matches that performance.

    Magnus

    Agreed, especially if you avoid the outer extremities. A steal at £54 for that quality.

    I find the 6mm to be a bit tight on eye relief, I'll be interested to hear how you get on with it.

    • Like 1
  5. 3 hours ago, Zermelo said:

    This is why I bought the AZ-GTiX, which has a stated capacity of 6kg one side and 10kg total.

    My previous mount was rated at 5kg, but when I uprated the finder, got a 2" diagonal, etc. it was pushing it.

    These mounts seem a lot happier with some counterbalance, either a second OTA or some weights. It turns a lot easier on the Az axis.

    btw, I bought a SW 1.75" steel tripod for mine.

  6. Stu has covered the essential points there. One lesser consideration is that if you have significant astigmatism in your observing eye, this tends to be more visible when using larger exit pupils. So, it can be preferable to obtain the same true field by using an eyepiece with shorter focal length but wider apparent field, the same tactic as for obtaining a darker background sky. As Stu says, it will be more expensive to get these wider fields that are well corrected to the edge. And it may force you into a 2" format.

    • Like 1
  7. M31 is (from our perspective) oval shaped. In a modest scope, especially in a light sky, you're essentially seeing the nucleus, which is also oval shaped. It's easy to imagine that you're seeing more of it than you are.

    With a larger scope/better skies/better dark adapted eyes, you see more of the outer regions, though it still looks oval. One thing that will change is the apparent distance to the satellite galaxies, M32 and M110. When I first looked at M31, I was surprised at the gap between it and M110 in particular, having previously seen the photos from Hubble, etc.

    • Like 1
  8. Don has previously linked to this bench review of zooms by Ernest Maratovich.

    The Svbony 7-21mm comes out particularly well. I have this, and the 9-27mm, and the (identical, OVL version of) the 7.2-21.5mm, and I find all three perform very well. The AFOV does vary a lot with magnification though, which is where the APM wins out.

    Svbony also do a 8-24mm, but I've not seen any reviews of that one. The Baader mk IV is widely liked.

    • Like 3
  9. "The darkness of the Horsehead is caused mostly by thick dust blocking the light of stars behind it.The lower part of the Horsehead's neck casts a shadow to the left. The visible dark nebula emerging from the gaseous complex is an active site of the formation of "low-mass" stars. Bright spots in the Horsehead Nebula's base are young stars just in the process of forming."

    Wikipedia

    • Like 2
  10. (i) There is inevitably some subjectivity in deciding whether or not there is a "black" dividing line. As already mentioned, as you move away from the centre of the Airy disc, the brightness tails off over a finite distance, it isn't immediate. So, for pairs that are on the cusp of being split, it will be a judgement as to whether or not the point half way between the stars is at the same level of blackness as the rest of the field. Obviously some observers will be more optimistic than others in making this call. I remember a previous thread where someone posted a graphic showing the light curve dimming and brightening between the stars; possibly @vlaiv  (but then I always think it was him).

    (ii) on the seeing: yes, I'm sure this can affect decisions too. When operating at high magnifications in less than perfect conditions, the stars can be jumping about quite a bit. In a very brief moment of stillness, I think the eye can be tricked into seeing a gap where there was none. I've also experienced observations where a star has appeared briefly to be - at the very least - resolved, but I suspect that it was another artefact of the seeing - the image of the star has been "flicked" very quickly to one side, and back again, and the persistence of vision suggests two adjacent discs.
    I expect the actual effects of imperfect seeing depend on the size and motion of the cells in the air column, and probably also the size of the instrument objective.

    • Like 3
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