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Thread: telescopes?

  1. #21
    Senior Member
    Join Date
    Feb 2002
    Perth Australia


    Quote Originally Posted by Stefen
    Thanks alot for all the responses.
    My requirements from this telescope is that you are able to people moving up the mountain. facial expressions, minor details are not necessary but color of jacket worn 5km away is definitely useful.

    The telescope will probably be mounted from basecamp, and not near the mountainside where its exposed to weather elements. portability and weight is definitely kept to a minimum as this item is not considered as an essential item.

    The primary purpose of this telescope is not to take sharp pictures, but to allow people from below to be informed of the team's realtime movements.

    Being able to take pictures will definitely be a bonus, esp if the pictures taken are of consideerable quality.

    Using long zoom lens have never been in the consideration as I doubt they are able to match up with telescopes in terms of magnification and cost.

    First up, long camera lenses just won't hack it, as their field of view is just too wide.

    Based on a 20m field of view at 5,000m you are looking at a field of view of around 5~6 arc mintues. That is not a very large field of view by terrestrial telescope standards.

    It means you are going to have to resort to eyepiece projection with a camera to obtain the needed image size on film and that means a slow effective aperture value.

    There are other bugbears to worry about apart from the physical size and weight of a telescope, you are going to have to deal with telescope vibration and also ground induced air currents, both of which will conspire to cause serious image degradation. Mountains are particularly bad as they frequently have updrafts and thermal eddies surrounding them.

    Given all of the above, I'd strongly recommend you not use a refractor, rather it would make more sense to opt for a SCT type telescope such as a meade ETX 90. It's going to cost you a lot more but it's small physical size and optical qualities are probably the best suited to the job.

    The Ang Moh from Hell
    Professional Photography - many are called, few are chosen!

  2. #22


    got your points on this.

    Thanks a lot! Will have to see if this exist in Singapore.

    Any good shops to recommend?

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