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ZEISS DTI thermal imaging cameras. For more discoveries at night, and during the day.

Recent content by Tringa45

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    Solar filter for spotting scope???

    Some years back I bought a sheet of Baader AstroSolar filter film and cobbled up a filter for my Swarovski 65 mm scope with some black card and duct tape. I missed the Venus transit in 2012 (it rained) but saw the Mercury transit in 2016 and set up the scope for the partial solar eclipse in 2021...
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    Upgrade to TSN-88 from TSN-883?

    If your 883 is still OK, save your money. The 883 had been available for about 15 years and it took a while for many to realize that it was just as good as, or better than the competition and less expensive too. Kowa used a minor facelift to justify a not so minor price increase. There have...
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    Needed - easy way to check collimation

    Dennis, To avoid slanging you on the open forum I wanted to PM you, but see you have blocked this. I wonder if you actually read threads before posting your worthless 2 cents. Joachim posted a really excellent test and then this "contribution". There are various tolerances for collimation but I...
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    Best Binocular for...

    There will be no visible difference in the performance of any one binocular at various distances. A typical 42mm binocular would have a focal length of around 150 mm. At a moderate 15 m that is still one hundred focal lengths! John
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    *Really* large rainguards for binoculars?

    Hermann, I'm just wondering what you are going to hang around your neck that has 50 mm eyepieces? :) Regards, John
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    Vignetting in Binoculars

    The introduction of 42 mm ELs, SFs and NLs all led to demands for 32 mm versions. So far Leica have deferred on a 32 mm Noctivid. Those values were only achieved before the introduction of long eye relief eyepieces for glasses wearers, for me a welcome development! I was not referring to...
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    Vignetting in Binoculars

    It's only a test to enable comparisons and was suggested by Holger Merlitz in his book. On "Cloudy Nights" Ed Zarenski referred to typical edge illumination on many binoculars being as little as 40%. Canip's photos would seem to support that. There is a potential problem with overall...
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    Vignetting in Binoculars

    Irrespective of the tilt direction, the orientation of the vignetted exit pupil to the field edge will always be the same. The tangential diameter will remain largely unchanged, whereas the radial diameter diminishes the closer it gets to the field edge. Btw, I should have written "up to 8°". I...
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    Vignetting in Binoculars

    That's the one I was thinking of. :)
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    Vignetting in Binoculars

    According to Holger the limit for BK7 is a focal ratio of f/5. As most binoculars are "faster" than that, some parts of the light cone will be too acute for total internal reflection leading to that squared-off effect. Of course, the glass path is part of the optical calculation, but for focal...
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    ES100 - maximizing FOV

    Unfortunately it's vignetting because the field stop of the 30 mm eyepiece is larger than the sealing window in the scope or the prism exit. Many birding scopes can be adapted to take 1,25" astronomical eyepieces, but for the same reason it doesn't always make sense to use a 32 mm Plössl or 24...
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    Vignetting in Binoculars

    This is a topic rarely discussed on Birdforum, but one that has an influence on the performance and perhaps subjective appreciation of binoculars. Vignetting is a loss of brightness towards the field edge and is present in all binoculars. It is caused by obstructions, usually baffles, in the...
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    Swarovski-Optik 30x SW Eyepiece

    One of the best birding scope eyepieces ever. Mine (2011 vintage) is merely designated 30x W. Try inserting in the "Wanted" section of Birdforum Classifieds. Good luck, John
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    A noob's view from a Swarovski NL Pure 12x42 and a Kowa Genisis 8.5x44.

    @kimsrk Steve, I agree that many reviews are governed by expectations, but some on this forum perform measurements or conduct objective tests. Henry Link's test of the Zeiss 8x54 HT and display of CA progression towards the field edge, or Canip's eye relief measurements come to mind. There...
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    A noob's view from a Swarovski NL Pure 12x42 and a Kowa Genisis 8.5x44.

    Hi Steve, That was an interesting comparison. As regards CA, there are two types, longitudinal and lateral. Eyepieces usually have fields of view (the AFoV you see in your binocular or scope) of >40° up to as much as 100° in some astronomical eyepieces. They all have off-axis aberrations and...
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