Larger the objective the better! (77 – 85 mm) = More Light!!!! Pretty self-explanatory. The smaller, compact (50-65mm) scopes are great to carry and probably provide 95% of the view you'll ever want, but they provide less light than the scopes with larger objectives. The old rule of thumb in photography states that you should shoot at a speed that matches your lens (1/500 sec. for the D70/Sigma400/1.4TC). Granted, we will be using a tripod, but we still want as much light as possible to increase our shutter speeds.
Coatings: APO, Fluorite, ED, HD APO (apochromatic) lenses are capable of converging three wavelengths of light to a single focal point. When you think Leica, you think APO Televid 77. Fluorite lenses (Zeiss), ED (extra-low dispersion glass from Nikon) and HD (high-definition glass from Swarovski) are the types of lenses one should look for in a spotting scope. They usually cost more than lenses that don't have these characteristics. Why? Their manufacturers have taken great pains to reduce the effects of Chromatic Aberration or CA. See next item, please...
Chromatic Aberration The dreaded CA is the term to describe light passing through a parabolic lens. Light is made up of different wavelengths (thus different energies) and pass through glass at different speeds, thus giving us the prism effect we cherish from Pink Floyd's Dark Side of the Moon album. Unfortunately, each wavelength converges at a different focal point, leading to what is called chromatic aberration. In a poor camera lens or spotting scope, this translates to an image with the subject surrounded by a blue-purple haze or outline.
Purple Fringing (camera micro lens CA) Purple fringing is chromatic aberration from the micro-lens of the compact digital camera. Sony (Zeiss), Nikon, and Leica put great effort into reducing CA in their cameras. Check out http://www.dpreview.com/ for extensive camera reviews and comparisons between different brands. -
- Nikon ED78; ED82
- Pentax PF-65ED II, -80ED
- Swarovski ATS80HD, STS80HD
- Swarovski ATX/STX 65/80/95
- Zeiss Victory Diascope 65/85T*Fl
- Zeiss Diascope 65/85T*Fl
- Zeiss Photoscope 85T*Fl
This should by no means suggest that scopes not listed here are no good for digiscoping. These are top-end scopes and some wonderful images have been acquired from them. If you are in the market for a scope and are interested in digiscoping with it, then check out these sites for reviews and forums regarding the scopes: Andy Bright's Digiscoping Forum and Better View Desired. Bottom line? Go to an optics store or bird fair and check out the scopes for yourself! Your eyes are unique and Brand X might provide a significantly better view than Brand Y despite the ramblings of the experts. I use the Zeiss 85T*Fl (purchased in 2003) and still enjoy the wonderfully-bright view ten years later.
Eyepiece - Fixed 20X or 30X Wide Angle - Zoom 20-60X It's an age-old question. Which is better? I have the 20-60X on the Zeiss and its wonderful. I've also recently tested the new Vario 20-75X Zoom eyepiece from Zeiss and love it. However, for digiscoping the best magnifications I use are either 20X or 60X as image quality and vignetting are issues at zoom settings in between. I would love to try the 30X Wide Angle for digiscoping, but it is now discontinued. Consensus is that the 40X fixed is too high a magnification for most situations, but I've gotten some wonderful images with it, albeit slightly softer than a 20X eyepiece would provide. Bottom line, best photos come from the lowest magnifications possible, so if you're starting out, set your zoom eyepiece to 20X and leave it there! I've found that cropping gives better results than increased magnification / softer images.