Swarovski STX 65 Spotting Scope - Initial Review - 26 Sep 2023

With a pending birding trip to the Bahia Region of Brazil my desire to bring a scope and tripod was too much to temper. My current Swarovski STX 85 mm Spotting Scope offers optical superiority but is a bit too bulky to pack for a long international trip. Plus, its weight requires more than my tiny Manfrotto BeFree 2in1 Travel Tripod can handle. So, with apologies to management I ordered the Swarovski Optik 65 mm Objective Lens Module  to reduce size and weight and give me the opportunity to take the scope and tripod on said trip.

First introduced in 2013 by Swarovski the Swarovski ATX/STX Modular Spotting Scope System offers the ability to swap between Angled, Straight and BTX Eyepieces and 65/85/95/115 mm Objectives depending upon the needs/desires of the day.

With a simple press of a button (located on the lower left side of the eyepiece) I'm able to twist and remove the 85 mm Objective and replace it with the just-received 65 mm Objective:  

For those new to the Swarovski Modular Spotting Scope system here are published specs:

 Optical Performance

• Optional eyepiece module required: straight (STX) or angled (ATX) viewing and binocular viewer (BTX) available
• 65mm objective lens balances aperture with portability
• Extra-low dispersion fluoride HD glass limits chromatic aberrations to produce clearer and sharper views with little or no color fringing
• Field-flattener lens system eliminates spherical aberrations to eliminate distortion at the edges of the field of view
• Anti-reflection SWAROTOP lens coatings reduce glare and improve contrast, color rendition, and clarity
• Scratch-resistant SWARODUR coatings protect exterior lens surfaces

Use and Handling

• Large focusing collar is easy to manipulate even when wearing gloves
• Rotating tripod mount allows for precise eyepiece placement
• M67x0.75 objective lens filter thread
• Tripod shoe is compatible with Arca-Swiss quick release plates; standard 1/4"-20 socket on bottom of shoe

Construction Details

• Lightweight and impact-resistant magnesium-alloy housing
• Rubber armor protects against impacts while providing a slip-resistant grip for more secure handling during setup and breakdown
• SWAROCLEAN non-stick coating on exposed lens surfaces allows sap and oils to be easily cleaned for clearer views
• Nitrogen filled and O-ring sealed to be dustproof, waterproof/submersible to 13', and resistant to internal fogging when moving through extreme temperature changes or environmental conditions
•  Broad -13 to 131°F operating temperature range
• Field of View: 124-68 ft/1000 yds w/ the 25-60X Eyepiece
• 2.37-1.30 ° Field of view degrees
• 57-71 ° Field of view apparent
• 6.9 ft Shortest focusing distance
• 750-1800 mm Focal length with TLS APO in mm.

On the Sony Full-Frame Alpha a1 the Zeiss 35 mm f/2.8 gives a focal range of 875 mm (at 25X) to 1500 mm (at 60X) on the scope. Note that magnification range is the same using the 65 or 85 mm Objective.

Using the Digidapter™ DLM to connect the camera to the scope eyepiece my first pics taken on this overcast day were of a nearby hummingbird feeder. I was focusing (Manual focus using Focus-Peaking) on the white flower surrounding the port and saw no discernible chromatic aberration (CA). A small vignette circle is visible at the corners of the image, and I'm ok with it since it helps to verify optical alignment.

  

If you look closely you can see a hint of a blue edge to the vignette circle in the corners of the image but it (CA) is negligible and an artifact of imperfect alignment of the lens w/ the eyepiece. More importantly is whether it is visible on high contrast edges within the image frame, itself. The image of the lily below shows the slightest hint of CA along the edge of the flower petal and dark background that is only visible when magnified several hundred times; again, I have no issues as it is easily removed in post-processing.

A slight hint of CA is also visible when I point the scope toward another subject of high contrast, a white window frame. 

The view through the 65 mm Objective is impressively sharp! With edge-to-edge sharpness there is only the slightest hint of CA in the outer 2% of the image range. The smaller footprint of the straight (STX) Eyepiece and the 65 mm Objective means that I can easily hand-hold the scope/camera combo for digiscoping if necessary. Of course it helps to have a camera w/ 20-30 fps Continuous Shooting and fast shutter speeds to overcome motion blur. I tried it out on the feeder and the neighbor's flower bed. 

On the Manrotto BeFree 2in1 Travel Tripod the Swarovski STX 65 Spotting Scope balanced very nicely atop a Manfrotto MH055M8-Q5 Photo/Video Fluid Head. I tested the rig out on some visiting House Finches, alternating between Manual Focus (using both Focus-Peaking and Focus-Magnifier) and Center-Fixed Autofocus.

The House Finch below was captured using Focus-Peaking (blue highlight around focused area). This guy seems to be recovering from a bout of conjuctivitis...

Feather detail is good and the image is sharp when relying on the blue highlights around the face, but optimized focus and sharper images come when using Magnified Focus-Peaking. The images below show a tad more improvement in image sharpness using this method:

On the Sony a1 I have a customizable button that allows me to use autofocus and center-fixed spot focus area. If I pre-focus using the scope I can press the AEF button for quick bird-eye AF. The images below appear sharp, but not as sharp as the Manual Focus-Magnifiied Peaking provided. This is in part my fault: the customizable button was set for f/4 (not f/2.8) so shutter speed dropped to 1/80 sec.). I will re-test after correcting the mistake...  

Below is a screen-capture of the image above at 300% "before" Denoise AI is executed in Lightroom Classic:

At 50% Denoise setting the program did a nice job of noise reduction at ISO 3200. This is "after" Denoise AI.

As a general rule I try to avoid using autofocus when digiscoping. This is true even when using the outstanding Sony a1 as a digiscoping camera. Because we are working with such shallow depths of field the accuracy of the focus points is reduced when shooting through the spotting scope lenses. I liken it to the AF  problems in the early day of the Sony a7RIV + 200-600mm lens at 600mm; the camera had a hard time obtaining sharp focus on moving birds because of focus-lag (a problem since fixed).

I tested focus of the Swarovski 65 on the tag below. The first example is Manual focus using Focus-Peaking, concentrating on the blue highlighted focus regions. 

Better focus was obtained when using Magnified Focus Focus-Peaking.

The two examples below highlight variability of autofocus. The first example is a bit soft while the second example is much sharper. Even on a flat surface with high contrast the autofocus can jump around. Thus, I prefer to use the Magnified Focus Focus-Peaking.

I'll continue testing both Manual and Autofocus modes on the Swarovski 65. In the meantime I'm very happy with how the scope behaves.