Problems to Overcome

Focus and Depth of Field

After linking camera and telescope and finding the subject in the camera’s viewfinder, the photographer’s first job is to achieve sharp focus. But without the aids that one might find in a rangefinder camera or on a split-image rangefinder viewing screen in an SLR, finding the sharpest point of focus using the camera’s finder poses a challenge.

Braymer could do little more than acknowledge the problem and offer only a handful of solutions. Since the image that appeared on a camera’s ground glass was too dim for a split-view rangefinder to be effective, he suggested using a plain ground glass with a clear center. Waist-level finders were best especially those with some kind of magnifier.

Users of modern digital cameras have tools at their disposal that are far better than what film photographers had to work with. The magnifying feature that most digital cameras include in their live-view monitors allow one to zoom in on a region in the image frame and achieve sharp focus.

Related to obtaining focus is the issue of depth of field. Especially with subjects at close range (around 20 feet), the depth of field can be extremely shallow. Greater distances offer more forgiving focus depth.

Exposure

With its catadioptric mirror-lens design and very long effective focal length (approximately 1270mm), the Questar telescope’s aperture is no faster for photography than f/16. One never stops down that aperture unless the subject is very close to the telescope (less than 20 feet or so), in which case a diaphragm ring is used in front of the corrector lens.

Because the Questar is so slow, subjects that are in bright daytime light or that are stationary for long exposure times are best.

Without much control over aperture and with a limited range of shutter speeds that work effectively at a high focal ratio, the sensitivity of whatever medium receives and records light (a film emulsion or digital sensor) is the only other way to make adjustments for a given subject. For action shots at a bird feeder, for instance, one is best served opting for a fast film speed or high ISO digital sensor setting. Stationary objects give the photographer the ability to shoot at a lower sensitivity.

Poor Seeing

If the brightness of daytime offers the best light, another problem emerges: the effect of atmospheric turbulence caused by the heat of the sun. One sees the effect of this by looking down a long highway on a hot summer day and observing the shimmering effect that appears immediately above the roadway pavement.

This effect is multiplied as magnification increases. In high-powered telescopic photography, it can be a showstopper. If the air is unstable, it’s impossible for one to achieve sharp focus.

Lawrence Braymer advised that the best time to use a Questar telescope for terrestrial photography is in the earlier morning hours when light is ample but before the sun has had the chance to bake the landscape and make the air above it unstable.

Vibration

Early on, Braymer complained about the indifference of SLR film camera manufacturers to the twin problems of mirror slap and shutter shock. Until they came up with better camera bodies, he was forced either to identify models that demonstrated minimal vibration or to modify existing models to make them better suited for use with a high-power telescope like the Questar.

This same problem persists even today. Many modern digital mirrorless cameras still have a mechanical mechanism that moves a physical shutter curtain in front of and then away from the image sensor when it starts an exposure. The best digital cameras to use with a Questar are those equipped with an electronic front curtain shutter (EFCS). Instead of the motion of a physical shutter curtain, cameras with EFCS begin an exposure electronically without the jarring motion that results in a blurry image.

Balance

Especially to those who are used to handling lightweight digital cameras, the typical film SLR camera body of the 1950s and ‘60s was a big, bulky, and heavy mass of metal. As a result, achieving balance with a camera attached to a standard fork-mounted Questar telescope was yet another problem the photographer had to contend with.

One solution was to engage a locking knob that held the telescope at a given altitude. Making adjustments required the photographer to hold the camera in hand to make sure that its weight didn’t cause the telescope to point upward suddenly and uncontrollably.

In 1963, Questar took up a suggestion from one of its clients and introduced a counterweight made of a lead-filled collar that attached to the front of the telescope. The accessory helped balance the weight of the rear-mounted camera.

Vignetting

For the first ten years of production beginning in 1954, Questar telescopes featured a design that allowed a photographer to attach an appropriate camera to the instrument. The internal dimensions of the hardware surrounding the light path, however, were on the tighter side. The result was significant vignetting on the outside edges of the full 35mm film image frame.

In early 1964, Questar introduced its so-called wide field construction. Brought to market at the same time as its Field Model, an unmounted variation of the Questar that the company developed specifically with the photographer in mind—indeed, the company’s early terminology identified this new Questar as the photographic model—the wide field construction featured better light throughput that reduced (but that did not totally eliminate) vignetting. Along with a number of improvements in the internal construction of the telescope, the most obvious difference was a significantly wider rear axial port.

Since Questar began departing from the earlier narrow field construction only ten years after beginning production—it took them another nine years to make it their standard option—the number of examples on the market with the older style is relatively low. Still, it’s something that may be a factor for some photographers.