Have you ever gazed up at the sparkling stars on a clear night and wondered what telescope would offer the optimal view of the Moon‘s craters or Saturn‘s rings? As an amateur astronomer, I‘ve spent countless hours peering through both refractors and reflectors debating those very questions. If you‘re looking to make an informed choice between these two major telescope designs for astronomy, this comprehensive guide will compare their histories, optics, strengths, weaknesses – and how they‘ve revealed the mysteries of the cosmos over four centuries.
The Stargazers‘ History of Discovery
Before assessing the intricate optics directing light inside ever-improving astronomical telescopes, it‘s worth tracing their origins back to early inventors and pioneering scientists who fashioned the first working models from available lensmaking and glassworking techniques.
1608 – After experimenting with different lens configurations, Dutch spectacle maker Hans Lippershey constructs the first documented refracting telescope design – a simple tube with a convex objective lens and concave eyepiece lens. Though low magnification, his ‘spyglass‘ system proves the concept.
1609 – Italian scientist Galileo Galilei, having caught wind of the invention, significantly improves the refractor‘s optics and magnification power to about 30x. His observations turn the tube skyward revealing mountains on the Moon, moons of Jupiter and phases of Venus.
1663 – Scottish mathematician James Gregory publishes an influential paper outlining a design concept for a reflecting telescope using parabolic mirrors over fragile lenses.
1668 – Isaac Newton, an English physicist and mathematician, constructs the first practical reflecting telescope base on Gregory‘s idea – a design that bears his name to this day.
From those humble beginnings, let‘s examine how these ingenious instruments collect faint light from stars and galaxies to modernize our understanding of space.
The Intricate Optics of Discovery
Though forms have diversified over centuries, most astronomical telescopes still adhere to refracting or reflecting optical principles. Let‘s compare the pathways of light through each system.
Refracting Telescopes
As demonstrated by Lippershey and Galileo, a refractor telescope employs a glass objective lens mounted at the opening of the tube to gather and focus diffuse starlight to a point within the tube itself.
Divergent light waves from a celestial object enter the front lens glass and are refracted (bent) causing the waves to converge at a focal point beyond the lens.
An ocular eyepiece lens, positioned close to this focal point, magnifies the image and projects it into the eye of the observer.
Advantages:
- Produces upright, correctly-oriented images
- Crisper views owing to all-lens optics
- Compact form factor, especially shorter refractors
Disadvantages:
- Objective lenses expensive with increasing diameter
- Can suffer chromatic aberration (color fringing)
- Large objective lenses are heavy
Over 400 years of optical engineering has finely addressed these limitations – particularly the advent of compound achromatic lens objectives using combined crown and flint glass types to minimize color distortions.
Reflecting Telescopes
Rather than lenses alone, reflectors utilize a concave mirror – commonly parabolic in shape – to collect incoming light waves and deliver them to a focal point where they can be observed.
Light enters the open end of the optical tube and travels rearward until it strikes the large primary mirror tilted at a slight angle toward the front.
The curved mirror surface reflects and concentrates the light to its focal point near the front of the tube.
A smaller secondary mirror mounted at this point diagonal to the tube axis deflects the light 90 degrees out the side of the tube and into the eyepiece. This produces an inverted image that is righted with accessory optics.
Advantages:
- Very large objective sizes possible at lower costs
- No chromatic aberration as with lenses
- Extremely lightweight construction
Disadvantages:
- Require regular mirror collimation
- Open design allows dust inside tube
- Complex types of optical aberrations
In Newton‘s original 1668 design, the eyepiece was located along the main tube behind the primary mirror requiring observers to climb a ladder to view images. But this awkward setup evolved quickly as secondary mirrors were introduced to divert light to more easily accessible angled eyepieces.
Now that we‘ve reviewed the optical guts steering light in either system, let‘s see how their advantages and disadvantages bear out in real-world performance across various astronomical targets.
Lunar & Planetary Observation
When pointed at solar system destinations like the Moon, visible planets and even brighter star clusters, refracting telescopes have some distinct imaging advantages:
Superior Contrast – Because lenses don‘t suffer internal reflections causing scattered light like mirrors, refractors offer higher-contrast views critical for resolving finer details on planetary and lunar targets.
Minimal Aberrations – The narrow visible spectrum of sunlight reflected from our system‘s worlds means well-made achromatic objectives yield tack sharp pictures relatively free of color fringing.
Ideal Magnification Range – Quality refractors in the 80mm to 150mm aperture range provide plenty of magnification for solar system observing without significant image degradation from atmospheric turbulence.
What do experts say?
"My personal preference is a refractor for lunar, planetary and double stars. Refractors are specially suited for these objects." – Ed Ting, noted astronomer and former editor of Amateur Astronomy magazine.
Based on optical performance plus their typically compact profiles, refractors make superb portable telescopes to take on trips for visual appreciation of our neighbors in space.
Deep Sky Observation
Far beyond our system‘s bounds, galaxies, nebulae and star clusters beckon in the deep sky. To collect precious photons from these faint tendrils millions of light years distant, larger aperture trumps all else. Here reflecting telescopes‘ low-cost scaling to monster sizes pays big dividends.
Excellent Value – Dollar for dollar, reflectors offer vastly more light grasp through objectives measured in feet rather than inches – try getting a 500mm refracting lens for under $30,000!
Sharper Images – Even with multi-element objective correctors, huge refractors still produce some visible chromatic aberration that diminishes contrast – less noticeable on diffuse deep sky objects.
Customizable Precision – Sophisticated amateur reflector designs allow tailored correction for coma and precise collimation to optimize performance on faint deep space galaxies and nebulae.
Survey says?
"Reflectors are my top pick for deep-sky objects like galaxies and nebulae. The current generation offers outstanding views at reasonable cost." – Sky & Telescope Magazine
If your sights are set on glowing star cities, stellar nurseries and luminous planetary clouds beyond our solar neighborhood, reflectors will get you there for less.
Recommendations by Target
Now that we‘ve weighed their relative merits on major astronomical targets, choosing the right telescope comes down to defining your priorities then selecting quality optics to match.
Best for lunar and planetary detail – 80mm to 150mm refractors from respected manufacturers like Explore Scientific, Orion, Celestron or Meade. Expect to invest $250 to $2,000+.
Top picks for deep sky spectacle – 8-inch and larger aperture Newtonian reflectors from Sky-Watcher, Orion, Zhumell or Dobsonian styles. Budget $300 to $1,000+ for superb views.
Ideal all-purpose mid-size scope – 6-inch f/8 achromatic refractor on equatorial mount like the Celestron Advanced VX 6". Combine portable planetary sharpness with bright deep sky reach for $900 and up.
Most portable astronomy setup – Short tube 80mm f/7 or f/5 achromatic refractor on altitude-azimuth mount like the Orion Sirius ED80. Weighs under 10 lbs but reveals tons of lunar, planetary and bright deep sky detail for $500-600.
I wish you clear night skies and even clearer telescope choices on your adventure peering across space and back in time! Feel free to contact me anytime with questions in the comments.
