Aperture is the single most important specification for an astronomy telescope. It refers to the diameter of the telescope's main lens or mirror - essentially, how wide the "light bucket" is.

Why aperture matters for astronomy:

The greater the aperture, the more light collected, and the brighter and clearer your view of night-sky objects.

Light-gathering power increases dramatically with aperture size because it's proportional to the area of the lens or mirror (which depends on the square of the radius).

For example, a 200mm telescope doesn't gather twice as much light as a 100mm telescope - it gathers about four times as much light. This makes a huge difference when viewing faint objects like galaxies and nebulae.

The key principle: Most astronomical objects are faint, not small. They need more light to see clearly, not greater magnification. A larger aperture will always outperform higher magnification when it comes to viewing deep-sky objects.

Aperture sizes for astronomy:

• 76-114mm: Entry level - good for Moon, planets, and bright star clusters
• 130-150mm: Mid-range - excellent for planets and brighter deep-sky objects
• 200mm (8") and above: Serious astronomy - reveals faint galaxies, nebulae, and fine detail

Unlike aperture (which is fixed), a telescope's magnification can be changed by using different eyepieces.

This flexibility allows you to adjust the view based on what you're observing and atmospheric conditions.

How magnification works:

Magnification is calculated by dividing the telescope's focal length by the eyepiece focal length. For example, a telescope with 1000mm focal length using a 10mm eyepiece gives 100x magnification (1000 ÷ 10 = 100x).

Maximum useful magnification:  Approximately 2 times the aperture in millimeters. For example, a 130mm telescope can usefully magnify up to about 260x. Beyond this, the image becomes too dim and blurry to be useful.

Why less magnification is often better:

Most visual astronomers prefer lower to moderate magnification because:

• You get a wider, fuller field of view
• You can see more complete objects (like entire nebulae or galaxies)
• The image stays brighter and clearer
• Atmospheric conditions often distort the view at high magnification

The trade-off: Increasing magnification makes the image larger, but it also makes the image dimmer and the field of view smaller. For most deep-sky objects, a wider, brighter view is more impressive than high magnification.

Portability is an important consideration when choosing an astronomy telescope, as it can directly affect how often you'll actually use it. The easier a telescope is to move, transport, and set up, the more likely you are to take it out for observing sessions.

The aperture vs portability trade-off:

As aperture increases, the telescope generally becomes larger and heavier. Larger telescopes gather more light and show fainter objects, but they can be more challenging to transport and set up, especially if you need to travel to darker skies away from light pollution.

Design matters:

The Cassegrain design SCT (Schmidt-Cassegrain Telescope) and Maksutov telescopes - significantly reduces the physical size of the telescope while maintaining good aperture.

A 200mm Cassegrain is much more compact than a 200mm reflector with the same light-gathering power, making it easier to transport.

Portability by telescope type:

• Reflectors on tripods: Mid portability - tube can be long but separates from mount
• Dobsonians: Lower portability - bulky base, though some models are collapsible for easier transport
• Cassegrains: High portability - compact design despite good aperture, easy to transport

Consider your situation: If you have a backyard with dark skies, portability matters less. If you need to drive to dark-sky sites or store your telescope in limited space, prioritize more compact designs or consider portability features like collapsible Dobsonians.

The mount can be just as important as the telescope itself for astronomy. It holds your telescope steady and determines how easily you can point at and track night-sky objects as they move across the sky.

Manual Mounts for Astronomy:

• Equatorial (EQ) Mounts: A traditional mount type for astronomy. EQ mounts are tilted to align with Earth's axis of rotation, allowing them to track stars and planets by moving in a single arc. This makes following objects easier once set up. However, EQ mounts can be less intuitive for beginners and require proper polar alignment to work effectively. They're ideal for those interested in astrophotography or who want to add motor drives for automatic tracking.

• Dobsonian Mounts: A simple, stable mount where the telescope tube sits on a base that swivels left-right and tilts up-down. Dobsonians are incredibly intuitive to use, very stable, and require no setup or alignment - just point and observe. This makes them excellent for visual astronomy, especially for beginners. Some models are collapsible for easier transport. While tracking requires manual adjustment, the smooth, natural movement makes this straightforward.

Computerized/WiFi Mounts and GoTo Systems:

These mounts automatically move your telescope to any night-sky object you select, either through a hand controller or smartphone app. Once aligned, they can find thousands of objects at the push of a button and track them automatically as they move across the sky.

GoTo systems are particularly helpful for: • Finding faint objects that are difficult to locate manually • Maximizing viewing time in short sessions • Astrophotography (precise tracking is essential) • Observing from light-polluted areas where fewer reference stars are visible

The middle ground - App-Guided Navigation (StarSense Explorer): 

A middle-ground option that uses your smartphone and an app to guide you to objects. You move the telescope manually while following arrows on your screen - no motors, batteries, or complicated alignment required.

Astronomy telescope prices vary widely based on aperture size, optical design, mount type, and features.

Understanding what to expect at different price points helps you make an informed decision.

Price is closely related to aperture: 

Generally, the bigger the aperture, the higher the price. However, optical design and mount type also play significant roles in the final cost.

Price ranges for astronomy telescopes in New Zealand:

$300-$600: Entry-level telescopes - Small reflectors (76-114mm) or mini-Dobsonians.

• Good for Moon, planets, and bright star clusters. Perfect for children or testing interest in astronomy. Some models include app-guided navigation (StarSense Explorer).

$600-$1,200: Mid-range telescopes - Larger reflectors (130-150mm) on EQ mounts, medium Dobsonians (150-200mm), or smaller telescopes with app-guided navigation.

• Excellent for planets and brighter deep-sky objects. At this price point, you're choosing between a larger manual telescope or a smaller one with technology assistance.

$1,200-$2,500: Advanced telescopes - Large Dobsonians (200-250mm/8-10"), quality reflectors with GoTo mounts, or small-medium Cassegrains.

• Larger apertures capable of revealing faint galaxies and nebulae with impressive detail. The aperture vs technology trade-off is most apparent here.

$2,500+: Premium telescopes - Large Cassegrains with computerized mounts, very large Dobsonians (300mm+/12"+), or high-end reflectors with advanced GoTo systems.

• Designed for serious / easy astronomy and astrophotography.

The aperture vs technology trade-off:

 At similar price points, you can often choose between a larger manual telescope or a smaller telescope with computerized features. For example, around $1,000 you might choose between an 8" Dobsonian (excellent aperture, manual) or a smaller computerized telescope with GoTo. Consider what matters more to you - light-gathering power or convenience.

Best value for aperture: Dobsonian telescopes consistently offer the most aperture for your money, making them a good choice for budget-conscious astronomers who want maximum light-gathering power, but remember the tradeoffs.

Reflector Telescopes: 

• Smaller reflectors (76-114mm) are great for Moon, planets, and bright clusters
• larger reflectors (127-130mm+) excel at deep-sky objects like galaxies and nebulae.

Affordable aperture. Not suitable for daytime use.

Dobsonian Telescopes:

• Ideal for astronomy - best aperture value, excellent also for deep-sky objects.

Astronomy only, not portable.

Cassegrain Telescopes (SCT/Maksutov): 

• Excellent for astronomy and astrophotography - compact, portable, versatile. Higher cost per aperture.

Refractor Telescopes: 

• Limited for astronomy - good for Moon and planets but aperture typically capped at 120mm, less suitable for faint deep-sky objects.

Reflector Telescopes: 

• 76mm - 150mm+
• Small to large apertures available

Dobsonian Telescopes: 

• 114mm - 400mm+
• Medium to very large apertures, best value for size

Cassegrain Telescopes: 

• 90mm - 356mm+
• Compact design despite good aperture

Refractor Telescopes: 

• 60mm - 120mm
• Max out at 120 due to daytime issues with heat haze / air turbulence etc.

Reflector Telescopes: 

• Alt-Az • Equatorial (EQ) • GoTo EQ • App-guided navigation (StarSense Explorer)

Dobsonian Telescopes: 

• Dobsonian base (manual) • Computerized Dobsonian GoTo • App-guided navigation (StarSense Explorer)

Cassegrain Telescopes: 

• Alt-Az GoTo • Equatorial GoTo • Often with computerized mounts

Refractor Telescopes: 

• Alt-Az • Equatorial • GoTo systems • App-guided navigation (for astronomy models)

Reflector Telescopes: 

• Mid - tube can be long but separates from mount

Dobsonian Telescopes: 

• Low to Mid - bulky base, though collapsible models available

Cassegrain Telescopes: 

• High - compact and portable despite good aperture

Refractor Telescopes: 

• Mid to High - compact, though larger apertures become less portable

Reflector Telescopes:

• Depending on aperture -Moon • Planets • Deep-sky objects (galaxies, nebulae, star clusters) • Visual astronomy

Dobsonian Telescopes: 

• Moon • Planets •Deep-sky objects • Faint galaxies and nebulae • Visual astronomy • Light bucket for maximum detail

Cassegrain Telescopes: 

• Planets • Moon • Deep-sky objects • Astrophotography • Portable astronomy sessions

Refractor Telescopes: 

• Moon • Planets • Double stars • Bright star clusters • Limited deeper-sky viewing - in addition to day time viewiing

Reflector Telescopes: 

• Good value for aperture, but typically more expensive than Dobsonians due to equatorial mounts.

Dobsonian Telescopes: 

• Best value for money - delivers the most aperture per dollar with simple, effective design

Cassegrain Telescopes: 

• Premium pricing due to advanced optics and compact design - highest cost per aperture but offers portability and versatility

Refractor Telescopes: 

• More expensive per aperture for astronomy use, but the premium pays for dual-purpose versatility - correctly oriented images allow daytime viewing of wildlife, landscapes, and terrestrial subjects