By Emile Cormier

With feedback from members of the
Royal Astronomical Society of Canada, New Brunswick Centre.

This guide is intentionally vendor-neutral and does not recommend any specific brands or models.

Released under the Creative Commons Attribution-NonCommercial-ShareAlike License - CC BY-NC-SA.

Version 1.1, 2021-11-01

A print-friendly PDF version can be downloaded here.

Contents

• Telescope Basics
• Common Optical Tube Types
• Common Mount Types
• Telescopes for under $1000 (CAD)
• Telescopes for over $1000 (CAD)
• Which Telescope Under $1000 is Right for Me?
• Which Telescope Over $1000 is Right for Me?
• Useful Upgrades and Accessories
• Gear for Taking Snapshots of the Moon
• Gear for Capturing Images of the Planets (and Close-ups of the Moon)
• Gear for Capturing Images of Deep Sky Objects

Telescope Basics

Aperture: Diameter of the objective lens or primary mirror

It is the main performance indicator of any telescope. More aperture means:

• More light gathering power.
• Faint objects (galaxies, nebulas) are brighter.
• More magnification possible to see finer details (limited by atmospheric conditions – see below).
• Narrower fields of view.
• A bulkier, heavier, and more costly instrument.

How much aperture? It depends on:

• Your budget.
• Your desired portability.
• Your desired performance.
• Your desired field of view range (wide vs. narrow).

Magnification: Ratio between apparent size and true size

Also called “power”. It is determined by the focal length of the telescope and the eyepiece that’s being used (eyepieces are interchangeable). It is fixed in most binoculars. Magnification is limited by one of two factors:

• The telescope’s aperture: ×50 per inch of aperture.
• The steadiness of the atmosphere (called seeing).

Atmospheric seeing depends on your climate and geography, but it generally limits useful magnification to around ×200 on most nights.

Common Optical Tube Types

Reflector (aka Newtonian)

• One looks through the side of the tube with this type, not the back.
• Quite affordable when bundled with a simple Dobsonian mount
• Less prone to dew than other types
• Requires occasional collimation (re-alignment of the mirrors)
  • A laser collimator tool makes this quick and easy.
  • Astronomy clubs can do this for free at their meetings.

Refractor

• Limited to smaller apertures (large ones are very expensive)
• Maintenance-free – no collimation required
• Achromatic refractors show discoloration of bright objects at high magnification (called chromatic aberration) – best used at low power.
• Apochromatic refractors show no discoloration but are more expensive – this is the most recommended refractor type for deep sky astrophotography.
• Makes a good portable “grab & go” telescope when paired with an altazimuth mount
• Mass-produced kits have flimsy mounts & lousy accessories. Best to purchase the mount & accessories separately. Seek recommendations from experienced observers.
• Also good for terrestrial and solar viewing with proper accessories

Schmidt-Cassegrain (aka SCT)

• Optical design combines lenses and mirrors
• More compact than a reflector of the same aperture, but also more expensive
• Usually bundled with a computerized mount in telescope kits
• Field of view is narrower than other types ‒ makes it difficult to obtain good deep sky imaging results. Choose an apochromatic refractor instead for deep sky imaging.
• Good for planetary/lunar imaging using specialized cameras and processing techniques
• Best compromise for both visual and imaging, but not particularly well-suited to wide-field deep sky imaging

Common Mount Types

Dobsonian

• Simple wooden box
• Simple left-right / up-down motions
• Always bundled with reflector optical tube
• Very cost-effective
• Not very portable

Altazimuth

• Simple left-right / up-down motions
• Folds down for compact transportation
• Some include slow-motion controls to aid in tracking objects
• Those bundled in telescope kits are usually inadequate ‒ better to buy components separately. Seek recommendations from experienced observers.
• A Dobsonian mount is cheaper for telescope apertures larger than 4 inches

German Equatorial

• Axes of rotation are relative to the celestial pole for better tracking
• Motions are not intuitive
• This is the mount type required for long-exposure deep sky astrophotography
• Requires polar alignment for accurate tracking in astrophotograhy
• Those bundled in cheap telescope kits are almost always inadequate.
• Does not pair well with reflector tubes for visual use ‒ eyepiece ends up in awkward positions

Telescopes for under $1000 (CAD)

Telescopes for over $1000 (CAD)

Which Telescope Under $1000 is Right for Me?

Which Telescope Over $1000 is Right for Me?

Useful Upgrades and Accessories

Gear for Taking Snapshots of the Moon

The Moon is the only nighttime celestial object that’s bright and wide enough to be photographed as a single snapshot and produce satisfying results.

Just about any decent telescope will allow you to take snapshots of the moon.

A phone adapter makes it easier to hold up and aim a phone camera against a telescope eyepiece.

Prime focus astrophotography (without a camera lens) using a digital camera requires:

• A camera t-ring adapter.
• Possibly a t-thread extender (sometimes combined with the nosepiece) – needed to achieve the required backfocus distance on certain Newtonian or refractor telescopes.
• A t-thread nosepiece for Newtonian and refractor telescopes.
• A t-thread to SCT adapter for Schmidt-Cassegrain telescopes.

There are camera adapter kits that combine the above. For Newtonian and refractor telescopes, make sure the nosepiece fits into your telescope’s focuser (1.25 inch or 2 inch barrel diameter).

Gear for Capturing Images of the Planets (and Close-ups of the Moon)

Due to turbulence in the atmosphere, still images of planets tend to be quite blurry.

Sharper details are achievable using a process called lucky imaging. This involves recording video of a planet through a telescope. The idea is to capture brief moments where the view is steady.

The ideal camera for this is a dedicated planetary imaging camera with a high-speed USB 3 output. It requires a portable computer to record the video data (ideally one equipped with a solid state drive). Good cameras cost over $200.

Specialized stacking software is required to process the best frames from the video and produce a still image. This image is then digitally sharpened to obtain a much clearer view of the planet than is possible with single snapshot.

A motorized telescope is pretty much required for this. The more aperture, the better.

Planetary imaging is not a casual endeavour! It’s not as simple as point and shoot.

Although less ideal, a smartphone mounted to the telescope via a phone adapter can also be used to record the video of a planet.

The phone’s video then needs to be converted to a format supported by stacking software.

A digital camera (DSLR or mirrorless) can also be used to record the planetary video (in movie mode). It’s not as ideal as a dedicated planetary imaging camera, but it can still allow you to try your hand at lucky imaging.

There are programs that can record the video from a digital camera tethered to a computer via USB.

Gear for Capturing Images of Deep Sky Objects

Prepare to spend several thousand for a minimal setup.
Much learning effort – not a casual endeavour!

Only a brief overview is provided here. This is a vast subject that cannot be adequately covered in this short guide.

Imaging deep sky objects (galaxies, nebulas, star clusters) involves taking minutes-long exposures using a telescope with good tracking. Hours worth of exposures are required, then need to be stacked using specialized software. This can be quite technical and is not a casual endeavour!

A short focal length refractor is the best way to start and achieve satisfying results. Avoid the temptation to use a large aperture instrument such as a Schmidt-Cassegrain – that way will most likely lead to frustration.

Mount options:

• German equatorial mount: best option for accurate tracking. Payload capacity should be twice the actual payload weight for mass-produced mounts.
• Fork mount with equatorial wedge: not recommended.

Main camera options (least to most expensive):

• Digital camera body (DSLR or mirrorless) with adapters
• Dedicated one-shot color (OSC) astronomy camera
• Dedicated monochrome astronomy camera with filter wheel. More efficient at gathering light and allows narrowband imaging.

If you don’t already own a digital camera (such as a DSLR), it’s better to start with a dedicated astronomy camera if you can afford it.

Auto-guiding is recommended for best results. A separate guide camera and special software is used to send corrections to the mount to keep an object centered.

Guider options (requires dedicated guide camera):

• Smaller guidescope mounted to the main scope.
• Off-axis guider (OAG) – uses part of main scope’s light.

A portable computer is necessary if using a dedicated astronomy camera, or for running autoguiding software.