Stargazer's Atlas Astronomy Tools & Reference
v1.0.0
Know what is up before you go outside
Find the faint things, not just the bright ones
The mount is half the telescope
TONIGHT'S SKY

Know what is up before you go outside

Twenty-eight pieces of equipment explained without marketing language, three calculators that show their working, and four interactive simulations — all free, all independent.

Browse the tools Open the 3D studio
M42 Orion Nebula17:23SEmag 4.0M31 Andromeda Galaxy12:32Nmag 3.4M45 Pleiades15:35SEmag 1.6M57 Ring Nebula06:39SEmag 8.8M51 Whirlpool Galaxy01:16Nmag 8.4M13 Hercules Cluster04:28SEmag 5.8M27 Dumbbell Nebula07:44SEmag 7.4M8 Lagoon Nebula05:50Smag 6.0M33 Triangulum Galaxy13:22SEmag 5.7M81 Bode's Galaxy21:43Nmag 6.9M82 Cigar Galaxy21:43Nmag 8.4M104 Sombrero Galaxy00:27Smag 8.0M1 Crab Nebula17:23SEmag 8.4M44 Beehive Cluster20:27SEmag 3.7M42 Orion Nebula17:23SEmag 4.0M31 Andromeda Galaxy12:32Nmag 3.4M45 Pleiades15:35SEmag 1.6M57 Ring Nebula06:39SEmag 8.8M51 Whirlpool Galaxy01:16Nmag 8.4M13 Hercules Cluster04:28SEmag 5.8M27 Dumbbell Nebula07:44SEmag 7.4M8 Lagoon Nebula05:50Smag 6.0M33 Triangulum Galaxy13:22SEmag 5.7M81 Bode's Galaxy21:43Nmag 6.9M82 Cigar Galaxy21:43Nmag 8.4M104 Sombrero Galaxy00:27Smag 8.0M1 Crab Nebula17:23SEmag 8.4M44 Beehive Cluster20:27SEmag 3.7

Independent & ad-free

No retailers, no affiliate links, no sponsored placements. Nothing on this site is paid for by a manufacturer.

Nothing for sale

We describe equipment and the physics behind it. We do not sell equipment, and we do not take a cut of anything you buy.

Free interactive 3D tools

Four 3D simulations — solar system, telescope, star wheel and image stacking — run in your browser at no cost and with no account.

Safety and dark-sky guidance

Solar observing warnings, light-pollution figures and night-safety notes appear wherever they are relevant, not in small print.

Equipment

Five groups, twenty-eight tools

Everything is grouped by what it does to the light, not by what it costs.

All 28 tools
Telescopes & Mounts The light-gathering end of the hobby — optical tubes, the mounts that carry them, and the support that keeps them steady. 6 tools Eyepieces & Optics Where magnification is actually decided — eyepieces, Barlows, reducers, diagonals and finders. 6 tools Filters & Solar Contrast tools for nebulae, plus the only category where a mistake can cost you your eyesight. 5 tools Imaging & Astrophotography Cameras, guiding, filter wheels and dew control — everything that turns photons into a processed image. 6 tools Observing Accessories Star atlases, planispheres, red lights, chairs and cleaning kits — the kit that makes a long night work. 5 tools

Method

How a session actually goes

Four stages. Most problems trace back to rushing the second one.

  1. Illustration for step 1: Plan & Locate 1
    Step 1

    Plan & Locate

    Pick targets that are actually up, high enough and suited to your sky. A planisphere or an atlas turns a vague intention into a list of coordinates.

  2. Illustration for step 2: Set Up & Align 2
    Step 2

    Set Up & Align

    Level the tripod, balance the tube, align the finder and — on an equatorial mount — the polar axis. Ten minutes here saves an hour later.

  3. Illustration for step 3: Observe & Track 3
    Step 3

    Observe & Track

    Start at low power to centre the target, then raise magnification only as far as the seeing allows. Let your eyes adapt and give faint objects time.

  4. Illustration for step 4: Record & Share 4
    Step 4

    Record & Share

    Log what you saw, with time, magnification and conditions. A written record is how you learn what your equipment and your sky can really do.

3D Studio

The solar system, running on real periods

Drag to rotate, scroll to zoom, click a planet for its data. The model loads only when this section reaches your screen.

All four 3D tools
Solar system preview Live
Drag to rotate · scroll to zoom · click a planet
Diagram of the inner solar system

The interactive preview needs WebGL, which this browser is not providing. Every figure it produces is still available in the Solar System Explorer.

Preview data

Positions are computed for today from mean orbital elements. Click any planet in the view to read its distance and period.

Solar System ExplorerTelescope SimulatorStar Wheel 3DAstrophotography Stacker

Simulations are teaching models. They are not an ephemeris and not a substitute for your equipment manual.

Popular

Nine tools people start with

See all 28
Technical line drawing of a refractor telescope Refractor Telescope A lens at the front, an eyepiece at the back — the simplest and most robust optical path. Telescopes & Mountssetup Technical line drawing of a reflector telescope Reflector Telescope Mirrors instead of lenses — the most aperture per unit of money, at the cost of collimation. Telescopes & Mountssetup Technical line drawing of a catadioptric telescope Catadioptric Telescope Lenses and mirrors folded together — long focal length in a short, portable tube. Telescopes & Mountssetup Technical line drawing of a equatorial mount Equatorial Mount One axis pointed at the pole, so tracking a star needs only one motor. Telescopes & Mountssetup Technical line drawing of a alt-azimuth mount Alt-Azimuth Mount Up-down and left-right, which is how you already think about the sky. Telescopes & Mountssetup Technical line drawing of a tripod Tripod The least glamorous component and the one that most often limits the view. Telescopes & Mountssetup Technical line drawing of a plössl eyepiece Plössl Eyepiece The symmetric four-element default — clean, cheap, and honest about its limits. Eyepieces & Opticsobserving Technical line drawing of a wide-field eyepiece Wide-Field Eyepiece 60° to 100° of apparent field — the whole object, with room around it. Eyepieces & Opticsobserving Technical line drawing of a barlow lens Barlow Lens A diverging lens that multiplies the effective focal length of everything behind it. Eyepieces & Opticsobserving

Calculators

Three that show their working

Diagram for the Telescope Magnification Calculator Telescope Magnification Calculator Magnification, exit pupil, true field, limiting magnitude and resolution from three inputs. Calculator Diagram for the Exposure Calculator Exposure Calculator Exposure time, ISO, frame count and integration time for a given target, optics and sky. Calculator Diagram for the Field of View Calculator Field of View Calculator Whether your target fits, and how much of the frame it fills. Calculator

From the blog

Reading worth doing before buying

Illustration for How to Start Stargazing: A Beginner's Guide Beginner14 January 20269 min read How to Start Stargazing: A Beginner's Guide The first month of astronomy is mostly about your eyes and your expectations. This is the order in which to do things. Mara Vance Illustration for Choosing Your First Telescope Telescopes28 January 202611 min read Choosing Your First Telescope Aperture, focal ratio, optical design and mount — and which of them should actually decide your purchase. Tobias Lindqvist Illustration for Understanding Magnification and Field of View Telescopes9 February 20268 min read Understanding Magnification and Field of View Four numbers govern every view through every eyepiece. Once they are intuitive, choosing eyepieces stops being guesswork. Tobias Lindqvist

Plan tonight properly

Pick a target from the object database, run it through the magnification calculator, then note what you actually saw. That loop is the whole hobby.

Open the object database Read the guides