Dew forms. The dark is the point.

Your next rig is a set of numbers, not a shopping list.

Dew & Dark works out whether the parts actually fit together before you buy them — payload margin, pixel scale, back focus — with a source on every figure and both sides of the arguments that aren't settled.

Open the calculators Start with the guides

Start here

All guides →
Mounts & Tracking The mount sets the ceiling on everything else. How much payload you can really use, harmonic versus German equatorial, and what counts as good guiding. 6 guides
Imaging OTAs Choosing the scope for the camera, not the other way round — focal length, refractor versus reflector versus SCT, and whether you need a flattener. 4 guides
Cameras & Imaging Train Sensor choice, sampling, and getting every spacer, filter wheel and OAG in the train to land on 55mm. 6 guides
Smart Telescopes & EAA What a smart telescope genuinely does well, what it cannot do at all, and how to tell which side of that line you're standing on. 2 guides
Observatory & Site Setup Power budgets for a full night, dew control that actually keeps up, and planning around the sky you have rather than the one you want. 4 guides
Ships at launch

Four questions in this hobby have arithmetic behind them.

Most gear advice is somebody's preference with a confident tone. These four aren't — they're calculations you can check, run against your own numbers, in the browser, free, no email required.

01Payload calculatorHow much of your mount's rated payload you can actually use for imaging — with the derating debate shown both ways instead of one blog's rule of thumb.Jump to it →02Pixel-scale matcherWhether your camera and scope sample the sky sensibly together, or you're chasing detail the seeing at your site will never hand over.Jump to it →03Back-focus builderAdds up every spacer, filter wheel and off-axis guider in the train against the 55mm standard, before you order the adapter that doesn't fit.Jump to it →04Power & battery calculatorAdd up what your rig actually draws, and see the battery size that answer implies at two very different usable-capacity assumptions — lead-acid/AGM and LiFePO4 are not close.Jump to it →
How to read these

Every figure a calculator uses is named where it is used, with the source it came from. Where the hobby genuinely disagrees — how far to derate a mount's rated payload is the clearest case — you get both positions and the reasoning behind each, not one of them presented as a manufacturer spec.

Open the calculators

What this site is

Dew & Dark is an editorial site about astrophotography gear decisions. Specs are verified against the manufacturer, not copied from another blog. Where the hobby genuinely disagrees — payload derating, mono versus colour, how much guiding accuracy is enough — you get both sides and the reasoning, not a verdict dressed up as consensus.

Verified specs, cited

Every number traces to the manufacturer's own documentation or a measurement we can point at. If a figure is disputed, it says so.

Both sides on real disputes

Some questions in this hobby don't have a settled answer yet. Those get the argument laid out, not a fake consensus.

"You don't need this yet"

The most useful sentence we write is often the one that talks you out of a purchase. That is the point, not a lapse.

Latest guides

All guides →
Hub:Observatory & Site SetupBuilding a Roll-Off Roof ObservatoryWhat a roll-off roof observatory actually requires — footprint, pier isolation, and the DIY-vs-built decision.
Hub:Smart Telescopes & EAAASIAIR Ecosystem GuideWhat an ASIAIR actually automates, which gear it works with beyond ZWO, and where its ecosystem stops.
Hub:Cameras & Imaging TrainGuide Scope vs Off-Axis GuiderSimpler and cheaper, or flexure-proof and finicky — the real tradeoff between a guide scope and an off-axis guider.

Who this is for

Being specific about what this site doesn't cover is more useful than pretending to cover everything.

This is for you if
  • You own a smart telescope and you're working out what a real rig would actually add.
  • You've settled on a camera and need to know what mount and scope it belongs with.
  • You want the source for every number, and the other side of every argument that isn't settled yet.
This is not the site for
  • "What telescope should I buy first?" We don't answer it. It's a genuinely different question, it's well served elsewhere, and answering it badly is how most astro sites start.
  • Visual observing, eyepiece selection, and planetary lucky imaging. Barely touched here.
  • Specific prices on Celestron, Sky-Watcher, ZWO and iOptron gear. Their dealer terms don't permit it, so you'll get a band and a link to check the current number yourself.

And plainly: the person writing this is a few steps ahead of you, not fifteen years above. Where that shows, it gets said out loud rather than papered over.