Why I built it
I am Paul Haworth, a landscape astrophotographer and filmmaker based in the Cambridgeshire Fens, in the east of England. I spend a lot of nights standing in the middle of nowhere waiting for the sky to do something worth photographing.
The problem was never a shortage of information. It was that the information lived in so many different places: one site for cloud, another for the moon, a light pollution map, a meteor calendar, a satellite tracker, and none of them answered the only question that matters at five o'clock on a Tuesday afternoon: is tonight worth it?
So I built the thing I wanted. It pulls the forecast, works out the astronomy on your phone, and gives you a straight answer. Then, if you are going out, it tells you when the sky will be darkest, what is worth pointing at, whether it will fit your lens, whether the aurora might treat you, whether to pack dew straps, and whether the mist is going to ruin it anyway.
It works anywhere. Give it a location and it reads the light pollution atlas, the forecast and the sky for that spot, in either hemisphere: the only thing that is particularly British about it is me.
It is free because it was always for me and my friends first. If it saves you a cold hour working something out on the back of your hand, you can buy me a coffee.
Common questions
What is the best time to photograph the Milky Way Core?
You need three things at once: full astronomical darkness (or close to it), minimal moon, and the galactic core above the horizon. When that happens depends on where you are: north of the equator the core season runs roughly February to October and the core stays fairly low in the south; from the southern hemisphere it climbs far higher, and the season shifts. Noctography works all three out for your own location and shows where they overlap. Don’t forget there are plenty of other fantastic parts of the Milky Way to photograph away from the core!
What is real-world Bortle?
The published Bortle class for a site describes a perfect, moonless night, which is rarely the night you are standing in. Real-world Bortle starts from the atlas value for your location, then adds moonlight, haze from humidity, and town glow scattered back down by thin cloud, and converts the result back to a Bortle class. A Bortle 3 site under a gibbous moon genuinely performs like a Bortle 5 one.
How long an exposure before the stars trail?
It depends on your pixel pitch as much as your focal length, which is why the old 500 rule is generous on a dense sensor. Noctography uses the NPF rule and gives you two readings: pin-sharp, meaning no trailing at all, and relaxed, meaning trailing you will not notice in normal viewing and printing. In the framing view it goes further and corrects for the fastest star actually in your frame, which near the pole is worth a stop or more for nothing.
Will I see the aurora, or only photograph it?
Often only photograph it. A dark-adapted eye runs on rod vision, which is colour-blind and roughly five to ten times less sensitive than a camera sensor, so your camera will frequently detect an aurora before you do, and sometimes it never gets bright enough to see by eye. Noctography draws the camera threshold and the eye threshold separately, and moves both with the moonlight, cloud and haze on the night.
How many meteors will I actually see?
Far fewer than the quoted ZHR, which assumes a perfect observer under a perfect sky with the radiant overhead. The real number falls with radiant height, moonlight, light pollution and cloud. A shower quoted at 100 an hour might realistically be 25 from a rural site at mid latitudes, and less again where the radiant never climbs high. Noctography will tell you which you are getting.
Can I see where the Milky Way will be before it gets dark?
Yes. Hold your phone up and the AR overlay draws the real sky over the camera feed, using the compass and tilt, so you can scout the spot in daylight and see where the core, the pole or tonight's subject will sit against the landscape. Every subject is a real photograph at its true position and size, and the Milky Way is photographed too, not a drawn line, so what you see is close to what the camera will record. Scrub the date and the core moves into season. It draws your lens as a rectangle over the top, and in Trails it draws the arcs your session would actually produce. It runs on the phone, offline, and nothing is uploaded.
How far should I rotate between panorama frames?
It depends on focal length, sensor, orientation and overlap. Thirty percent overlap is the minimum for reliable stitching; forty to fifty is safer for night skies, where there is little detail for the stitcher to grip. A 24mm lens on full frame, portrait, at forty percent overlap needs about 44 degrees between frames. For very wide lenses, where vignetting can be strong, I often overlap up to 80%.
Why do clear nights sometimes end up misty?
Radiation fog forms on exactly the nights that look most promising: a clear sky lets the ground radiate its heat away, the air cools to its dew point, and with no wind to mix it, mist forms at ground level. Noctography warns when those three line up. It doesn’t mean a night is unusable – mist can help create stunning images.
What is a planetary conjunction, and when is the next one?
Two bright things appearing close together. Noctography flags every pairing among Mercury, Venus, Mars, Jupiter, Saturn and the moon that closes to within five degrees, which is about a fist at arm's length, and only when both stand at least five degrees above your horizon in a dark or nearly dark sky. The positions are computed on your phone from orbital elements, so it works offline and for any date. If one falls tonight it gets a card on Tonight, with the closest time, how high it will be and which way to face; otherwise look at the Conj row of the fifteen-night grid.
Can I keep a record of what I shot?
Yes, in the Log tab, and it stays on your own device. One tap stamps the time and the night's conditions, so the record is true even if the forecast moves on; you add the composition and the settings whenever suits, including the morning after. Nights you wrote on show up on a calendar, and the whole thing copies, emails or prints. Nothing is uploaded and there is no account, which also means nothing is backed up: it reminds you to take a copy off the phone every twenty entries.
Is it free?
Yes, and there is no account. You provide no personal information. Your location is shared anonymously to fetch weather and tide data. But otherwise everything stays on your device.
