The Sky Gives Me Crumbs
Field Notes · Planning & Observation
The April clouds handed me something useful — a reminder that the sky runs on its own calendar, and summer is not your friend.
The clouds rolled in at 9:10. I'd been home from a meeting for maybe ten minutes, looked up, seen actual stars, and made the mistake of going inside to check Astrospheric. By the time I walked back out, it was over. Classic April.
I went back inside and started poking around Telescopius — not to plan anything, just out of habit. I pulled up the Eastern Veil, the target I've been waiting on since the Rosette experiment stalled. I wanted to see when it would actually be usable. The imaging window looked reasonable. But then I noticed something I'd been taking for granted: how short astronomical night actually gets in June.
Four hours. That's what the sky offers at this latitude in midsummer. And it's not just short — it's shallow. The sun barely drops past −18° before it starts climbing back. The darkness you get in June is thinner than what you get in January, even if the clock says the same number of hours. Winter darkness has weight to it. Summer darkness is a suggestion.
I hadn't really thought about astronomical twilight as a variable before — just as a threshold you cross. But looking at how it changes month to month, it's really a seasonal rhythm you're always working within, whether you notice it or not. In January from Park Ridge, astronomical night runs roughly eleven hours. By June that's collapsed to four. The summer solstice is the trough of the curve.
The sky doesn't go dark all at once. Sunset starts the process, but scattered light lingers for well over an hour. Nautical twilight — sun 6° to 12° below the horizon — is when brighter deep-sky objects begin to emerge. Astronomical twilight ends when the sun clears −18°, and skyglow finally drops below the threshold where it competes with faint signal. That's the moment the real work begins, and the clock I'm always working against.
Astronomical night length by month · Park Ridge, IL (42°N) · Mid-month approximations · Sun below −18°
The U-shape is striking once you see it. Deep winter on both ends, a hard dip through summer. April, where I'm sitting right now, is already well into the slide — six hours and falling. By the time the Eastern Veil is well-placed in the evening sky, I'll be working with roughly four hours between astronomical dusk and dawn.
That's not a reason to avoid summer targets. The Veil is worth it — it's one of the strongest OIII emitters in the sky, and I already have a benchmark FRA300 image to compare against. But it does reframe what "a good session" means in June versus January. In winter I can run sequences for hours and still have time to spare. In summer, four hours is everything — setup, acquisition, and all. There's no slack.
The other thing worth noting: the orange dots mark my Veil window. Right at the bottom of the curve. The target I've been waiting all spring for arrives exactly when the sky gives me the least time to shoot it. I find that clarifying rather than discouraging. It means every clear night in June counts. It means sub-length matters even more — which brings the S30 Pro versus FRA300 experiment back into sharp focus. Shorter subs aren't just a hardware question in summer. They're a time budget question too.
April clouds are still annoying. But they gave me ten minutes with a planning chart and a clearer picture of what I'm working toward. Sometimes the sky closes on you for a reason.
Clear skies / Pete // bortle9astro.com