● Backfocus Solver · live
The advisor that isn’t paid by the sale.
First Rig takes the four things you actually know — your budget, your sky, what you want to photograph, and how much fiddling you’ll tolerate — and returns a validated, fully priced build, including what it can’t do.
It starts where the expensive mistakes start. The Backfocus Solver takes your corrector, your camera and the rings you own, and returns the stack in order — or tells you, to the tenth of a millimeter, why your rings can’t get there.
| Baader 2" MPCC Mark III coma correctordatum: the T-2 (M42x0.75) thread | datum |
|---|---|
| ZWO M48-M42 adapter (0 mm)M42x0.75 → M48x0.75 · thread-in-thread | 0.00 mm |
| ZWO M42-M48 16.5 mm extenderM48x0.75 → M42x0.75 | 16.50 mm |
| ZWO M42 21 mm extenderM42x0.75 → M42x0.75 | 21.00 mm |
| ZWO ASI2600MC Proflange to sensor | 17.50 mm |
| Required, ±1.00 mm | 55.00 mm |
The rings are the ones in the box with the camera (ZWO ASI2600 Pro supplied extenders). Open this train in the solver
What the catalogue holds
- cooled cameras
- 60
- DSLR & mirrorless mounts
- 10
- flatteners, reducers & correctors
- 42
- thread adapters
- 22
- camera spacer kits
- 8
- rows we couldn’t confirm with the manufacturer — marked in the tool, never guessed
- 22
Every row links to the manufacturer page, manual or drawing it was re-keyed from.
Why the solver asks before it answers
ZWO prints “17.5 mm” for both of these. It means two different things.
On the ZWO ASI2600MC Pro it is the bare body. On the ZWO ASI533MC Pro it is the body plus an 11 mm ring that comes in the box. Fit the ring to the wrong camera, or leave it off the right one, and the train is 11 mm out — 11× the ±1.00 mm the Baader 2" MPCC Mark III coma corrector allows.
ZWO’s own manuals don’t agree on which figure to headline for mechanically identical cameras. So the solver doesn’t guess: for 23 of the cameras in the catalogue, it won’t show a result until you say which configuration you have.
Three commitments
Ranking is never influenced by commission.
Where affiliate links exist they are labeled, and they never move a position. The scoring weights are published, so you can check a ranking against your own priorities and disagree with ours on the numbers.
Every recommendation states what it can't do, and what it resells for.
Every build has a ceiling — focal length it can't guide at, targets that won't fit the sensor, a mount that runs out of payload the moment you add an OAG. You get told where the ceiling is before you buy, and what the kit is worth if you sell it in two years.
We tell people not to buy.
When the honest answer is a $349 smart telescope, or “you need 40% more budget than you think”, that is the answer you get. A sale we talk you out of costs us nothing worth having.
What comes next
The same rigor, applied to the whole rig.
Backfocus is one check. A build also has to clear payload with every component summed, sampling for your sky, and a twelve-month cost that includes the parts nobody lists. That engine needs a gear catalogue keyed the way this one is — one manufacturer page at a time, with the source on every row — and that’s what is being built now.
The name is about where the decision usually starts, not who the site is for. The engine that keeps someone out of a mount that can’t carry their scope will tell a third-rig imager whether a mono camera and a filter wheel is worth $4,000 over the one-shot color they already own.