Tools Rig Reality Check
Rig Reality Check
You enter four things: budget, sky, what you want to photograph and how much fiddling you will tolerate. You get back builds that hold together, priced from dated catalogue prices, checked against the mount’s imaging payload, and each with what it cannot do.
Ranking is never influenced by commission. The weights are published below, in full. When the right answer is a smart telescope, or more budget than you planned, the tool says so.
For the first year itemized at three budgets from this catalogue, read what the first year costs.
Your constraints
Mount, tripod, optics, corrector and camera.
Your position stays in this browser. The only request is for the 5° square of map it falls in, about 550 km across, and the coordinates are never put in the link.
What do you want to photograph?
How much fiddling will you tolerate?
Portability
Your sky, stated plainly. Enter your usable clear nights per year and this turns them into hours of integration and calendar time per project. Only you know that number for your site; a regional average can be well off for a single backyard.
Refine: guiding, and your own part weights
Weights of parts the catalogue does not hold. Blank uses the assumption shown, which is a round placeholder, not a measurement.
Catalogue: 29 mounts · 45 telescopes · 8 smart telescopes · 70 cameras. Some cameras, correctors and tripods have no dated price yet; a build that uses one is listed apart, never ranked on a partial total.
Builds
Still needed: your budget, your sky, as a Bortle class or an SQM reading, what you want to photograph, how much fiddling you will tolerate.
Or start from one of these:
How this is computed
imaging mass = OTA + rings/dovetail + corrector + camera + filter drawer + guiding + cables/dew/focuser
utilization = imaging mass / rated payload gate: ≤ 60 % or not offered
FL = native FL × the corrector's stated factor (or the maker's FL with an included corrector)
image scale = 206.265 × pixel[µm] / FL[mm] "/px
FOV = 2 · atan(sensor[mm] / 2·FL[mm]) degrees, each axis
sampling = seeing FWHM / image scale
guiding demand = guided RMS / image scale needs < 0.8 × scale to be comfortable
fill = max(major / FOV width, minor / FOV height)
score = budget + payload + sampling + guiding + framing + complexity (+ uncooled)A build is offered only when its payload can be computed from catalogued figures and sits at or below 60 % of the mount’s rated capacity, and its image scale and field can be computed. It is ranked only when every part has a dated price and the total is within budget. A build missing a price is listed apart, with the missing part named, rather than ranked on a partial total. A scope that needs a separate corrector is priced with the cheapest priced corrector its catalogue row names; a scope that names none shows the corrector as unpriced, and a scope whose maker says the corrector is in the box lists it as included and prices none. A mount sold without a tripod is priced with the cheapest tripod whose maker names that mount; where no maker names one, the tripod line stays unpriced.
A reducing corrector changes the focal length, so image scale, field, sampling and framing use native focal length × the factor the corrector’s maker states (a 0.8x reducer on 416 mm images at 333 mm), or the focal length the telescope’s maker states with its included corrector. A corrector whose maker publishes no factor leaves the build at native focal length, and the card says so; nothing is read from a product name.
A missing price is never a reason to tell you not to buy. The smart-telescope answer and “you need more budget” appear only when every build that passes the checks is over budget on its priced parts alone, or nothing passes. When builds fail only because a part has no price yet, the page says the catalogue is incomplete.
The OTA weight is the manufacturer’s, and so are the camera and corrector weights where the manufacturer publishes one. Rings, guiding and cables are not in the catalogue, so they are assumptions until you enter your own (0.9, 0.8 and 0.35 kg: the prototype’s round placeholders, not measurements). The camera and filter drawer together are assumed at 0.7 kg when the camera has no published weight; when it has one, that figure is used and only the drawer and filter are assumed (0.2 kg). A corrector with no published weight is left out of the sum, and the build says so. A camera whose maker states a built-in guide sensor (ZWO’s DUO and Air cameras) carries no guiding mass and is listed with no guide camera or guide scope; one with a built-in controller (the Air cameras) is listed with no control computer. Every build says how much of its mass is assumed. Moment arm is not modeled: a long tube loads a mount harder than its mass says, and the reference gives no formula for it.
Resale value is not yet estimated. There is no data source for it, and we will not publish a percentage we cannot source. The essentials (guiding, dew control, filters, power, control, storage, a focus mask) are listed on every build, each priced with a typical, commonly bought product (as a rule, the in-stock item with the most customer reviews at High Point Scientific, fitted to the build by filter size, aperture or camera support) with its dated source. They are shown, never scored: the ranking and the budget check use hardware only. The headline shows a twelve-month total only when every essential and every hardware line is priced; otherwise it shows the priced hardware and counts what is missing. Tube rings are priced only where a catalogue row names the telescope's tube diameter and a set that fits it (the maker's own holder, or a pair whose listing gives the diameter); any other scope with no supplied dovetail keeps an unpriced rings line. Processing software is $0; the free chain is sufficient.
The scoring weights
Signed off (2026-09-27)These tables are every term in the ranking. No term takes commission, retailer margin, brand or seller as an input. The explanations are in docs/rig-reality-check-weights.md.
Budget use (u = priced hardware ÷ budget)
| Range | Points |
|---|---|
| u > 0.95 | 4 |
| 0.5 < u ≤ 0.95 | 10 + (u − 0.5) × 8 |
| u ≤ 0.5 | 5 + u × 10 |
Payload: reference § 4 bands (rule of thumb)
| Utilization | Verdict | Points |
|---|---|---|
| < 40 % | Headroom for a future upgrade | 17 |
| 40–50 % | Comfortable | 14 |
| 50–60 % | Workable; more sensitive to wind, little room to grow | 8 |
| > 60 % | Do not recommend | not offered |
| > 70 % | Reject outright | not offered |
Sampling: reference § 1 bands (scored; sampling never rejects a build)
| Factor | Meaning | Points |
|---|---|---|
| < 0.8 | Badly undersampled: the pixel is wider than the seeing disc, so stars land as blocky squares | -9 |
| 0.8 – 1.4 | Undersampled; the standard, deliberate wide-field trade | 9 |
| 1.4 – 3.2 | Practical band for typical seeing | 15 |
| 3.2 – 4.5 | Oversampled: lower per-pixel signal and tighter guiding; binning recovers most of it | 9 |
| > 4.5 | Heavily oversampled: the atmosphere limits resolution long before the pixel does | 0 |
When you ask for wide targets, "undersampled" scores as practical (15): deliberate undersampling is the right trade there.
Guiding demand: reference § 4 bands (rule of thumb)
| RMS ÷ scale | Meaning | Points |
|---|---|---|
| < 0.8 | Comfortable: errors hide inside the seeing disc | 12 |
| 0.8 – 1.3 | Achievable with careful polar alignment; expect some rejected subs | 7 |
| > 1.3 | Elongated stars in many subs | -5 |
| no RMS given | Manufacturers publish periodic error, not guided RMS. Not scored. | 0 |
Framing, per target
| Fill | Fit | Points |
|---|---|---|
| < 0.25 | tiny in the frame | 0.4 |
| 0.25 – 0.92 | fills the frame | 3 |
| 0.92 – 1.4 | tight crop | 0.5 |
| ≥ 1.4 | needs a mosaic | -2 |
Summed over the five targets, × 2.2. If the first (headline) target’s fill is above 1.5, -7 more.
Complexity against your patience
points = 8 − |complexity − target| × 1.6; target is 4 for “none”, 6 for “some”, 8 for “lots”. Complexity sums: mount (tracker 2, strain-wave 2, GEM 3); optics (petzval and refractors 1, SCT and Maksutov 2, Newtonian, RC and RASA 3); a separate corrector +1; guiding +1; a cooled camera +1. An uncooled camera adds -3 to the score.
Other thresholds
“Needs a mosaic” in the can’t-do list above a fill of 1.2; “too small” below 0.12. A field narrower than 25′ or wider than 150′ gets its own line. A mount over 55.00000000000001 % loaded “cannot grow”. A narrowband filter is listed from Bortle 5 for emission targets. The shortlist holds 3 builds, no two on the same mount and telescope.
The pictures, your sky and portability (none of them scored)
Framing check. Each target is drawn at its OpenNGC angular size against the sensor field at the build’s focal length (reduced where the corrector’s factor is catalogued), at one scale for both, with the major axis along the frame’s width as the fill figure assumes. The glow and stars are synthetic and seeded; no survey imagery is used.
What your data will look like. Sky and target rates are e = F₀ · 10^(−0.4·m) · A · s² · QE and each frame’s SNR is the stacked CCD equation, both from the Exposure Planner’s physics (reference §§ 2–3). Assumed: 4-minute subs, a 21.5 mag/arcsec² stand-in target, no filter, dark current or obstruction. Read noise and QE come from the camera’s sensor profile, or a labeled placeholder. The frames are noise of σ = 1/SNR over a synthetic scene.
Your sky, stated plainly. Hours a year = your clear nights × usable hours a night (an assumption you set, 4 h by default); calendar time = project hours ÷ hours a year × 12 months, for an example 20-hour project. The Moon, season and target visibility all cut into it.
Portability. Display only. Every build shows what you carry (mount head, counterweights, tripod and OTA, from their catalogue rows). “Travel” flags builds over 10 kg (our judgment of one trip from a car without a cart, not a sourced figure) and never changes the ranking. The budget is checked on hardware only; a build whose first year, essentials included, runs past it is flagged “over budget in year one”, again without changing its rank.
Rules of thumb in this tool
- Imaging payload should stay within 50–60 % of the rated capacity; the number on the box is a visual figure. (Cloudy Nights, “Mount weight capacity for imaging — disconnect”: “for astrophotography one should not use more than 50% to 60% of stated capacity”; a CGE Pro rated 90 lb “began to lose precision once I exceeded 70 lbs”. Forum practice, not a manufacturer specification.)
- The five utilization bands (< 40, 40–50, 50–60, > 60, > 70 %). (docs/03-physics-reference.md § 4, a presentation of the derate evidence above.)
- A finished imaging payload runs 30–40 % over the bare OTA. (docs/03-physics-reference.md § 4 (“in practice”). A cross-check only; the tools sum components instead.)
- Guided RMS should sit comfortably below the image scale (bands at 0.8 and 1.3). (docs/03-physics-reference.md § 4, “Guiding demand”, labeled a rule of thumb there.)
- Moment arm is a separate penalty from mass and is not modeled. (docs/03-physics-reference.md § 4 gives no formula or bands for it.)
Target sizes: OpenNGC by Mattia Verga (tag v20260501), CC BY-SA 4.0. This table is shared under the same license. Source and license
Source: docs/03-physics-reference.md §§ 1 and 4; Cloudy Nights, “Mount weight capacity for imaging — disconnect”. Implemented in packages/physics/src/payload.ts, optics.ts, scoring.ts and rig-reality-check.ts, each with unit tests from the reference's worked examples.
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