Two numbers – aperture and focal length – define most of what a telescope means to the rest of Astro PM: field of view, image scale, sampling, and light grasp all flow from them. The telescope editor captures those, the optical character around them, and the mechanical details worth keeping on record.
The Fields #
| Field | Notes |
|---|---|
| Name / Brand / Model | your display name is independent of brand/model, so “Dome A Main OTA” works fine |
| Optical Design | Achromat, Apochromat, Newtonian, Ritchey-Chrétien, SCT, Maksutov, CDK, Classical Cassegrain, RASA |
| Aperture (mm) | the light bucket – drives flux and resolution figures |
| Focal Length (mm) | the magnification side of every FOV and image-scale computation |
| Reducer Factor | 0 = none; e.g. 0.7 for a reducer – downstream calculations automatically use the reduced focal length |
| Obstruction (%) | linear central obstruction; 0 for refractors, typically 25-45% for Newtonians and SCTs |
Optional data – image circle, backfocus, on-axis/edge spot sizes, weight, tube length, focuser travel and mm/turn – stored for reference and used by the Focal Length Calculator where relevant.
The Telescope Library #
Adding a scope? Start typing in the Telescope Library picker and select your model – aperture, focal length, and design pre-fill from the built-in catalog. Everything remains editable afterward, so a tuned RC or a custom reducer setup is a two-second correction rather than a data-entry session.
Computed Stats #
The stats panel derives the optical character live as you type:
| Stat | Formula |
|---|---|
| Focal ratio (native / reduced) | FL / aperture; reduced FL / aperture |
| Airy disk @ 550nm | 2.44 × λ × f-ratio (µm and arcsec) |
| Dawes limit | 116 / aperture (arcsec) |
| Rayleigh limit | 138.4 / aperture (arcsec) |
| Light gathering power | (aperture / 7)² vs. the dark-adapted eye |
Where Telescope Data Is Used #
- Focal length + reducer – image scale (206.265 × pixel size / FL) and FOV everywhere: Sky View’s framing rectangle, mosaic panel geometry, target thumbnails, the Sampling Calculator, and exposure math.
- Aperture – photon flux in the Exposure Calculator, resolution limits, light grasp.
- Design + backfocus + focuser specs – the Focal Length Calculator’s mirror-adjustment guidance.
A telescope is one third of every Imaging System. Correct a focal length and every FOV rectangle, sampling figure, and framing preview updates immediately across all projects on rigs using that scope – deletion is blocked while anything references it.