telescope
William Optics
Zenithstar 81 II
81mm Apo doublet FPL-53 · 478mm f/5.9
Doublet astrograph.
Best for
- Large emission nebulae and star clusters
- Full-frame astro cameras and DSLRs
Specifications
| Optics | |
| Type | refractor |
| Optical design | Apo doublet FPL-53 |
| Aperture | 81mm |
| Focal length | 478mm |
| Native f/ratio | f/5.9 |
| Image circle | 44mm |
| Full-frame support | Yes |
| Physical | |
| Weight | 3.6kg |
Typical FOV & image scale
With Full-frame (36×24mm, 3.76µm)
FOV 4.32° × 2.88°
Scale 1.62″/px
With APS-C (23.5×15.7mm, 3.76µm)
FOV 2.82° × 1.88°
Scale 1.62″/px
With IMX533 square (11.3×11.3mm, 3.76µm)
FOV 1.35° × 1.35°
Scale 1.62″/px
Typical targets
- IC IC 434 — Horsehead NebulaEmission Nebula · 60′
- NGC NGC 869/884 — Double ClusterOpen Cluster · 60′
- NGC NGC 2264 — Christmas Tree ClusterEmission Nebula · 60′
- NGC NGC 6992 — Eastern VeilSupernova Remnant · 60′
- NGC NGC 7822 — Cepheus HII RegionEmission Nebula · 60′
- Messier M48 — Open Cluster M48Open Cluster · 54′
Recommended cameras
28.4mm sensor · 4.78µm px · cooled
Compare pairing28.3mm sensor · 3.76µm px · cooled
Compare pairing28.3mm sensor · 3.76µm px · cooled
Compare pairing