Celestron EdgeHD 8 OTA with Player One Ares-C Pro
0.38″ per pixel across a 0.32° × 0.32° field, at 2032 mm and f/10.0. 12 of the catalogue's 29 equatorial mounts carry the 9.02 kg train within the imaging derate.
Every figure is computed from catalogue rows that link their maker's page. Rows marked provisional have not yet had a second, human check.
Optics
At the native focal length. The other configuration is in the table below.
| Configuration | Focal length | Ratio | Scale | Field |
|---|---|---|---|---|
| Native | 2032mm | f/10.0 | 0.38″/px | 0.32° × 0.32° |
| Celestron 0.7x Reducer for EdgeHD 800 (#94242) | 1422.4mm | f/7.0 | 0.55″/px | 0.46° × 0.46° |
Image circle: 42 mm, the telescope's stated figure (Celestron EdgeHD 8 OTA). Source
Sampling
Seeing divided by image scale: how many pixels a star's core spans. Each band is a tradeoff, and wide-field work is undersampled on purpose.
At 2.5″ seeing a star’s core spans 6.55 pixels on this sensor. Heavily oversampled: the atmosphere limits resolution long before the pixel does. Binned 2 × 2 it spans 3.28.
| Seeing | Native · 2032 mm | 0.7x · 1422.4 mm |
|---|---|---|
| 1.5″ | 3.93pxoversampled | 2.75pxpractical |
| 2.5″ | 6.55pxheavily oversampled | 4.59pxheavily oversampled |
| 3.5″ | 9.17pxheavily oversampled | 6.42pxheavily oversampled |
- Oversampled: lower per-pixel signal and tighter guiding; binning recovers most of it.
- Heavily oversampled: the atmosphere limits resolution long before the pixel does.
- Practical band for typical seeing.
Framing
The 13 catalogue targets against this field, by the fraction of the frame each fills along its tighter axis.
M31 Andromeda Galaxy fills 929 % of the frame and M27 Dumbbell Nebula 35 %. Of the 13, 4 fill the frame, 2 are a tight crop, 7 need a mosaic.
| Target | Size | Native · 2032 mm | 0.7x · 1422.4 mm |
|---|---|---|---|
| M31 Andromeda Galaxy | 178′ × 70′ | 929%needs a mosaic | 651%needs a mosaic |
| M45 Pleiades | 150′ × 150′ | 784%needs a mosaic | 549%needs a mosaic |
| NGC 7000 North America Nebula | 120′ × 30′ | 627%needs a mosaic | 439%needs a mosaic |
| NGC 1499 California Nebula | 160′ × 40′ | 836%needs a mosaic | 585%needs a mosaic |
| IC 1805 Heart Nebula | 60′ × 60′ | 314%needs a mosaic | 220%needs a mosaic |
| M42 Orion Nebula | 90′ × 60′ | 470%needs a mosaic | 329%needs a mosaic |
| NGC 2237 Rosette Nebula | 80′ × 50′ | 418%needs a mosaic | 293%needs a mosaic |
| M101 Pinwheel Galaxy | 24′ × 23′ | 125%tight crop | 88%fills the frame |
| M27 Dumbbell Nebula | 6.7′ × 6.7′ | 35%fills the frame | 25%small in the frame |
| M51 Whirlpool Galaxy | 13.7′ × 11.7′ | 72%fills the frame | 50%fills the frame |
| M81 Bode's Galaxy | 22′ × 11.3′ | 113%tight crop | 79%fills the frame |
| M13 Hercules Globular Cluster | 16.5′ × 16.5′ | 86%fills the frame | 60%fills the frame |
| NGC 4565 Needle Galaxy | 16.8′ × 2.9′ | 88%fills the frame | 61%fills the frame |
Target sizes: OpenNGC by Mattia Verga (tag v20260501), CC BY-SA 4.0. This table is shared under the same license. Source and license
Spacing
The corrector rows this telescope links in the Backfocus Solver's catalogue, with the face each figure is measured from.
No separate corrector is needed. The maker: “EdgeHD is an aplanatic, flat field Schmidt-Cassegrain telescope that produces aberration-free images across a wide visual and photographic field of view.” Source
Celestron 0.7x Reducer for EdgeHD 800 (#94242)
- Backfocus
- 105mm
- Measured from
- manufacturer figure (4.13"), sheet Figure 1, from the reducer's rear to the camera focal plane; the sheet names no face
- Focal length
- 0.7x, 1422.4 mm
- Image circle
- not published
Mounts
The catalogue's equatorial mounts that carry this train within 60 % of their rated payload, the imaging derate. The sum is the Rig Reality Check's.
On the saddle this train weighs 9.02 kg, 2.25 kg of it assumed. 12 of the 29 equatorial mounts in the catalogue carry it within the derate; the smallest rated is the Celestron CGEM II, at 50 %. 17 more would run it over 60 %.
| Mount | Rated | Used | Band |
|---|---|---|---|
| Celestron CGEM II | 18kg | 50% | Workable; more sensitive to wind, little room to grow |
| iOptron CEM40 (with tripod) | 18kg | 50% | Workable; more sensitive to wind, little room to grow |
| iOptron HEM44 | 20kg | 45% | Comfortable |
| Pegasus Astro NYX-101 | 20kg | 45% | Comfortable |
| Sky-Watcher EQ6-R Pro | 20kg | 45% | Comfortable |
| WarpAstron WD-20 | 20kg | 45% | Comfortable |
The other 6 mounts that carry it
| Mount | Rated | Used | Band |
|---|---|---|---|
| ZWO AM7 | 20kg | 45% | Comfortable |
| Losmandy GM811G (LW tripod) | 22.7kg | 40% | Headroom for a future upgrade |
| Celestron CGX | 25kg | 36% | Headroom for a future upgrade |
| iOptron CEM70 (iPolar) | 31.8kg | 28% | Headroom for a future upgrade |
| Sky-Watcher CQ350 Pro (with tripod) | 35kg | 26% | Headroom for a future upgrade |
| Sky-Watcher EQ8-R (head with counterweights) | 50kg | 18% | Headroom for a future upgrade |
What the 9.02 kg is made of
| Component | Mass | Basis |
|---|---|---|
| OTA: Celestron EdgeHD 8 OTA | 6.35kg | maker’s figure |
| Rings and dovetail | 0.90kg | assumption |
| Camera: Player One Ares-C Pro | 0.42kg | maker’s figure |
| Filter drawer and filter | 0.20kg | assumption |
| Guide scope and guide camera | 0.80kg | assumption |
| Cables, dew strap, focuser motor | 0.35kg | assumption |
| Total | 9.02kg |
Assumptions are the Rig Reality Check’s round placeholders, not measurements; replace them with your own figures there.
Run the Rig Reality Check with the Player One Ares-C Pro as yours, then give it your budget, sky and targets.
Sub length
The shortest sub at which read noise adds no more than 5 % to the stack's noise, from the Exposure Planner. Each figure opens the planner with the same inputs.
At gain 125 (high conversion gain on, 1.376 e⁻ read noise), 203.2 mm at 2032 mm. Under a Bortle 6 sky it is 22 s with no filter and 402 s through a 7 nm dual-band filter.
- This design has a central obstruction, which the catalogue holds only in prose. The figures are computed unobstructed, so each is a floor: the obstruction lowers the sky signal and lengthens the shortest sub. The planner takes the obstruction as an input.
- Under 30 s, download and dither time dominate, so the planner raises shorter results to 30 s. The dual-band column uses the reference’s approximation: Dual narrowband 7 nm (Ha + OIII).
Prices
Dated readings from the maker's store or a major US retailer, with the page each came from. A first-year total needs a mount and the essentials, which the Rig Reality Check adds.
| Part | Price | Read |
|---|---|---|
| Telescope: Celestron EdgeHD 8 OTAProvisional | $1,499 | manufacturer, 2026-09-27OTA with CGE dovetail, 9x50 finderscope, 1.25" star diagonal, 40mm Plössl eyepiece. Sale price (regular $1,699.00, 'You Save: $200.00 (12%)'); OUT OF STOCK on celestron.com 2026-09-27. |
| Camera: Player One Ares-C ProProvisional | $799 | manufacturer, 2026-09-27camera only (the page's 'Camera' option); import tax may be extra |
Provisional rows have not yet had a second, human check against their source. The Rig Reality Check prices whole builds, essentials included.
How this is computed
scale["/px] = 206.265 × pixel[µm] / focal length[mm]
field[°] = 2 × atan(sensor side[mm] / (2 × focal length[mm])) × 180/π
sampling = seeing FWHM["] / scale["/px]
frame filled = max(major axis / field width, minor axis / field height)
utilization = Σ imaging mass[kg] / rated payload[kg]
shortest sub = R² / (e_sky × ((1 + p)² − 1)), p = 5 %Focal length is the telescope’s, times a corrector’s factor only where its maker states one. The image scale and field use the exact forms; the worked example shows the arithmetic. The sampling bands are the physics reference’s presentation choice, and every band is printed so the tradeoff can be read in full.
The payload sums every part on the saddle, the way the Rig Reality Check does, and the bands encode the 50 to 60 % imaging derate, which is forum practice rather than a maker’s figure. Spacing figures are the Backfocus Solver’s rows; sub lengths are the Exposure Planner’s.
Source: docs/03-physics-reference.md §§ 1, 3 and 4. Implemented in packages/physics (optics.ts, payload.ts, exposure.ts, scoring.ts), each with the reference's worked examples as unit tests.
Last updated Computed from the catalogue when the site is builtEvery camera on the Celestron EdgeHD 8 OTA