Askar 103APO with ZWO ASI585MC Pro
0.85″ per pixel across a 0.91° × 0.51° field, at 700.4 mm and f/6.8. 20 of the catalogue's 29 equatorial mounts carry the 8.05 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 700.4 mm, with the Askar 1.0x Full-frame Flattener for 103APO. The other 2 configurations are in the table below.
| Configuration | Focal length | Ratio | Scale | Field |
|---|---|---|---|---|
| Askar 1.0x Full-frame Flattener for 103APO | 700.4mm | f/6.8 | 0.85″/px | 0.91° × 0.51° |
| Askar 0.8x Full-frame Reducer for 103APO | 560.3mm | f/5.4 | 1.07″/px | 1.14° × 0.64° |
| Askar 0.6x Full-frame Reducer for 103APO | 420.2mm | f/4.1 | 1.42″/px | 1.52° × 0.85° |
Image circle: 44 mm, the corrector's stated figure (Askar 1.0x Full-frame Flattener for 103APO). 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 2.93 pixels on this sensor. Practical band for typical seeing.
| Seeing | 1.0x · 700.4 mm | 0.8x · 560.3 mm | 0.6x · 420.2 mm |
|---|---|---|---|
| 1.5″ | 1.76pxpractical | 1.41pxpractical | 1.05pxundersampled |
| 2.5″ | 2.93pxpractical | 2.34pxpractical | 1.76pxpractical |
| 3.5″ | 4.10pxoversampled | 3.28pxoversampled | 2.46pxpractical |
- Practical band for typical seeing.
- Oversampled: lower per-pixel signal and tighter guiding; binning recovers most of it.
- Undersampled; the standard, deliberate wide-field trade.
Framing
The 13 catalogue targets against this field, by the fraction of the frame each fills along its tighter axis.
M45 Pleiades fills 488 % of the frame and M27 Dumbbell Nebula 22 %. Of the 13, 5 fill the frame, 7 need a mosaic, 1 is small in the frame.
| Target | Size | 1.0x · 700.4 mm | 0.8x · 560.3 mm | 0.6x · 420.2 mm |
|---|---|---|---|---|
| M31 Andromeda Galaxy | 178′ × 70′ | 325%needs a mosaic | 260%needs a mosaic | 195%needs a mosaic |
| M45 Pleiades | 150′ × 150′ | 488%needs a mosaic | 390%needs a mosaic | 293%needs a mosaic |
| NGC 7000 North America Nebula | 120′ × 30′ | 220%needs a mosaic | 176%needs a mosaic | 132%tight crop |
| NGC 1499 California Nebula | 160′ × 40′ | 293%needs a mosaic | 234%needs a mosaic | 176%needs a mosaic |
| IC 1805 Heart Nebula | 60′ × 60′ | 195%needs a mosaic | 156%needs a mosaic | 117%tight crop |
| M42 Orion Nebula | 90′ × 60′ | 195%needs a mosaic | 156%needs a mosaic | 117%tight crop |
| NGC 2237 Rosette Nebula | 80′ × 50′ | 163%needs a mosaic | 130%tight crop | 98%tight crop |
| M101 Pinwheel Galaxy | 24′ × 23′ | 75%fills the frame | 60%fills the frame | 45%fills the frame |
| M27 Dumbbell Nebula | 6.7′ × 6.7′ | 22%small in the frame | 17%small in the frame | 13%small in the frame |
| M51 Whirlpool Galaxy | 13.7′ × 11.7′ | 38%fills the frame | 30%fills the frame | 23%small in the frame |
| M81 Bode's Galaxy | 22′ × 11.3′ | 40%fills the frame | 32%fills the frame | 24%small in the frame |
| M13 Hercules Globular Cluster | 16.5′ × 16.5′ | 54%fills the frame | 43%fills the frame | 32%fills the frame |
| NGC 4565 Needle Galaxy | 16.8′ × 2.9′ | 31%fills the frame | 25%small in the frame | 18%small in 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.
This telescope needs a corrector. The maker: “1x flattener (optional) ... The flattener corrects field curvature and coma, resulting in flatter field edges and finer star points.” Source
Askar 1.0x Full-frame Flattener for 103APO
- Backfocus
- 55mm
- Measured from
- base of the M48x0.75 male thread on the flattener's M54-M48 adapter
- Focal length
- 1.0x, 700.4 mm
- Image circle
- 44 mm; this sensor is 12.78 mm
Askar 0.8x Full-frame Reducer for 103APO
- Backfocus
- 55mm
- Measured from
- base of the M48x0.75 male thread on the reducer's M54-M48 adapter
- Focal length
- 0.8x, 560.3 mm
- Image circle
- 44 mm; this sensor is 12.78 mm
Askar 0.6x Full-frame Reducer for 103APO
- Backfocus
- 55mm
- Measured from
- base of the M48x0.75 male thread on the reducer's M54-M48 adapter
- Focal length
- 0.6x, 420.2 mm
- Image circle
- 44 mm; this sensor is 12.78 mm
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 8.05 kg, 2.25 kg of it assumed. 20 of the 29 equatorial mounts in the catalogue carry it within the derate; the smallest rated is the iOptron HEM27, at 60 %. 9 more would run it over 60 %.
| Mount | Rated | Used | Band |
|---|---|---|---|
| iOptron HEM27 | 13.5kg | 60% | Workable; more sensitive to wind, little room to grow |
| Rainbow Astro RST-135E | 13.5kg | 60% | Workable; more sensitive to wind, little room to grow |
| WarpAstron WD-17 | 13.5kg | 60% | Workable; more sensitive to wind, little room to grow |
| Celestron Advanced VX (AVX) | 13.6kg | 59% | Workable; more sensitive to wind, little room to grow |
| Pegasus Astro NYX-88 | 14kg | 58% | Workable; more sensitive to wind, little room to grow |
| Sky-Watcher HEQ5-R Pro | 15kg | 54% | Workable; more sensitive to wind, little room to grow |
The other 14 mounts that carry it
| Mount | Rated | Used | Band |
|---|---|---|---|
| Sky-Watcher Wave 150i | 15kg | 54% | Workable; more sensitive to wind, little room to grow |
| ZWO AM5N | 15kg | 54% | Workable; more sensitive to wind, little room to grow |
| Celestron CGEM II | 18kg | 45% | Comfortable |
| iOptron CEM40 (with tripod) | 18kg | 45% | Comfortable |
| iOptron HEM44 | 20kg | 40% | Comfortable |
| Pegasus Astro NYX-101 | 20kg | 40% | Comfortable |
| Sky-Watcher EQ6-R Pro | 20kg | 40% | Comfortable |
| WarpAstron WD-20 | 20kg | 40% | Comfortable |
| ZWO AM7 | 20kg | 40% | Comfortable |
| Losmandy GM811G (LW tripod) | 22.7kg | 35% | Headroom for a future upgrade |
| Celestron CGX | 25kg | 32% | Headroom for a future upgrade |
| iOptron CEM70 (iPolar) | 31.8kg | 25% | Headroom for a future upgrade |
| Sky-Watcher CQ350 Pro (with tripod) | 35kg | 23% | Headroom for a future upgrade |
| Sky-Watcher EQ8-R (head with counterweights) | 50kg | 16% | Headroom for a future upgrade |
What the 8.05 kg is made of
| Component | Mass | Basis |
|---|---|---|
| OTA: Askar 103APO | 4.75kg | maker’s figure |
| Rings and dovetail | 0.90kg | assumption |
| Corrector: Askar 1.0x Full-frame Flattener for 103APO | 0.58kg | maker’s figure |
| Camera: ZWO ASI585MC Pro | 0.47kg | 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 | 8.05kg |
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 ZWO ASI585MC 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 200 (high conversion gain on, 1.1 e⁻ read noise), 103 mm at 700.4 mm. Under a Bortle 6 sky it is 9.7 s with no filter and 176 s through a 7 nm dual-band filter.
| Sky | No filter | 7 nm dual-band |
|---|---|---|
| Bortle 421.00 mag/arcsec² | 61 s50 s to 73 s | 18 min15 min to 22 min |
| Bortle 619.00 mag/arcsec² | 9.7 s8.0 s to 12 sbelow the 30 s floor | 176 s145 s to 209 s |
| Bortle 817.90 mag/arcsec² | 3.5 s2.9 s to 4.2 sbelow the 30 s floor | 64 s53 s to 76 s |
- The read noise is read off the maker’s chart; the small figures give the range its reading uncertainty allows.
- 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: Askar 103APOProvisional | $1,199 | retailer, 2026-09-27OTA only (SKU ASK-103APO); flattener/reducers sold separately |
| Camera: ZWO ASI585MC ProProvisional | $599 | manufacturer, 2026-09-27variant ASI585MC Pro |
| $599 | retailer, 2026-09-27 | |
| Corrector: Askar 1.0x Full-frame Flattener for 103APOProvisional | $219 | retailer, 2026-09-27SKU ASK-103APO-1FLAT |
| Corrector: Askar 0.8x Full-frame Reducer for 103APOProvisional | $219 | retailer, 2026-09-27SKU ASK-103APO-08XR |
| Corrector: Askar 0.6x Full-frame Reducer for 103APOProvisional | $329 | retailer, 2026-09-27SKU ASK-103APO-06XR |
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 Askar 103APO