NexStar 6SE Eyepiece Calculator
The NexStar 6SE is a 150mm f/10 Schmidt-Cassegrain with a 1500mm focal length. It ships with one 25mm eyepiece (60x). This page loads the 6SE into the calculator so you can see what any eyepiece, Barlow, or the f/6.3 reducer will do before you buy.
- Telescope
- Celestron NexStar 6SE: 150mm aperture, 1500mm focal length, f/10
- Max useful magnification
- ~300x (2 × aperture in mm). Celestron lists 354x. Most nights the atmosphere allows ~200–250x.
- Min useful magnification
- ~21x (7mm exit pupil)
- Widest true field
- 1.03° with 1.25" eyepieces
Choosing eyepieces? See the best eyepieces for the 6SE.
| Eyepiece | Magnification | Exit pupil | True field | Moon widths | Best for | Notes |
|---|---|---|---|---|---|---|
| 25mm (50°) | 60x | 2.5mm | 0.83° | 1.7 | Deep sky, Moon | – |
| 12mm (60°) | 125x | 1.2mm | 0.48° | 1 | Moon, Planets | – |
| 9mm (60°) | 167x | 0.9mm | 0.36° | 0.7 | Planets, Double stars | – |
Gaps in your set
- Gap between 60x and 125x: an eyepiece around 17mm (~87x) would fill it.
The 6SE numbers
| Aperture | 150mm |
|---|---|
| Focal length | 1500mm (f/10) |
| Eyepiece(s) in the box | 25mm (60x) |
| Max useful magnification | ~300x by the 2 × aperture rule; Celestron lists 354x |
| Min useful magnification | ~21x |
| Widest field, 1.25" eyepieces | 1.03° |
| Rear baffle opening | ~27mm (fields wider than 1.03° vignette) |
Specs from Celestron’s product page, checked 2026-10-07.
What’s different about the 6SE
- 1.25-inch is the practical ceiling. Celestron gives the C6 rear baffle opening as about 27mm, the same as the largest 1.25" field stop. A 2" diagonal adds little extra field on a 6SE. The widest clean view is about 1.03° (two Moon widths), from a 32mm Plössl or 24mm 68° eyepiece.
- Eyepieces longer than ~32mm don’t show more sky. A 40mm 1.25" Plössl hits the same 27mm field stop, so it gives a smaller image of the same 1.03° field.
- Max power on paper vs at the eyepiece. Celestron lists 354x; the 2 × aperture rule gives 300x. Most nights the atmosphere holds the 6SE to about 200–250x, so a 7mm (214x) is the shortest eyepiece most owners use regularly.
- The f/6.3 reducer is the route to wider views. It turns 1500mm into about 945mm, so the stock 25mm gives ~38x and ~1.3°. Beyond about 1.03° the 27mm baffle darkens the edges, so expect some vignetting.
Common eyepieces on the 6SE
Typical focal lengths and apparent fields. Your exact eyepiece may differ slightly; enter it above for its numbers.
| Eyepiece | Magnification | Exit pupil | True field | Moon widths | Best for | Notes |
|---|---|---|---|---|---|---|
| 32mm (50°) | 47x | 3.2mm | 1.03° | 2.1 | Deep sky, Moon | – |
| 25mm (50°) | 60x | 2.5mm | 0.83° | 1.7 | Deep sky, Moon | – |
| 24mm (68°) | 63x | 2.4mm | 1.03° | 2.1 | Deep sky, Moon | Nearly the same as 25mm (60x) |
| 18mm (60°) | 83x | 1.8mm | 0.72° | 1.4 | Moon, Planets | – |
| 12mm (60°) | 125x | 1.2mm | 0.48° | 1 | Moon, Planets | – |
| 9mm (60°) | 167x | 0.9mm | 0.36° | 0.7 | Planets, Double stars | – |
| 7mm (60°) | 214x | 0.7mm | 0.28° | 0.6 | Planets, Double stars | – |
| 5mm (60°) | 300x | 0.5mm | 0.2° | 0.4 | Planets, Double stars | Most nights the atmosphere limits useful power to about 200–250x. Save this for very steady nights. |
With the f/6.3 reducer/corrector
The reducer multiplies the focal length by about 0.63 (1500mm → ~945mm). Use it for wide views and imaging; take it off for planets.
| Eyepiece | Magnification | Exit pupil | True field | Moon widths | Best for | Notes |
|---|---|---|---|---|---|---|
| 32mm (50°) + f/6.3 reducer (×0.63) ≈ 50.8mm | 30x | 5.1mm | 1.64° | 3.3 | Wide field, Deep sky | Wider than this scope's ~27mm rear baffle passes cleanly (~1.03°): expect darker edges (vignetting). |
| 25mm (50°) + f/6.3 reducer (×0.63) ≈ 39.7mm | 38x | 4mm | 1.32° | 2.6 | Deep sky, Moon | Wider than this scope's ~27mm rear baffle passes cleanly (~1.03°): expect darker edges (vignetting). |
| 18mm (60°) + f/6.3 reducer (×0.63) ≈ 28.6mm | 53x | 2.9mm | 1.14° | 2.3 | Deep sky, Moon | Wider than this scope's ~27mm rear baffle passes cleanly (~1.03°): expect darker edges (vignetting). |
| 12mm (60°) + f/6.3 reducer (×0.63) ≈ 19mm | 79x | 1.9mm | 0.76° | 1.5 | Moon, Planets | – |
FAQ
What is the lowest useful magnification on a 6SE?
About 21x (150mm ÷ 7mm pupil). With 1.25-inch eyepieces you will not get that low without the f/6.3 reducer; a 32mm gives 47x.
Should I buy a 2-inch diagonal for my 6SE?
Usually not. The 6SE’s rear baffle is about 27mm, the same as a 1.25-inch field stop, so the gain is small and vignetting appears. The f/6.3 reducer is the usual way to widen the view.
What eyepiece gives the best planetary views on a 6SE?
Something between 9mm (167x) and 7mm (214x) on most nights. Go shorter only on unusually steady nights.
Next steps
- Best eyepieces for the 6SE: what to buy for each job
- 6SE guide: every accessory guide for this scope
- Main eyepiece calculator: any telescope, custom aperture and focal length
- 8SE eyepiece calculator
- Evolution 8 eyepiece calculator