Dedicated hydrogen-alpha solar telescope
Lunt Solar Systems LS40THa B500
A small refractor built around an etalon that passes one wavelength of red light and nothing else. Prominences standing off the limb, filaments across the disc, and a Sun that changes by the hour. The most expensive 40 mm of aperture you will ever buy, and the one most likely to make you say something out loud.
€990seen 7 Oct 2026 at Astroshop
- 40 mmAperture
- f/10.0Focal ratio
- 1.2 kgTypical weight
- 7–80×Useful magnification
Should you buy it?
- Yes if what you mainly want is taking it with me: that is what this family does best.
- No if your priority is the moon and the planets, nebulae, clusters and galaxies, by eye, learn my way around the sky: other families do better for the same money.
- The price is for the tube alone; add a mount before you compare.
Computed from its family's per-goal scores and its own numbers — not a rating, not one evening's opinion.
Where to buy
Also search at First Light Optics · Optique Unterlinden · Pierro Astro · Teleskop-Express (searches; neither price nor stock checked)
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What it shows, really
A solar instrument. It exists to show the Sun, so the night-sky views this page normally computes do not apply.
The numbers
Photo: Astroshop| Aperture | 40 mm |
|---|---|
| Focal ratio | 400 mm · f/10.0 |
| Mount | Optical tube only — mounts on any photo tripod via a 1/4" thread — not included |
| Typical weight | 1.2 kg |
| Useful magnification | 7× to 80× at 40 mm |
| Resolution (Dawes) | 2.9″ — the tightest double star this aperture can split |
| Faintest star, suburban sky | around magnitude 9.3 |
| Observed price | €990 seen 7 Oct 2026 at Astroshop |
Made for
- The Sun
Prominences standing off the edge, filaments across the disc, and a Sun that changes by the hour. The instrument is the filter: its etalon and blocking filter are built in, and nothing else is needed. Every time: certified filter over the front · finder capped · never an eyepiece filter · an adult with children · never without the filter.
- Taking it with me
One tube on a photo tripod. Solar observers take these on holiday.
Not made for
- The Moon and the planets
Never. The etalon passes one wavelength of sunlight and blocks everything else, including the Moon.
- Nebulae, clusters and galaxies, by eye
Never.
- Learn my way around the sky
There is one object, and the instrument cannot see any other.
The Sun, safely
No solar filter in the box
The Sun with this model
The instrument is the filter: its etalon and blocking filter are built in, and nothing else is needed.
Prominences standing off the edge, filaments across the disc, and a Sun that changes by the hour.
Every time
- A certified solar filter over the FRONT of the instrument, fastened so it cannot slip or blow off.
- Cap or remove the finder. It is a second telescope, and it has no filter.
- Never a filter at the eyepiece end: the concentrated sunlight there can crack it in an instant.
- With children, an adult is there every time.
- Never look, or point, without the filter on. Check it before each use; a scratched or torn filter goes in the bin.
Sources for the Sun
- American Astronomical Society — How to View a Solar Eclipse Safely — filters on optics go on the front; eclipse glasses never with optics; children supervised
- American Astronomical Society — Solar Filters for Optics — eyepiece filters are dangerous; the finder capped, removed or filtered; the filter attached securely
- American Astronomical Society — About the ISO 12312-2 Standard — EN ISO 12312-2:2015 covers naked-eye viewers only; no international standard covers filters on telescopes, binoculars or lenses
- Société astronomique de France — Guide des observations solaires — a filter at the front, never one screwed into the eyepiece, the finder capped
- NASA — Keep Your Eclipse Glasses to See the Sun's ‘Freckles’ — a large enough sunspot shows through eclipse glasses
- AAVSO — Le Guide d'Observation Solaire de l'AAVSO, v1.1 (2017), p. 6 — archived copy — “Les ouvertures plus grandes que 100 à 125 mm sont généralement limitées par les effets de turbulence atmosphérique”; 50 to 80 mm is enough to count sunspots
The family it belongs to: Dedicated hydrogen-alpha solar telescope
What it does well
- Prominences, filaments, plages and flares — the living Sun, not the flat disc white light shows
- Changes visibly over an afternoon, which nothing else in the sky does
- Small, light, and the target is up in daytime
What it costs you
- It shows the Sun. It shows nothing else, ever, at any price — there is no night-time use
- Tune-able etalons are a skill, and the view on a mistuned one is a disappointing red disc
- A 40 mm costs what a 250 mm Dobsonian costs. Be certain the Sun is what you want before this is what you buy
Worth knowing about this model
The current entry point to hydrogen-alpha since the Coronado PST went out of production. The B500 blocking filter suits visual use; imaging wants the B600 or larger. Needs a tripod you already own.
Same family, other sizes
Read next
€990seen 7 Oct 2026 at Astroshop
Where to buy