4-inch telescopes are basically for amateur astronomers and kids. On average, they provide 450-1350 mm focal lengths, and a range of focal ratios from f/3.9-f/9. They can magnify objects 204-236x times the human eye. They also can resolve double stars at 1.15 arcsec. You can get 4-inch telescopes from different brands in the price range of 262-5,200$.
What is a 4-inch telescope?
A 4-inch telescope has an aperture (the diameter of the objective lens) of 4-4.75 inches (100-120 mm). 4-inch telescopes are in the category of small-size telescopes.
What can you see with a 4-inch telescope?
- The Moon and its craters.
- The phases of Venus and Mercury.
- Mars’ polar ice caps.
- Jupiter’s cloud belts, the Great Red Spot, etc.
- Saturn’s rings, the division in them, and several moons.
- Uranus and Neptune as dots.
- Stars in the galaxies like in M13, M15, M92, etc.
- Nebulae, such as M27, M57, the Cat’s Eye, etc.
- NGC objects like M42, the Orion Nebula, and M8, the Lagoon Nebula.
Types and Technical Specifications of 4-inch telescope
Types (Optical Design)
Doublet Refractor: Example: Takahashi FC-100DF f/7.4 Fluorite APO Refractor, Sky-Watcher Evostar 100 ED APO Refractor Telescope, Celestron Omni XLT 120 Telescope, Celestron Omni XLT 120 Telescope, Celestron Omni XLT 102 Telescope, Celestron AstroMaster 102AZ f/6.5 Doublet Refracting Telescope, Sky-Watcher StarTravel 102AZ3 f/4.9 Doublet Refracting Telescope, Takahashi FC-100DC F/7.4 Fluorite Refractor, Sky-Watcher Evostar 120ED APO – 120mm Refractor Telescope, Celestron StarSense Explorer DX 102AZ Smartphone Telescope, Celestron Inspire 100AZ Refractor
Triplet Refractor: Example: Sky-Watcher Esprit 100mm ED Triplet APO Refractor, Orion EON 115mm Triplet Apochromatic Refractor, Sky-Watcher Esprit 120mm ED Triplet APO Refractor, Takahashi TS-120 120 APO Refractor with 3-inch FeatherTouch Focuser from SI
Newtonian: Example: Celestron AstroMaster 114EQ Telescope, Celestron Explorascope 114AZ f/10 Modified SCT Reflecting Telescope, Celestron Cometron 114 AZ Telescope, Takahashi TSA-120 Triplet APO Refractor, Celestron PowerSeeker 114 EQ Telescope, Unistellar eVscope 2 Smart Telescope & eVscope Backpack, Celestron 114LCM Computerized Telescope, Celestron 114LCM Computerized Telescope, Unistellar eVscope eQuinox Smart Telescope, Celestron StarSense Explorer LT 114AZ Smartphone Telescope
Sextuplet: Example: Sharpstar Z4 F/5.5 Fully Air-Spaced Sextuplet,
Petzval: Example: Takahashi FSQ-106EDX4 f/5 Petzval Refracting OTA Telescope,
Maksutov Cassegrain: Example: Celestron Nexstar 4SE GoTo Telescope, Explore Scientific Firstlight MAK100mm White Tube Maksutov Cassegrain with Twi-Nano
Technical Specifications
Aperture: 4-4.75 inch (100-120 mm)
Focal Length: 450-1350 mm
Focal ratio: f/3.9-f/9
Highest Magnification: 204-236x
Light Gathering Power: 212-270x
Price: 262-5,200$
Images taken with 4-inch telescopes
Examples of 4-inch telescopes
4-inch
- Takahashi FC-100DF f/7.4 Fluorite APO Refractor
- Sky-Watcher Esprit 100mm ED Triplet APO Refractor
- Sky-Watcher Evostar 100 ED APO Refractor Telescope
- Celestron Omni XLT 102 Telescope
- Sharpstar Z4 F/5.5 Fully Air-Spaced Sextuplet
- Celestron AstroMaster 102AZ f/6.5 Doublet Refracting Telescope
- Sky-Watcher StarTravel 102AZ3 f/4.9 Doublet Refracting Telescope
- Takahashi FC-100DC F/7.4 Fluorite Refractor
- Celestron Nexstar 4SE GoTo Telescope
- Celestron Inspire 100AZ Refractor
- Celestron StarSense Explorer DX 102AZ Smartphone Telescope
- Celestron 114LCM Computerized Telescope
- Explore Scientific Firstlight MAK100mm White Tube Maksutov Cassegrain with Twi-Nano
4.25-inch
- Takahashi FSQ-106EDX4 f/5 Petzval Refracting OTA Telescope 106 mm (4.25″)
4.5-inch
- Celestron StarSense Explorer LT 114AZ Smartphone Telescope (114 mm (4.5″))
- Celestron AstroMaster 114EQ Telescope (114 mm (4.5″))
- Orion EON 115mm Triplet Apochromatic Refractor 115mm (4.5″)
- Celestron Explorascope 114AZ f/10 Modified SCT Reflecting Telescope 114mm (4.5″)
- Celestron Cometron 114 AZ Telescope 114 mm (4.5″)
- Celestron PowerSeeker 114 EQ Telescope 114 mm (4.5″)
- Unistellar eVscope 2 Smart Telescope & eVscope Backpack 114 mm (4.5″)
- Unistellar eVscope eQuinox Smart Telescope 114mm (4.5″)
4.75 inch
- Celestron Omni XLT 120 Telescope (120 mm (4.75″))
- Sky-Watcher Esprit 120mm ED Triplet APO Refractor 119 mm (4.75″)
- Takahashi TSA-120 Triplet APO Refractor 119 mm (4.75″)
- Sky-Watcher Evostar 120ED APO – 120mm Refractor Telescope 120 mm (4.75″)
- Takahashi TS-120 120 APO Refractor with 3-inch FeatherTouch Focuser from SI (119 mm (4.75″)
How do 4-inch telescopes compare to other size-telescopes
4-inch vs 5-inch telescope
5-inch telescopes provide a focal length of 650-1900 mm with a focal ratio of f/5-f/15. In contrast, 4-inch telescopes vary from 450-1350 mm in focal length with a focal ratio of f/3.9-f/9. Moreover, 5-inch telescopes provide 225-260x the highest magnification, versus the 204-236x of 4-inch telescopes.
| 4-inch telescope | 5-inch telescope | |
| Aperture | 4-4.75 inch (100-120 mm) | 5-inch (127-130 mm) |
| Focal Ratio | f/3.9-f/9 | f/5-f/15 |
| Focal Length | 450-1350 mm | 650-1900 mm |
| Highest Magnification | 204-236x | 225-260x |
| Price | 262-5,200$ | 279-8,400$ |
4-inch vs 6-inch telescope
4-inch telescopes have less aperture than the 6-inch telescopes. They offer a focal ratio of f/3.9-f/10 whereas the 4-inch telescopes vary from f/3.9-f/9. However, 6-inch telescopes offer a focal length of 162-1800 mm whereas the 4-inch telescopes vary from 450-1350 mm in focal lengths. 6-inch telescopes provide the highest magnification of 295-320x, whereas 4-inch telescopes can magnify 225-260x.
| 4-inch telescope | 6-inch telescope | |
| Aperture | 4-4.75 inch (100-120 mm) | 6-inch (150 mm) |
| Focal Ratio | f/3.9-f/9 | f/3.9-f/10 |
| Focal Length | 450-1350 mm | 162-1800 mm |
| Highest Magnification | 204-236x | 295-320x |
| Price | 262-5,200$ | 310-15,070$ |
4-inch vs 7-inch telescopes
4-inch telescope has less aperture than the 7-inch telescopes. They offer a focal ratio of f/2.8-f/15 whereas the 4-inch telescopes vary from f/3.9-f/9. Besides, 4-inch telescopes offer a focal length of 450-1350 mm whereas the 7-inch telescopes start from 500 mm to 2700 mm mm in focal lengths. Moreover, 7-inch telescopes provide 360x the highest magnification, whereas 4-inch telescopes can magnify up to 225-260x.
| 4-inch telescope | 7-inch telescopes | |
| Aperture | 4-4.75 inch (100-120 mm) | 7-inch (180 mm) |
| Focal Ratio | f/3.9-f/9 | f/2.8-f/15 |
| Focal Length | 450-1350 mm | 500-2700 mm |
| Highest Magnification | 204-236x | 360x |
| Price | 262-5,200$ | 1,350-5,500$ |
4-inch vs 8-inch telescope
8-inch telescopes provide focal lengths of 800-2415 mm (f/4-f/11.5), while 4-inch telescopes vary in focal lengths from 450-1350 mm (f/3.9-f/9). On average 8-inch telescopes provide the highest magnification of 300-480x, whereas 4-inch telescopes can magnify 225-260x.
| 4-inch telescope | 8-inch telescope | |
| Aperture | 4-4.75 inch (100-120 mm) | 8-inch (203 mm) |
| Focal Ratio | f/3.9-f/9 | f/4-f/11.5 |
| Focal Length | 450-1350 mm | 800-2415 mm |
| Highest Magnification | 204-236x | 300-480x |
| Price | 262-5,200$ | 570-5,000$ |