Observing
Planets are bright but tiny: Jupiter is under 50 arcseconds across, Mars often under 20. Seeing detail on them needs aperture, magnification and, above all, steady air. The telescope sets the ceiling; the atmosphere decides how close you get to it.
The finest detail a telescope can show shrinks as the aperture grows. An 8-inch telescope such as the NexStar 8SE resolves detail twice as fine as a 4-inch: the Cassini Division, the Great Red Spot, Mars’s polar cap.
Long focal ratios give high magnification with comfortable eyepieces and sharp images. On a fast telescope, a good Barlow such as the three-element X-Cel LX 2x does the same. An eyepiece with generous eye relief, like the X-Cel LX 12 mm at 16 mm, makes long looks comfortable.
The air moves. Watch for several minutes and moments of sharpness appear. Let the telescope cool to outside temperature first.
A blue filter can raise contrast on Jupiter’s belts and a red or orange one on Mars. They help a little, cost light, and are cheap; a set like Neewer’s lets you try which works. See Wratten numbers.
A planetary camera such as the SVBONY SV205 records thousands of frames; software keeps the sharpest. The result shows more than the eye can.
A few planets are within reach of a modest instrument. The rest is a matter of patience.
A planet’s position changes, and so does its apparent size. That is part of the interest.
After the Moon, this is the target that works best with an audience.
| What you would like | What decides | What has no effect |
|---|---|---|
| More detail | The sky | The magnification |
| A sharp image | Reaching temperature | The price |
| A steady image | The mount | The aperture |
| More contrast | Collimation | The filters |
Planetary observing is done at high magnification, which reveals everything an instrument gets wrong. An instrument not at temperature or badly collimated shows it here first.
This site publishes stated specifications and describes no evening at the eyepiece.
8-inch (203 mm) Schmidt-Cassegrain · computerized GoTo single-arm mount · 40,000+ objects · SkyAlign
Celestron's NexStar 8SE: an 8-inch Schmidt-Cassegrain with StarBright XLT coatings on a computerized single-arm GoTo mount, with the NexStar+ hand control, a 40,000-object database and SkyAlign.
Best for: Serious aperture that still fits in a car trunk and sets up in minutes
≈ $1,499
12 mm (0.47 in) · 60° apparent field · six elements · 16 mm eye relief · fully multi-coated
Celestron's X-Cel LX 12 mm: a six-element, fully multi-coated eyepiece with a 60-degree field, 16 mm of eye relief, blackened lens edges, a twist-up eyecup and a treaded rubber grip.
Best for: The eyepiece that stays on the planets, used with glasses or gloves on a cold night
≈ $93
2x Barlow · three apochromatic elements · fully multi-coated · brass compression ring · 1.25 in filter thread
Celestron's X-Cel LX 2x: a three-element apochromatic, fully multi-coated 1.25-inch Barlow with a brass compression ring, a rubber grip and a filter thread.
Best for: An eyepiece collection worth protecting, where the compression ring and apochromatic glass are the reasons to pay
≈ $100
Seven 1.25 in filters · red, orange, yellow, green, blue · Moon and skyglow · CPL · no Wratten numbers
Neewer's seven-piece 1.25-inch set: five color filters (red, orange, yellow, green, blue), a lunar and skyglow filter and a circular polarizer, with a sentence for what each color brings out.
Best for: A first set of planetary filters, bought to find out which color helps on which planet
≈ $23
7.05 MP IMX415 color, 1/2.8 in · 1.45 µm pixels · 1080p at 30 fps, 3264 × 2160 at 15 fps · USB 3.0 · 1.25 in
SVBONY's SV205: a 1.25-inch color planetary camera with a 7.05 MP Sony IMX415 sensor and 1.45 µm pixels, 30 fps at 1920 × 1080 in MJPG or 15 fps at 3264 × 2160 uncompressed, over USB 3.0.
Best for: Lunar and planetary video through a 1.25 in focuser, on a Windows, Linux or macOS laptop
≈ $100
With 4 to 5 inches: Jupiter's two main belts and four moons, Saturn's rings and sometimes the Cassini Division. With 8 inches on a steady night: the Great Red Spot, more belts and finer ring detail.
Usually the air. Turbulence blurs the image; on most nights 150x to 200x is the useful limit whatever the telescope.
Yes, with a planetary camera that records video and software that keeps the sharpest frames. The SVBONY SV205 publishes its pixel size and frame rates.
For observing: Serious aperture that still fits in a car trunk and sets up in minutes
Where it is strong: Eight inches: about 1.8 times the light of a 6-inch
Where it is weak: Single-arm mount is at its limit with this tube; it shakes when touched at high power
For observing: The eyepiece that stays on the planets, used with glasses or gloves on a cold night
Where it is strong: 16 mm of eye relief at 12 mm focal length: comfortable with glasses
Where it is weak: About three times the price of a 12 mm Plössl
For observing: An eyepiece collection worth protecting, where the compression ring and apochromatic glass are the reasons to pay
Where it is strong: Three apochromatic elements, fully multi-coated
Where it is weak: Nearly three times the price of the Omni 2x
For observing: A first set of planetary filters, bought to find out which color helps on which planet
Where it is strong: Seven filters for about $23
Where it is weak: No Wratten numbers, so colors cannot be compared with other sets
For observing: Lunar and planetary video through a 1.25 in focuser, on a Windows, Linux or macOS laptop
Where it is strong: Pixel size and frame rates published
Where it is weak: Small 1/2.8 in sensor
$16 – $37
10 models
$60 – $100
11 models
$160 – $1 699
10 models
Model against model, where the comparison is already published.
The models above are taken from the catalog of this site. Specifications are the ones the maker publishes and the ones on the Amazon page; prices are the Keepa reading for the date shown, and both change. Ranking uses declared specifications, the weight of stated strengths against stated limits, and price. Nothing here has been pointed at the sky by us, and the page makes no such claim.
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Any figure written into the body of this page was true on the day it was written. The amount shown next to each instrument is requested from the retailer as the page loads, and it is that amount, not the text, that stands.
