🔭 Observing Guides

The 8SE finds objects only as well as it's aligned. Five minutes of care here saves a night of frustration.

Before you align

• Level the tripod and set the optical tube roughly level, pointing the fork arm's index marks to their home position.
• Enter accurate time, date, timezone, and location. Time matters most — even a few minutes off throws GoTo aim noticeably.
• Let the scope cool to outside temperature (20–40 min) while you align.

SkyAlign (easiest)

Pick any three bright objects spread across the sky (stars or bright planets), center each in the eyepiece, and confirm. The NexStar works out what they are — you don't need to name them. Choose objects far apart and avoid three in a line.

Two-star align (more precise)

If you know a couple of named stars, a two-star alignment plus calibration stars usually gives tighter pointing for imaging.

Driving it with SkyPortal WiFi

With the SkyPortal WiFi module you can run alignment and GoTo from the SkyPortal app on your phone — tap an object on the chart and the scope slews to it. The hand controller and app can be used interchangeably.

The mount points the scope; this kit decides what you actually see through it. Four kinds of accessory do four different jobs, and they stack together in a predictable way. Get the mental model and you'll always reach for the right piece.

The one formula that runs everything

Your 8SE has a focal length of 2032 mm and an aperture of 203 mm (8″), native f/10. Magnification is just:

• Magnification = telescope focal length ÷ eyepiece focal length. So a 25 mm eyepiece = 2032 ÷ 25 ≈ 81×; a 6 mm = 339×.
• True field of view ≈ eyepiece's apparent field (AFOV) ÷ magnification. More power always means a narrower patch of sky.
• Exit pupil = aperture ÷ magnification = 203 ÷ mag. This is the width of the light beam leaving the eyepiece (in mm) — it tells you how bright the image is.
• Max useful power ≈ 2× the aperture in mm ≈ 406× on the 8SE. Push past that and you just get a bigger, dimmer, fuzzier blob — "empty magnification."

① Eyepieces — the lens you look through

The eyepiece sets your base magnification. Shorter focal length = more power, narrower field, dimmer and fussier to use. Your set, low to high power:

• 25 mm (≈81×) — widest field, brightest. Your finder eyepiece: start here to locate and center every target.
• 17 mm (≈120×) / 13 mm (≈156×) — the deep-sky and general workhorses: clusters, nebulae, the whole Moon.
• 8 mm (≈254×) / 6 mm (≈339×) — high power for planets, the Moon's surface, and splitting double stars.
• 4 mm (≈508×) — beyond the 8SE's useful limit on its own, so it's usually too much; it only earns its keep on the steadiest nights, and even then the Barlow + a longer eyepiece often beats it.
• 20 mm Erecting — a daytime/terrestrial eyepiece (see ③).

② Barlow lenses — magnification multipliers

A Barlow sits in front of the eyepiece and multiplies the system's focal length — effectively giving you a second set of eyepieces. Your 2.3× and 3× Barlows work with any eyepiece:

• They multiply the magnification by their factor (a 13 mm at 156× becomes ≈359× behind the 2.3×).
• Effective focal length = 2032 × Barlow factor, so they also slow the f-ratio (handy for planetary imaging — see the NexImage guide) and shrink the exit pupil (dimmer view).
• Stacking two Barlows multiplies their factors, but you lose light and sharpness fast — rarely worth it.

③ Erecting pieces — for daytime use

Astronomical eyepieces give an upside-down (and often mirror-flipped) image. In space that's irrelevant, so for the night sky you can ignore orientation entirely. Erecting pieces flip the image right-way-up for terrestrial viewing:

• 20 mm Erecting eyepiece — a normal low-power eyepiece that also corrects the image for daytime scenery.
• 1.5× Erecting piece — an erecting Barlow: it both amplifies (1.5×) and turns the image upright. There's a small light/contrast cost, so reach for it for daytime or casual use, not for chasing faint detail.

④ Filters — tune colour and brightness, not power

Filters thread onto the bottom of the eyepiece barrel and change only the light that gets through — they have zero effect on magnification, field, or exit pupil. Two families:

• Neutral-density / Moon (your ND .9) — cuts ~87% of the light so the bright Moon is comfortable and crater detail pops. Use at any power.
• Colour / planetary (No. 58 green, 25 red, 12 deep yellow, 21 orange, 80A blue, 56 light green) — each boosts contrast on certain features by passing some colours and blocking others. Examples: red/orange lift Martian surface markings and polar caps; blue brings out Jupiter's Great Red Spot and Venus cloud patterns; deep yellow is a gentle all-rounder for Jupiter's belts.

Putting it together at the scope

1. Find low, then zoom. Center the target in the 25 mm first — wide field, easy to catch — then swap to a shorter eyepiece (or add a Barlow) to push the power up.
2. Let seeing set the ceiling. On an average night the air won't support much past ~200×; only steady nights reach toward 300–400×. If detail gets mushy, back off the power — a sharp 150× beats a boiling 300×.
3. Match exit pupil to the job. Big exit pupil (low power) for faint, spread-out deep-sky; small exit pupil (high power) for the Moon, planets, and double stars.
4. Add a filter last, chosen by target, not by power — then use whatever eyepiece/Barlow combo gives a bright enough view.
5. Re-focus after every change. Swapping eyepieces, adding a Barlow, or threading on a filter all shift focus slightly.

Planets are tiny and the atmosphere is always moving, so we don't take one photo — we shoot a fast video of thousands of frames and keep only the sharpest. That's lucky imaging.

At the scope

• Drop the NexImage 20 straight into the focuser (prime focus). Add a 2× or 2.5× Barlow to reach a good image scale — aim for roughly f/15–f/25 effective.
• Open iCap, then find and center the planet at low power first; it helps to GoTo and fine-tune.
• Set a small ROI (region of interest) around the planet to push the frame rate up — more frames = a better stack.
• Balance exposure and gain so the planet is bright but not clipped (keep the histogram off the right edge). Then nail focus — small, patient moves.
• Capture 60–180 seconds as an AVI or SER. For Jupiter, keep runs under ~90 s (it rotates fast).

On the computer

1. AutoStakkert!3 — align and stack the best 20–40% of frames.
2. RegiStax 6 — apply wavelet sharpening gently to draw out belts and detail. Resist the urge to overdo it.
3. For Jupiter, de-rotate multiple runs in WinJUPOS to stack more data without smearing.

The NexYZ clamps your phone over the eyepiece and lets you nudge it on three axes until the camera looks straight down the barrel. Simple, and brilliant for the Moon.

Mounting

• Focus the view by eye first, then attach the NexYZ and adjust X/Y until the bright circle is centered, and Z (height) until it fills the frame.
• Use a low-power eyepiece (e.g. 25 mm) to start — it's far more forgiving to align.

The Moon

Tap to focus on the terminator, lock focus & exposure, then drop exposure until the surface isn't blown out. A fast shutter and low ISO give a crisp single frame. Use the volume button or a timer to avoid shake.

Planets

Bright but small. Lock exposure low so Jupiter or Saturn doesn't burn to a white blob; some phone apps let you record video you can stack later like the NexImage.

Deep-sky (stretch goal)

Use a manual camera app: max ISO, a few seconds per frame, and shoot 20–30 frames. Stack them in Sequator and stretch in Snapseed. Field rotation from the alt-az mount limits single exposures to a handful of seconds — stacking many short frames is the way around it.

A Schmidt-Cassegrain like the 8SE holds collimation well but drifts over time. Tiny misalignment robs you of planetary detail. You collimate it on a star with the three screws on the secondary mirror (the small disc at the front).

The star test

1. On a steady night, center a medium-bright star at high power (a short eyepiece or with the Barlow).
2. Defocus slightly until the star becomes a small disc with a dark central shadow (the secondary's silhouette). If that shadow sits off-center, you're miscollimated.
3. Turn one secondary screw a tiny amount; the star will drift. Re-center it with the hand controller and look again. Adjust the screw that moves the shadow toward the middle.
4. Iterate, making smaller moves, until the shadow is dead-center and the diffraction rings are concentric.

Three different things decide what a night is good for — and they rarely all line up.

• Seeing — how steady the air is. Great seeing = sharp planets and high magnification. This is the limiting factor for the NexImage work.
• Transparency — how clear the air is. Great transparency = faint galaxies and nebulae show through. Often best on cold, breezy nights — which tend to have poor seeing.
• Darkness (Bortle) — how light-polluted your sky is. Matters enormously for deep-sky, not at all for the Moon and planets.

So, tonight…

Rock-steady but hazy? Image planets and the Moon. Crystal clear but twinkly? Hunt deep-sky. Bright moon up? Stick to the Moon, planets, and double stars.

What you'll see

With a proper white-light filter the Sun shows as a sharp disc with sunspots (cool, dark regions), faculae (bright patches near the limb), and limb darkening toward the edge.

Imaging it

• Fit the front filter, then frame the Sun at low power before swapping in the NexImage 20 at prime focus (f/10 native is plenty).
• It's bright — use a low gain and short exposure, then capture and stack a short run in AutoStakkert just like a planet.
• Check the filter for pinholes or scratches every single time before use.