Astronomy Troubleshooting Guide: Problems & Solutions

A compact reference work: symptom → likely cause → concrete solution for all recurring problems of amateur astronomy – from “I see nothing” via GoTo dropouts and guiding frustration to dew, solar-filter safety and the “optics lottery”.

Compiled from the advisory practice of the specialist retailer (Teleskop-Spezialisten), the major astronomy forums (Cloudy Nights, Astrotreff.de, astro-forum.de, Astronomie.de, Reddit r/telescopes & r/astrophotography) and established expert resources (including Gary Seronik’s collimation guide, the PHD2 manual). Forum contributions are summarised as community consensus – without invented quotes. Prices are snapshots.

Quick diagnosis: symptom → chapter

1. Visual Optics & Image Quality

Problem: “I see nothing – only grey”

Possible causes (by frequency, forum practice): 1. Objective/front cap still on – the absolute classic. Also check: the cap on the finder’s front lens! 2. Focus is far off (especially on Newtonians after transport). 3. Finder not aligned with the telescope → the eyepiece doesn’t see what the finder shows. 4. Eyepiece not clamped in / star diagonal cap in place. 5. Dark adaptation not yet complete (20–40 min).

Solution: Do a daylight check: remove caps → aim at a bright distant object (chimney/treetop) with the lowest-power eyepiece (25 mm) → focus roughly, then finely → only then align the finder cross (see 12 for an introduction). Only then start at night.

Problem: The image won’t come to focus / stays mushy

Possible causes: 1. Missing cool-down – mirror/lens optics need 30–90 min to reach ambient temperature (closed systems take longest). 2. Atmospheric seeing – the image “swims”; the atmosphere is at fault, not the optics. 3. Collimation (Newtonian/SC) shifted – transport! 4. Tube thermals: warm air rises inside the tube (Dobson cap hole, fan). 5. Eye: eyeglass correction wrong at the eyepiece exit; no dioptric compensation.

Solution: Set the scope outside 30 minutes early (with the tube opened), start with the lowest-power eyepiece, try planets after midnight (seeing is often steadier). Newtonian: check collimation with Cheshire/laser (Gary Seronik method: 1. primary roughly, 2. position the secondary, 3. fine-tune the primary – most nights only step 3 is needed, in 1–2 minutes).

Problem: Stars “boil” / twinkle hard

Cause: Seeing (atmospheric turbulence) – plus tube thermals when the telescope was just brought out. Don’t swap the instrument!

Solution: Reduce magnification (seeing limits the useful magnification from above), wait (gusts come in waves), pre-cool the tube, avoid roofs/heated structures at the site (heat plumes from houses), plan planets for after midnight.

Problem: Bright objects show a coloured fringe (violet/blue)

Possible causes: 1. Achromatic optics – the typical (normal!) colour fringe; strongest on Venus/Sirius/the lunar limb. 2. Focus is off (the fringe appears “asymmetric”). 3. Eyepiece/prism quality (cheap Amici prisms add colour). 4. Achromat chroma + the yellow/green filter question.

Solution: Set focus precisely (Bahtinov for photo; visually hunt colour-free focus by “rocking” through), try yellow/green filters, ED/apo for perfectionists – forum consensus: “The colour fringe is the price of the big achromat; on faint objects you never see it.”

Problem: Stars are sharp only in the centre / “comets” at the edge

Possible causes: 1. Collimation – wedge-shaped “comets” always pointing the same direction = Newtonian out of collimation. 2. Coma on a fast Newtonian (f/4–f/5): normal at the edge without a coma corrector (MPCC). 3. Weak eyepiece at the edge (Plössl at f/5). 4. Field curvature at wide fields (not a fault – physics).

Solution: First collimate (Cheshire + laser; secondary first, primary fine), then a coma corrector for f/4–f/5 Newtonians, then edge-corrected eyepieces. Gary Seronik’s ground rule: “You collimate to put the best part of the focal plane into the eyepiece.”

Problem: The image looks dim / low in contrast

Possible causes: 1. Moon filter still in place (the classic when switching to deep sky!). 2. Exit pupil chosen badly (too small = too dim, too large = light loss at the eye). 3. Dirty front lens/corrector (dust hardly matters – wet films/dirt do). 4. Ageing pupil (<5 mm): large exit pupils (7 mm) waste light.

Solution: Remove the filter! Check the eyepiece combo (exit pupil = aperture/magnification; target window 1–5 mm), clean optics only when necessary (see 11), choose shorter eyepiece focal lengths (more magnification).

Problem: Shadow/silhouette at the edge of the field (“pipe view”)

Cause: The focuser drawtube intrudes into the light path (racked out too far), or a long chain (2” diagonal + 1.25” adapter) vignettes; your own eye’s floaters drift through the field at small exit pupils.

Solution: Don’t rack the focuser out fully, use a shorter chain, centre the eye on the eyepiece; glasses wearers: eyepieces with more eye relief.

Problem: Planets show no detail

Possible causes: Seeing (no. 1), missing cool-down, magnification too low, adaptation disturbed (bright sky/Moon), missing patience – the eye “trains” details out only after minutes.

Solution: Aim for 150–250x depending on aperture and seeing, sit down, try colour filters (#56 green on Jupiter, #21/23A on Mars), moon filter in bright surroundings. Forum wisdom: “Seeing beats aperture.”

2. Mechanics, Focuser & Focus Knob

Problem: After focusing, the image wobbles for 5–8 seconds

Cause: Optics–mount pairing (payload exceeded or lever too long) and/or a thin original tripod; body heat + standing observing adds micro-tremor.

Solution: Check payload matching (rule of thumb: use max. 2/3 of the manufacturer’s rating), steel/wood tripod instead of small aluminium photo tripods, weight on the tripod hook, observing chair (the forums’ number one: “sitting means no trembling”), use fine focus, a focus motor (EAF) for calm fine movement. Otherwise: a smaller scope.

Problem: The focuser slips with heavy eyepieces/cameras

Causes: Crayford focuser without sufficient tension; too little clamping force with heavy 2” eyepieces; SCT/Mak: primary mirror shift (the image “hops” while focusing – a normal design topic).

Solution: Crayford: tighten the tension screw; rack & pinion: check grease; on SCT/Mak always approach focus from one direction only (“approach from the same side”), long-term: external focuser/motor focus (EAF) – focus then runs via the drawtube instead of the primary mirror (eliminates mirror shift).

Problem: The focus knob spins free / grinds / the mirror moves with it

Causes: Drive pinion loose (especially after installing a focus motor – coupling screw!), the focuser pulls itself out of its cell (known SkyMax 127 case: oily smear trail, grinding noise), hardened grease after years.

Solution: Tighten the focus motor’s coupling on the shaft; for the SkyMax case, the shop’s telephone repair: with the tube vertical, loosen the grub screws (the mirror can then be pressed ~1 cm without resistance), fix the focus knob directly to the housing with new grub screws – after that it works again. With hardened grease: workshop service rather than DIY.

Problem: Eyepiece jams in the focuser / falls out

Cause: Compression ring under- or overtightened, corrosion/dirt in the clamping area, a 2” sleeve without a locking ring for heavy eyepieces.

Solution: Clamp only as firmly as necessary; clean the sleeve and eyepiece barrel (dry microfibre cloth, no liquids!), for heavy eyepieces choose focusers with compression rings instead of a single screw.

Problem: A clamping/collimation screw broke off

Cause: Overtightened; sometimes a weak point in the material (the community knows cases on altitude and clamp parts).

Solution: Don’t force it further – drilling out the remains and re-tapping is workshop work. Report to the dealer: material breaks are typically reviewed with goodwill (“the customer can’t help it, even if he overtightened”). Replacement screws are usually catalogue items.

3. Mount, GoTo & Control

Problem: GoTo never lands centred in the eyepiece

Possible causes: 1. Date/time/location wrong – the evergreen: daylight-saving sign, wrong longitude (east/west!), site 100 km off. 2. Alignment stars too close together / too low / too faint. 3. No sync after slewing (the pointing model stays wrong). 4. Cone error: tube/rail not perpendicular to the RA axis. 5. Small field of view (long eyepiece focal length/Maksutov) – the object IS in the field, but the field is small.

Solution: Check time/date/coordinates (daylight saving!), use 2–3 widely separated bright stars for alignment, synchronise on a nearby reference star after the first slew, then slew to targets near the reference; at long focal lengths use a reticle eyepiece for centring; refresh a one-star sync at the start of every session. The shop’s documented case “longitude 6.73° E can’t be entered after a factory reset” shows: hardware clarification cases go via dealer/ importer.

Problem: The object slowly drifts out of the field

Possible causes: 1. Wrong tracking rate (e.g. lunar/solar instead of sidereal; the known Star Adventurer case: RA ran ~7 % fast – the cause was lunar mode). 2. Hemisphere/model set wrong. 3. Clutch not engaged (the axis only half follows).

Solution: Set the rate to “sidereal” (Moon: lunar, Sun: solar), check the hemisphere, engage the axis clamps after slewing. On GoTo mounts: let the mount track, don’t “correct” the motors by hand.

Problem: The motors hum, but the axis doesn’t move

Causes: Axis clutch still engaged, motor-to-shaft coupling loose, belt slipped, hard stop reached.

Solution: Release the clutches, check the coupling, feel for the stops by hand; only then suspect the electronics.

Problem: The mount is dead / keeps restarting

Cause (forum consensus + shop experience): 99 % power supply. PSU too weak (sag under load), poor cigarette-lighter connections, cold solder joint, reversed polarity, corrosion.

Solution: Cross-test: swap PSU/cables for known-good ones, check cigarette plugs for play/corrosion, 12 V load capacity ≥ sum of all consumers + 30 %. Only then send it in (“important” note on the package).

Problem: Hand controller freezes / error 16 or 17 / display dead in the cold

Causes: Cables/sockets (intermittent), firmware state, a known temperature topic (documented case: a new HC stops responding at −1 °C while the old HC works); at Celestron, errors 16/17 are, per the importer, “various device combinations, not necessarily indicating a defect”.

Solution: Swap cables/plugs (a patch cable often does the job!), document the FW version (but: “never change a running system” – updates only for a concrete fix), test an alternative HC in cold cases, then RMA via the dealer (Celestron goes via Baader, SkyWatcher via Optical Vision).

Problem: Wi-Fi/app connection drops (AZ-GTI, Fusion, ASIAIR, StellaVita)

Causes: 2.4 GHz band congested/disturbed, distance/steel-concrete, phone battery saver killing background connections, device-specific weaknesses (StellaVita: reliable only at 2–3 m).

Solution: Get close (under 5 m), disable phone battery saving, check channels/5 GHz environment, use the hand control as fallback (Fusion practice: “the supplied hand control is more reliable”), for StellaVita: USB EQDir instead of Wi-Fi dreams. For AZ-GTI with custom-firmware phenomena: inform the importer (known case, shop → SkyWatcher).

Problem: After the meridian flip, tracking/guiding stops

Causes: Automation not configured, plate-solving exposure too short (known ASIAIR case: 2 s in haze → suspected software bug), lax polar alignment.

Solution: Automate the flip (NINA/ASIAIR), raise the solve exposure to 3–5 s+, let sync/re-alignment run after the flip; if only polar alignment brings tracking back: train the alignment skill (see also 6).

Problem: Tracking “judders” periodically / periodic error (PE)

Causes: Normal worm PE (every worm-gear mount has it), bearing play set wrongly (never completely play-free!), belt mounts: pulleys run slightly out of round (normal EQ6-R behaviour, compensated by the belt drive).

Solution: PE is barely visible visually – guiding compensates it; at a fixed site: set bearing play to the average between summer/ winter (workshop matter), for guiding “kicks” see 6. Shop experience: “The imaging problems are usually somewhere other than in the EQ6.”

4. Power Supply

Problem: Device restarts sporadically during the night (mount, ASIAIR, camera)

Cause: Voltage sag under load – PSU undersized, long thin cables, cold solder joints, cigarette-lighter adapters.

Solution: PSU ≥ sum of all consumers + 30 % (field standard: 12 V/10 A class), short thick cables (2.5 mm²), LiFePO4 station (Bresser 13 Ah / PowerTank class), split consumers: motors on a separate output from sensitive electronics. Forum reality: almost every “defect thread” ends here.

Problem: The battery drains faster than specified

Causes: Cold (capacity loss), consumer budget underestimated (cooled camera + heater + mount + hub), watt- vs amp-hour confusion, ageing battery.

Solution: Add up 12 V consumers (labels!) + reserve, compare capacity in Wh (Wh/Ah at 12 V ≈ factor 12), throttle the dew heater with a PWM controller, LiFePO4 instead of lead-gel (lighter, more usable capacity), flying: capacity limits + UN 38.3.

5. Astrophotography: Imaging Artefacts

Problem: Star trails in every frame

Possible causes (diagnostic order): 1. Insufficient polar alignment. 2. Tripod/wind/ground (footprints, soft surface). 3. USB/power dropouts (camera/control). 4. Payload/lever too high → swinging. 5. Clutch/tracking (see 3, 6).

Solution: Follow the diagnostic order: 1. polar alignment (SharpCap/iPolar/ASIAIR), 2. tripod + hook weight, 3. shorter exposures + more subs, 4. enable dithering, 5. only then suspect the mount. “Unguided is realistically 30–60 s” – longer needs guiding (6).

Problem: Egg-shaped / spiral-drawn stars

Causes: Walking noise (no dithering, long unguided exposures), tracking/rate error, tripod settling after wind, balance/clutch interaction.

Solution: Enable dithering (standard in NINA/ASIAIR), shorter exposures + stacking, balance slightly offset (east-west) instead of perfect, increase “settle” time after dithering.

Problem: Donuts (round dark spots) / colour gradients / corner veils

Cause: Donuts = dust on sensor/filter → flats missing; gradients = light pollution/Moon; corners = vignetting of the train.

Solution: Take flats (flat panel/twilight sky, same gain), remove gradients with GraXpert/APP (free!), hide vignetting with flats and a bit of cropping.

Problem: Halos/rings of light around bright stars

Cause: Filter coating (the known duo-band topic), not the optics; occurs even at f/7 apos. No software fix.

Solution: Change filter brand (Askar DNB “largely under control”), accept/mask the brightest stars, when buying prefer coating-checked series.

Problem: Extreme spikes/ray artefacts on all stars

Cause (the practical classic): a hair/lint on the filter! Then: reflections in the train, camera front glass.

Solution: Pull the filter and inspect against the light, blow off (don’t rub!), check the train for lateral light sources (LED on the tripod!).

Problem: Stars sharp only at the centre, corners distorted

Causes: Wrong backfocus (classically 55 mm corrector→sensor, plus ~1/3 of filter thickness), sensor tilt, reducer at its sensor-size limit, coma on a fast Newtonian without a corrector.

Solution: Refine with spacer rings (0.2/0.3/1 mm), tilt test: rotate the camera on the rotator (does the error rotate with it = optics/train, does it stay = camera/tilter), small sensors are more forgiving than APS-C/full frame, “from f/5 you see EVERY imaging flaw”. Coma corrector for Newtonians.

Problem: Image white/completely bright, no stars (photos only)

Causes: Wrong filter in the wheel, exposure far too long, Moon in the field, gain far too high, camera lens cap, focus far off.

Solution: Test shot on a bright star at 1–5 s, consult the camera’s gain table (unity gain as a start), check the filter wheel position, set focus with a Bahtinov mask.

Problem: Hot pixels / “a sky full of fixed points”

Cause: Sensor temperature too high, darks missing; uncooled cameras in summer show many by nature.

Solution: Regulated cooling at −10 to −20 °C, darks with exactly the same time/temperature/gain, dithering + sigma clipping when stacking.

Problem: Sensor fogs up / ices over (cooled camera)

Cause: Window heater activated AFTER cooling – dew freezes; moisture in the housing (desiccant exhausted).

Solution: Sensor heater 30 min BEFORE cooling, cool in steps, replace desiccant/paper sachets (ToupTek: behind the front cover), after a moisture event work with cold drying (off, cap open, silica).

Problem: Stripe bands at the edges of flats

Cause: Normal behaviour of many CMOS sensor single frames (shop diagnosis: “totally normal”) – not a camera defect.

Solution: Flats with low exposure + averaging; the stack evens it out; document and ignore.

Problem: Red/blue colour cast at the horizon

Cause: Atmospheric dispersion (target low in the sky) – physics, not a fault.

Solution: Observe higher (altitude >30°), a dispersion corrector (ADC) for planetary work, the rest in processing.

Problem: “Live stack stays grey / shows nothing”

Causes: Exposure/gain too low, target too faint for aperture and Bortle class, Moon/sky brightness, focus.

Solution: First stack a bright reference star/cluster, stretch the histogram more, test 10–30 s exposures, narrowband filter (emission nebulae even under the Moon – “sometimes even during moonlight”).

6. Guiding & Tracking (Photo)

Problem: PHD2 loses the guide star / doesn’t find one

Causes: Guide exposure too short for the seeing (1 s “chases” seeing – pointless), clouds/haze, search region too small, guide star too faint (small guidescope), OAG prism blocking.

Solution: Guide exposure 1.5–3 s (longer in bad seeing), choose a brighter guide star, increase the search region, check the SNR display, adjust the OAG prism sideways.

Problem: High guiding RMS / star jumps around

Causes: Aggressiveness too high (pulsing), chasing seeing, DEC backlash (zigzag in one direction), wind/tripod, USB packets, extreme balance.

Solution: Run the PHD2 Guiding Assistant, enable Min-Motion for DEC (backlash compensation), dither only between subs with sufficient settle time, at long focal length use an OAG instead of a guidescope (against differential flexure).

Problem: Guiding values good, but photos still show trails

Causes: Differential flexure (camera suspension vs. guidescope shifts), cable pull on the drawtube, tripod sag after hours, torn-out frames (USB hang-ups).

Solution: Use an OAG (eliminates flexure), route cables with strain relief, check the train’s rigidity, more shorter subs instead of fewer long exposures.

Problem: After dithering the star is gone

Cause: Settle time too short / the re-centring motion wasn’t waited out.

Solution: Settle to 10–15 s, moderate dither amplitude (1–2 px in the guider image), check the PHD2 log (the star is re-acquired).

Problem: Centring problems in NINA/ASIAIR with EQMod (EQ6-R)

Cause: Usually software-related (shop remote diagnosis): solve exposure too short, PHD2 pulses too short, settle time too small; DEC play is normal and temperature-dependent.

Solution: Increase solve exposures (RGB/Lum 10 s, narrowband longer), increase PHD2 pulse duration, raise settle after dither; remote diagnosis via a PHD2 screenshot with the guiding values sent to the dealer.

7. Software, Apps & Firmware

Problem: Camera/mount not recognised by the PC (ASCOM)

Causes: Driver package missing/outdated, 32/64-bit mix, wrong COM port (EQDir adapter!), native-vs-ASCOM driver confusion (ToupTek: needs its own driver package, “ASIAIR/ASICAP will NOT work”), unpowered USB hub.

Solution: Install the manufacturer’s driver package, check the device manager (COM port number!), use the ASCOM diagnostics, test the camera with native then ASCOM drivers, use a powered hub.

Problem: Stellarium/CPWI slews to the wrong place

Causes: Hemisphere/setting swapped (north/south), stale sync data, EQMod/adapter configuration, time zone/daylight saving.

Solution: Set the hemisphere correctly, one-star sync after alignment, check the EQMod/CPWI connection type (EQDir vs. HC pass- through), check time/date including daylight saving.

Problem: Plate solving fails

Causes: ASTAP index files missing, exposure too short/sky too bright, focus poor, pixel scale misconfigured.

Solution: Install the ASTAP index (H17–H19 standard), solve exposure 3–10 s, set focus, check pixel scale in the profile; if it only rarely succeeds: raise the exposure dynamically (NINA option).

Problem: Stacking (DSS/Siril/APP) aborts / result is grey

Causes: Defective frames in the set, RAM limit, registration fails (too few stars), histogram unstretched.

Solution: Pre-sort frames (FWHM/star-count filters), stack in batches, “remember: without flats stacks look grey”, activate histogram/curve stretching in the viewer, try Siril for free (“gets you surprisingly far” – forum consensus).

Problem: Firmware update went wrong (device “bricked”)

Causes: Interrupted update, wrong FW for the generation (AZ-GTI custom-FW case!), Windows drivers.

Solution: Re-flash the original shipping firmware (manufacturer website), if impossible: dealer/importer (SkyWatcher collection campaigns for defective hand controls exist), principle: “never change a running system” – updates only for a concrete fix.

Problem: ASIAIR/Ekos/NINA session “hangs” after hours

Causes: USB/Wi-Fi dropouts, phone battery saver, SSD full, meridian flip conflict.

Solution: Disable phone battery saving, Wi-Fi under 5 m, route USB cables separately from motor wiring, check storage, configure flip automation with a safety margin.

8. Observing Conditions

Problem: Optics/front glass fogs up (dew)

Cause: The optics radiate into the night sky and cool below the dew point; open tubes plus a cold front plate.

Solution: Dew shield (extends time to dew point), active heater bands (USB/12 V, regulated – throttling saves battery), tube fans, sensor heater BEFORE cooling (5). Emergency: hair dryer on low – but beware of heat/moisture differentials.

Problem: The object is “there” per the app, but invisible

Possible causes: Object too faint for aperture/Bortle class (galaxies need dark skies!), focus, finder misaligned, precession/ J2000-vs-JNow catalogue discrepancy, target too low (extinction).

Solution: First try bright reference objects in the same sky region (the “M13 test”), averted vision + 1–2 min “eye exposure” (see the Complete FAQ, chapter B), check catalogue epoch (J2000), plan targets above 30° altitude. Galaxies realistically need Bortle ≤5.

Problem: Everything looks mushy under a full Moon

Cause: Sky brightness kills adaptation + contrast; deep sky is impossible, planets/Moon are fine.

Solution: Switch programme: Moon (with filter!), double stars, bright clusters; or narrowband filters (emission nebulae: “sometimes even under moonlight”); UHC/OIII instead of generic LPR.

Problem: Light pollution – deep sky from the city

Reality: Bortle 6–8 = Moon/planets/double stars work well, emission nebulae possible with narrowband, galaxies mostly no.

Solution: Choose the programme to match, narrowband filters (UHC/OIII, duo-band), plan drives to Bortle ≤4 sites (forum standard: “Your road into the hobby is the road out of the city” – half joke, half plan).

9. Solar Observing ⚠

Life-safety rule first: No look without a certified objective solar filter (ISO/film marked “visual”), NEVER a filter at the eyepiece, NEVER look unprotected through the finder. Photographic film is NOT eye-safe. Before every session inspect the filter for holes/cracks (hold it against the light).

Problem: I can’t find the sun in the telescope

Cause: It’s bigger than you think, but the finder field is small – and looking unprotected into the finder is TABOO.

Solution: Tube-shadow method (minimise the tube’s shadow on the ground), the shop’s GoTo trick: “Set the mount up east of the sun – the mount reliably finds the sun”, cover or remove the finder (with the same filter), put the telescope filter on BEFORE the first look into the eyepiece.

Problem: White-light image is white, without detail

Causes: Wrong film (photographic instead of visual!), aged/defect filter, focus off, seeing/cool-down, small aperture for granulation.

Solution: Check the film marking (“visual”/ND5), inspect the filter against the light for cracks, focus precisely (solar limb as reference), a sunspot programme instead of granulation at small apertures, take breaks (“never observe in one long stretch”).

Problem: H-alpha: only a “sweet spot” is sharp / prominences vanish

Cause: Etalon tuning (tilt) not set centrally; after focus/ temperature changes the tuning shifts; missing cool-down; bandpass systems need acclimatisation.

Solution: Turn the tilt ring until contrast is uniform, re-tune after cool-down, keep the diagonal/zoom combo simple, per customer experience reports: choose devices with the dealer’s pre-delivery check (“sun finder precisely aligned, best image quality set” – shop practice before shipping).

Problem: H-alpha camera gets only soft images

Cause: Camera without an IR-blocking filter in the light path (the known Heliostar topic: IR-leak discussion), working distance not respected.

Solution: IR block filter for the camera setup (the shop adds a second filter free of charge with these systems), working distance per the manufacturer, test image at edge vs. centre.

Problem: “Checking a white-light filter through fingers/holes” – how?

Solution: Hold the filter against a bright sky (not the sun!) BEFORE attaching it – any irregularity = don’t use. If in doubt: replace, don’t risk. ISO 12312-2 for eclipse glasses.

10. Cameras & USB Hardware

Problem: Camera not recognised / disappears during the night

Causes (shop debug standard): Cable (length/quality/USB2 vs 3), hub without its own power, driver, port failure, power sag (4).

Solution: First cross-test: another cable, another port, another PC (“first test on another computer + clarify where it was bought, then send it in”), route USB cables separately from motor wiring, hub with its own power, drivers up to date.

Problem: Slow data rate / dropouts in video (planetary)

Causes: Daisy-chained hubs, USB bandwidth (several cameras on one bus), cables >3 m unpowered, buffering limits of the capture software.

Solution: Camera directly to PC/control unit, shorten serial length, disconnect USB consumers, use SER format + RAM buffering for video.

Problem: Images intermittently faulty / “never in the stack”

Cause: Rarely a real sensor problem – usually cable/PSU/software setting (shop diagnosis: “That sounds like a setting in SharpCap”).

Solution: Cross-test NINA/SharpCap/ToupSky, swap cable+PSU, document the artefacts (report them for future warranty cases).

Problem: USB devices fail after hours

Causes: Hub voltage sag, Wi-Fi interference (2.4 GHz band vs. USB3 noise), cable stretching in the cold.

Solution: Powered hubs with 12 V input, keep USB3 devices away from 2.4 GHz Wi-Fi, lay cables with slack, secure overnight with watchdog/reconnect scripts (NINA/ASIAIR reconnect function).

11. Maintenance, Storage & Ageing

Problem: Fungus/veils in the objective / on the corrector plate

Cause: Damp storage (basement, garage, damp alcoves), desiccant exhausted.

Solution: Specialist service immediately (optical cleaning service) – DIY makes it worse; then store dry (replace silica bags, “dry, temperature-stable”), corrector plates only via the manufacturer/importer (Baader/Celestron – “outrageously expensive”; compare used devices instead).

Problem: Mirror grey / image dimmer than it used to be

Cause: The aluminium coating ages after 10–20 years (normal ageing, not a care failure); damage from aggressive cleaning.

Solution: Re-coating (services are sporadic, shipping + waiting time) or a replacement mirror on budget scopes; never rub a mirror dry – compressed air, then a damp microfibre cloth in circles.

Problem: Axis grease hardened (years outdoors)

Cause: Grease ages thermally; several years “outside on the pier” stresses clutches and gears (the known EQ6 permanent-outdoor case: grinding noise).

Solution: Workshop overhaul (grease change after several years is normal – “you can have that done in a few years”), bearing play set to the average, never completely play-free.

Problem: Stains on the mirror back / rust on the cell

Cause: Moisture (water damage case); the back is optically irrelevant.

Solution: No intervention needed as long as the mirror surface is intact (“The stains on the mirror back have no influence on image performance”); dry the cell, protect if needed.

Problem: Spare parts take forever / old devices are dead

Reality: Importer spare parts take “at least 3 months” (partly from China); for old devices (the Meade era) supply has practically ended; the importer runs collection campaigns for defective hand controls.

Solution: Order via the dealer (who offers reservation and follow-up service), alternative: used parts/devices (classifieds – “You should get rid of the mount for a similar price on the open market fairly quickly”), upgrade instead of a botch job on critical mechanics.

12. Buying, Used Gear & Service Cases

Problem: The “optics lottery” – two units, two qualities

Cause: Manufacturing spread (factory collimation, gluing, lens cell).

Solution: Buy from a dealer who checks and collimates before shipping (shop standard: every telescope/mount checked, bearings set, tripod thread re-cut), book a quality certificate (star test + Ronchi for refractors as a shop service), use your exchange right when in doubt. Direct China import: “We can’t match the China prices. They’re all below our cost” – the service (checking, introduction, repair) is the difference.

Problem: Buying used – what to look for?

Checklist (forum consensus): - Newtonian/Dobson: test collimation, mirror surface (grey = re- coating due soon), drawtube play, axis grease. - Refractor: lens cell never “improved” by the previous owner (tool marks = warning), fungus? clear corrector? - SCT/Mak: front glass, mirror shift, focus play. - Mount: GoTo test, motor noises, axis play, electronics age, parts availability. - Proof: a defocused bright star = symmetric diffraction rings.

Problem: Defect right after purchase – what now?

Process (shop standard): Report the fault by email with photos/ video → remote diagnosis (often PSU/cables!) → if needed send the device in (“important” note on the package) → the shop reproduces the fault → importer/RMA or in-house repair → often an immediate replacement from stock. 2 years warranty is standard.

Problem: Third-party device with a running warranty – may the shop touch it?

Short answer: Better stay with the original dealer – otherwise the warranty claim may lapse (the classic warning). Adjustment/ checking is possible; warranty repairs belong to the sales channel.

Problem: ChatGPT/the internet recommended me wrong adapters

Real case: Z instead of F mount, 1.25” instead of 2” – the shop added the correct adapter free of charge. Solution: For combos (camera + optics + filter wheel), have the dealer assemble the train – “The adapters are sourced together and I’ll ship them with it.”

13. Sources & Further Reading

Expert articles & guides (on the internet): - Gary Seronik: A Beginner’s Guide to Collimation – garyseronik.com (basis of the collimation passages) - Astro-Baby’s Collimation Guide – astro-baby.com (image-by-image Newtonian collimation) - PHD2 Guiding – openphdguiding.org (manual + troubleshooting) - NINA – nighttime-imaging.eu · Siril – siril.org · GraXpert – graxpert.com · ASTAP – hnsky.org · AutoStakkert!/RegiStax - Stellarium – stellarium.org · Telescopius – telescopius.com · astronomy.tools · Clear Outside – clearoutside.com · Astrospheric

Forums & communities: - Cloudy Nights (cloudynights.com) – the world’s largest EN forum - Astrotreff.de · astro-forum.de · Astronomie.de – German classics - Reddit: r/telescopes · r/astrophotography

Safety & organisations: - Baader Planetarium (baader-planetarium.de) – AstroSolar films/ filters, Celestron service DE - AAVSO – aavso.org (variables, citizen science) - Sky & Telescope – skyandtelescope.org (weekly sky, reviews)

And always: - Teleskop-Spezialisten, Grubmühl 20, D-82131 Gauting (near Munich), Germany - Tel. +49 (0)89 68050200 · SMS/WhatsApp/Signal/Threema - info@teleskop-spezialisten.de – remote diagnosis via photo/video on WhatsApp explicitly welcome; every mount/telescope is checked and collimated before shipping.

As of: October 2026 · Additions welcome – clear skies!