Mini-Test Check (10s → 20s → 30s → 60s)
Start directly after your EQ alignment with a bright star field or an object at medium to high altitude. Go through the steps 10s → 20s → 30s → 60s and answer only the two core questions per step: Stars round? and Rejection rate?. Optionally mark wind gusts – this helps with cause detection. The tool gives you a traffic-light decision and a recommended exposure, so you don't "blindly" force 60s, but quickly land on a stable value.
EQ Mini-Test: Progressive Exposure Stability Checker
This tool guides you through a 4-stage progressive exposure test to determine the maximum usable exposure time for your Seestar setup in the current conditions. Instead of guessing, you take test shots at 10s → 20s → 30s → 60s, report the star shape and frame rejection rate at each stage, and the tool evaluates your equatorial mount alignment and tripod stability.
- 10-second TestPoint at a bright star near the meridian (60–70° altitude ideal). Take 5 frames at 10s. Examine star shape: perfectly round = tracking is working; elongated = problem at this exposure already; check polar alignment and level before continuing.
- 20-second TestTake 5 frames at 20s with the same star. Note the frame rejection rate in the Seestar app's live stacking view. A rejection rate above 40% at 20s indicates polar alignment error or vibration that needs correction before extending exposure further.
- 30-second TestExtend to 30s. This is the minimum exposure length where EQ mode provides a clear advantage over alt-az for deep-sky objects. If star shapes remain round and rejection rate is below 25%, your alignment is sufficient for 30s imaging.
- 60-second TestThe full EQ mode target exposure. Take 5 frames at 60s. Round stars + rejection rate below 20% = excellent polar alignment. Any elongation or rejection rate above 35% = refine polar alignment further before running a full imaging session at this length.
Star Shape Diagnostic Guide
The direction and shape of star trailing tells you exactly what needs to be corrected. Learn to read these patterns from your test exposures:
| Star shape | Direction | Cause | Fix |
|---|---|---|---|
| Round points ✓ | – | Polar alignment is good for this exposure length | None needed — extend to next test |
| Short arcs / elongated (all same direction) | E–W | Polar alignment azimuth error (pointing too far E or W of True North) | Adjust azimuth of polar axis; repeat test |
| Short arcs (all same direction) | N–S | Polar alignment altitude error (tilt angle off from latitude) | Adjust wedge tilt angle; repeat test |
| Arcs with varying lengths across frame | Radial from center | Field rotation — alt-az mode or severely misaligned EQ axis | Verify EQ mode is active; redo polar alignment |
| Stars doubled or "comet-tailed" | Any | Vibration from wind, tripod, or nearby footsteps | Add weight to tripod; use wind shield; wait for calm |
| Consistent blur (not elongated) | – | Focus drift (thermal) or initial out-of-focus | Run autofocus; check dew on lens |
| Stars round but frame rejected by app | – | Cloud pass, satellite trail, or stacking algorithm threshold too strict | Check sky transparency; adjust rejection threshold in app settings |
Setup Stability Scoring: What the Test Evaluates
The tool calculates a stability score from your reported results across the four exposure stages. Here is how each factor contributes:
Star Shape Score
Round = 3 pts; slight elongation = 1 pt; clear trailing = 0 pts. Weighted 50% of total score. The most direct indicator of tracking quality.
Frame Rejection Rate
<20% = 3 pts; 20–40% = 1 pt; >40% = 0 pts. Weighted 30%. Rejection rate captures both tracking errors and transparency issues that star shape alone cannot detect.
Wind Effect
Enter wind speed (Beaufort or km/h). Above Beaufort 3 (gentle breeze, >12 km/h), tracking stability degrades significantly. Score deduction: B3 = −0.5 pts, B4+ = −2 pts at 60s.
Tripod Rating
Heavy aluminum/carbon tripod = +0.5 pts; standard tripod = 0; lightweight travel tripod = −0.5 pts at 60s exposures. Ground type also matters: concrete > grass > soft soil.
Score interpretation: 8–9 pts = Excellent (60s+ sessions viable); 6–7 pts = Good (30–60s sessions, avoid very windy nights); 4–5 pts = Marginal (stick to 20–30s); <4 pts = Poor (troubleshoot alignment and stability before imaging).
Frequently Asked Questions
Which star should I use for the mini-test?
Choose a bright (magnitude 1–3), isolated star at 50–70° altitude, near the meridian (due South in the Northern Hemisphere). Avoid stars near the zenith (>80°) as tracking errors are harder to see there. Good choices for Central Europe: Capella (winter), Vega (summer), Arcturus (spring/summer), Fomalhaut (autumn). Avoid stars close to the horizon (<30°) where atmospheric refraction can cause false elongation that mimics tracking errors.
What frame rejection rate should I aim for in EQ mode?
Target: <20% rejection at 30s and <30% at 60s for good conditions. In practice, 20–35% rejection at 60s is common even with good polar alignment, because occasional clouds, satellites, and atmospheric turbulence unavoidably affect some frames. A rejection rate persistently above 50% at 30s always indicates a systematic problem (polar misalignment, vibration, dew on lens, or tracking failure) that needs to be addressed before continuing the session.
How do wind conditions affect the test results?
Wind is the most underestimated factor in Seestar EQ session quality. At Beaufort 2 (light breeze, leaves rustling), a properly polar-aligned Seestar on a good tripod performs excellently. At Beaufort 3–4 (gentle to moderate breeze, small branches moving), you will see intermittent frame doubles or comet-tailed stars that increase the rejection rate significantly. Practical mitigations: use the Seestar's carry case as a windbreak, add a sandbag to the tripod center hook, and schedule long-exposure sessions for calm nights (midnight and later typically offer lower wind speeds).
Can I use this test for alt-az mode too?
Yes, with modified expectations. In alt-az mode, run only the 10s and 15s stages. At 20s+, field rotation artifacts in alt-az mode will appear at the image corners regardless of tracking quality — these will be incorrectly flagged as "poor" in the full EQ test. The tool has an "Alt-Az Mode" switch that adjusts the scoring and diagnosis to reflect alt-az limitations and only evaluates tracking accuracy within the shorter exposure range where the mode is viable.
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