How exact an angle must be to count as an aspect, plus the 4 minor aspects the app uses beyond the 5 major ones.
An aspect is the angle between two planets. But it isn't only counted at exactly 90° or 120°. The orb is the range of degrees an angle can be off from exact and still count as the same aspect.
Orbs by aspect
Stellog uses these orbs by default. The closer an angle is to exact, the stronger it's considered.
Conjunction
0° · orb 8° · Neutral
Sextile
60° · orb 4° · Harmonious
Square
90° · orb 6° · Challenging
Trine
120° · orb 6° · Harmonious
Opposition
180° · orb 7° · Challenging
The 4 minor aspects
Semi-sextile
30° · orb 2° · Neutral
An angle of 30° between two planets. Neighboring signs meet, pointing to small adjustments and learning.
Semi-square
45° · orb 3° · Challenging
An angle of 45°, half a square (90°). It points to friction and stimulation that are milder than a square.
Sesquiquadrate
135° · orb 3° · Challenging
An angle of 135°, a square plus a semi-square. It points to where built-up tension comes out into the open.
Quincunx
150° · orb 3° · Neutral
An angle of 150° between two planets. It links signs that share neither element nor modality, so it points to an awkward pairing that needs ongoing adjustment.
Minor aspects are read as weaker than the major ones. When ranking the contacts between two people in synastry, the semi-sextile, semi-square and sesquiquadrate are left out, and the quincunx is given little weight.
Harmonious, challenging and neutral
The app gives each aspect a character. Trines and sextiles are harmonious aspects; squares, oppositions, semi-squares and sesquiquadrates are challenging aspects; conjunctions, quincunxes and semi-sextiles are neutral. A conjunction can work smoothly or tensely depending on the two planets that meet.
Applying and separating
Applying and separating aspects
If a moving planet is heading toward the exact angle, the aspect is applying; if it has passed exact and is moving away, it's separating. Applying aspects are usually read as stronger.
The current sky chart also shows whether an angle is becoming exact or has already passed exact. An applying aspect means the theme is building; a separating one means it's passing.
Why orbs differ between services
Reports use narrower orbs to suit their purpose. The narrower the orb, the more only the tightest angles remain.
Daily Horoscope
Only angles of 4° or less between today's planets and your birth planets are used, starting with the most exact.
Yearly Horoscope
It looks for when Jupiter and Saturn come within 2°, and Uranus, Neptune and Pluto within 1.5°, of your birth chart.
Solar Return
Angles to your birth chart, contacts with the angles and the big life cycles are all read within 3°.
Node Axis
The 5 major aspects other planets make to the North Node are read within 3°.