While astrologers compare the inter-aspects between both charts, they almost always neglect midpoints in synastry (which is a natal chart comparison between two partners), missing some most important information.
In our opinion, a midpoint comparison is a must if you want a reliable and accurate way to assess the relationship of a couple.
Especially the most exact midpoints (orb 00°00' - 0°01') nail the relationship down in its essence and work out accurately during the whole life span of the relationship.
How to proceed in using the midpoints in synastry between both charts?
Fortunately, thanks to computer software, this is not too difficult anymore.
Some software programs already have the option to do a full midpoint comparison between two charts.
However, most software in the English language do not (yet) feature this option.
If that's the case, you can print a list of all the natal midpoints of each chart in the 45° dial, list, modus or modulus (8th Harmonic) -- sorting the midpoints by degrees.
Compare the midpoints between both natal charts by looking at the listed degrees.
This way, you can easily spot which planets and/or bodies at a certain degree in the chart of partner A coincide with (equal) midpoints in the natal chart of partner B (and vice versa).
All midpoints that are within the 1° orb are of interest, but, again, the very exact ones (orb 0°00' - 0°01') prevail and overpower everything else.
We're only focussing on the planets to midpoints combos, not the midpoint to midpoint combinations for now (that's way too advanced and will confuse you enormously).
If the Sun at 33° (in the 45° dial/list) of partner A equals the Venus/Saturn midpoint at 33° (45° list/dial) of partner B we write this down as SO=VE/SA.
We can look up the meaning of this midpoint right in The Combination of Stellar Influences (CoSi).
If the Sun/Mars midpoint at 12° (in the 45° dial/list) of partner A equals the Jupiter/Saturn midpoint at 12° (in the 45° dial/list) of partner B we don't take this combination into account and disregard it (for now) because it's less important.
So, we're only looking for planets/bodies to midpoint combinations.
The more auspicious the contacts are, the better.
In matters of love, the Sun (SO), Moon (MO), Venus (VE), Mars (MA) and the Moon's Node (KN) are very important.
If there are no midpoint combinations in the chart comparison that include these planets/points, there is no love relationship.
Aside from looking at the coinciding midpoint-planet combinations between the partners following the 45° dial/list sorted by degrees, you can also look at the chart comparison in another way.
You can also look if certain midpoints related to love in the natal chart of partner A coincide with (equal) a planet/body in the natal chart of partner B (and vice versa).
The most important midpoints related to love are:
If the Sun/Moon midpoint of partner A equals Saturn of partner B, we get the SO/MO=SA picture that we can look up in The Combination of Stellar Influences (CoSi).
Saturn in any midpoint combination or planetary picture brings some restrictions or separation (not always bad because the outcome depends upon the whole picture/image of the puzzle).
A single midpoint combination or planetary picture does NOT tell the whole story yet, it's just one piece of the puzzle.
The more midpoint combinations there are, the more pieces of the puzzle and the better we get the image of the puzzle in the end.
Using the midpoints in synastry requests some structure in the way you work.
Also, combining these single parts (midpoints) into a larger whole (the puzzle) has to be learned by practice.
Learning to use the midpoints in synastry may result in jaw-dropping insight and will show you that the Universe is really working in a very very systematic, structural, organized and geometrical way.
This all makes astrology more 'scientific' too.