Few apartments would be big enough to contain the giant egos of a group of "fire sign" flatmates. It would be a case of theatrics at dawn and very little attention to the practicalities, like basic domestic hygiene. However, a flat full of housework-shy drama queens might be marginally preferable to the mausoleum-like ambience of an "earth sign" abode, where competing TV zappers till dusk is about as exciting as it gets - although there would always be some nice food in the fridge. But adding "No earth signs need apply" to that accommodation sharing ad, and basing flatmate compatibility purely on sun signs can be too simplistic an approach, according to astrologer John Little, who advocates a more complex technique called Synastry. Little e-mailed Apartment Living following last week's article on the importance of choosing the right flatmate to share a confined space. He believes that all the glowing bank and work references in the world aren't going to help, if there is inharmonious cross contact between the Moon, Venus, Mars and Ascendant (the point that was rising in the east at the hour of birth) in two horoscopes.

"At the end of the day, it's about being completely at ease with the people you live with, particularly if you live in a small space. When you get home after a long day at work, the last thing you need is more stress in your life. It helps if there is a sense of familiarity like being with family or in your granny's. Synastry is about fast-tracking the process of discovery into how we may or may not be able to exist in a small space with someone we do not know."

Sceptical? If the answer is yes, you wouldn't be alone. As a nation we are still very much in the astrological closet, says Little, who is amazed that letting agencies have been slow to avail of his services, even as an experiment.

As quizzing a potential roomie about their exact time of birth could arouse suspicion and alarm, Little says he can base calculations on noon on their day of birth. He believes there is nothing unethical about using a person's birth date against them, if you have to.

"It saves a lot of time and potential heartache. In time I believe it is going to be standard practice. It's good to know in advance what you are getting into and it's also useful for landlords when choosing tenants. They want to know that someone is not going to split owing rent or ruin their place."

He believes that one day people will consult astrologers as openly they do other experts. "If a person is buying a house, they will see a mortgage broker, a surveyor, an auctioneer and an astrologer as part of the mix."

To most of us it seems a scenario based mostly on surreality but Little defies anyone to put his Synastry analysis to the test. I supplied him with my birth date and that of my flat mate Deborah.

Although I am Aries and Deborah is Capricorn, he said both our moons are Capricorn, which suggests harmonious cross contact and a possible past-life relationship.

"You probably both run an efficient house and there is more likely to be calming, soothing music on the stereo than heavy metal. Your moons are conjunct which is classically considered a meeting of minds and souls. Your ups and downs, highs and lows all coincide. You share a lot of frank exchanges and would talk a lot about boyfriends. Your Moon, Mercury and Mars are all clicking into place which means you are broadly from the same cultural background which means instant recognition."

While this is a fairly accurate assessment, one could possibly argue that most female friends gossip about boyfriends. Coincidentally, another pair of female room-mates comprises an Aries sharing with a Capricorn.

"There are no unduly negative cross contacts between these girls' horoscopes. Their mutual space is cheery and stylish. There is no routine, and possibly a happy mayhem.

"They enjoy company and may encourage outsiders to visit and even stay.

"They decided to share a flat on a whim or impulse and may part almost as impulsively.

"Why do I sense that the past few weeks have been unusually volatile for this association? According to the Mercury method, the two girls are in harmonious aspect. "I sense a broad similarity of interests, lifestyle patterns and even similar tastes in TV shows, music, men and clothes.

"Ms Capricorn seems to be hugely fascinated by Ms Aries; this could, under certain circumstances, even assume a rather manipulative, obsessional or coercive tone, perhaps a subconscious urge to delve into Ms Aries's secrets. "In a past life, Ms Capricorn held some sort of hold or control over Ms Aries - echoes of this persist in this incarnation.

"In a sense they both act as one another's shrink. Topics of conversation will not be trivial.

Ms Aries considers Ms Capricorn a bit obsessive, stubborn and often secretive, moody or evasive."

The Ms Aries in question proclaimed the reading "surprisingly accurate. It has put some sense on some of the less than harmonious undercurrents that have been rocking our home life. He has also put some clear-sighted rationale on situations that I had always put down to nothing more than emotional mood swings."

If the Mercury element of two people's charts are out of kilter, it means that they will rarely be on the same wavelength. "When one is low, the other will be high" says Little.

"Messages might go astray, they will find it difficult to communicate. When Mercury is in harmonious contact, even if two people are from different cultures and speak different languages, they will still manage to communicate, there will be a subtext going on there all the time."

Sun sign horoscopes are a colloquial form of astrology that people can understand. While less dependable than Synastry and somewhat limiting, there are some rules of thumb, says Little. "I am a Saggitarian so generally I would be mismatched with someone five signs forward or five signs back, so Cancerians and Taureans would be out."

John Little can be contacted on 01-8337158 or www.octile.com