I have a water Grand Trine,between the Sun(Pisces26º00'),Pluto(Scorpio20º13')and my Chiron/South Node conjunction(Cancer 21º and 26º15',respectively)between houses 3,10and7,respectively.Grand Trines offer much talent and are the source of great creativity,though they characteristics depend greatly on the element of the configuration.
Water grand trines endow people with great compassion,sensitivity to other other people's emotions and an innate ability to 'perceive' the world,a powerful intuition that allows them to navigate through life with their eyes closed and even amazing psychic gifts sometimes.On the down side,these people can be emotionally manipulative,exaggeratly sensitive and over-reactive,fretting over little things and going through great ammounts of pain because of their innability to step back and look objectivly at events;they wear their hearts out on their sleeves and perceive the world through their emotions,being almost impossible for them to 'shut off' their emotional side when needed.
People with Earth grand trines are blessed with staying power,preserverance,loyalty and the ability to navigate through the pratical world.These people always know where the car keys are,where they left their sunglasses,when to turn the gas off.Their patient,solid,reliable character makes them pilars of reference in the lives of others.Earth grand trine people are the kind of people you want to have next to you in times of crisis,because they keep their cool and always know what to do.Material security is key for them,and they usually put much effort into ensuring they have money saved for a rainy day.They can come up with creative solutions for everyday's little problems,while being also very smart when it comes to business and building up a career.On the downside,they lack a connection to the spiritual world and can easily become greedy and unsatisfied with what they have,always wanting more and more and more.They're so careful and cautious in their approach to life that they can end up missing out great opportunities,simply because they were too afraid to take the leap or took too long to decide.Or sometimes,they are lazzy,plain and simple,prefering to stick to what they know,since security is extremly important for them.It may be hard for them to see past the exterior of things.
Air grand trine people live in a mental world.They are communicative and witty,possessing great mental skills and the ability to recognize patterns and see connections between things.They are usually good with words,and are 'social animals',enjoying social gatherings and get togethers.They love anything new,be it new ideas,new connections,meeting new people.They are extremly curious about everything,be it the universe or the neighbour's life,and love to learn and absorb as much knowledge as they can.They can make great writers and are keen observers.Their creativity is more mental/linguistic than anything.Yet,there's not much drive to take action in these people,and they can refuse to see other people's point of view and become stubborn in debates and discussions.They can't focus on something for long and rarely accquire specialist knowledge,since they prefer to have a wide range of interests rather than focusing on one thing,wasting their great mental abilities.
People with Fire grand trines are active,spontaneous and full of positive energy.They enjoy life and are full of optimism.They are usually self-confidence,even to the point of becoming arrogant,though their neverending energy and spontaneous atitude can be very atractive to others.They are outgoing and extroverted,loving to make new social connections.They usually enjoy traveling and sports as well;anything that keeps them moving is good.On the other hand,they are extremly impulsive,and their restless nature will probably drawn out everyone around.They also have a tendency towards selfishness,being hard for them to see things from other people's point of view.
For more info on Grand Trines:
http://www.lunarliving.org/astrology/grandtrine_kite.shtml
http://www.bobmarksastrologer.com/GrandTrine15.2.htm
http://en.wikipedia.org/wiki/Grand_trine
I would love to help you interpret your Grand Trine,but I don't work with asteroids,and I don't get what you refer to as 'Mid',so I can't really see wether you have a Grand Trine or not