Budhaditya Yoga

Budhaditya or Budhaaditya yog is formed when Sun and Mercury join together (i.e. are conjunct) in a house. This yog, in a person’s chart, is said to give lots of talent, success, honour among his/her peers and fame in society.
Mercury is the first planet in the Solar System and is very close to the Sun. As a result, it cannot be more than one sign away from the Sun in the rashi chart. This yog, therefore, appears in a lot of charts, but not all the charts can have the qualities mentioned in the first paragraph.
Any yog materializes only when all the planets involved in the yog are strong. They should be placed well in a chart and also should not themselves be badhakas for the chart, e.g. by being lord of dusthanas. Budhaditya yog is best formed when Sun and Mercury are in signs of Aries, Gemini, Leo and Virgo. The logic is simple - Aries is exaltation sign for Sun, Gemini and Leo are ruled by Mercury and Sun respectively and Virgo is exaltation/moolatrikona sign for Mercury. It is natural to think that these signs would be more conducive for this yog. In other signs, this yog would not fair that well and would give mixed results.
Ownership of Leo by Sun and Gemini and Virgo by Mercury make it a fairly tricky yog. Looking at all the lagnas, it is difficult to find a case both Mercury and Sun are rulers of good houses. Consider the case of Aries lagna where Mercury is a difficult planet as it rules house number three and six at the same time. Sun is an owner of a good house - house number five, but its association with Mercury may not be considered good for the person. 
This yog would give good results for Taurus, Leo, Libra and Aquarius lagna. For Sagittarius lagna, Sun and Mercury should be considered auspicious raj-yog karak. Based on Parashari principles, many astrologers might disagree with this observation. They could attribute Mercury to be afflicted because of ownership of two kendra houses at the same time. I am of the opinion that in this case Budhaditya yog still exists.
Apart from house ownership considerations, Mercury should not be extremely close to the Sun. It may be considered combust if it is within six degrees. During the recent transit of Mercury across the solar disc (November 8-9, 2006), Budhaditya yog would get canceled.
I do not know what happens to this yog if Mercury were to be retrograde when conjunct with Sun… I sincerely request an astrologer reading this to consider me a mere student and educate me and other readers of this blog on this matter.