This question relates to the Crab nebula, the Crab Pulsar and the known concurrent supernovae event as recorded by Chinese astronomers in 1054.
I'm wondering, I'm looking at the history of the discovery of the Crab pulsar...and I'm wondering what the reason is (or suspected to be) as to why European records show a discernible lack of observations?
Of the three known medieval supernovae (in 1006, 1054, and 1181 AD), only SN 1006 was definitely recorded by Europeans, and even then, was only discussed in any detail in a single European source (the annals of the monastery of St. Gall in Switzerland). Although there are multiple accounts (some quite detailed) of the supernova of 1006 in Arabic/Islamic records, there is only one known Arabic record of SN 1054, and none for SN 1181.
Since SN 1006 was by far the brightest of the three, the simplest explanation would be that SN 1054 was, like SN 1181, just not bright enough or long-lasting enough to merit sufficent widespread commentary in Europe. (Remember that China in the 11th Century was a much more advanced society than Europe of the same time, with a dedicated tradition of government-supported astronomical/astrological observations.)
Apart from observational parameters (Peter's answer), astronomy was not that 'hot' in that period. One main reason is indeed that the Christian church did not promote it.
Quoting from the section Medieval Western Europe on the Wikipedia History of astronomy page:
After the significant contributions of Greek scholars to the development of astronomy, it entered a relatively static era in Western Europe from the Roman era through the 12th century
According to an article on the Portal to the heritage of astronomy it wasn't until the 12th century that astronomy got a more modern scientific twist:
Chronologically, the Middle Ages are conventionally divided into an Early Medieval and a Later Medieval period. A chief marker of this division is the re-emergence of urban society in the 12th century, which was accompanied by several changes that transformed medieval astronomy. The first was the movement of astronomical study from monasteries and cathedrals to the emerging universities. Accompanying the rise of the universities was the change of the content of astronomical study, since both astronomy and geometry took on a renewed quantitative aspect founded on the study of ancient texts. The rise of urban life saw the development of learned and skilled professions, including architects who applied this astronomical knowledge in their work.
The introduction at the Tom L. Perry Medieval Astronomy collection dates the revival of astronomy just around/after the 11th century:
Astronomy was revived in Europe during the eleventh century with the arrival of the astrolabe, a device for measuring the position of heavenly bodies which was introduced to Europe from the Islamic world. Planetary observations were useful for astrological predictions and for medical practice, since the planets and the zodiac were thought to correspond to the organs of the human body. Over the next century, the writings of ancient Greek astronomers like Ptolemy were rediscovered by the West, further enriching Europe’s knowledge of the universe.
Sir Robert Wilsons's book Astronomy through the ages, when discussing Islamic astronomy in the period 8th–15th century, has this to say about the influence of the church in western astronomy:
During the great period of Islamic astronomy, scientific endeavors and inquiry were virtually absent in Christian Europe, largely because of the lack of encouragement (some would say active discouragement) for such endeavors by the Christian church, which believed that thruth and spiritual guidance could come only from holy scripture and that natural knowledge and understanding was best revealed by ancient writings.
