I will review the progress, challenges and lessons learnt in ensuring long term preservation of astronomical data
ranging from photographic astronomical data prior to the 1980's, through the digital age. I will cover the approaches used by
astronomers working at different wavelengths from radio to the X-rays and both ground based and space based observations. Key issues are metadata, data compression and software than can read the data. As well as preservation I will describe progress in data discovery. Whilst I will primarily focus on astronomical data many of the lessons learnt (some painful and recurring) are relevant to other domains.