The final piece of the Great Telescope in Birr, Co Offaly, its mirror, is to remain in the Science Museum in London. The mirror, listed in Victorian times as one of the wonders of the world, is too fragile to be moved from the museum where it was placed in 1914 for safe keeping.
The six-foot polished mirror was one of two made by the third Earl of Rosse with the help of workmen at the Birr demesne, then the focal point of so much scientific research. No one knows the whereabouts of the other mirror.
However, this week it was learned that work is well under way on an aluminium mirror at University College, London, and the optical system for the telescope will be put in place by autumn.
Its design was agreed by Sir Bernard Lovell and Mr Michael Tubridy, the engineer on the project, and Mr Bob Strunz, of the University of Limerick.
The contract for the optics for the telescope's fully-restored wooden tube has been signed and the University of London will deliver in the autumn.
A camera will focus on the eyepiece so that, while astronomers are gazing at the stars, their observations will be recorded and shown at the observatory gallery at the historic science centre in the castle grounds.
Since the plan to restore the telescope was put in place, the second phase of the restoration of the centre has already started.
This involves the conversion of the 19th-century stables and coach houses into science galleries. These will focus on the pioneering work of some of the great Irish scientists.
They will look at the astronomical achievements of the third and fourth Earls of Rosse, the pioneering photography of Mary, Countess of Rosse, and the botanical work of Michael and Anne Rosse during this century.
This phase of the restoration will be open to the public in the summer. People have already shown a huge interest in the work already been completed at the demesne.
The building work, which is being carried out by Frank Murray and Co, of Roscrea, Co Tipperary, will be finished by May 1st and it will house the science galleries which will be open to the public on July 1st.
Ms Ann Scroope, the Nenagh-born designer, who has worked in Australia and London with exhibition designers and is best known for her work on Kilmainham Gaol museum, is currently designing the Birr exhibition.
Work is also continuing on the gardens where a FAS team, supervised by Mr Peter Hynes, is restoring the once-beautiful grounds.
The FAS team has already uncovered a lovely tracery of paths, the base of a summerhouse, and a rockery beside the "winter garden", leading from the Cross Avenue to the castle.
Another FAS team is building an entrance to the demesne. It will also build a turbine house where hydro-electricity will once again be generated.
The restoration of the telescope tube has stirred great interest and in 1996 some 27,000 visitors went to the site.
By the end of last year, this had risen to 36,000, a considerable achievement bearing in mind the falling visitor numbers to the Shannon region.
The Great Telescope project was inaugurated in April last year by the former president, Mrs Mary Robinson. She described it as the best-known man-made artefact from Ireland worldwide.