I am doing a project on Isaac Newton. Ive looked at his impact on the development of the telescope, in particular, the reflecting telescope. Ive researed this a bit and have found conflicting dates. Some sources say he built the first relflecting telescope in 1671 but others go as far as 1684. Can you define which year it actually was in and source it for me from somewhere reliable?

http://en.wikipedia.org/wiki/Reflecting_telescope

"Sir Isaac Newton is credited with constructing the first "practical" reflecting telescope after his own design in 1668.[1]"

The note [1] above refers to this book:
Reflecting Telescope Optics I, R. N. Wilson, A&A Library, Springer, 1996 (ISBN 0941-7834)

Also ---
http://brunelleschi.imss.fi.it/museum/esim.asp?c=200601
Scroll down to Newtonian telescope.

I'd be glad to. The Newtonian telescope was a great advance in telescope making and is still used today. It is easy to make with large apertures. It was very popular with amateur telescope builders for a long time. I also found (using Google) claims ranging from 1668 to 1689 for when he made his first reflecting telescope.

This quote, from
(Broken Link Removed) seems to be the most believable:
<<Reflecting telescope named after its inventor Isaac Newton (1643-1727), who built it in 1668 (a second copy, which survives, was presented to the Royal Society in 1672). The Newtonian telescope consists of a parabolic primary mirror, which serves as the objective, and a small plane elliptical mirror located on the optical axis and inclined at 45° to the axis. >>

To verify the accurate year Isaac Newton built the first reflecting telescope, we can refer to reputable sources. Here's a step-by-step process to find the answer:

1. Start by searching for credible sources related to Isaac Newton's development of the reflecting telescope. Academic or scientific websites, biographies, or historical archives would be reliable sources to explore.

2. Once you've found a potential source, carefully read through the information provided about Newton's work on the reflecting telescope. Look for specific details, including the year(s) mentioned.

3. During your research, note any conflicting dates you find and make a list of the sources that provide these differing accounts. Having a record of these sources will allow you to cross-reference and compare the information later.

4. To determine the most reliable source, prioritize texts published by renowned experts in the field, scientific journals, or well-regarded historical accounts. Pay attention to the author's credentials and reputation.

5. If possible, try to access primary sources from Newton himself, such as his writings, letters, or manuscripts. The information directly from the source can often be the most trustworthy.

6. After gathering all the relevant information, evaluate the credibility and consistency of the sources. Look for a scholarly consensus or the weight of evidence that supports a specific year.

By following these steps and systematically evaluating different sources, you should be able to identify the most accurate and reliable year Isaac Newton built the reflecting telescope. Remember to cite your sources properly in your project to provide attribution for the information you gather.