I haven't lived or worked in the greater D.C. area for almost 8 years, and it was 2002 when I was last in the Smithsonian's National Air & Space Museum. This last fall I had a couple who I have become friends with and who own a XX12i go back to the D.C. area for a family event. While there they very kindly thought of me and took some pictures while at the Air & Space Museum of William Herschel's 20 foot telescope which is on display there. Here is the image they shared with me:
The Twenty Foot Wooden Telescope is above. Here's an image from the Smithsonian's site looking down the wooden tube.
Information on William and his sister Caroline.
From the Smithsonian's Website is the following information on this telescope:
"This long wooden tube is from William Herschel's 20-foot telescope. He began observing with the telescope in 1783, and though he went on to build even larger ones, his 20-foot remained his favorite. In 1820 Herschel and his son John rebuilt the telescope, which had deteriorated after decades of use, salvaging what they could from the original. The tube displayed here is a product of that reconstruction."
So if your in the area, drop by and take a look at an instrument that one of the most famous visual observers used to catalog many of the objects he observed. You can also see the 100 foot Observing Cage from the Hooker Telescope from Mt. Wilson It is one of several interchangeable cages that were used and this one along with the camera attached to it was used by Hubble during his study of nebulae and galaxies. See this image to view the display.
They also have a copy of the backup mirror for the Hubble Space Telescope. The link above will take you to where you can get the initial information or you can view the mirror here.
On a personal note, it was clear and ready for observing last night, but I have become dreadfully ill. I haven't felt myself since Thanksgiving time, mid November and I am going in tomorrow for tests to determine what is going on. I fear it may impact my observing for awhile as I am greatly fatigued, become winded very easily from tasks I have done that just don't wind me (to the point I am gasping for breath), feel a tightness in my chest/lungs. Hopefully I can get over this and start taking advantage of some time off and get back to observing. Then again though, overall the clouds and weather have really hampered this area this year. I have recorded only 5 observable days in November and December and of those I have observed 2 of them.