improved galileoscope assembly instructions

The folks over at the Detroit Science Center have put together better instructions for the galileoscope. They’re highly detailed, including how to get stuff out of the box.

Galileoscope_Instructions

JPL “what’s up” podcast

The “What’s Up” podcast for August is up, and there’s a lot this month. From the most famous Meteor shower to the return of Mars to the night-time skies (but not as big as the full moon)

http://www.jpl.nasa.gov/videos/whatsup/whatsup20090806/whatsup20090806-640-i.m4v

galileoscope review

I got my galileoscope just in time for a trip to Philadelphia to see Galileo’s ’scope (there’s some irony there…). It was cloudy and rainy the whole time there, so I didn’t really get the chance to try it out on the night sky until we got back. I am both impressed and unimpressed at the same time.

First, putting it together.  The instructions get off to a great start.  The pictures and drawings make it (mostly) clear how everything is supposed to go together. I’ll have another post on this latter.  Everything was going really well up until we got to the eyepieces. They say to follow the images.  But the images are small and don’t show the lens orientation. Now I know this is supposed to be an educational tool, but trial-and-error may not be the most educational. We of course quickly figured it out, but most people out there haven’t taught upper level optics labs. And there was so much discussion about the printed materials last summer that I was rather disappointed that there wasn’t a single telescope diagram in the whole thing.  Nothing even noted that the Galilean eyepiece would be right side up and the Keplerian would be inverted. Most of the documentation is online, but not easily search-able.

As for the telescope itself, it is sturdy (if put together right) and fits my camera tripod nicely. The sights align easily and accurately, which is something I can’t say for most of the telescopes in the $50 – $200 range. It has a 1/4 – 20 threaded nut, so it easily mounts to a camera tripod. It focuses by sliding the eyepiece  in and out, which is a little hard to do. On the other hand, they eyepieces won’t fall out when you’re looking near zenith, so that’s probably a good trade off. And once we figured out how the eyepieces worked, it was relatively easy to put them together and to assemble the barlow.

Of course the view through the ’scope is the most important part. Well, it’s not C8, but it’s no Tasco either.

The treees behind the apartments across the street through the galileoscope (with fingerprint on eyepiece...)

The first thing we looked at (being the midle of the day when it arrived) was, of course, a tree.  Specifically, a horizontal branch from a tree arcoss the road. The view was actaully a bit better than it looks in the image.  For one thing, it was in better focus for my eyes. The sky was heavily overcast, which is actually ideal for this sort of thing. The image is fairly clear and bright for such a small ’scope, and it looks like there is very little chromatic aberration. The edges are definatly a little warped and fuzzy, but the center of the image was amazing for such a small, inexpensive ’scope.

After we got back from our trip, we took a look at alberio. it was nearly at zentih, so I got a kink in my neck looking, but I coud clearly see two stars and one was blue and one was orange. It did actually look rather more orange than I am used to, so I am wondering more about the quality of the lenses.

We also took it to the Detroit Observatory, where we were able to see Jupiter rise.  It was too low to look with the Fitz, so I can’t tell how the two actually compare (’cause it’s certainly fair to compare a cheap 2″ plasitc telescope that could be called a toy to a 12″, 150 year old carefully crafted ’scope buit for research…), but we were able to resolve all 4 moons and maybe even some banding on the  planet (the problem with knowing what something is supposed to look like is that you sometimes see what should be there.)

All in all, it’s at least as good as Galileo’s telescope, and probably better.

Next step: try a little astrophotography!

Of course clouds are forecast for the next few days…

How Galileo made his telescopes

Galileo’s lone surviving in-tact telescope paid a visit to the Franklin institute this year.  The telescope is there until September 7, when it will return to Italy.Until then it is part of an exhibit on Galileo and the age of the Medici, and there is another special exhibit related to telescopes and optics right outside the exit.  Included in that exhibit was a display on how Galileo assembled his telescopes.

Objective end of the telescope assembly

The display case showing how the telescope was assembled has two cut-aways, one unfinished (the lower one) and one finished. There are 3 basic pieces to the telescope: the objective, the eyepiece and the tube.

The tube is a series of wood strips glued to a black felt liner and formed into a tube.  It doesn’t show up well on these images, but the outside of the unfinished tubes looked almost as if they had pinstripes. This was the felt showing between the tiny gaps in the strips of wood. Incidentally, they didn’t say what kind of wood Galileo used.  The model was pale and very fine grained, and I suspect was made of something good for modeling, like poplar.

When the tube was completed, it was covered with leather that was tooled and dyed.  The leather would help add stability and structure to the tube, and give it a smoother more attractive outer appearance.

Cut away showing construction of the eyepiece end of the telescope.

The eyepiece and objective have similar  construction. Again, a tube is constructed by gluing wood strips to black felt. You can actually see the “pinstripe” appearance of the eyepiece in this second image. The cell that holds the lenses is larger in diameter than the tube, and is mounted to a smaller diameter tube that will slip inside the main tube. This probably allows the lens to slide in and out, to obtain a good focus.

The eyepiece lens is sanwiched between two aperature stops, which then fits into the front of the lens holder.  The objective is a little different. It has it’s own cell, about an inch long and two different diameters (see the topmost image). The lens sits in the wider section between two aperature stops and held in place with a metal tension ring. The narrower end fits into the cell. You can see how this looks in the last picture.

The objective end of the assembled models. Note the serperate lens carrier for the objective in the finished model.