Astronomy Archives - Page 67 of 71

May 28, 2015December 16, 2020

Jupiter 5/28/2015

Wednesday evening, during a rare clear night in May, I was able to capture this sequence of events happening on Jupiter. At the very start you can see Jupiter’s moon Ganymede over to the left and its shadow on the face of the planet. Almost immediately you will see the shadow of another moon, Io, appear on the right and start chasing the shadow of Ganymede. Each frame represents 2 minutes of real time and the entire sequence is an hour and 40 minutes long. As you watch, you will also notice the Great Red Spot moving along with the shadows and if you look closely you might notice Io itself transiting the disk of Jupiter but it is not nearly as obvious as the shadow. You might also notice the difference in the size of the shadows. Ganymede is the most massive moon in the solar system while Io is quite a bit smaller. Eventually Io leaves the disk and becomes visible against the black background. Finally at the end the two shadows merge as Ganymede eclipses Io. Jupiter was dropping into the trees as this happened so I was not able to capture the end of the eclipse when the two shadows separated. I want to thank my friend Carl Freyaldenhoven for bringing this event to my attention. The images were taken from my backyard in West Little Rock.

May 25, 2015

Telescope Makeover

In the latest episode of Extreme Makeover: Telescope Edition, Jim makes more rings, a box, and something to put in the box. First, I made two plywood rings that will be the basis of the secondary cage which holds the secondary mirror, the focuser, a finder, and maybe a soda. Next I worked on the mirror box and primary mirror cell which I started on yesterday. You can see the cell sitting in the open box, the back side of the cell with its collimation screws salvaged from the original tube, and finally the cell back in the box with the upper surface of the box.
Next up, not necessarily in this order will be to finish the cell and mae it with the primary mirror, construct the secondary cage, build the truss arms, assemble, determine the balance point so that I will know where the previously covered altitude bearing will be attached then build the rocker box, sand, paint, get the soda from its place in the secondary cage and enjoy.

May 23, 2015May 23, 2015

10″ Dobsonian Makeover Project

About 18 months ago, someone contacted CAAS about a 10″ Coulter Odyssey OTA that her brother had owned and asked about how to sell it. That sparked an interest and I wound up buying it. I made a quick and dirty mount for it, remember it was an OTA only, but once I got it assembled I realized that that for whatever reason the focuser was too close (or maybe it was too far) to come to focus. Disappointed, I set it aside until another day. Since that time I’ve been thinking about performing a makeover on it to turn it into a more compact (for storage at least) and usable scope.

I’ve done research and come up with ideas. Last weekend I did my first router work and cut an 18″ circle out of MDF. This was actually meant to be a test of the process but when I was done it was pretty good so I may well use it. Regardless this or another circle will be cut in half and probably hollowed out a bit to make the altitude bearings. Hollowed out to save weight.

This afternoon I disassembled the old OTA bagging up the parts I want to bring forward to the new scope. These are the focuser, the secondary, the telrad finder, and the primary (of course). The primary was well attached to the original MDF mirror cell with silicone that though pliable was not separating easily. I finally decided I was going to damage the mirror if I didn’t try another way so mirror and MDF cell are soaking in warm soapy water right now. I hope to be able to remove the ruined cell easily when done and have a clean mirror to boot. Making a new cell should be straight forward.

The original secondary and holder are rather plain, a straight rod that runs across the tube with a mirror attached. Of course, Coulter was in bang for the buck business and you can’t expect Obsession at Odyssey prices. It works and I might try to use it at least to begin with but that may have to be replaced.

The focuser is an aftermarket ScopeStuff Crayford model and might be the most valuable part after the mirror itself so its a keeper.

A couple years ago, someone gave me the carousel part of a Dobsonian. Probably a 12″. I’m not obligated the use it but that would be a part I didn’t have to make if I do. The size would make for stability but it might also look a 6 year old walking around in his dad’s shoes. Of course in my case dad and I had the same size feet when I was six.

More later.

Below is the 18″ MDF round that I cut.