Things are coming together. I’ve recently painted everything that needed painting. If I had to do it over, I think I would have gone with stain but it’s too late to fret over that and I can’t rebuild something until I build it first. The red is a little darker than some of these pictures. More like the last picture than the second.
The first picture shows the mirror cell resting on the threaded rods that will be used for collimation. In the center of the cell is a fan and at the edge is a push button toggle to turn it on/off. The fan will be used to help the mirror reach equilibrium. I decided early on to go with a simple cell with 18 felt pads in the best locations for support.
Next, we see the 16″ (or 0.4 meter) mirror safely in the box resting on the cell. You can see the three collimation knobs that will allow me to collimate from the top rather than the bottom. Hidden behind the knob on the right is the push button from the other picture that will let me turn the fan on or off.
Finally, for this post, is the upper tube assembly with the secondary mirror and spider. Next I need to attach the board for the focuser and focuser itself. After that I can place the mirror box above and the UTA below on jig to determine the optimal separation and from that the length of the truss rods.
I’m hoping for first light in about a month.
That sounds better than Penumbral Eclipse of the Moon which is more accurate. I was on my way out the door when I saw and remembered the eclipse so I ran back in for the camera. I was surprised about how easy it was to see this non-umbral eclipse. That said, look to the upper left near the Mare Frigorus area. That looks darker there. I don’t know how close the umbra came tonight but its easy to imagine it’s right there off the edge of the Moon.
Here’s a picture of the left to right from this evening. The Moon and Venus are, respectively, always the second and third brightest objects in the sky not counting occasional supernova. Mars on the other hand gets really bright for a couple months every two years and then fades to relative obscurity. So it is here. The Moon is about 500 times brighter than Venus and Venus is perhaps 100 times brighter than Mars right now. For this picture, I used a regular DSLR with a 300mm lens set to 6400 ISO and a 1/80th second exposure. That was the shortest exposure that showed Mars and while longer exposures showed the ruddy color of Mars they also blew out the Moon and Venus. So, I had to compromise.
The custom made secondary holder and spider should be here by month end.
I have 7 1.25” aluminum poles, one as a spare. May get one more if I have the opportunity to avoid cost of shipping.
Here is a prototype truss connector I made yesterday plus another picture showing it attached to a simulated upper ring with a cam latch. I’m hoping that will work, one of the scopes I’ve studied uses them and they will be very convenient. Finally a shot of all six. You can tell they are handmade and each is unique. Later I may revisit this but for now I’ve had enough of working with aluminum. Fortunately I have enough aluminum channel (barely) to redo them.
Here we have a simple plywood disk mirror cell in the mirror box. there are 18 felt pads at the calculated points for support of the mirror.
Here I’ve cut out two 30″ diameter altitude bearings and matching rocker box sides from a single 2’x4’by3/4″ sheet of plywood.
Here we see the altitude bearings attached to the mirror box, resting on the rocker box with the mirror resting on its cell.
It’s the seed from which a 16″ lowrider dobsonian telescope will grow. I’ve been daydreaming about building a larger telescope for a while when I came across this on the Cloudy Nights classifieds for a nice price. 16″ has been in the back of my head for years as a good size. On the cusp of being a large scope but not really having to deal with big scope problems like weight, cool down, or $$$. 16″ would typically just be $$ not $$$. More to come as I build stuff to go around it.
I took this shot of Polaris and the Little Dipper last night at the River Ridge Observatory. Nothing fancy, just a 30 second image a 6400 ISO with my widest angle lens. Polaris is the bright star just above the center and a little to the left. The Little Dipper extends almost horizontally and drooping a little as it does to the left. The thin clouds add a nice touch I think though normally I don’t like them.
I used my Canon Rebel tonight to do some simple astrophotography. It was connected to my Nexstar mount for tracking and running BackyardEOS on the laptop to control it. After spending quite some time manually focusing and trying different ISOs and exposures I settled on ISO 1600 and 30 seconds. It was supposed to be clear but there were thin clouds all over. The bright “star” on the left is Mars and if you look closely in the lower left quadrant you’ll see the teapot of Sagitarrius. I was also hoping to capture the nova currently in Sagitarrius just above the spout and if I zoom in I can see a star right where the nova is but it’s none too impressive.