Thursday, October 29, 2009

Fall NGC galaxies

Two weeks ago, a rare break in the cloudy, windy, and rainy weather came just as it started to get dark. At the usual darker sky site the local club uses at a very long private airstrip, I was ready to take advantage of it with my 10-inch Dob, which is equipped with digital setting circles. The two drawings of the galaxies above are just a few of the objects I looked at that night, which included the Lagoon Nebula, the Veil Nebula and the bright globular clusters M-15 and M-2. After giving a couple of visitors a look at some bright showpiece objects, I returned to my main focus, hunting down less well known NGC and IC objects.

NGC-6962, NGC-6964 and NGC-6967 are a trio of galaxies in far western Aquarius. As such they're seen from behind the fringes of the Milky Way, and it's vast clouds of interstellar gas and dust that dim the light of objects that pass through them. Even so, the brightest galaxy NGC-6962 appeared right away in the field at 150X.

When I boosted the magnification to 188X, two other very small, dim and oval  objects became noticeable with averted vision. After scanning the area for a few minutes, it became clear the other faint fuzzy ovals were real and they turned out to be the galaxies NGC-6964 and NGC-6967. These galaxies are very small and faint, NGC-6967 especially with a listed magnitude of 14, which is seemingly too faint given the light pollution that affects the site. The trio seem to be the brightest members of a small galaxy group that nearly sit on the border between Aquarius and Aquila. Two more galaxies of about the same magnitude as NGC-6967 are also nearby, but I didn't look for them. I plan to the next time I return to this field.

NGC-6928 and NGC-6930 are the two brightest galaxies of a small group in Delphinus some 200 million light years away. They are also subject to a good deal of interstellar absorption from the gas and dust between the stars in our galaxy. However, NGC-6928 was easy to spot at medium power. Showing a somewhat odd spindle shape with a bright core, it and the much smaller and fainter NGC-6930 are orientated at nearly right angles to each other. The galaxies NGC-6927, NGC-6927A and several other UGC galaxies are also present in the field, but I saw no sign of them. NGC-6930 was also spindle like, and at first hard to spot among the numerous field stars. Both made a nice galaxy duo at 188X.

Other objects I observed and sketched included the whimsical asterism French 1, which looks like a toadstool from Alice in Wonderland, and at the base was a small but quite apparent elliptical galaxy. The galaxy NGC-7015 in Equuleus, the only deep sky object at all easy to find in amateur telescopes was also an easy mark, along with the planetary nebula NGC-6842 in Vulpecula. A short hop and a few minutes searching brought me to the reflection nebula NGC-6813. Finally, just before I packed it in for the night, I tool a little tour of some of the objects in Perseus. The open clusters NGC-1220 and 1245 made a marvelous view, as did the galaxies NGC-1023, 1275 and 1161. Curiously, the nearby galaxy NGC 1160 eluded me, therefore I plan to return too and redraw the field. The open clusters NGC-6834 in Cygnus and NGC-6939 were also nice sights as well.

Since my web page is no longer available online, I will publish some of my drawings here for the time being.

Wednesday, October 28, 2009

Ground board made.

After assembling the rocker box, I made the ground board from two layers of 3/4-inch plywood cut to the same diameter as the rocker bottom. To make the cut, I used my router, a circle cutting jig and a 1/4-inch spiral bit to cut out the ground board. I then used my drill guide and 1/2-inch Forstner bit to drill a hole all the way through. After that, I used a 1/2-inch rounder over bit on my router to round off the edge. Next I made three feet from a scrap of Ash I found in my shed, and cut them out with a hole saw on my drill press. I then glued them to the bottom 120 degrees apart near the edge. When the glue was dry, I began to use wood filler on it and the rocker to fill up voids in the plywood's edges and repair dings in the surface, then sanded the rocker box with a random orbit sander and 220 grit sanding disks.

I also drilled a 1/2-inch hole in the center of the rocker box bottom, then applied contact cement to it and the Formica that will slide over the Teflon pads. After the cement became tacky, I pressed the laminate into place with a roller then removed the excess using a rotary tool and a laminate trimming bit. Then I primed the inside of the rocker box with Kilz primer and followed that with two coats of flat black paint. On the outside, I did a final sanding and followed that with the first coat of exterior grade glossy polyurethane.

To secure the ground board and rocker box together, I will use a 1/2-inch stainless steel hex bolt and two three by three-inch steel plates I made from flat stock. In the center of each, I drilled a 1/2-inch hole. At each corner I drilled a hole for a #8 screw. To one I welded an all-metal lock nut. When the bolt is screwed into the nut, it will not rotate and confuse the digital setting circles that will be added later. The other metal plate was screwed to the bottom of the rocker box and will act as a fender washer and bearing for the bolt to prevent wandering. After cutting, drilling and welding, they were primed and painted flat black.

Wednesday, October 21, 2009

Rocker box

After completing the mirror box with the exception of adding the pole blocks to it, I turned my attention to making the rocker box. The first attempt to make it failed because the plywood I used warped in the bottom and side, forcing me to start over. That forced me to cut off an inch from the one side that was still usable, which I used as a pattern to make a new side with my router and 3/4-inch top bearing trim bit. I also cut off the front corner of the mirror box to ensure it would not hit the bottom of the rocker box. However, I had taken into account the fact the collimation bolts could strike and crush the azimuth encoder for any digital setting circles I will install. I bonded the sides to a single sheet of 3/4-inch plywood with a 12-inch diameter hole routed in the center. Then the front and back pieces, made of 1/2-inch plywood were added. To the bottom of the rocker box I then glued a 20-inch diameter circular piece of 3/4-inch plywood. Now I have a stable rocker box and plenty or clearance for protecting the encoder and primary mirror as well from damage. The next steps will be boring a 1/2-inch hole for the azimuth pivot bolt, rounding off all outside edges, adding laminate to the rocker bottom then painting the inside of the rocker flat black. The final steps will be varnishing the outside and inserting threaded inserts into which the wheel barrow handles will thread.

Wednesday, October 7, 2009

Altitude bearings mounted

After installing the threaded inserts and giving the altitude bearings two more coats of polyurethane, it was time to mount the altitude bearings on the mirror box. I used four 1/4-inch by 2-inch stainless steel machine screws for each bearing. On each bearing two of the screws thread into the threaded inserts, while the other two pass through a hole in the mirror box. On the other side is a stainless steel flat washer, lock washer then a hex nut. Both bearings are now in place, clearing the way for the next step, painting the interior of the mirror box flat black. I applied one coat of Kilz oil based primer and allowed it to dry. Then it will be covered with two coats of flat black paint, the second of which will be flocked with saw dust. The bolts for the pole blocks clamping knobs will also be installed before painting. After the box's interior is painted and completely dry, I will then bolt the steel tailgate in place inside the box.

Friday, October 2, 2009

Pole seats and altitude bearings completed

After purchasing some threaded inserts, I installed them in the pole blocks along with a handle with a threaded 1/4X20 stud attached. The inserts tend to pucker the wood around the hole, so I beveled the edge around them to prevent that without complete success. In between the wedge and the rest of the block I inserted a spring. The pole seats are not completed and attached to the upper cage.

After searching for suitable Formica, I obtained a large piece from a local cabinet supply shop. I cut two 1 1/2-inch wide strips and coated the back side and the outer edge of the altitude bearings twice with contact cement, then pressed the Formica into position. A router with a trim bit and a cloth soaked in acetone removed excess contact cement and Formica.

To attach the bearings to the mirror box, I had originally planned to use threaded inserts entirely, but given the trouble I had inserting them into the pole seats, I will only use them where I cannot simply use a nut and washer. I counter sinked each hole throughly, then used a block of wood with a piece of all-thread through it to insert the threaded inserts. That allowed me to ensure they are going in straight, and a dab of marine epoxy glue will ensure they will not loosen.