Saturday, November 28, 2009

Inserts and brackets installed


After painting the handles with glossy black enamel paint, it was time to put the inserts into the rocker sides for the stainless steel eye-bolts. To make insertion of the eye-bolts easier, I bored out the holes with a 7/16th-inch drill bit, then used a magnet to remove the metal shavings that remained in the tubing. I drilled four 1/2-inch holes through the rocker sides using a template to accurately place the holes. Then I used a 3/8-inch by 16 thread per inch bolt and nut to drive the inserts into the holes after coating them with epoxy. This was done to prevent them from coming back out. The brackets were made by welding a 2 and a 1-inch wide by 1/8-inch thick flat bar together. That was accomplished with first an outside corner, than a fillet weld on the inside corner, then rounding off the outside so it will fit in place. A miter saw with a cut off wheel was then used to cut off two sections which were then drilled for the mounting bolts, primed and then painted with glossy black enamel paint. I had a left over hole in the altitude bearings so I used them and them drilled a two pairs of 3/8th-inch holes in the mirror box. I then inserted more threaded inserts, again coating them with epoxy. Stainless steel fasteners hold the brackets in place. The altitude bearings are now braced and no longer are springy while the telescope is aimed near the horizon. Because of paint sticking to the bottom of the mirror box sides that contact the rocker, I sanded the affected areas then applied a thin coat of polyurethane. I've also purchased four 3/8-inch stainless steel eye-bolts and used them to test fit the handles to see if they fit the rocker box correctly, which they do. When the wheels are in place, lifting the handles a couple of inches then pushing or pulling will be all that's needed to move the telescope.

Friday, November 20, 2009

Nebulae recently observed


While my favorite objects to observe are galaxies, I also look for nebulae that are in reach of my telescopes wherever they're found. Recently I came across four lesser known examples of planetary and reflection nebulae that can be observed even from fairly hazy and light polluted regions. The first object is NGC-6813, a very small reflection nebula in the constellation Vulpecula. It was almost hidden among the hordes of field stars as a tiny, fuzzy object that would not focus. At 188X it's nebular nature was apparent and it was quite bright. Instead of a circular or oval outline, it had an fuzzy and irregular shape with a star shining within it.


The next object was much larger and easier to pick out from the background stars. NGC-6842 is a large and faint planetary nebula that was not visible until I screwed a O-III filter into the eyepiece. At 103X it was large, about an arc-minute across with no central hole, central star or brighter rim. NGC-6842 is the only other planetary nebula in Vulpecula aside from M-27. Quite featureless but a good test of one's observing skills and sky conditions.


The next objects is the small and quite bright planetary nebula IC-2003 in Perseus. Small and bright, I observed it from my driveway with a 5mm eyepiece and my 10-inch Dob. It was immediately apparent among the surrounding stars with direct vision thanks to the use of an O-III filter while the central star glimmered in the center. This is a surpisingly easy object to observe from the suburbs.


The final object is the tiny and rather elusive planetary nebula IC-351, also located in Perseus. This tiny and round planetary nebula appeared  featureless with no sign of a central star. It was very difficult to locate among the surrounding stars, and required  a magnification of 262X to identify. It was visible without a nebula filter but the use of an O-III made seeing it easier. A good challenge object but not nearly a nice object to observe as M-76 or even IC-2003.

Thursday, November 5, 2009

Base assembled


After finishing the ground board, I installed the Teflon pads for the altitude and azimuth axis, then installed the locknut and plate assembly. Then I inserted a 1/2-inch bolt and tightened it into the lock nut until a small gap remained between the plate and the head of the bolt. However, I found the rocker box was snagging the mirror box when pointed straight up, so I took my sander and sanded off the face plies along the top of the rocker sides. It wasn't elegant but I sanded it smooth and when the new coats of flat black paint dries the fix will not be noticeable since it will be hidden by the mirror box anyway.

Now that the base is nearly complete, the wheelbarrow handles are next on the to do list. Months ago I measured and cut steel tubing left over from the tailgate, then welded it into handles shaped like a dog leg. This way I won't have to stoop as far when it's time to roll the telescope. I marked and drilled holes to hold the stainless steel eyebolts that will thread into threaded inserts that I will put in the rocker sides. I'll bore them out to 7/16th of an inch to make threading them into the inserts in the rocker box sides easier. The steel handles will be painted with glossy black enamel paint. The eye bolts will be retained in the handles with stainless steel all-metal lock nuts. A larger hole at the end will hold a 1/2-inch bolt that will attach the wheel to each handle. For those I'm going to use a 10-inch pneumatic or air-filled wheel with a 1/2 ball bearing hub, the sort that is used for hand dollies. Eventually I'm going to put some foam rubber on the handles so the steel tube won't be so cold on the hands after a winter night of observing and some bumpers to protect the finish on the sides of the rocker box.