Thursday, April 14, 2011

Moving telescopes more easily

As every amateur astronomer knows, telescopes get bigger and heavier really quickly as the aperture increases. That was why I built the 15-inch as a truss-tube, there would be no way I could even get it into and out of the house if I built it with a solid tube. Indeed, it would possibly weigh at least as much as I do and it would require a truck or van to take to a dark site. That is why a 10-inch F/4.5 or F/5 is the biggest telescope where a solid tube is practical, at least for one that has to be put into the family car. While I can carry my 10-inch, it's quite heavy and I have to carry it over steps too. Then I have to connect and disconnect all the dew heaters and other electrical equipment when I set it up and take it back into the house.


Therefore I took at look at the handles I made for the 15-inch, and realized they will also work on the 10-inch too.  I bought four threaded inserts and placed them in the sides of the rocker box in such a manner the wheels just clear the ground. Before driving them home with a bolt, nut and wrench, I coated them with epoxy glue to keep them from coming back out. Now I can roll the 10-inch outside in one trip, with everything connected and ready to go. Having one set of wheelbarrow handles that can be used for more than one telescope not only saves time and money, but space as well because they are bulky and heavy items in and of themselves. It seems to me that wheelbarrow handles as standard equipment  would be a good idea to include with any Dobsonian of 10-inches or more in aperture. This way it's much easier to set up and use the "hot water heater" Dobs even for those who have back or other problems that make moving heavy objects impossible or diifficult.

Tuesday, April 5, 2011

First time at a darker site

Last Saturday night was the first opportunity to take the telescope to a site that's darker than the severely light polluted skies that prevail at home. With little space to spare, the telescope fit into my car, even the wheel barrow handles fit into the trunk. The only awkward aspect of transporting the telescope is lifting the mirror box out of the rocker box and putting it in the back seat. Once the telescope was set up, I collimated it and ran the cooling fan for about 45 minutes to cool the primary mirror down.
Once it grew dark and I aligned the finderscope, the hunt was on. The first object I looked at was M-42, also known as the Orion Nebula. Through an O-III filter, the whole field was overun with streaks and clouds of nebulosity, and the dark nebulae intermingled with them appeared as deep pools of black ink. The six visible stars of the Trapezium blazed in the center as I traces loops of nebulosity farther than I ever did through the 10-inch from the same site. The view was so detailed, that in order to do M-42 justice I would have needed to spend the greater portion of the night sketching it, and that was not possible because Orion was already getting low in the western sky.
The next objects I looked at were NGC-2359, NGC-2362 and NGC-2467. NGC-2359 is a bubble of hot gas thrown out from a Wolf-Rayet star in Canis Major. From a dark site it looks a lot like a helmet, and in fact it's known as Thor's Helmet. The horns were not obvious though because of hazy conditions at the site, and the light pollution from several cities wasn't helping either. Nearby NGC-2362 fared far better, it's an open cluster that is magnificent even though a small telescope. The emission nebula NGC-2467 in Puppis did however show considerable detail, I could see a brighter arc along one side and patchy variations in brightness all across the nebula. It actually appeared as a turbulent, chaotic cloud of hot gas, which is what an emission nebula is.

The next object I looked at was NGC-2261, also know as Hubbles's Variable Nebula. It is a small comet shaped reflection nebula surrounding a newly formed star. It's high surface brightness makes it able to take high magnificatuons very well, and an odd bluish tint appeared at 250X. The star like object at the apex was not a sharp pinpont, it was fuzzy. That is the inner nucleus of the nebula, whose appearance changes because of dust clouds in orbit close to the star. As they move, they cast shadows that sweep across the nebula, causing it to vary in shape and appearance from week to week and even night to night.
The next object I turned the telescope to was M-97, the Owl Nebula. This is a large but dim planetary nebula in Ursa Major that has a dim central star and two darker reagions that give it the appearance of an owl's face at 153X. The "eyes" were in fact dimly visible through an O-III filter despite the not so good skies above me.

After unsucessfully looking for NGC-2403 in Cameleopardalis, I paid the galaxies M-81 and M82 a visit. M-81 was incredibly bright, the nuclear bulge was a blazing mass of light and the disk of the galaxy seemed streaked as well. The real show was M-82, which not only sported the dark bands, I could actually see a couple of the H-II regions with no trouble at all. At 250X, it spanned one third of the field of view!
I then moved over to Canes Venatici to look at a pair of interacting galaxies called NGC-4485 and 4490. A supernova appeared in NGC-4485 a few years ago and both are disturbed by their mutual gravitational tug of war. The larger galaxy appeared as a bright oval object with a brigher core, the smaller galaxy was oddly shaped with a small brighter region in the center.

Next I just had to see how my favorite edge on galaxy would look like through my new telescope, and it did not disappoint either. I've never seen NGC-4565 so bright, and there was signs of it's signature dust lane that spans most of it's length. A short hop then brought me to another galaxy that sports a shiner as though it was in a barroom brawl, M-64 also known as the Black Eye Galaxy. Indeed, the large dusty region was shockingly apparent, unlike the view through my 6-inch under the same skies. A small but intense inner nuclear region in the center is also visible at 153X .

Next I moved over to the bright globular clusters M-53 and M-3, both of which were fully resolved into stars. In fact, they looked like piles of shattered glass, with the cores being very bright at 153X. The only difference between them was their apparent size, M-53 is smaller and much farther away from us than M-3. I then turned the telescope on M-13 and M-92, which again looked just like the others, piles of shattered glass wiuth intensely bright cores. All of them showed far too many stars to count.
I then took at look at one of my most favorite spots oin the sky, Marakrian's Chain. This is a chain of galaxies that starts with M-84 and M-86 and extends more than two degrees into Coma Berenices. Every member was of course easily visible and I could see the odd shape of  the interacting galaxies NGC-4435 and NGC-4438, also known as "The Eyes." Like M-42, I will have to return to this field at a later time, I could spend an entire night observing just this one area, there's that many galaxies to see there. Then I went on to look at one of the best galaxies anywhere in the sky for small telescope, M-104. This nearly edge-on spiral galaxy is also known as the Sombrero Galaxy. At a distance of some 40 million light years, it shines at about 8th mangitude and shows a very prominent nuclear region and central bulge. Along one side the dust lane was visible as a dark zone that spanned the width of the central bulge. By 1:30 in the morning, fog was rolling in but before I started to take down the telescope and load it into the car, I stopped to look at Saturn. Six of it's moons were visible and the Cassini and Encke gaps were apparent in the rings. The colors on the planet were very apparent, making the view look as though it was a color pen and ink drawing at 250 and 400X.

I was very happy with how the views turned out, even though sky conditions were quite poor. The views vindictated the money, time and effort I spend building the telescope, now I can enoy the rewards for many years to come.

Saturday, April 2, 2011

Baffled the upper cage

I initially was planning to make a light baffle for the upper cage out of black Kydex. However, it soon became apparent there was a problem, I couldn't find any at local plastics companies. They did have sheet plastic that was an eight of an inch thick, but it would have made my telescope top heavy. Fortunately, I discovered a substitute that is lightweight, obtainable and stands up to moisture while still being stiff enough to act as a light baffle. At a local cabinet supply shop, I found shelf lining, which is nothing but thin Formica that is used to cover shelves. I was able to get a big piece that is enough to make several light baffles for about twenty five dollars. After cutting it to shape, some flat black spray paint on the inner surface made a nice, dull black light absorbing surface. On the other side, six tabs of Velcro mate with six tabs on the upper ring of the secondary mirror cage on the opposite side of the focuser. The result is the telescope acts like a deep, dark well, without annoying stray light to wash out and fade the views. 
The result it a light baffle that not only keeps glare from getting into the eyepiece directly, it doesn't negatively affect the balance of the telescsope and lies flat or can be rolled up for storage. Indeed, the telescope is perfectly balanced with the baffle in place. Tonight will the the night when I will test the effectiveness of the baffle and the telescope overall on dimmer objects than I have been able to see from home.