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Medium 9780596100605

Counterweight a Dobsonian Scope

Robert Bruce Thompson O'Reilly Media PDF


Counterweight a Dobsonian Scope


Counterweight a Dobsonian Scope


Balance your Dob perfectly without using springs, clutches, or other kludges.

Hack #41

Traditional equatorial and alt-azimuth mounts lock the scope into position and drive it using gears. For small changes in direction, you move the scope by driving the gears with motors or manual slow motion controls. For large changes in direction, some mounts allow you to disengage the gears, pivot the scope, and then re-engage the gears. But while you are observing, the scope is always clamped into position.

Conversely, a Dobsonian mount uses simple friction bearings that allow the optical tube assembly (OTA) to move freely. When you want to point the

OTA in a Dobsonian mount to a different part of the sky, you simply push the OTA up or down, right or left. The bearing friction must be small enough to allow smooth motions, but at the same time the friction of the altitude bearings—the bearings that support vertical movement—must be large enough to keep the OTA from shifting position under its own weight.

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Medium 9781491908945

19. Nonstandard Apps

Jonathon Manning O'Reilly Media ePub

For the majority of this book, we’ve talked about GUI applications designed to run on either OS X or iOS. These applications receive user input via the mouse, keyboard, or touchscreen, display information via the screen, and are launched by double-clicking them on OS X or tapping them on iOS.

However, not every piece of software that you write is a traditional app. In some cases, you might want to create something that the user doesn’t need to interact with—for example, a background application that automatically downloads files from the Internet. Another case where you don’t want to build a traditional app is when you want to create a preference pane, which the user can access via the System Preferences application.

In this chapter, you’ll learn how to build apps for OS X that don’t fit the mold of standard applications. Specifically, you’ll learn how to build command-line tools (which don’t use a GUI), system preference panes, and applications that add an item to the system-wide menu bar. Finally, you’ll learn how to make apps on iOS that can use more than one screen.

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Medium 9781550225778

122. When adding pineapple to Jell-O, why can we use the canned variety but not the fresh?

Dr. Joe Schwarcz ECW Press ePub

The substance is nickel, and legislators enacted the law because nickel is an allergen. The word nickel comes from the German for devil, because the metal interfered with the smelting of copper; German miners in the 1700s called it Kupfernickel, or copper devil.

Nickel really may be the devil to some people because of its allergenicity. Researchers in Finland have recently reported that body piercing is likely responsible for a dramatic increase in nickel allergies. Nickel-allergy sufferers can remain sensitive to the metal for life, and they also have a greater risk of developing other allergies. Many sensitized people have trouble finding wristwatches, belt buckles, or eyeglass frames that they can wear. The researchers discovered that even jewelry that tested negative for nickel by a standard color test involving ammonia and dimethylglyoxime released nickel when exposed to artificial sweat. Jewelry intended for pierced tongues, cheeks, and genitals fared the worst: eleven out of the twelve pieces sampled exceeded safety standards.

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Medium 9781591200666

4. Choosing an Exercise Plan

Lovitt M.A., Michelle Basic Health Publications ePub

Choosing an Exercise Plan

Now it is time to choose your fitness plan. This chapter helps you determine which plan is right for you. This choice will be based either on your predominant muscle fiber type, determined using the techniques explained in Chapter 3, or on your own personal fitness goals, regardless of your muscle fiber type. Either way, we help you focus on what you want to achieve and then pick the best workout to give you the greatest chance for success.


There are five exercise plans to choose from—the Fast-Twitch Plan, Slow-Twitch Plan, Combination Plan, Hard Body Plan, and the No-Twitch Plan. Deciding which one is right for you begins by looking at your results from the muscle fiber typing tests and your individual goals.

If you are not directed by a particular predetermined goal, the first step is to look at your results from the muscle fiber testing. The graphs and calculations you did during your test(s) should clearly tell you where you fall: fast-twitch, slow-twitch, or combination. The only tough decision might be if you are on a borderline area on the Sayers Power Curve or the Standing Broad Jump curves. If you happen to be on the line between combination and slow-twitch or combination and fast-twitch, we recommend that you move up one level. For example, if you are on the line between combination and fast-twitch, you should go with the Fast-Twitch Plan. If you are on the line between slow-twitch and combination, choose the Combination Plan. Otherwise, go to the plan that corresponds with the muscle fiber type indicated by your test results to exercise your body in the most personalized and efficient way.

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Medium 9781855759848

CHAPTER NINE: Religion and consciousness

Neville Symington Karnac Books ePub

I believe that “revealed religion” is antithethical to consciousness, whereas “natural religion” is conducive to it. This chapter is an attempt to substantiate this statement. In order to do this, I need, first, to define the difference between revealed religion and natural religion, then to elaborate my theory of how something comes to consciousness, and, finally, to show how revealed religion prevents it, whereas natural religion favours it. As each of these elements in the argument is in itself a huge topic and each is open to debate, this chapter is necessarily a sketch or an outline that requires considerable elaboration.

When people say that they are religious or not religious, they conceptualize religion according to one particular form of it—the form that has been transmitted into Western civilization through the agency of the Judaeo–Christian community of the faithful. I include Islam in the Judaeo–Christian tradition. The idea that this one particular form constitutes the whole of religion is such a deeply rooted assumption that, I have found it usually takes more than just intellectual argument to open people to the notion of any religion other than this one. I shall try first to outline what is meant by revealed religion.

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