Posts Made By: Alex McConahay

"- There have been no further successful terrorist attacks on US soil since 9/11"

If this is an example of how well you have checked your facts, I would suggest you do a google on Anthrax.

And this is an important point. At the height of our concern about terrorism, with as much protection as we could muster, we had two anthrax attacks. Neither of them solved. But instead of saying "We only have had two," you claim "we have had none. Now there are several ways to make your statement correct. Basically, they involve qualifiying it--"Outside terrorism." or maybe "SUCCESSFUL" attacks. If you contend that these qualifications of your original statement leave your statement true, then you are engaged in a sad manipulation--you have fooled yourself. If you don't, then you have to see that your statement is false--as are some of your other generalizations.

The point is, we are not safer. Spreading the war to Iraq, and then doing it poorly, has hurt us. It has done what many people said it would do--made a fertile ground for recruitment of terrorists.

And let us look at this another way. What if there is an attack tomorrow. Does that mean we have more or less reason to re-elect the man who brags (as in "mission accomplished") he has made us safe. I dare say you wil come down on the side of re-electing him. This would have you using the argument "He kept us from having a terrorist attack" the day before the attack, and "This terrorist attack shows us how much we need him, now" the day after the attack.

Alex

Just to add to Walter's excellent response--

You mentioned photography. This finder extension is useful for lots of things, but for its price does not really help enough on critical focusing. When you double (and a half) the magnification you cut down on the amount of light available--and that is as much as anything the problem with critical focusing.

In short, if you need something to make it more convenient to see the viewfinder, it works fine, and it does help a little in focusing. But it is not the answer to focusing difficulties.

Alex

Kevin,

If you are really looking to get into astrophotography, you will need a much larger investment, particularly in a mount.

Sorry, I'm not familiar with the scopes you mentioned, but the mounts look to me like they would not last long in astrophotography.

Alex

I had a similar problem with my mount not long ago. Just before packing it up for Meade, I set it up to see exactly what was wrong. In doing so, I noticed one of the buttons on the hand control had somehow gotten pushed, and was stuck under the faceplate, and thus remaining in a permanently "stuck" or pushed position. Just for the heck of it, take a look. Are all your buttons free? It was a cheap and quick fix.

Alex

I can't answer your first question about whether the LPI uses a regular cable.

However, I have had the same thing happen to me. I had to "reinstall" my LPI half a dozen times. It just keeps getting lost. I do not know whether it is an issue of needing to go into the same USB port, or it gets lost when I install a different USB device after I installed it, or what--but every second or third use of the thing, I have to "reinstall."

Alex

The most common camera adapters in fact do fit into 1.25 focusers. They are quite usable. They do suffer some vignetting, but it can easily be cropped out. (And some can be compensated in the computer darkroom.) Just remember that you will be losing some of the image around the edges. But as long as you know that, and compose for it, it is not that big a deal.

I prefer adapters that use and take advantage of 2 inch focusers. Note, however, that they, too, do not offer a 2 inch throughput, since the camera bayonet does not allow for 2 inches--and in fact the camera frame is hardly two inches across. (all this assumes 35 mm.)

Alex

If you could actually perfectly align your telescope, a second axis may not be necessary. Try it if you already have an equatorial mount. If you like your results, then save yourself the trouble.

Fact is, though, that it is nearly impossible to get everything lined up (polar alignment) just perfectly. ANd the second axis can compensate for some of the error. It may also help if things shift ever so slightly during exposure (depending on your guiding setup).

And it also depends on what you camera and exposure times are. If you are webcamming, or putting together lots of digital shots, you don't have to worry about guiding so much. If you are into emulsion, it will be more critical.

Alex

I can't quite understand your question. Just as an overview, what you have to do with an off axis guider is to attach the camera to the main tube, and a reticle eyepiece to the off axis side. Then bring the camera to focus as well as you can. Then locate the guide star of your choice, and move the guiding eyepiece in and out of its holder until the star becomes sharp.

Having said that--
Just what do you mean that the off axis guider does not focus well? I am interpreting this to mean that you got your camera in focus, but that you cannot get sharp stars in the reticle eyepiece. There are two cases of this:

--that you cannot get it to the focus point (i.e., you are moving to focus and the star is getting smaller and it never quite gets there before you run out of focuser travel--in this case your eyepiece bottoms out or extends beyond the eyepiece holder),

--or that it does not look sharp when you do get it to focus (the stars get smaller and smaller, and then start to get larger, but never get really sharp).

If it is the first, you need more travel in your eyepiece holder. You need to shorten the drawtube or lengthen the eyepiece, depending on whether you are running out on the way in or out of the drawtube. You can add an extender to the eyepiece. To shorten the tube, you may need to cut off a piece. One alternative is to find an eyepiece whose field stop is closer to the end of its tube. Also, you may have a parfocal ring that has been installed that needs to be removed to give you extra travel.

If it is the latter problem--you move into focus and then out, but never get sharp stars--you are probably talking about one of the difficulties of off axis guiding--You are working with a star on the edge of a field, and by nature the optics are not as sharp out there. Or you may have an eyepiece that is somehow out of whack. One nice thing is, of course, that the star you are using to guide does not have to be in good focus--It helps, but it is not an absolute.

Now, as far as getting the camera in focus in the first place--that is a whole 'nother skill that needs a thread of its own.

Alex

David,

What Jarad says is pretty much the answer. However, I would say that you would not only have to have side by side instruments, and perfectly matched everything else, and a lot of experience, and maybe some fancy instruments to tell the difference. In other words, there is not that much difference in the coatings in practice. Where it starts to count, though is when you have multiple surfaces. The difference between 98% x 98% and 88% x 88% is the difference between 96% total transmission and 77%. Curiously, unless you really know how to look, even this is not too noticeable. One compromise is to have the primary with a standard coating and the secondary with an enhanced.

Alex

the thought is very true.

But shouldn't it be over in the "Politics" forum!

Alex