Posts Made By: Alex McConahay

Let me start by saying I have never used such a scope. So what I am about to say is theory.

>>>>>the do's and don'ts of buying eyepieces?

There is lots of advice going on down in the "eyepiece" Forum. But it may be a little too dogmatic for you till you have some experience with your scope and eyepieces. In general you want to buy the best eyepieces you can afford. They will be with you forever, even as you change tubes. I'd say if you have a 20-60 zoom coming with it, you are set for a while.

>>>>Can it use barlows?

Don't know, but if it can use any 1.25 eyepeices, it should be able to, at least optically.

>>>Are some types of eyepieces too powerful (e.g. Pentax XW 3.5)?
Yes, it is possible to overpower a scope. Generally, one can get approximately 50 power per inch of aperture in a quality refractor, so you could expect about 140 or so power in this scope before the image starts to get fuzzier than you like (assuming your tripod can hld it still). There may be a different number daytime users apply because they are dealling with different conditions, but that is the astronomical rule of thumb.

Your scope has a focal length of about 500 mm. If you divide 3.5 into 525, you get that the eyepiece/tube combination is delivering 150 power--just about at the rule of thumb limit. So, yes, this would be overpowering the scope, or close to it. (It depends on a lot of things.)


>>>>>Will some eyepieces not focus properly because of size?
That would have nothing to do with the size as in "focal length" of the eyepiece (i.e., 3.5 mm eyepiece, or 7 mm eyepiece). It would have to a lot to do with the "mechanical size" of the eyepiece. If the eyepiece barrel is particularly long, for instance, the focuser may not be able to get it close enough at infinity to allow it to reach focus. This is not an optical question, but a mechanical one. But before I make a categorical statement here, I would have to look at the focusing mechanism....Just how much travel does it have? The telescope focuses an image at an exct plane, despite where you put your focuser. The location of that plane is entirely dependent on the focal length of the optics (which essentially do not change). "Focusing" is merely moving the eyepiece back and forth until its field stop in where the telescope focuses that image. Whether an eyepiece can focus in a telescope is a mechanical question of whether the focusing tube can move it to the proper place.

>>>>>I just see lots of eyepieces from Meade, Celestron, Vixen, Televue, etc and I need to know if I can buy and use any reasonably.

You also said "It is suppose to take any 1.25 astronomical eyepiece." If that is true, than theoretically, you can. (Again, I have never seen your scope.)

>>>20X60 zoom, I am assuming I mostly need to buy eyepieces in the 4-7 mm range for higher magnification.

Your eyepiece would have an effective focal length of about 8.75 yo about 25 mm. So, yes, if you plan to buy more eyepieces, you would tend to the shorter lengths than 8.75.

>>>>But would a 10mm or 12mm astronomical eyepiece give me better field of vision or some other quality that I could not get out of the zoom at the same magnification?

Zooms are famous for having a narrowed field of vision than the equivalent dedicated eyepiece. I would have to look up what the "Apparent Field Of View" is for your zoom, but I would suspect that with a good set of plossl's wyou would get wider fields. This is not only aesthetically more pleasing, but makes it easier to find and follow things.

Most important advice I would give is to use your scope for a while, and especially to show up at a star party near you and try out some other people's eyepieces. See what you like.
(Oh, and wait for an answer from somebody who knows what he or she is talking about!)
Alex

It is just one of those things that happen. Let it go. (I think not getting back a "Thanks, but I've moved on to something else....." is rude on the part of the inquirer--but why point out rudeness.)

As for a zero rating--the system says that you leave ratings only on completed deals....And this one was not complete. (This is, in my opinion one of the problems with the rating system.)

Alex

I believe that is the first time this question has ever been asked. Therefore, it must be considered off topic in the Astromart FAQ Forum.



(Just kidding--you can ask, but I cannot imagine there being a satisfactory answer!).

Alex

Sure, it is as simple as your local hardware store or Radio Shack or electronics wharehouse.

You need a plug that has two six conductor RJ11 (I can never remember what RJ # is--it might be RJ45 or something) female input jacks and one RJ11 (45?) male output plug. They sell them as "telephone couplers" or "Splitters" and are common enough to come in a blister pack at your local store.

Just take your hand controller in to the store and tell them what you want. Plug your hand controller into one of the female jacks just to make sure it fits right. It will. The plastic plugs on these things come in just a few standard sizes (called RJxx).

The thing you have to be sure of is that you get the SIX conductor version. They sell these things in two, four, and six conductors.

Now, this should work fine. One little problem you might have is that they double the width that you need to plug in your device. And this causes a problem with the power cord in the very next plug on the digital drive faceplate. You cannot get the power plug in because the splitter is in the way. You can solve this in a couple of ways. One is to buy a splitter that is top/bottom instead of side by side. Another is to buy a six conductor extension cord (either with a built in splitter or a single jack for a separate splitter). A third solution is to plug the power cord from the G-11 into the out plug instead of the in plug. (I've never tried that solution, but I have heard it many times.)

And, be sure your autoguider can communicate directly with your G-11 before you plug it in. The ST-4 can. The ST-7 cannot. As a matter of fact, the ST-7 can fry things if you try.

What are you trying to plug in?

Alex

Tyler,

Don't know if you noticed this in the Beginner's section:

http://www.astromart.com/forums/viewpost.asp?forum_post_id=544824&poll_id=&news_id=&page=2

It is very much the same question.

Alex

A polar alignment requires you to move your polar axis (the one with the right ascension hours) so that it is parallel to the true pole of the earth. This does not mean north or south pole, but the actual pole that represents the axis on which the earth spins.

Your clock drive in your telescope will then move the scope to the west so that it can follow the stars.

Your clock drive can move one way if you are aligned to the north pole, and the other way if you are aligned to the south pole, so you can align to either pole, as long as you tell the motor which one you are lined up on.

If you are north of the equator, I believe you have to align on the north pole (you don't have to be able to see Polaris to do this, however) and tell your motor you are so aligned. (If you bought your telescope north of the equator, and it has never been south, it is almost assuredly already thinking it is north.)

So, you want to align to the north pole. You can use a compass (corrected for the magnetic anomaly for your location) to point the forks north, and the latitude adjustment to make sure the forks are at the proper latitude. What matters is the forks.....not the tube.

If this is not an accurate enough polar alignment for your uses, then you can do a drift alighment, or an iterative two star alignment. If you are north of the equator, you use directions for those north of the equator, and your forks will point roughtly to the north star (even if you cannot see it).

And this should answer your question about looking south. The only thing that matters is that in fact your mount's axis (which is the central axis of the forks) is aligned to the pole. The tube can point wherever you want it to, including to the south. In this way, a "north polar alignment" allows you to see all the way to your southern horizon.

Alex


Alex

Adam,

In short answer to the Telescope or Mount question--if going visual, get a good scope. If taking astrophotos, put yuur money into the mount. You will change tubes and cameras as they develop. Mounts stay with you and are much more critical.

I don't know much about the Denk equipment. I've seen them, and used them, but they did not interest me enough to evaluate them. (And that in itself is not a comment on them.)

On the mount issue, with all due respect, you are kinda asking us what money is worth to you.

The G-11/Gemini is the best mount for its price, and probably half again its price. (Although I do not know of any in its weight class under $4500.) If $1500 does not mean much to you (the difference between the G11 and where the next tier starts probably) go for the better and more expensive.

But a real question is--Just what do you intend to do with it and just what do you intend to put on it? If you are talking astrophotography, and money does not mean much--go for the more expensive mount. If money matters, go with the G11 even if you are doing astrophotography. If you are doing visual, then you really will never need more than the G-11. Unless you mean to load a whole lot of weight up there. Then get yourself a bigger mount.

Never evaluate a prospective purchase by reading comments in a support forum. I mean, you can get some information.....but the people who aren't having problems don't bother to write in very much. Or to put it in other words--go visit the Software Bisque Paramount support website.....and see all that can go wrong with a five figure mount.




Alex

So, it seems that orthogonality has to be in the mount (where the Dec meets RA) rather than in the scope. At least as far as tracking goes.

As for goto and DSC, one may need to shim the scope, depending on whether the computer can figure out the degree of misalignment and compensate for it.

Alex

Be careful of those beautiful knobs, Floyd. They can reach out and snag a cabloe or wire very easily. I believe that you will find in the long run that snaggy beautiful knobs are easier to use to adjust the latitude, but not so easily kept clear when all the camera cables, etc. start getting used.

Alex

Tell lme about this Photoshop for Astrophotographers.....Is this a special edition? Did I miss something?

Alex