And why?<br />
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I used to think my favorite design was called Schiefspiegler. But now i'm thinking it's an offset Newtonian. If you use an offset mask on a regular Newtonian, you get the effect i'm looking for. Unobstructed reflector. Its a simple, low cost design with the advantages of a APO refractor. High contrast, sharp images.<br />
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http//seds.org/~spider/scopes/schiefi.html<br />
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On the other hand, i have a Newtonian, and several binocular style refractors.<br />
I'm not a huge fan of Cassegrains. They are more compact, and might fit in my car, but even a 10 inch is a monster to get onto the tripod. And then there's cost. An 8 inch Cassegrain is more expensive than a 10 in Newtonian. Yet, their compactness makes for easier and better astrophotography. My 10 inch Newtonian fits in my car and has quick setup.<br />
The offset that i'm talking about doesn't require high focal length or focal ratio. Let's say you want a 10 inch offset scope with a 4 inch offset. You start with a 28 inch mirror, and cut a 10 inch circle starting at one edge. The center of focus is now 4 inches outside the mirror, so you can put an eyepiece there and neither it nor your head is in the optical path. No astigmatism, etc. And, you have the portability of a 10 inch. And this is the kind of thing you get with an offset mask. But my 10 Newtonian lets me have maybe a 3.25 inch offset mask without any obstructions. That's a 3.25 inch APO reflector (82 mm). An 80 mm APO (without tripod) is maybe $650 - which is more than a 10 Newtonian. I'd rather have a 10 reflector, though.<br />
I just picked up some 10x50 binoculars at a sporting goods store for $25. The optics appear good. Though i have a good tripod, i'm working on an alternative mount - a DIY project.<br />
Please, please, please do not buy a telescope at Walmart. It will turn you off to the hobby. Wobbly mount, frustrating focuser, eyepieces way overpowered for the aperture, finder scope that is hard to align to the main scope, and doesn't stay aligned, and so on. If you've only got $25, go to a sporting goods store, pick up some 10x50's, keep the receipt, check to see if they're aligned at night on real stars, and treat them like fragile delicate glass art work (since that's what they are). Get the best tripod you can afford, or build something.<br />
Corolus you've got binoculars like the Keck and LBT. That's twin telescopes that happened to be aligned with each other.<br />
<br />
The HST is a Richie Chretien telescope design. You can get ground based models for much less than $10 billion.<br />
<br />
I used to think my favorite design was called Schiefspiegler. But now i'm thinking it's an offset Newtonian. If you use an offset mask on a regular Newtonian, you get the effect i'm looking for. Unobstructed reflector. Its a simple, low cost design with the advantages of a APO refractor. High contrast, sharp images.<br />
<br />
http//seds.org/~spider/scopes/schiefi.html<br />
<br />
On the other hand, i have a Newtonian, and several binocular style refractors.<br />
I'm not a huge fan of Cassegrains. They are more compact, and might fit in my car, but even a 10 inch is a monster to get onto the tripod. And then there's cost. An 8 inch Cassegrain is more expensive than a 10 in Newtonian. Yet, their compactness makes for easier and better astrophotography. My 10 inch Newtonian fits in my car and has quick setup.<br />
The offset that i'm talking about doesn't require high focal length or focal ratio. Let's say you want a 10 inch offset scope with a 4 inch offset. You start with a 28 inch mirror, and cut a 10 inch circle starting at one edge. The center of focus is now 4 inches outside the mirror, so you can put an eyepiece there and neither it nor your head is in the optical path. No astigmatism, etc. And, you have the portability of a 10 inch. And this is the kind of thing you get with an offset mask. But my 10 Newtonian lets me have maybe a 3.25 inch offset mask without any obstructions. That's a 3.25 inch APO reflector (82 mm). An 80 mm APO (without tripod) is maybe $650 - which is more than a 10 Newtonian. I'd rather have a 10 reflector, though.<br />
I just picked up some 10x50 binoculars at a sporting goods store for $25. The optics appear good. Though i have a good tripod, i'm working on an alternative mount - a DIY project.<br />
Please, please, please do not buy a telescope at Walmart. It will turn you off to the hobby. Wobbly mount, frustrating focuser, eyepieces way overpowered for the aperture, finder scope that is hard to align to the main scope, and doesn't stay aligned, and so on. If you've only got $25, go to a sporting goods store, pick up some 10x50's, keep the receipt, check to see if they're aligned at night on real stars, and treat them like fragile delicate glass art work (since that's what they are). Get the best tripod you can afford, or build something.<br />
Corolus you've got binoculars like the Keck and LBT. That's twin telescopes that happened to be aligned with each other.<br />
<br />
The HST is a Richie Chretien telescope design. You can get ground based models for much less than $10 billion.<br />