My comments about the scope I would use the most was related to set-up time and portability only. Says nothing about what technology. I don't know enough about that yet.
So let's discuss that 4.5" dob. Is there a cool down/warm up period for something like that? Any feeling for how long that might be, on average? And don't those need to be aligned before you use them?
"Then again, if you have a short focal length refractor, costing the better part of $2,000, and you want to view planets, a Maksutov Cassegrain reflector that costs $400 might be the better scope for you, and you'll use that more often for planets. You certainly wouldn't use a short FL refractor for planets."
Great info but I dont' understand it. Explain to me why I would want a Mak Cass for planets rather than a short FL refractor? And what would you consider short FL? 700 mm? 1000 mm?
If a refractor is not good for planets then what is it good for?
you mentioned a Mak Cass for planets. Does that mean that I would not use a 4.5" dob for planets? So, what would I use the Dob for?
Is field of view a decision point for these scopes or do they have similar FOV characteristics?
I have been reading like crazy but I have not internalized any of it yet. This is one of those areas that tells me I am not ready to buy anything yet. I understand binoculars sufficiently to know why to go to a 15X70 and roughly how that would compare to my 10X50s. So that is a safe move from that point of view, but does it take me where I want to go? I don't know.
Any decision will be a compromise, I understand that. But I don't understand what the decision points are.
So, I don't understand your statements about telescopes. I would need to understand in order to know what to buy and why. And how would a 4.5" Mak Cass relate to a 4.5" SCT to a 4.5" Dob.
I don't see many moderately priced refractors over 100 MM, about 4", so let's assume reflector above that.
Where does each fit in, from a view and use case point of view? If I buy one that is good for planets then can I not use it for stars and clusters and galaxies?
And what about Goto? My understanding is that SCT and Mak Cas have a lot of go to options, but no so much with Dobs.
I want to look at all of it. I want to see the planets, the moon, stars, clusters, galaxies and all. I likely can't afford, nor do I have a place to store 3 telescopes of significant aperture so how do I select and what is the best compromise? If I make a mistake and can't view the sky I am going to be very bummed out.
My inquiring mind wants to know.
Okay, let's go through this from the beginning. Almost every telescope, and even binoculars, require a period of thermal stabilization. The larger and more complex the telescope, usually, the longer the stabilization requires. Mirrors and glass optics need to have time to stabilize, and obviously, the larger the mirrors and optics, the longer it will take. You also need to take into account the temperature difference. Say you got a Dob, and left it in the garage, properly covered. There wouldn't be any need, since it would already be at ambient temperature.
As to 'aligned', do you mean collimated? Collimation is the proper alignment of the mirrors to make sure everything is 'on axis.' You may need to collimate it once in a while, but if you're careful, not every time. Some observers collimate every session, and it takes three or four minutes to do, others don't unless things are really bad. More for astrophotography than casual visual observation. I never collimated my first telescope, a 127mm Mak Cass.
Telescope Design and Magnification.
If you look through your binoculars at a star, or if you look through the most powerful visual telescope on earth, you're going to see the same thing, a white pinprick of light. Unless you're looking at Sol, you'll never see a disc. In the universe, stars are pretty small objects, and of course, planets, even smaller.
Now, the basic rule for magnification says the focal length of a telescope divided by the focal length of the eyepiece equals the magnification. So, a 1,000mm telescope using a 25mm Eyepiece will give you 40 times magnification. The same telescope with a 10mm eyepiece will give you 100x magnification. However, as you increase magnification, your target will become dimmer. For planets, which are very bright objects in the sky, this is not a problem.
Download the free program Stellarium. In it, there is something called the Ocular Plug In, and it allows you to simulate the view (although not the brightness) of a telescope and eyepiece combination.
Now, as an example, I have an older 80mm refractor telescope. Refractors are the 'classic' telescope, long tube, and you look in the end of it. The 80mm refers to the diameter of the 'objective', the same as the 50 refers to the size of the objective in your binoculars. My telescope, therefore, is about 3.1" in diameter. The 'focal length' is the distance the light is refracted before coming into focus at the end of the tube. So, let's take Saturn, which is still in the summer sky.
With a common 25 or 26mm eyepiece, I'll be able to see two very close dots, next to each other. One is Saturn, the other it's larger moon Titan. If I'm lucky, I may make out a slight oblong shape to Saturn, which denotes it's rings. I also might see a couple of other dots, which would be other moons.
Switching to a 10mm eyepiece, there might be some distance now between Saturn and her moons, and you might see Saturn and four or five other dots, her moons. If I move to a 6mm eyepiece, and the viewing is very good, I may start to see the actual rings, and the space between the rings and the planet. About the best I can expect from that scope would be with a 4mm eyepiece, and I should be able to make out several of Saturn's moons and her rings, but she will still be very small on the eyepiece. This is about 200 power.
Now, if we switch telescopes to, say a 127mm Maksutov-Cassegrain, with a 1,500mm focal length, Saturn will still be small in the eyepiece, but using that 4mm eyepiece, we'll push the magnification up towards 350x magnification, and her moons will show nicely, and the rings will, or should be, nice and clear. You may even, upon close inspection, see the Cassini division in the rings. Saturn, still though, is going to be a little dot, and won't be filling your eyepiece.
Now, if you have an 8" Schmidt Cassegrain, with a 203mm aperture and a 2,032mm focal length, you MIGHT, on a really good night of seeing, be able to make out the inner moons of Saturn, details in the ring structure, and even some of the banding on the planet, by using a good 2-3mm eyepiece.
When I originally spoke of a 'short focal length' telescope, I was talking about one in the 400-500mm focal length range. I would not reasonably expect to be able to use anything smaller than a 6 or 7mm eyepiece, so Saturn would be nothing more than a larger dot, with a few smaller dots around it for her moons. No rings or anything like that.
But, that's not what the design is supposed to be used for, either. Small refractors like that are designed for wide field observing. The Andromeda Galaxy is almost 3° in width, six times larger than our moon! With that same small refractor and a 26mm eyepiece, I can fit the entire Andromeda Galaxy into view, at about 16 power. I could fit either the Heart Nebula or the Soul Nebula into the field of view with a 26mm eyepiece, but not both together.
Using the aforementioned 127 Mak, the Soul Nebula overflows even my widest eyepiece of 32mm. The Andromeda Galaxy I can only see the center half of the galaxy.
So, you can see that there are different telescopes for different objects in space. What is good for lunar and planetary viewing is too much for many Deep Space Objects, and what is good for DSOs may not even allow you to notice a planet as a planet.
A refractor may be very good for planets, I've seen some wonderful views of Saturn from a refractor, but as there are different sized scopes, so it applies to refractors as well. Remember that focal length of the telescope divided by the focal length of the eyepiece equals magnification. So, if you had a refractor of 1,500mm focal length, it would give you the same magnification as the Mak-Cass we discussed earlier.
Here is a refractor that also has a 1,500mm focal length.
Notice that the length of the telescope is almost 5 FEET long. In comparison, here's that 127 mm, 1,500mm focal length Mak Cass.
It's 13" long.
Also, notice the price difference. Same view, just two different ways of getting there.
As to using a Dobsonian for planets, you can. You can use it for anything you want, with the same limitations. Your focal length determines magnification. The 4.5" Dob also has the same focal length as my old achromat refractor, 900mm. But, it has an inch and a half more aperture, so you will get more light, and more detailed views. It'll be the same size in the eyepiece, but you'll get more details. That accounts for a lot.
As to FOV, that is dependent on both of your telescope and your eyepiece. Even changing eyepiece design will change your FOV for the same telescope. There are calculators for that.
As to your lack of knowledge, this is why Cloudy Nights is such a great place, you will get so much information and so many points of view and so much information that you will, when you're ready to buy a scope, know exactly what you want.
Everything is a compromise, unless you're really rich. Most people, you will find, have more than one telescope. But, the nice thing is that for many of them, one single mount can be used, and then the telescope that's best for that night's planned viewing can be used. But, they aren't all the size of that Dobsonian, either.
My collection began last year when I bought a mount to do astrophotography, and all I planned on doing was using the mount and my camera, didn't care about the telescope. Well, the telescope came with it. I still have the scope, the mount was garbage and didn't last, nor did it work properly. Now, I have a new mount, and also a larger telescope, so I have two scopes now. I'll also have a smaller, third one in a couple of weeks. That's where I'm drawing the line for a year or so. Each one will be for a specific purpose.
However, in my opinion, the best starter scope, for someone who is just getting into telescopes, is a Dobsonian Mount Reflector telescope. They are easy to use, provide startlingly good views of a number of objects in the night sky.
This image was taken with an 8" Dob.
Here's Mars, taken with a 6" Dob.
This is the Orion Nebula taken with an 8" Dob.
Feel free to ask questions of this community, they are a good bunch of people here, and will answer what may seem to be the silliest questions, because they know they aren't silly.