All the Common Dobsonian Reflector Sizes Compared! Which One is Right for You?

hello and welcome back to the channel today we're taking a look at all of the common sized solid tube dobsonian reflector telescopes now if you've wandered into this channel from YouTube land and wondering what the heck is going on here well these are astronomical telescopes designed for looking up at the night sky the purpose of a telescope is to gather light so let's take this guy here and you can see that there is a mirror in the back that gathers light sends the mirror into the focuser here this is the focuser this is where you look into the side of the telescope to change magnifications you change eyepieces the mount is something called a dobsonian mount it's just a fancy term that means that the mount moves left and right and it moves up and down named after San Francisco astronomer John Dobson credited or popularizing its design so we do have all of the common sizes here we have the four and a half inch there's actually two of them ones on the ground and one's on your left here we have the six inch the eight inch which you just saw me move the 10 inch and the 12 inch so there's no big surprise at the end of this review these are all recommended you pick the size that fits your need and your budget but there is one that I do recommend more than any of the others we'll find out when we get there now these aren't the only sizes of the dobsonians you'll see out there Mead and Orion had 16-inch sonotube dobs I have a complete review of the meat I'll link that below Discovery and Celestron had 17 and a half inch units and then there are the cultures from the 1980s and 1990s I consider those to be a special case and I may wind up doing a special video just on those but by and large if you see a dobsonian telescope at an astronomy club or at a star party the odds are overwhelming it's going to be one of these sizes so the dobsonian reflector is the class of telescope that gets recommended probably more than any other for serious amateur astronomers reasons are not hard to find they are very simple to use they gather a lot of light and they are relatively inexpensive so let's take a look okay the four and a half inch dobsonians these are the babies of the group and these are awfully cute people who come to the house very often will gravitate towards these as opposed to the larger ones because they are so adorable looking now these are normally the smallest and least expensive telescopes that I recommend for the beginning amateur astronomer try not to go below this level there are just too many compromises there's a couple of ways you can play this there is the tabletop model this is known as the Orion star blast it is also known as the zumel z114 and it may be known by other name brands by the time you see this video it's a four and a half inch F4 tabletop dobsonian and it works just like any of the others mirror in the back and there is a focuser here the floor standing model is the same four and a half inch aperture except it is an f8 so the Optics are going to be a little bit sharper and you might be able to get away with setting it on the ground although you are seeing one of the major disadvantages here it does have to be on the ground I went through a phase not too long ago where I was trying to use only this telescope for my personal use and for public star parties it got to be a little bit challenging even small kids if you're looking at something down at the Horizon you see the eyepiece is awfully low but either of these are recommended and if you don't have any money at all this model is the prototype for what we are using for our library telescope programs our club donates these to the libraries all across the state we have over 180 of them placed in various libraries across New Hampshire you can check them out for two weeks just like a book the major problem with this one you're seeing right now you have to find something to set it on I have it on one of these tables whatever you do set it on has to have a couple of traits first of all it has to be sturdy enough to hold the telescope second of all it has to be something that you can walk around because you're going to be moving all around the telescope and third you want to have if possible some sort of a grip or lip on the outside because in the dark and I have seen this you could accidentally push the thing off I have seen that happen drawbacks to both of these models the major thing you're going to hear is that the focusers are made of plastic they look like they're made of metal but they're actually made of plastic painted to look like metal spare parts used to be easy to find they are becoming much harder to find these days and when we have repairs that have to be done to our library telescopes the focuser is one of the main things that usually breaks so do be careful with that thing if you buy one of these otherwise these are recommended for beginners you're going to have a lot of fun you can see phases on the moon you can see the rings of Saboteur you can see moons around Jupiter you can see dozens of deep Sky objects including showpieces like the Orion Nebula the Andromeda galaxy the Pleiades the double cluster and many more okay now we're moving into the heart of the lineup the six the eight and the ten these three models are recommended more than all of the others combined and it's not hard to see why they were a good trade-off between portability and light Gathering when you move up to a six-inch class telescope form a four and a half a six inch gathers twice as much light so things are going to be a lot brighter when things are brighter they are easier to find I'm finding that the six inches kind of a forgotten model these days as everybody kind of moves up to the eight and the ten so I'm going to go ahead and put in a plug for the good old six inch reflector you know when I was growing up a six inch was considered a large telescope if you had one people would drive large distances just to come and look at it not look through it just look at it although telescope prices have gone up lately these are still relatively reasonably priced at around 450 dollars for the base model and a little over 500 or so if you want an upgrade package what's the major disadvantage of the six inch well there is one but they have rectified it lately on this Orion model in the mid 2000s they switched to this plastic focuser it is very similar to the plastic focuser I showed you before on the four and a halfs but while such an item might be acceptable on a portable tabletop telescope a plastic focuser starts to become unacceptable on a 450 to 500 dollar six inch telescope the reason it's been rectified is after Decades of complaining about this getting no results Orion has reintroduced the xt6 into their catalog with a two inch metal focuser did I have anything to do with that I don't know I don't care it's great for the hobby but I do want to point this out because they made many of these through the years and if you find one on the used Market it may have the inch and a quarter plastic focuser on it some people have asked why can't I just change the focuser well you can in the past they used to offer these things as spare parts but these days spare parts are becoming harder to find you can find a third party focuser and put it on but you want to be aware of a couple of things first of all the mounting centers may be different than the ones that are already on here which may require you to drill extra holes in your tube you may not be willing to do that even if you get around that the bore of the focuser draw tube may be slightly wider than the bore of the focuser that's already on there requiring you to remount the hole you may not be willing to do that but perhaps most importantly is this thing called the stack height this focuser here is calculated so that the eyepiece height is focuses right here if you buy what they call a low profile focuser that will sit closer to the tube and you may not be able to find focus with your eyepieces after putting the new focuser back on so do get be sure you calculate that stack height and make it right before you go ahead and do that other than that this is a very solid package and recommendable to all beginning amateur astronomers so now we move up to the eight inch dobsonian I'm going to go ahead and leave the six on the side here for scale so that you can see the comparison when you move up to an eight inch model you're Gathering a bit more light an 8 inch telescope gathers almost 80 percent more light than a six inch what does that mean I've often had people ask me well why don't you show some diagrams as to what you can see through individual telescopes and I'm usually hesitant to do that for at least a couple of reasons first of all what you see through a telescope is largely dependent on where you live you're seeing conditions where I am right now used to be considered a very good location but as civilization has encroached there's more light pollution and it's getting harder to see things but I will go ahead and show this with that caveat that you may not be able to see what I'm seeing if you live in the city for example you may not see anything at all if you live out in the country you may see significantly more than what I'm about to show you but using the Galaxy's m81 and M82 in the Big Dipper I've got a comparison here between the four and a half the six and the eight notice there are no huge major differences it's not like one is on and one is off things get a little bit brighter with each iteration the second thing I want to point out is that people's ability to see also differs when you're new at this you may not see much at all but as you get experience you'll start to see things that were invisible to you just a short time earlier those galaxies m81 and M82 I showed you before I have gone to dark sites where those were very prominent in the eyepiece and first-time telescope users reported they couldn't see anything at all now some of those people by the end of the evening as they went around the star party and went around the field came back to me and said okay I get it now so seeing is something that has to be learned it's an art as well as a skill note that the basis of the eight and the six weigh about the same but since the 8-inch Optical tube is heavier it's going to be slightly less steady than the six although I find that's not a huge difference I find in this eight inch model I can track by hand for at 125 to 150 power or so with very little difficulty also note that the six inch is an f8 the eight inch is in F6 they have the same focal length for any given eyepiece they will show you the same magnification the only difference is that the eight will be slightly brighter I should probably also show this this is one of the advantages of such a simple telescope Orion uses the spring tension system here and the advantage of this is the entire telescope is only two pieces there's the optical tube and then there's the base so once you get this unpacked I can sometimes be set up and observing in less than two minutes and perhaps even more importantly at the end of the evening when I'm tired I can be packed up in only a couple of minutes as well having said all of that in eight inch dobsonian reflector is the kind of telescope I recommend more than any other to beginning astronomers and I've been recommending it for 20 plus years it seems to sit in a Sweet Spot between price portability light Gathering ability and performance now we come to the two large models in the lineup this is the 10 inch notice on the 10 and the 12 I have them on rolling platforms so that I can get them around a little bit more easily compared to the eight inch the 10 inch gathers 56 percent or so more light notice that is a smaller leap than the leap from the sixth to the eight but there is a somewhat larger leap in terms of the weight and the subjective bulk of all of this I'm finding that these days people are gravitating towards tanning dobsonians they're skipping the six and the eight they're going straight for the ten and that's fine but there's two things about the 10 I do want to draw to your attention first of all when you get to this level the weight of the optical tube starts to get to the point where this axis the Azimuth the one that goes back and forth starts to get a little stiff now if you compare this motion to the one on the eight it is a little bit jerkier to move around and if you're trying to fine tune something in the sky it can be a little bit more difficult the second thing about a 10 inch telescope isn't the scope itself it's you I find due to the slightly larger weight and bulk that these get used a lot less often my rule of thumb is over the long term long term now 10 inch telescopes get used about half as often as an eight the telescope that shows you the most is the one that you use the most and eights and sixes tend to get used for example if you came home from work and you're tired or maybe it's partly cloudy out you have a tendency to take out a smaller telescope more readily than you'll take out something like this now I'm not trying to talk you out of getting the 10 inch telescope if this is what you really want go ahead and go for it if the Azimuth motion starts to bother you what you can do is open up the base there and put replacement Teflon pads down there there are numerous forums and do-it-yourself instructions online to how to do that you'll notice this telescope looks a little bit different from the ones that I've shown you before that's because this is a new class of telescope that's come out that has some electronic Aids on it so the traditional dobsonian experience is a very purest one if you think about it it's two mirrors you and the sky people have tried to marry Electronics to varying degrees of success with the obsonians for many years none of them have really stuck but this one might so this one is a Celestron star sense and this complicated looking device here holds your smartphone once you download the app and calibrate it it will show you where you are in the sky so you don't have to go looking at Star Charts or Star hopping around it's actually kind of fun to play with I do have a complete review of this model describing how to do that I'll leave a link in the description below if you want to see it so with those caveats I just described before the 10 inch dobsonian is still recommended I still think however that an 8-inch is still The Sweet Spot for most people it's your call so now we come to the 12 inch oh boy the 12 inch so if you take the statements I made about the 10 inch and scale them up you get the 12 inch but it seems to be a little bit worse than that for example this telescope weighs close to 90 pounds depending on what you have on it and not only that the optical tube alone just the tube weighs more than the entire 10 inch telescope it's getting to the point where this Azimuth axis here this left right Axis is becoming unacceptably stiff and no amount of tricks that you play by adding extra Teflon or the flooring laminate on the other side or any of these other things that we do to make that motion simpler seem to work anymore in addition you start having problems on the other axis as well this altitude axis this tensioning knob just never seems to be right it's either too stiff or it's too loose and you can't seem to have any kind of Middle Ground where things are okay I actually don't like the Celestron system they've since come out with a better tensioning system but I'm stuck with this one but there are going to be those people who have aperture fever and are going to want the biggest possible light Gathering ability that they can get I do want to point this out to you because remember how I told you the 10 inch gets used about half as often as an 8 inch in my experience a 12-inch telescope gets used about a tenth as often and I'll use myself as an example I have this thing on this rolling platform in the garage probably about five feet from the opening of the garage door I could be out observing with this thing in less than five minutes I think it's been well over two years since I've looked through this every year I have to try to talk somebody out of buying one of these things I'm not going to name any names but when the person sees the size of the cartons that show up at their doorstep sometimes again it happens at least once a year they never opened the cartons they just put it in the basement they never open the thing up so sometimes people who see this thing ask what are these colored handles here these make carrying the optical tube a little bit easier those were referred to as scope totes and they may or may not be available by the time you see this video so again the 12 inch I I find this is a specialty instrument I don't think that the solid tube design serves a 12-inch dobsonian very well I think when you get to the 12 inch level in open trust design makes more sense but if this is what you have to have go for it just don't say you weren't warned if you truly do have aperture fever and only the biggest will do there are companies out there who will accommodate you here I am playing with a 20 inch obsession I'll leave a link in the description below if you want to check out that review okay now that you've selected which one of these you're going to buy I'll try to answer some common questions I get among beginning amateur astronomers number one what else should I buy should I get additional eyepieces filters accessory kits this sort of thing my normal answer to that is no don't buy anything normally when you buy one of these they give you enough stuff to keep you busy for a very long time if you're going to buy anything get a set of star charts and a couple of books to get you started I would tend to avoid buying IP sets and filters most of the time you'll wind up not using those things and if you find you did need those things you can always purchase them later second question I get many of these telescopes come in several trim levels the eight in particular seems to have any number of options that you can put on it from electronic systems to accessory kits to upgrade kits and this sort of thing which one should I buy well you're not going to go wrong with any of these but I would tend to steer you towards just the base unit that's what I tell people to usually do a lot of those upgrade packages I actually refer to them as downgrades another question I get I have these orions and I have a couple of celestrons here you may notice similar looking units with different names on them which one should I buy and the answer is any of them just get any of them these appear to be all based on the same platforms coming out of China they'll have different names on them they'll put different accessory packages on them the tensioning system that you see here may be a little bit different they all tend to work pretty well I would say if you're looking for one buy the one that happens to be offering the best deal at the time you happen to be shopping and or the one that happens to be in stock another question I get can you do astrophotography with these telescopes the short answer uh no you might be able to get one of those smartphone holders and take quick snaps of the Moon and possibly the planets I have never had very much luck doing that if you're interested in long-term deep space astrophotography you're going to run into a lot of problems here and I wouldn't recommend it the main problem being these are manual only telescopes there are no motor drives attached to them they do not compensate for the rotation of the Earth even if you got rid of that problem the weight of the camera will often pitch the front of the scope downwards very often the camera won't even be able to find Focus there are no coma correctors that are matched for these things even if the mount track there are no auto guide reports and there are a half a dozen other problems you probably haven't thought of keep in mind no telescope is perfect and this is one of the drawbacks of this design however we do find that the dobsonian reflector offers the least number of compromises for the beginning astronomer and that's why these get recommended so there you have it a look at all of the common solid tube dobsonian reflectors on the market I hope this video has helped you to decide which one of these is right for you thanks for watching and I'll see you soon

Channel: Ed Ting

Views: 44,343

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Id: E2Fq7ecjBvQ

Length: 21min 26sec (1286 seconds)

Published: Sun Jul 30 2023