I have always been interested in Astronomy. A couple years ago I bought a 4.5" meade reflector (4501) with hopes that I could see the planets and possibly nebulae with it.
Well, it is quite good for lunar observing (IMHO) but I have a real hard time resolving anything else with it, IE the rings of Saturn or the disc of Mars. The Orion nebula looked, well, kinda like mars but fuzzier
Now, I am a very amateur “amateur” but I do realize that items like filters really help, but I think that my present scope is lacking.
I know magnification is not nearly as important as light gathering ability is, a generalization in my mind is that the bigger the better (dia of mirror).
So I guess the question I have is this. I am looking at “upgrading” from my mediocore at best 4.5" meade. I am considering an 8" Dobsonian. This is the one in particular http://www.khanscope.com/sky8f6.htm I am mostly interested in observing Mars, Jupiter and Saturn and deep sky object like nebula and maybe galaxies (I understand you need a good scope to get any detail on Galaxies though, so I may be pushing it). Do you think that 8" one should fit the bill for me?
Price is a bit of an issue here, but I know your not going to get a quality scope for $200. I would have a hard time getting the wife to accept anything even near $1000.
bernse a 4.5-inch reflector should be plenty good enough for Saturn’s rings (I could make them out just fine with a 2-inch refractor that I used to have), Jupiter and its moons, Mars, etc… are you sure that you are using it correctly?
Do you have any friends who have some experience with telescopes who might be willing to help you?
Nebula, on the other hand, are a different story entirely…
Even through the biggest scope, most nebula/galaxies/etc. just look like blurs of light. Those picyures that you see are all the results of long-term photographs, so don’t expect to see anything like that with the eye…
Yes, look through a bunch of scopes first. Heaven forbid you should pay a thousand dollars and find that it’s still not as impressive as you thought it would be.
Me, I get knocked out looking at the Orion nebula with a 3 inch scope.
The rings of Saturn should be pretty easy with a 4.5" telescope. Are the optics properly aligned ? Do you have any decent eyepieces ? If you buy a cheap 8" you’ll probably end up needing to get some good eyepieces anyway. It might make more sense to get one and try it before you get a new scope.
I’m with Squink on this… seems to me like something must be wrong. Can you use the scope in the day time, say focusing on a distant tree or something? If so, is the image sharp and clear?
Dobsonians are affordable because of the simplified mount. They are very easy to use and perfectly functional for low magnifications, which is all you need for observing deep-sky objects such as nebulae and galaxies. However, Dobsonians are difficult to use at high magnification, which you need for observing planets. It’s not impossible, but observing planets with a Dobsonian is a frustrating experience and I wouldn’t recommend it.
I don’t know how good your 4.5" is, but most telescopes that size are good enough to clearly show you the ring of Saturn and a couple of bands on Jupiter. You might want to find a local astronomy club and see if you can get someone knowlegeable to take a look at your telescope.
Sky and air conditions are important. Some days the air just isn’t stable enough to get a good high-magnification view, especially if, say, Saturn is visible just above your neighbor’s black roof which has been baking in the sun all day. For deep-sky objects, don’t even try to observe from the city, drive as far as you can away from the city. A pair of binoculars under dark skies give a far more impressive view than a 10" telescope in the city.
I’m not trying to discourage a Dobsonian purchase - they are definitely great tools for deep-sky observations. Just understand the limitations before you whip out your credit card.
That is the best advice you can get. Talk to others with experience and see if they can help you with the 'scope you bought. If you still want more aperture, they’ll be happy to advise you. Try here for a list of clubs in your area: http://www.badastronomy.com/bitesize/astroclubs.html
The two things you need to worry about with the optics of your scope are aperature and focal length: Bigger aperature is always better (aside from minor details like price and portability), and will improve both resolution and “speed” (i.e., how faint things look). With focal length, you’ve got a tradeoff: Longer focal lengths will give you better resolution, but worse speed, and vice-versa. There’s also the general quality of the optics to consider. Meade is a good company, so you shouldn’t have any trouble in this regard with their components, but are you maybe using a lousy eyepiece?
I’ll also second or third or whatever the suggestion to look up a local astronomy club. There’ll be plenty of experts there, and they usually hold star parties pretty frequently. If you don’t get a big scope, then this will give you a chance to look through other folks’ big scopes for free, and if you do get a big scope, you’ll manage to get a lot of folks jealous of you. It’s a win-win.
For what it’s worth, by the way, I’ve never had trouble holding a planet in the field with a Dob. In fact, unless it’s got a clock drive, I personally find it easier than with most equitorial mounts. I would actually recommend a Dob mount for anything other than astrophotography, but your milage may vary.
I have to agree with Chronos, I have no trouble at all viewing planets at about 266X with a 4.5 mm eyepiece(to calculate mag divide focal length in Milimeters/eyepiece aperature in mm)with my Orion 8" dobsonian. Now the sky can ruin this with just a little instability or Poor Seeing, so i usually observe planets at 188X (~6mm)
The field of view is small, and it takes practice,also the more you train your eye the more detail you will see in the low contrast of a 'scope- but a dob is the best all around observational telescope for the money. If you were an astrophoto nut, it would be different and you’d need a more automated rig.
I’d bet you a beer that your scope is horribly out of collimation, which means that the primary and secondary mirrors are not “aimed” at eachother and the scope cannot come to focus. Collimation is a PITA but not all that hard. If you want the procedure post a reply and I’ll email or you can search yahoo for “ATM +collimation”
We have no “astronomy clubs” in my area. So thats out.
We have no universities. I do however have a community college. The problem is that there are no programs even remotely connected to astronomy. Damn good advice, but not possible.
On land based targets my scope is crystal clear. Lunar targets its crystal clear (IMHO). I believe it to be in adjustment. How can I verify?
I have 2 eyecpieces. A 25 and 9 mm. I also have a barlow lens. They came with the scope. Quality is probably comperable to the scope. Its a MEADE 4501.
Looking at a “bunch” of scopes is not an option. I live in a small city of 40000 people. There just aren’t any stores that inventory them. Whatever I buy will more than likely be mail order/shipped to me.
As mentioned earlier $1000 is not an option right now. I know a good scope isn’t cheap, but that doesn’t mean there is no such things as a good buy. I agree with you on the Orion Nebula. Problem is, it sounds like it looks better on your 3 then my 4.5.
I have heard nothing but good things about the ease of use with a Dobsonian.
Are you SURE there are no astronomy clubs in your area? Did you do a web search? Where are you? I’ve yet to see an area in the US, no matter how small, not have a club within 100 miles or so. I strongly suggest you search for one - if you can go to a star party, chances are you’ll figure out why you can’t see stuff with your scope. Someone will take the time and figure out the problem. Also, you’ll be able to look through everyone else’s scopes, and get the one you really like.
You say that the Moon and land targets are “crystal clear”, what about stars ? Are they nice round points with maybe a few spikes coming off them from the secondary mirror holder, or are they more an oval shape ? Stars are much harder to image correctly than the moon or a sailboat, and any problems you have seeing them will end up reducing the amount of detail you can see when you’re looking at planets and Nebula. Galileos’ scope was had only a 1 inch lens and he discovered the moons of jupiter etc. with it. You should be able to do much better with 4.5 inches.
There are instructions on the web for testing and fixing your mirror alignment. [Of course I can’t seem to find them this A.M. Spend a few hours with Google and phrases like “adjusting a telescope mirror”.] Depending on how old your scope is you might also have a warped mirror. Sometimes this is also fixable.
Telescope dealers frequently skimp on the quality of eyepieces in order to keep their prices down. A bit of research on the design of the eyepieces you have could tell you whether this is a problem.
I can confirm that with my 60 mm (about two inces) refractor, I can make out Saturn’s rings pretty clearly, and see a couple of stripes across Jupiter.
I went out Friday night with a friend to look at Mars with his eight-inch Dobsonian reflector. I was disappointed with Mars, because we couldn’t even make out the polar ice caps. We also looked at the ring nebula, which I was more impressed with. I found the mount of the Dob to be a pain, since you couldn’t easily make fine adjustments in the position. You had to push the telescope body, so to make a small adjustment, I the position would go back to where it started when I stopped pushing. Unless I pushed a little harder, when it would completely overshoot what I wanted to see.
What I would like to find is a web site that shows what you can typically see with various sizes of small telescopes. Here’s what the ring nebula looks like with an eight-inch Dob, here it is in a 4.5" reflector, here’s a 2" refractor. Here are Saturn’s rings with the same three. This kind of thing. Does such a web resource exist?
The easiest way to check collimation is a ‘star test’
Center polaris as accurately as you can and go to the highest power you have.
You then rack the focus in and out slowly. What you should see is a set of diffraction rings around the out of focus star that should be exactly concentric. If the star seems to have a tail or the rings are eccentric (sp?) the mirrors need alignment. The exact procedure for collmation will vary for each scope, but basically you make sure that the Secondary mirror is exactly centered in the eyepiece axis and then center the primary to it and lock it level.
The shorter the FL, the more critical and exacting these alignments are and the first time you do it you will most likely get frustrated as it’s kinda like tuning a musical instrument, part science, part perception
If you could swing it, I’d suggest an Orion 10" Dob - it’s being heavily advertised in the astro magazines. 10" is definitely better than 8", and 8" is way better than 4.5. I think that the Orion is a well-made but relatively inexpensive Dob. A friend here got one and is very happy.
Bigger (aperture) is often better, but quality of optics and the kind of scope are important factors too. SCTs have central obstructions that tend to reduce contrast and light-gathering a bit. High-end APO-refractors are very expensive, but can often produce sharp, color-correct, high-contrast views that far exceeds their smaller aperture ratings. Newtonian reflectors can produce astonishing deep-sky views (especially in the larger apertures),
but if the mirrors are mediocre, then you won’t get the full benefit of the aperture. And, frequent collimation checking and/or tuning is always key for SCTs and reflectors.
I’d say that you should seriously check out Orion 10" Dob, and look around on the web for telescope review sites.
I don’t live in the US. I live in a small city in northern Alberta, Canada. Last time I checked (last year) there wasn’t any clubs. The closest observatory is in Edmonton and thats 4 hours away.
I guess thats why I am a bit unsure here. I have to be more or less self educated and get advice from people such as yourselves over the 'net.
I stand corrected. It’s been a while since I’ve used a Dobsonian.
As for resolving Saturn - are you sure you are looking at Saturn? It’s possible that you are looking at a nearby star, which can look vaguely planet-like if the atmosphere is unstable. During the day, check that the finderscope is aligned by pointing the telescope to some distant building or object and making sure the finderscope and the main telescope are pointing at the same place. Then use the lowest magnification eyepiece to find Saturn or Mars. Even at the lowest magnification it should be obvious that planets are much larger than stars.
Me too. I have a 4.5" Reflector too. The rings of Saturn should be easily apparent as being separate from the planet (although you may have a hard time seeing the Cassini division within the rings). Jupiter’s 2 equitorial cloud bands should be easily visible along with its 4 largest moons (points of light). A crescent Venus should be apparent (filter may help here). I’ve had a tough time with Mars…it should appear as a small disk but you may or may not see any details depending on how good the “seeing” is on the night you go out. You need to stare at Mars for a long time & hope for a clear moment in our turbulent atmosphere.
I’d check the alignment of your optics & the fitting of your eyepieces.
Start with the 25 mm eyepiece…center the object…and then put in the 9 mm eyepiece…you should see some details with that altough it may be hard to focus on a turbulent night. Try getting a 12.5 mm eyepiece…it would be easier.
Well, I have been doing a bit of research on my scope over the usenet and stuff. I am coming to the conclusion that the scope itself is OK, but the eyepieces that come with it are crap.
So, just for kicks, I think I might buy one decent eyepiece and see how it performs. I just hate putting any more money into it if I am going to sell it…although I guess I can always keep the eyepiece for my new one, right?
