Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Stargazing What Telescope to buy?

  1. Apr 21, 2009 #1

    I'm new to PF, but I just wanted to ask about telescopes. I'm new to astronomy, and I am looking to buy a new telescope for under $400. I mainly have been doing astronomy with binoculars (16x50), and I believe that I want a telescope with a relatively wide viewing field and high resolution rather than one with a really high magnification. I'm looking for something that I can move around in a car, and that has a low enough magnification that I don't need electronic tracking (since that seems to really add price). The main objects I would like to be able to see are nebulas and galaxies 10th magnitude or below (especially the Messier objects).

    Does anyone have any suggestions or additional considerations I should make? I live in a very dark location, so light pollution/ filters are not an issue. Thank you in advance for any advice!
  2. jcsd
  3. Apr 21, 2009 #2


    User Avatar
    Gold Member

    Do you have any astronomy clubs near where you live? If so, you should attend a few meetings, and at least one or two star-parties. That way, you can get to "sample" the 'scopes that are available. For the price-point, you'll probably end up with a Dobsonian of some kind. Let the club-members know that you're looking for a 'scope. Lots of amateur astronomers are gear-junkies, and you might just get a sweet deal on a used Dobsonian from a member that wants to upgrade to a larger scope or perhaps try to finance part of a small refractor with guide-capability. Good luck.
  4. Apr 22, 2009 #3
    Yes, I agree. Go for a Dobsonian. You’ll get the biggest bang for your aperture buck.

    A simple Dob mount would be sufficient for what you require. There is no point in spending extra money on equatorial or fancy mounts.

    As suggested definitely check out your local astronomy club. Look at some scopes and also they may know of local scopes in good shape on the market.

    The largest aperture mirror with a focal length ≈ 4.5 you can afford or transport in your car would be best for chasing down Messier objects and nebula.

    Eyepieces in the 20 - 32mm range will give a wide angle. However it is nice to have 6mm to drop in for planetary or lunar observing.

  5. Apr 22, 2009 #4


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Try http://www.cloudynights.com/classifieds/showproduct.php?product=18058&sort=&cat=10&page=1" [Broken]

    The second one is easier to move around in a car but the first one isn't too much more difficult.
    Last edited by a moderator: May 4, 2017
  6. Apr 22, 2009 #5
    A was actually looking mainly at Dobsonian mounts, and so I'm glad I had a generally accurate idea of where to look.

    What do you mean by "The largest aperture mirror with a focal length ≈ 4.5"? By 4.5 do you mean a focal ratio of f/4.5?

    Also, what is the role of the eyepiece in determining field of view? I must admit that my high school course does not really have an in-depth coverage of the characteristics of telescopes, so I am not sure I understand the relationship between field and eyepiece.

    I was actually looking at this model:

    Is this a reliable brand and set of specifications? It looks like it has a focal length of around f/8- Is this too high to be really effective?

    Thank you all for these responses, I realty do appreciate your help.
    Last edited by a moderator: May 4, 2017
  7. Apr 22, 2009 #6


    User Avatar
    Gold Member

    You would get a LOT more bang for the buck with the 8" classic from Orion.


    I want to encourage you, however, not to jump right in and buy a 'scope until you have had a chance to look through a number of them. You may decide that you want to bust your $400 budget just a bit to get something that suits you a little better. You may also find a member of a local astronomy club who is willing to sell you a used 'scope with maybe some extra accessories, like a nice finder, etc.
  8. Apr 22, 2009 #7
    As an example in generalization because all eyepieces are not the same;

    The telescope you referred to is 1100mm FL and primary mirror 135mm.

    A 40mm eyepiece will have a magnification of 23X.
    True field of view of 1.82 degrees.

    A 25mm eyepiece will have a magnification of 44X.
    True field of view of 1.44 degrees

    A 5mm eyepiece will have a magnification of 220X
    True field of view of 0.23 degrees.

    On the other hand a 1200mm FL and primary mirror 203mm

    A 40mm eyepiece will have a magnification of 30X
    True field of view of 1.47 degrees

    A 25mm eyepiece will have a magnification of 48X
    True field of view of 1.04 degrees

    A 5mm eyepiece will have a magnification of 240X
    True field of view of 0.21 degrees.

    I agree with Turbo, if your interest is Messier and deep sky the 8" would preform better than the 5.5" provided it was not a high focal length.

    You are looking for light gathering capacity first, magnification second.
    When it comes to light, size matters.

    Most people I know into astronomy usually started with mid range f/7 or f/8 8" dob.
    Anything higher is good for lunar or planetary observing but lacks in deep sky.

    Again, if you have an local astronomy club check it out.
  9. Apr 22, 2009 #8


    User Avatar
    Science Advisor
    Gold Member

    If you are near a club, that is a plus. Pre-owned scopes can often be had at a good price from people moving up in aperature. Optics do not degrade from use. I would prefer a lower f ratio - 4.5 to 6.0. you might be able to acquire a very good 8" Newtonian in that price range. Lower f ratios are also excellent for photography. If you think that might be a future interest, you should lean towards an equatorial mount. The price difference between a Dobsonian and equatorial mount is not enough to justify the loss of photographic capability, IMO. If portability is your biggest issue, I would look for a ~4 inch catadioptic. They are extremely portable and obtainable [second hand] in the price range you have in mind.
  10. Apr 23, 2009 #9
  11. Apr 25, 2009 #10
    Thanks for all of these great responses! I agree that a club would be ideal, but unfortunately I live in a rather provincial area. I have been mainly consulting my astronomy teacher for input.

    Based on what I've seen here, the telescope that I am now really considering ishttp://cgi.ebay.com/WHITE-6-NEWTONI...|66:2|65:12|39:1|240:1307|301:1|293:1|294:50"

    Does this seem like a reasonable choice? It seems to come with several eyepieces for different observation types. Any suggestions?

    Thanks again for your continued help!
    Last edited by a moderator: Apr 24, 2017
  12. Apr 25, 2009 #11
    Well, I think you made an excellent choice for an entry scope.

    Since you are interested in Nebula and such the f/5 will certainly accommodate this.
    Using the the EQ mount will accustom you how these things work.
    The motor drive for this unit should be well within your budget if you ever consider it.

    Please drop back and let us know how you get along.

    Clear skies
  13. Apr 27, 2009 #12


    User Avatar
    Science Advisor
    Gold Member

    Looks like a great buy to me. Short tube, EQ mount, good eyepiece selection.
  14. Apr 27, 2009 #13
    So, I read some reviews and discussed this with my astronomy teacher, and he believes that this scope has too large a secondary relative to the primary, so it blocks more light than it should (this is verified by some online reviews). He also does not like the eyepiece options (he explained to me the relationship between eyepiece and magnification)

    He thinks I should consider http://cgi.ebay.com/Celestron-Power...66:4|65:12|39:1|240:1318|301:0|293:1|294:200"

    It has a bit of a high focal ratio, but it is a reliable brand and i can use the extra cash to get a set of nice eyepieces. Any suggestions?

    Thank you all so much for your continued advice. As you can imagine, my first telescope purchase is a little daunting so I really appreciate your help!
    Last edited by a moderator: Apr 24, 2017
  15. Apr 27, 2009 #14


    User Avatar
    Gold Member

    With your last couple of options, you would be paying for German equatorial mounts and tripods. This is not such a bad thing, but that means that you won't be getting the best optics for the buck. Not only that, those mounts are marginal at best, so you can't add more equipment to the scope (like a large finder) without dealing with stability problems.

    PLEASE attend an astronomy club meeting or two, and at least one star-party so that you can look through other peoples' scopes. The reason that I suggested the Dobsonian option is because they typically feature large aperture for the money, and the mounts are so simple that the manufacturers can afford to equip them with better optics than similar-priced 'scopes on equatorial mounts. I own a really nice 6" APO refractor on a heavy German equatorial mount, and if I were to buy another scope, it would be a 10" or larger Dob for visual use. Fast setup, lots of light-gathering power, and easy to use.
  16. Apr 28, 2009 #15


    I have several scopes of different types and aperture. However, I purchased a 10 inch f4.5 dob 2 years ago for the same reasons you pointed out.
    I am quite happy with it for DSO and use it often.

    Wil3 had mentioned he was interested in deep sky objects. I suggested a dob for the same reasons you sited.

    The equatorial mount is fine for learning how polar align and such and if one has any aspirations of astrophotography. However, my >persona<l view; I would put my bucks into a dob and the money I saved on mounts would go onto aperture.

    A 6" APO.......very very nice. I would imagine you get some fantastic observing with that.

    Have you ever used a DSLR or CCD on it?

    In the next year or so I think I will be able to see my way clear and get another scope. I have been considering a 5 or 6 inch APO.

    A friend has a 25 inch Obsession. It's a beautiful machine. However, something like that is not in my budget, and cumbersome to transport. But the views are awesome....
  17. Apr 28, 2009 #16


    User Avatar
    Gold Member

    The 'scope is an Astro-Physics 6" f:8. I bought it before Roland's 'scopes were well-known and the waiting list was less than a year. I have never stuck a digital camera on it, but I did film-based astrophotography for a few years using an Olympus OM-1 (mirror lock-up, manual shutter, etc).
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: What Telescope to buy?
  1. Buying a telescope (Replies: 4)