Author Topic: Did you know of these different types of telescopes? (Thread from a beginner to  (Read 27657 times)

Niro Hardy

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Well,

That is meant to be a newcomer thread from a newcomer to a newcomer as I'm pretty sure everyone else already knows about these.  I thought I would only share with new folks what I found on my trip of merely choosing a telescope great for my own needs (still continuing at the time of writing).

3 Chief Kinds of telescopes:

1.)  Refractors: All these are lense-based telescopes.  Based on quality of the telescope these comprise anything between 6 and 2.  Straightforward refractors suffer "purple-fringing" surround particularly vivid themes (ak chromatic abberations) which are the result of different colours of the light spectrum being bent to different degrees.  To fight this symptom, higher quality lenses were created.  Telescopes which have these lenses are called achromatic telescopes.  More sophisticated setups contain various concave and convex lenses to focus different colours into a single focal point.  These types of telescopes are called apochromatic telescopes.  Because these telescopes contain many lenses that have many surfaces, so that every have to be finely crafted, they are the most expensive.  Prices grow rapidly. . .and for these telescopes it isn't too rare to see costs as large as 10K for a reasonably sized siystem (5-6").

To begin however, someone doesn't need to pay exorbitant sums.  Here are a few (largely achromatic) telescopes:

- 102mm Achromatic Refractor: 4" telescope with great wide field of vision.  I have seen sale costs as low as $399 for your OTA only.
- 127mm Achromatic Refractor: 5" telescope with greater lighting capture then the model above.  Regular costs are approximately $599.

I have read many excellent reviews.  Fantastic price for quality attained.  Obviously, at those prices you're not likely to completely eliminate purple-finging, but it shouldn't be that noticeable with those achromats.  Larger sizes are also available, however they, in my view start getting unwieldly big.  Smaller dimensions are going to be more economical of course, but for those you'll be limited to brighter objects (like planets, and the very brightest and biggest nebulas and DSOs)

2.)  Reflectors: All these are "mirror-based" telescopes.  Rather than mirrors, lenses are used to bundle the lighting.  They are far more economical because, rather than polishing 4-12 surfaces, one just needs to do a good job on the principal mirror (1 coating).  It's common wisdom that in terms of bang for the bug, this is where you will likely find it.  I personally have been researching 5" newtonians onto a Go-To bracket, and found that essentially, the OTA is the exact same piece of gear in each of these.  Examples below:

- Celestron Skyprodigy 130:
- Celstron 130 SLT: The link for this is actually a review significance to show that despite the issues under, individuals can be happy with these sorts of systems.
- Orion Starseeker IV 130:

Individuals on these forums will quickly point out that there are several issues with those scopes.  Despite excellent optics of the mirror, these scopes come on very undermounted tripods - at the Skyprodigy and SLT system.  I can attest to this as I looked at the tripods for its initial 2 models.  I have yet to see that the Starseeker IV tripod.  It seems to be more solid and might be okay actually.  The other piece I WAS able to confirm though is the Celestron telescopes mentioned previously have a plasticy looking focuser piece.
Individuals on the forum say these focusers will prevent great accuracy at greater (~200x) magnifications.  Again, I have never been able to confirm that for the Orion model.

When I had been in two different shops, I found it kind of intriguing: Newtonians under 6" were made in the cheapest possible way.  Most were afflicted by the above type issue.  I could not find well-built telescopes under 6".  If the community or searcher did locate Newtonians of this sort do point it out!  What I found instead was that 6" somehow signifies the magic boundary for for well-built Newtonians with solid tripods (of class, 1 purchase tripod/mount and ota separately but somehow this is not as cost effective).  I really don't understand why this is, but one outstanding example I presume is your below:

- Celestron Advanced VX 6" Newtonian: Comes with all the well-built Celestron VX GoTo EQ bracket (by itself this costs $799 if not on sale), and Celestron's 6" Newtonian (by itself $299).  You will save $100 if you get the bundle as the bundle cost is $899 if not onsale.
- Celestron XLT 150 OTA: This is actually the telescope just.  Fantastic optics.  Fantastic mechanics, also!  You will notice 150mm = 6" roughly.

3.)  Catadioptric telescopes utilize both (a corrector) lense plus a mirror.  Concerning pricing, it's common wisdom that these are between reflectors and refractors concerning price.  This is also where it gets a bit more complicated.  There are two common types of catadioptric telescopes.  The so-called "Cassagrain" design employs a corrector lense in front, a primary mirror in the back, and also a secondary mirror in front where the corrector is to reflect the light back to the rear of the telescope.  This light-folding pattern results in very compact OTAs.The 2 flavors are Schmidt-Cassegrain and Maksutov-Cassegrain.  The most important difference between those two scopes would be that in the instance of the mak telescope, the corrector is a meniscus type lense, and the secondary mirror is merely the silvered central part of the meniscus lense.  It's said that the smaller barrier in mak telescopes contributes to greater contrast at the cost of more magnication/but smaller fields of view.  Walking into a telescope store, and online, the possible buyer will quickly come across the Celestron NexStar or Evolution Series.  These are the models I looked at from a very beginnery point of view.  Evidently, the more income you possess the bigger you'd wish to go (up to 8" in my view).  I'll just list the Nexstar versions here as they are more cost-effective.  But if you like very techie goods with items like neighborhood wifi, phone and tablet attributes etc, look to the Evolution collection.  Take note though these attributes will likely cost you at least $200 more in contrast to an equivalently sized Nextstar model.

Celestron Series (below are the models I had been mainly considering for costs and portability):
- Celestron Nexstar 4SE
- Celestron Nexstar 5SE
- Celestron Nexstar 6SE

Orion sells Maks:
- Orion Starseeker IV 127mm

There is some discussion going on concerning the FoVs of those telescopes.  Fact: The FoVs will be narrower than comparable Newtonains or refractors.  This is why all those systems largely come on computerized mounts: with lean FoVs, a fresh beginner would quickly lose patience discovering objects without computer assistance.  The open question is: With computer aid, are narrow fields of visions a drawback.  There is a different thread for this particular discussion.  In this thread, I am only raising this because a stage the possible buyer should know about.

In my hunt what I found most surprising was that there are other variants too, things like: Maksutov-Newtonian, or Schmidt-Newtonian.  You will guess from the name which these scopes are basically newtonian telescopes with either the Schmidt or Mak edition of a corrector.  Their most important advantages are that these plates may fix for "aspherical abberations" nicely - something standard, bigger Newtonians are more likely to.  An example of this sort of extent can be found under:

- 152 Comet Hunter Maksutov-Newtonian: 6" OTA.  Cost when not on sale $699.  You will need to purchase a solid tripod/mount to decide on this OTA.  Because I need a GoTo bracket, I would need to consider the VX bracket which runs another $799.  For a novice, I believe this is pushing the outside boundaries of initial expenses.  The upside is that extent + proper mount would last a long time.

I will end this post by pointing out that in addition to the extent, an individual should plan in a budget to purchase at least 1-2 added great excellent eye bits along with a barlow lense.  This previous statemen in itself could be a whole new chapter of discussion.  However, since this post is already pretty long, I'll keep it brief and finish it here.

Anyhow, This Isn't the end-all, be-all manual, but perhaps this sharing of that which I have found so far will probably be useful to some other fresh community members also on the hunt for the holy scope :--RRB-

Cheers!