Author Topic: Did you know of these different types of telescopes? (Thread from a beginner to  (Read 51607 times)

William Mendoza

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Well,

That is supposed to be a beginner thread from a beginner to a beginner as I'm pretty sure everyone else knows about them.  I thought I'd just share with new people what I discovered in my journey of just picking a telescope great for my own needs (still continuing at the time of writing).

3 main Kinds of telescopes:

1.)  Refractors: 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 bright subjects (ak chromatic abberations) that are the consequence of different colours of the light spectrum being bent into different degrees.  To combat this symptom, higher quality lenses were developed.  Telescopes which have these lenses are called achromatic telescopes.  More complex setups contain different concave and convex lenses to focus different colours into one focal point.  These sorts of telescopes are called apochromatic telescopes.  Because these telescopes contain many lenses with many surfaces, so that each have to be finely crafted, they are the most expensive.  Prices increase quickly. . .and for all these telescopes it isn't too rare to see costs as large as 10K to get a moderately sized siystem (5-6").

To begin though, someone does not have to pay exorbitant amounts.  Here are a couple of (mostly achromatic) telescopes:

- 102mm Achromatic Refractor: 4" telescope with great broad field of vision.  I have observed purchase costs as low as $399 for the OTA only.
- 127mm Achromatic Refractor: 5" telescope with greater light catch then the model above.  Regular costs are approximately $599.

I have read many good reviews.  Great price for quality achieved.  Obviously, at those prices you're not likely to completely remove purple-finging, but it shouldn't be very noticeable with those achromats.  Bigger sizes are also available, but they, in my opinion start getting unwieldly big.  Smaller sizes are going to be cheaper of course, but for those you will be Limited to brighter objects (such as planets, and the very brightest and largest nebulas and DSOs)

2.)  Reflectors: These are "mirror-based" telescopes.  Rather than lenses, mirrors are utilized to bundle the light.  They are MUCH cheaper because, instead of polishing 4-12 surfaces, one just wants to do a fantastic job on the main mirror (1 coating).  It is common wisdom that when it comes to bang for the insect, this is where you will likely discover it.  I personally have been exploring 5" newtonians onto a Go-To bracket, and discovered that basically, the OTA is the exact same piece of equipment in each of them.  Examples below:

- Celestron Skyprodigy 130:
- Celstron 130 SLT: The hyperlink to this is in fact a review significance to show that despite the concerns under, people can be happy with these sorts of systems.
- Orion Starseeker IV 130:

Individuals on these forums will quickly point out that there are numerous problems with those scopes.  Despite excellent optics of the mirror, these scopes come on quite undermounted tripods - at the Skyprodigy and SLT system.  I can attest to this as I looked at the tripods for the first 2 models.  I have yet to see that the Starseeker IV tripod.  It appears to be more solid and might be okay actually.  Another piece I managed to confirm though is the Celestron telescopes mentioned above have a plasticy looking focuser piece.
Individuals on the forum say these focusers will stop great accuracy at greater (~200x) magnifications.   I have never been able to confirm that for the Orion model.

When I was in two unique shops, I found it sort of intriguing: Newtonians under 6" were made in the cheapest possible manner.  Most were afflicted by the above type issue.  I couldn't discover well-built telescopes under 6".  If the community or searcher did find Newtonians of this kind do point out it!  What I discovered instead was that 6" somehow represents the magical border for for well-built Newtonians with strong tripods (of course, one buy tripod/mount and ota individually but somehow this is less cost effective).  I don't know why this is, but one outstanding example I think is the below:

- Celestron Advanced VX 6" Newtonian: Includes the well-built Celestron VX GoTo EQ bracket (alone this prices $799 when not on sale), and Celestron's 6" Newtonian (alone $299).  You may save $100 when you buy the bundle as the bundle cost is $899 when not onsale.
- Celestron XLT 150 OTA: This is actually the telescope just.  Great optics.  Great mechanics, too!  You may notice 150mm = 6" roughly.

3.)  Catadioptric telescopes utilize both (a corrector) lense plus a mirror.  Concerning pricing, it is common wisdom that these are between reflectors and refractors concerning cost.  This is also where it gets somewhat more complicated.  There are two common types of catadioptric telescopes.  The so-called "Cassagrain" design uses a corrector lense in front, a main mirror in the back, and a secondary mirror in front where the corrector would be to reflect back the light to the back of the telescope.  This light-folding pattern results in quite compact OTAs.The 2 tastes are Schmidt-Cassegrain and Maksutov-Cassegrain.  The main difference between these 2 scopes are that in the instance of the mak telescope, the corrector is a meniscus kind lense, and the secondary mirror is just the silvered central part of the meniscus lense.  It is said that the more compact barrier in mak telescopes leads to greater contrast at the cost of greater magnication/but smaller fields of view.  Walking into a telescope shop, and online, the possible buyer will quickly come across the Celestron NexStar or Evolution Series.  These are the models I looked at from a really beginnery perspective.  Obviously, the more income you have the larger you'd wish to go (up to 8" in my opinion).  I'll just list the Nexstar versions here as they are more cost-effective.  But if you like very techie goods with things such as local wifi, tablet and phone control features etc, visit the Evolution collection.  Take note though these features will likely cost you at least $200 more compared to an equivalently sized Nextstar model.

Celestron Series (below are the models I was mostly considering for prices and reliability):
- Celestron Nexstar 4SE
- Celestron Nexstar 5SE
- Celestron Nexstar 6SE

Orion sells Maks:
- Orion Starseeker IV 127mm

There's 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 mostly come on automatic mounts: with lean FoVs, a fresh beginner would quickly eliminate patience finding objects without computer help.  The open question is: With computer aid, are narrow fields of visions a drawback.  There's a different thread for this particular discussion.  In this thread, I am only raising this as a stage the possible buyer ought to know about.

In my hunt what I found most surprising was that there are other variations as well, things such as: Maksutov-Newtonian, or even Schmidt-Newtonian.  You may guess from the title which these scopes are essentially newtonian telescopes with the Schmidt or Mak edition of a corrector.  Their main advantages are that these plates may fix for "aspherical abberations" nicely - something regular, larger Newtonians are prone to.  An example of this Type of extent can be found under:

- 152 Comet Hunter Maksutov-Newtonian: 6" OTA.  Price when not on sale $699.  You'll have to buy a good tripod/mount to decide on this OTA.  Since I need a GoTo bracket, I would have to think about the VX bracket that runs another $799.  For a beginner, I believe this really is pushing the outside boundaries of initial expenses.  The upside is that this extent + proper mount would persist for a long time.

I will end this article by pointing out that along with the extent, an individual should plan in a budget to buy at least 1-2 added great quality eye bits along with a barlow lense.  This last statemen in itself may be a completely new chapter of conversation.  But since this post is pretty long, I'll keep it brief and end it here.

Anyway, This Isn't the end-all, be-all manual, but maybe this sharing of that which I have found so far will be useful to other new community members also about the hunt for the holy scope :--RRB-

Cheers!



KevinKat

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