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Thread: Advantages and Disadvantages of Refractor Telescopes

  1. #11
    Don Trinko's Avatar
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    IMO; Better contrast, very portable in the smaller sizes. Most 5" refractors are considerably heavier that a 5" refrector.
    I have a 2 element ED type and do not notice any color fringe unless I use my cheap zoom EP. Don T.
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  3. #12
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    I had a D&G 6"f15,it was the telescope Iused the most,almost every day,but it was on an permanent home made eq mount.of course i'd love panetary views.
    jorge

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    Welcome Jorge.

    Thank you for your introduction to D&G. Never heard of them until now.

    D & G Optical - High quality lenses, mirrors and components for the optical industry - Manheim, PA
    Meade 16" LightBridge; Celestron G-8N Bird-Jones/motorized EQ5; Orion 127 Mak/go-to EQ5; Burgess 127f8 refractor; Sky-Watcher 5" F/5 collapsible dob; 90mm Mak/motorized EQ2; Royal Astro 76/910-GEM; Meade 60x700 refractor/alt/az; Zhumell 25x100 Coin Ops; GalilleoScope. Celestron 8mm-24mm zoom; lots of fixed EPs,some good, some..not so much. A small collection of surveying instruments; a forest of tripods; Canon Rebel Xti. Confirmed gadget junkie; Custodian of the Magnetic North Pole (Send $1.00 to Pierre each time you use a compass.)
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  6. #14
    DaveW's Avatar
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    As an added benefit, if you go with a D&G achromat your telescope will match your wife's handbag. Maybe that will increase the SAF.
    Zhumell Z10, Celestron AstroMaster 114EQ, 10x50 and 15x70 Binoculars
    Zhumell 2" UHC Filter
    Hyperion 8mm GSO Superview 30mm and a whole case full of Plossls

    Saskatoon, SK - 106W, 52N

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    Refractor vs. reflector is the most beaten topic in modern amateur astronomy.If anyone asks an advice on it , my bet is - he will be advised a lot in favor of DOB reflectors. They're great scopes with exceptional value for money and are really easy to use by a novice. But a lot of other factors will need to be considered - like space allowance to keep the scope, availability of decent vehicle to transport it, extra money to buy some trolley to move it around, laser collimator to have a play with collimation. Also wife's (girlfriend's) sense of aesthetics. Let's start then with some Cassegrain and short-tube refractor. They will be considerably more expensive per inch of aperture, especially APO or ED refractors. However, they're lighter, more compact, and better looking scopes. They're perfect scopes for the city conditions. The difference between them will be that APO refractors will offer you sharper pictures and will need no servicing whatsoever (if maybe only once) for life. Cassegrain may need to be collimated once a few years in an astro shop. Rare, but may be expensive. And a DOB will need to be collimated even more often, especially the large one (10" or more). As for optical performance, 4" aperture refractor is roughly equal or better than 5" to 6" Cassegrain or 6" DOB. There are also Bird-Jones scopes. These are short tube reflectors with long focus. If one sees a scope 114/1000 with an open tube just 500mm long - it's the one. They're not for beginners - but rather for people who find an extreme pleasure in quirks of collimation. Definitely not a match for refractors.
    A refractor or SCT (Shmidt-Cassegrain) may be very good as a starter scope and perfect as a second scope.
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    Great post MPlanet.

    Are there going to be same thread for Mewlon, CDK/MDK, R/C, mod R/C, SCt. MCt?

    The only reason everyone here doesn't own a great triplett apochromat refractor is beacuse the cost - so that conversation is NOTHING about optics and all about money. But great optics of any make and flavor cost a lot of money! And the difference is far more than the oft quoted 10%. The eye can detect very subtle differences, as can the ear... like a quintet of intruments not in tune at all vs. in tune. How do you like your music? I prefer as close to in tune as possible. What is the difference between noise, near noise, near music, and music?

    So can we please not turn this into a discussion of economics and keep it on optics and star gazing? [at least all the expensive optics I've owned i was able to sell for what I paid, all others I've taken a loss - rental fee I call it, so if you want to discuss economics of quality optics lets start a new thread just about that please] I expect to be flamed for asking it, but I just must do it.

    Achromat refractors suffer from a tuning problem, it may be more noticable on certain tunes than others, and then sometimes not at all. (But you need to know not all the light is getting into the frensel plane at ep focus) This out of tune does not bother some folks, and there are filters that minimize it depending on if the out of focus light is sent one direction ->blue, vs, the other ->red , generally visual refractors are optimized no matter what to the the greenish wavelength which the human eye is most sensitive to.

    I think ANY other comparison needs to be apples to apples, ie f/8 152mm refractor to f/8 152mm newt or 152mm f/8 SCt(if you could locate mass prod - you can't)whatever otherwise it's just apples and oranges. Less expensive models, especially mass produced ones save money in various places, focuser most important and then dew shield, rings/DTP, and overall build materiald and execution including the paint...

    Here is a link to amature telescope optics in general, and has loads of info about refractors in a comparative sense. Here is another take on optic quality in refractors and this from same source... and then one more...
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  11. #17
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    Ive owned 2 APO refractors, a 94mm triplet & a 2 lens ED80mm.
    In this battle of comparisons I can speak from first hand use that unless your strickly into Astrophotography aperture rules even over the APOs, that is UNTIL the APO refractor is a large one say 5" or more & a triplet. Focus is the most crisp & snaps into focus on a APO but on a well collimated Mak or reflector most stars look the same except the really bright ones, they show spikes in the reflector. Spiral secondary holder may stop that prob, im considering one for my Zhumell 8"er just to see if it will indeed remove the spikes.
    The smaller APOs under 4" just do not have the required aperture for light grasp for dim star clusters, galaxys, & hi Planetary mag. They do make good grab and go scopes so long as you realize the object size will be very small in the eyepiece. For taking photos tho they excell on a good mount. I don't miss either APO & I enjoyed them for what they were but 8" is 8"............................Reflectors will always rule the sky for the average soul who cannot afford $10,000 for a hi quality triplet 5" APO & mount. Not when you can buy 8" of easily portable scope for $329. Im really amazed by the quality of the primarys on the reflectors considering the cost factor. I sure wouldn't consider making one for what they cost these days. I remember when an 8" reflector was NOT a cheap item. Times have changed & for the better at least as far as equipment goes for the average Joe financially.
    The seeing really makes a big difference also, a $10,000 triplet is usless on a windy bad seeing night as well as any other scope.
    Im very happy with what ive finally settled down with after owning so many types of scopes, I think ive finally found my comfort level in size(portability), price range & light grasp.
    Dave
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    I agreed with you Dave

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    Dave - Agree with you as well. Got a ten inch reflector as my main scope and a five inch sct as a grab-n-go. Love 'em both, but would also like a refractor, since each has complimentary strengths and weaknesses.

    Thanks to all of the posters. The posts have been well written and thoughtful.

    Clear, stable, and dark skies to all - Gene

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    A biased view follows - I have a 8' ExploraDome with a 29" wide shutter opening...Oh and my interest is limited to imaging. The Eyepieces are for the Finder Scope, in my case.

    Plus
    Easy to get round Stars
    A quality APO will rarely need collimation, as typically the Factory gets it right.
    In my Dome, I have yet to have a Refractor frost.
    Using Clam Shell mounting really reduces Scope flexture.
    Typically have sufficient back focus to allow for Filter Wheels, AO, FF and/or FR
    Camera mounts at the rear, making it easy to get to.
    Focusing does involve mirrors, so never any mirror flop
    Important to me->Diameter is small, so side by side Refractors don't take up shutter width, meaning longer imaging sessions than say, my AT8RC.
    Long life, as good lens tend to stay functional. The glass tends to be more stable than some optics, such a mirrors open to atmosphere
    Does not require fans and wiring for same

    Downside
    Tend to be limited on Focal Length
    Focal length grows the length, which makes for a dangerous baseball bat swinging in the Dome. Not Good!
    To get longer Focal Lengths requires longer Scope length and increasing the Focal Ratio. Higher Focal Ratios tend to make imaging DSO tougher, as longer data collection time is required. Especially true for Ha imaging.
    As already stated, cost is high. The better the imaging Scope, generally, the higher the price.
    Long Scopes are awkward to handle.
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