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Thread: Building a refractor

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    Default Building a refractor



    I am interested in building a refractor and have not found much information regarding construction. Does anyone know of any good plans for building one? I have tried searching, but most results include cheap little refractors. This will be my first DIY scope, so my knowledge is very limited. I figured I would buy my lens from SurplusShed, but other than that, I have not figured out what to do. Any help would be greatly appreciated! Thanks
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    More ATM folks build reflectors, primarily Dob's because it is less complex, generally less expensive, and a bit more forgiving, especially for larger apertures.

    Most surplus primary cells for a refractor are achromatic, so about 130mm is the limit, because chromatic aberration and cost become prohibitive as the objective cell sizes increases. When you can find them, SurplusShed achromats in the 120mm - 130mm size with suitable focal lengths are in the $120 - $160 range. A similar size achromat from a supplier like Edmund Optics (new) is about $1000 for comparison.

    Another issue is size, both the length and weight of the OTA as you move above 130mm.

    That being said, there are a few folks who go down this road. The usual process is to first search for a primary objective cell that you find suitable in terms of aperture, optical quality, design, and cost.

    Once the primary cell has been acquired, you'll have the data you need to actually begin a design. There is a well-done shareware utility known as MODAS that can be used to support the optical design.

    MODAS requires the physical measurements of the objective cell components (each lens element), along with the properties of the glass in each element. Using that data, MODAS produces the necessary supporting materials including ray diagrams, tabulation of critical measurements, and performance estimates.

    This material gets collected, and then transformed into a working sketch or drawing which forms the basis of the refractor's working design.

    There is a fairly common design, most often know as the "SurplusShed 127mm Refractor" that's floating about the internet. This is the most common style amateur refractor about these days.

    I'll sort through my reference collection and see if I can find suitable design references for you - I'll add them to this thread.
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    Here is the annotated "short list" of links/references from my library:

    First and foremost, from Willman-Bell, Norman Remer's "Making A Refractor Telescope":

    Making a Refractor Telescope, How to Design, Grid, Polish, Test, Correct and Mount a Doublet Lens by Norman Remer

    Though the focus is on grinding your own achromat, the reference is complete, and if you're serious about a DIY refractor, this is a must-have. It comes with a spread-sheet based utility for design support.

    The "classic" Surplus Shed 127mm refractor:

    Telescope Reviews: Surplus Shed 127 mm refractor build

    The level of activity on this thread/reference varies with the availability of the SurplusShed 127mm objective. In its current incarnation, its been live for more than a year. If you search Astromart, you can find a guy who now makes a collimatible cell for the elements from the SS 127mm - it replaces the thermoplastic shell and allows collimation.

    Here is a paper from Larry Browning at SDSU that describes his PVC refractor:

    http://www.engineering.sdstate.edu/~...lans/scope.pdf

    This is small aperture, but well done.

    Here is another small 80mm refractor that's low-to-no-tech:

    Brent's Astronomy Pages - Deep Sky Objects

    Here is **** Parker's 6" refractor - there are no instructions or plans, but a good description of the undertaking/ideas:

    Dick Parker's Telescope Mirror Workshop: Refractor Telescope Project

    And last, but definitely not least, a link to MODAS, which is invaluable, excellent, and a definite necessity for ATM folk, whatever you're building:

    MODAS Optical Design Program - software overview
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    I'm gonna stick this thread.
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    Hi boye, i completed my refractor last year. Here is the link:MY 4" DIY Refractor

    To start with you need to decide on the objective. Lot of chinese achromats are available at ebay. here is the link: Achromat lenses at ebay stores

    You require aluminium tubing, focusser, diagonal & viewfinder. Cell adaptor to be machined that holds the lens cell & the tube in place then the cradle section. Follow my pictures, that should help you.


    Regards,
    Anil




    Quote Originally Posted by boye8117 View Post
    I am interested in building a refractor and have not found much information regarding construction. Does anyone know of any good plans for building one? I have tried searching, but most results include cheap little refractors. This will be my first DIY scope, so my knowledge is very limited. I figured I would buy my lens from SurplusShed, but other than that, I have not figured out what to do. Any help would be greatly appreciated! Thanks
    santosh83, JFD and Frankus like this.
    http://anilmn.blogspot.com/ [ MY DIY PAGE]

    4" CARTON Refractor @ f/13

    If god had intended us to use reflectors he would have aluminized the back of our eyeballs.

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    Quote Originally Posted by boye8117 View Post
    I am interested in building a refractor and have not found much information regarding construction. Does anyone know of any good plans for building one? I have tried searching, but most results include cheap little refractors. This will be my first DIY scope, so my knowledge is very limited. I figured I would buy my lens from SurplusShed, but other than that, I have not figured out what to do. Any help would be greatly appreciated! Thanks
    Try looking for the definitive book on the subject by Albert G. Ingalls , , Ameteur telescope making , vol 1-3.
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    Quote Originally Posted by AustinPSD View Post
    Here is the annotated "short list" of links/references from my library:

    First and foremost, from Willman-Bell, Norman Remer's "Making A Refractor Telescope":

    Making a Refractor Telescope, How to Design, Grid, Polish, Test, Correct and Mount a Doublet Lens by Norman Remer

    Though the focus is on grinding your own achromat, the reference is complete, and if you're serious about a DIY refractor, this is a must-have. It comes with a spread-sheet based utility for design support.

    The "classic" Surplus Shed 127mm refractor:

    Telescope Reviews: Surplus Shed 127 mm refractor build

    The level of activity on this thread/reference varies with the availability of the SurplusShed 127mm objective. In its current incarnation, its been live for more than a year. If you search Astromart, you can find a guy who now makes a collimatible cell for the elements from the SS 127mm - it replaces the thermoplastic shell and allows collimation.

    Here is a paper from Larry Browning at SDSU that describes his PVC refractor:

    http://www.engineering.sdstate.edu/~...lans/scope.pdf

    This is small aperture, but well done.

    Here is another small 80mm refractor that's low-to-no-tech:

    Brent's Astronomy Pages - Deep Sky Objects

    Here is **** Parker's 6" refractor - there are no instructions or plans, but a good description of the undertaking/ideas:

    Dick Parker's Telescope Mirror Workshop: Refractor Telescope Project

    And last, but definitely not least, a link to MODAS, which is invaluable, excellent, and a definite necessity for ATM folk, whatever you're building:

    MODAS Optical Design Program - software overview
    I bought a 103mm/1575mm jaegers lens from surplus shed, crystal clear from edge to center, that aperture & focal length has very little Chromatic Aberration also. I'm still working on it though although I did build a mock-up out of PVC 1st to check tube length.
    I got the collimatable lens cell, dew shield, & focuser from crawford machine;

    nice site, he takes calls too.

    Crawford Machine - Home

    here are three sites for tubes:

    Tubing

    Parallax Instruments, Inc. - Aluminum Telescope Tube Pricing

    Aluminum Tube, Pipe, & Plate | 6061 Aluminum Tubing | Aluminum Suppliers | Aluminum Round Tube

    Good luck,
    Z

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    That's a long slow tube Z - Mounting should be fun...
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    Already have two mounts for it, one's a go-to, the other a sealed bearing alum. fork mount. It's a great planet killer, and with that focal length, there's no need for Barlow lenses.
    A 155mm APO ED's coming up next.
    Z

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    Boye,
    A couple of things about f/15's is that they make excellent "planet killers", moon too. Even some of the brighter galaxies like m-81.
    Then to make things even easier, since magnification is better on longer scopes, you don't need Barlow lenses, and once you get focused on an object, you don't need to keep adjusting, in fact, I've focused in on Venus before, then pointed at Jupiter (When Jupiter was still visible) and didn't need to re-focus! no kidding. I could even point it at the moon after Venus & same thing, maybe a little twist. But that is an advantage of long scopes, you can keep your hand off of the focus knob.

    When deciding which f/ratio to get, determine what you want to use the scope for.
    f/15's are slow scopes which means less light and the longer a camera shutter would need to stay open if you're taking pix, the stutter would open & shut SLOWER, hence the name "slow".

    Short f/ratios have less magnification,and shorter tubes, but allow more light in and are termed "fast telescopes" (stutter can open & shut more quickly since more light enters the tube. These scopes are good for deep sky and dimmer galaxies & nebula's.

    Sometimes a good compromise for a 1st telescope is something in between like around f/8 - f/9. However, an f/15 is a good 1st scope too, due to the fact that Surplus Shed's 103mm lenses are cheap, approx $149.95 & like I said, great for planets, moon, some galaxies etc...

    (Looking through the f/15, the moon is more awesome than any picture you've EVER seen, and even some shorter scopes too, no kidding!)
    The only con would be length, but as I told my son who is 18, it is a good "young man's" scope because a young guy like him would have no problem moving it around for obvious reasons! Different than an older guy like me who probably needs a little pocket scope that's easy to carry! (I'm just kidding you guys!)
    Truth is, f/15's aren't really that heavy anyway.

    Magnification's also interesting and here is a cool site on the subject:

    Magnification (Power) and Using Eyepieces | SpaceRef - Your Space Reference

    Looks like several people have offered advice and specs on scopes, the advice & specs are all good, so you really can't go wrong, if you choose f/15, I'll give you my specs.
    Z
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