Star Optics in QLD have the skywatcher ED80 with finder, diagonal, eyepieces and case listed for $799. Andrews prices have increased considerably in recent months and are no longer automatically the best prices.
The ED80 is very easy to sell used due (i think) to the high performance lens - very close to a true apochromat.
Ok I am back after checking the website and have a confession to make.
I have been trying to find a bigger scope than the 80mm refractors. However I think this may need to change.
My initial target was the 100/110mm ED doublets, but for the same price I can get a 80mm triplet (well thats the case of the Stellarvue scopes at least).
My initial hesitation with the 80mm scopes stems from my lack of understanding about what I should expect to see therough them. I want to know whether I will be able to visually observe DSO's with an 80mm tripolet ED APO?
Having never looked thrrough a refractor I really need to calibrate my expectations before I buy, so as to avoid dissapointed.
80ED are usually a widefield scope which are very good for astrophotgraphy but for visual work aperture generally rules and a large DOB or Newt would do better for those DSO's
One scope doesn't suit all purposes. You need to get an 8" or 10" for DSO visual observation. How about an 8 or 10 inch dob now for visual use, followed by an ED80/portable mount for quick looks and solar observation(with the correct filter), then down the track an EQ6 to mount both of those scopes on for imaging?
You'll be sorely disappointed with the DSO views through a 3" or 4" refractor.
Filters do make a difference, like the Sirus -V I have on loan. However, no free lunch, they can give a yellow cast and dim the view some what.
Still I love my 150mm refractor and I am used to the violet fringing.
I will include a pic of a bright moon done with the Achromat, -V filter.
Keep in mind a Newtonian is a masive bang for your buck and are totaly color free. I also have a 12" dob thats awesome.
Just flicking through some sources on the web a lot of copy and paste but I hope this helps you understand the differences.
Types of Refractors
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Achromatic Refractors
This refractor type is the least expensive and is traditionally a two- or three-lens system made from crown and flint glass. These types of glass were developed in the 1880's to reduce "chromatic aberration", or color fringing around bright objects. While the 60mm altazimuth or equatorial refractor is a popular choice as a first telescope, consider spending a little more and investing in either an 80mm or 90mm refractor. The glass is usually of higher quality, the coatings are better and the additional light-gathering will allow you to see brighter images in greater detail than those produced through a smaller, mass-produced lens.
Brapochromatic Refractors
The first apochromatic (also referred to as "APO") lens was invented by the German physicist, Abbe. Instead of basic two-element designs like the achromatic, the apochromatic refractor uses either three or four lenses, each made of a different material; a two-element lens, one of which is fluorite; or a newer two-element design of ED, or "extra-low dispersion" glass. The use of these newer materials and designs allows for a system which is virtually free of color fringing or chromatic aberration, which is the biggest obstacle to overcome when producing any refractor. Faster focal length refractors, while sought after because of their portability, also have the most stubborn color fringing, so the invention of the apochromatic design is a boon to those of us who want to take our refractor everywhere. Of course, apochromatic refractors are more expensive, but the views through them are exquisite, providing a velvety background and pinpoint star images.
Pro's:
Provides sharp images coupled with rugged construction
Longer focal lengths provide better contrast while shorter APO/ED focal lengths give great contrast AND portability
Because there is no central obstruction, there is also no power that is "too low"
Closed tube prevents dust & moisture from entering the system
Lenses very rarely need to be collimated or "aligned" (Lucky you)
Smaller models are less susceptible to thermal currents
Makes a good spotting scope because image is "right-side up"
New, apochromatic designs (shorter focal lengths) of 4" or less are extremely portable
Con's:
Becomes expensive over 90mm (most expensive per inch of aperture of all designs)
All refractors except the more expensive APO designs have at least some chromatic aberration (purple fringing around bright objects)
Narrow field of view in the longer focal lengths
Long focal length refractors become very cumbersome in apertures over 90mm, and need a heavy mount to support them There are two basic
Mounts
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Altazimuth
Altazimuth mounts (also called "Alt-Az" for short) are the most simple to operate, and work best for spotting scopes or a telescope where the bulk of it's intended use is for daytime viewing. These mounts move the optical tube in straight lines... either up and down or back and forth (north/south/east/west), and include the tripod. Some alt-az mounts have "slow-motion control cables" to help you move the telescope slowly in any of these directions whilst viewing an object. On alt-az mounts, these cables hang down for easy access to your hands, or else exist as knobs or dials on an equatorial mount. Camera or video tripods would be a good example of an alt-az mount.
Equatorial
To put it simply, an equatorial mount allows you to follow objects as the earth rotates, which causes those objects to seem to move through the sky. The mount is set at your latitude (mine is 33° North), and then is polar-aligned (to either the North Celestial Pole in the Northern Hemisphere or the South Celestial Pole in the Southern Hemisphere). After that, you just need to move the telescope, usually via it's slow-motion control cables or dials, in either Right Ascension (east to west movement of the stars, or celestial latitude) or Declination (north-south movement of the stars, or celestial longitude) to follow a planet or deep-sky object as it slowly moves through the field of view as seen through your eyepiece. This type mount is a bit more bulky than an altazimuth design, but it is desirable in that you can usually attach an optional motor to the mount, which counteracts the earth's rotation automatically. These mounts also come standard with a tripod attached.
Report Card
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E = excellent VG = very good G = good F = fair P = poor
3” to 4.5” reflectors
Portability: E
Ease of setup: VG
Ease of use: VG+
Performance on the Moon: E
Performance on comets: F
Performance on double stars: VG
Performance on galaxies and nebulas: F
Performance on planets: VG
8” reflectors
Portability: F
Ease of setup: F
Ease of use: VG+
Performance on the Moon: E
Performance on comets: VG
Performance on double stars: VG
Performance on galaxies and nebulas: VG
Performance on planets: VG
I was reading through Hartung's bible and noted that the author recommends Refractor prime for astrophotography. Furthermore, there is a mention of how the false detail is presented to observers. It might be worth reading more about this.
Last edited by Manav; 24-09-2009 at 05:15 PM.
Reason: Adding content
Filters do make a difference, like the Sirus -V I have on loan. However, no free lunch, they can give a yellow cast and dim the view some what.
Still I love my 150mm refractor and I am used to the violet fringing.
I will include a pic of a bright moon done with the Achromat, -V filter.
Keep in mind a Newtonian is a masive bang for your buck and are totaly color free. I also have a 12" dob thats awesome.
David,
I'm assuming it's the Skywatcher 150mm achro you have. Can you tell me please, is there a perceptible difference when viewing the moon and planets through the refractor versus the dob. I understand they're very different sizes so it may be difficult to make a comparison. But I'd appreciate your thoughts.
Paul, the 12" dob is a big and heavy, difficult to set up. It has killa views of deep sky objects.
I find the 150mm refractor much easier to transport and set up. The wide field views with a 30- 40mm wide angle eye piece gives me super contrast and pin point stars.The planerary views are very contrasty albeit with some violet fringes.
I will be able to do some deep sky imaging with the refractor but not the dob.
It's horses for courses and I guess thats why I have both.
Also remember the dob takes quite a while to cool to give it's best performance and is more affected by atmospheric conditions.
Last edited by DavidU; 24-09-2009 at 07:19 PM.
Reason: spelling
You'll be sorely disappointed with the DSO views through a 3" or 4" refractor.
Whilst I agree with most of what you said, I have to disagree with the above. A good quality 4" scope from dark skies, combined with a quality UHC filter will give you many hours of pleasure imho. Sure, a larger aperture scope will show more, that's not even going to be debated.
Paul, the 12" dob is a big and heavy, difficult to set up. It has killa views of deep sky objects.
I find the 150mm refractor much easier to transport and set up. The wide field views with a 30- 40mm wide angle eye piece gives me super contrast and pin point stars.The planerary views are very contrasty albeit with some violet fringes.
I will be able to do some deep sky imaging with the refractor but not the dob.
It's horses for courses and I guess thats why I have both.
Also remember the dob takes quite a while to cool to give it's best performance and is more affected by atmospheric conditions.
Yep,
understood old boy. Thanks for that. I have a 12" LB, but I'd quite like a refractor as well. Hmmm ....
hi paul
i have the skywatcher 6" refractor, it has some colour on jupiter and the moon, but on most DSO you wont see any, i have bought a baader semi-apo filter for the colour, and im really pleased with it, it adds almost no color to the image, like the cheaper minus-v filters do.
thanks for that. How do you find the views (of the moon or Jupiter for example) through the refractor differ from the same thing viewed through a dob or mak? Is there a difference? Some say they are much more contrasty and all round nicer for moon and planets, - what are your thoughts Alfi?
Another note on using refractors for visual observation..
I have owned quite a lot of scopes.. whilst the current 80mm triplet refractor is by far the best quality scope I've owned, views through it on the other hand are sorely disappointing.. my 8" newt that cost me $350 gave much better views than this 80mm triplet, photographcially, the 80mm triplet provides sharper, more contrasty images, but through an eyepiece, there is no magical replacement for aperture.. no type of fancy glass in a 80~110mm refractor is going to beat 200mm of aperture.. just like 200mm is not going to beat 300mm.. Visual astronomy is about the only time where size really does matter, and there is no such thing as too big..
As others have said. there is no single scope for every task.. the 80mm ED refractors are great for lunar observation, and great for wide field photography, an SCT or newtonian might be better for DSO's...
As far as refractors go...
Stellarvue scopes are great, William optics scopes are of similarly high quality, the Skywatcher ED80 is well renowned for great quality optics, the focuser leaves a little to be desired, but thats a cheap fix.. the Orion ED80 is a great scope too, however they are hard to come by.. On the second hand market, the Orion and Skywatcher ED80's come up regularly...
As for the triplet/doublet debate... I would rather a top quality doublet than a cheap triplet. Call me crazy, but I tend to think that a high end doublet will outperform a cheap, poorly made triplet...
If second hand for the refractor is an option - I strongly recommend you look at astromart.com in the US. You'll save a packet, the dollar is strong and the dodgies are very scarce in the astronomy community.
The second hand EP's i've secured from the states at a bargain is amazing.
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