From Eddgie's graph you can see that they are almost at the level of a perfect 4-inch telescope. For example the Orion EON 110ED f/6.0 Apochromatic Refractor sold for about $2000, a price comparable to a triplet's price (like the larger EON 130ed). I am thinking that is why you don't see BK7 as a flint in ED and SD "apo" doublets. So not cheap when it is not consistent IMO. But they impressed me mightily in terms of optical performance as compared to refractors that I spend far more money on. Otherwise people would, BK7 itself is the cheapest glass. So my calculations are a little different then yours. Retinae are more sensitive to contrast that is easier to achieve in a good doublet. Should be almost indistinguishable from an APO triplet.,,,not just for visual but for imaging as well. I'd prefer a triplet. Tips and tricks I avoid the use of "cheap" because it has too many possible interpretations, it can mean poor quality, shabbily made, or it can mean "inexpensive." Dramatically better. Next up would be an FPL 51 doublet. So without knowing all the parameters, will be hard to tell. It would be almost impossible to see any chromatic defocus even on the brightest targets when used visually. You currently have javascript disabled. Being a visual observer only I'd prefer a doublet. For example, a perfect 6" will have lost 50% contrast at about .4 times its limiting frequency, while the 6" f/8 achromat will have lost about 70% contrast and for detail this size, will not be that much better than the best 4" Apos.. I've had three triplets and two of them had collimation issues. My AT102 confirms a lot of the buzz about this ED. a Doublet), Apochromat brings 3 wavelengths to focus (i.e. I have never seen one in person, but mechanically, the scope looks nice. That is what my comments meant to reflect... Well don't know if what you are saying is a reasonable qualification for "cheap" since it is sliding too much. In last place would be a doublet using non-ED glasses. For visual use at 4", an FPL51 triplet is sensibly perfect. Cool down time is better and scope is lighter. Why is using a Lanthanum flint with FPL-53 or FCD100 a better combination than using a BK7 flint? SV503 ED Doublet objective is designed with one SPL-51 ED Glass and one Lanthanide glass. ED stands for Extra-low Dispersion, glasses and fluorite with significantly lower dispersions than normal crown glasses. If the goal is visual use I prefer the doublet. $1300 seems more reasonable. Plus, the Tessar doublet makes it a better performer than a Cooke triplet. From above statement I can see no point what so ever for visuel purposes as you are splitting hairs in optical gain it’s not the facts or figures which is the most important or the type of glass it’s the veiws at the end of the eyepiece that counts. The best doublets are superb performers that most triplets cannot reach in sharpness and contrast under real world observing conditions in most climates. One was an Orion, one was a Vixen, both had superb optics) I think they are a good value. Ah, but what if you want to image. Several functions may not work. A good triplet scope will always be more expensive than a similar quality doublet. Aperture isn't so important either, as a top class figure on a 100mm scope has more impact on the planetary view than the extra aperture of a not so well figured 130mm scope. We are talking like 1/20th wave difference in color correction or 1-2% difference in mid-spatial frequency MTF. I think the Lanthanum flint in the doublet is a big deal. There are a number of them that are quite distinguishable also LOL........If you aren't going to do imaging then buy a quality doublet and spend that extra money on some great EP's........ For 3 pieces of glass to be made to the same degree of perfection as 2, it will take 50% more time and effort than with 2. Cheap is obviously relative to one's situation. I think it might be driven based on the intended use. A camera lens (also known as photographic lens or photographic objective) is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media capable of storing an image chemically or electronically.. So it is worthwhile, but one could do so much better with a better flint. For Lunar however I find the Triplets a little more "clean" (purer tone) which I find aids in contrast. As you can see, a 4" FPL 53 f/9 doublet (Skywatcher 100ED f/9) can have better contrast on some larger detail than a 6" f/8 non-ED scope (Achromat)!!!!! I will let others discuss the differences between an ED doublet and an APO triplet. The Orion EON 110mm ED doublet sold for $1300 and the EON 130 APO triplet sells for $3000. Now if one could have a CG4/100EDf9 delivered to the door for $500 I would call it cheap and expect a new Golden Age of backyard stargazing. Thanks Eddgie, that cleared a lot up for me. The Vixen doublet always works and I will likely never buy another triplet. If you want an ST80 cheap for $50, you are saying 50% off street price. The reason would be cost. For me the deciding factor would be the figure. Edited by Craven, 14 February 2021 - 02:55 PM. This plot shows how much contrast is lost for the perfect aperture.
Cid Moosa 2 Release Date, Declaratory Judgment Motion, Firewatch Ps4 Amazon, Wow Bestiary Pdf, Kak Horosho Bernadette Meaning, Djurens Parti Valresultat 2018,
