Achromatic or Apochromatic??

[trevorw]

I have both the ED is better for photographic work.

[Eclipse]

I have a Stellarvue 102ED. Built like a tank, came with a Feathertouch focuser - a joy to use, and fantastic views. Worth the extra.

[star drop]

Hi Eclipse,

Welcome to Astronomy forum.

[Eclipse]

Thanks, nice to be here.

[admin]

Hi Eclipse welcome to the forum I am not sure what the difference is yet (not enough research) but I am quite happy with the ED100 refractor - no psychedelic colors here.

[matthewota]

I have and ED-80 (doublet) apochromat and I am quite satisfied with the optics. A great value at $500.

[Tom Clark]

Sorry for butting in, but I saw your post and thought I would put in my penny's worth. I vote for the plain old achro.

To explain, I am not really a refractor guy, but a visual astronomer. However, I have looked thru thousands of scopes over the years. I have had a 5" f/5. Horrible color!
Next was a 4" Televue. Nice scope but dim views. Current is a 5" f/9 achro. Cost a whopping $400. When used as a wide field scope the views are fantastic! The star images are like tiny bright diamonds. Every one who looks thru it asks what kind of scope it is. I just say that is a P.O.S. Chinese refractor. (Use your imagination.)

Note, when it arrived it was way out of collimation. I collimated it with my Cheshire right away. Pay attention to collimation, no matter what kind of scope you are talking about.

It is perfect for my needs, and a triplet would not be any better. Bottom line is what are you going to use the scope for? Many friends in my neighborhood have small refractors that they paid thousands for, and their astrophotos are wonderful. But that is another side of the coin.

Sorry to butt in. I'll go back to the reflector column now…

[MarkM]

Originally Posted by Carlos_dfc

I absolutely love my ED100, if financial considerations meant I had to sell my gear, the ED would be the last thing to go.

Although I can see RussL's point, I'm afraid that I couldn't 'take' the drop in resolution that would happen by dropping from 100mm aperture to 52mm (the size of the mask built into my ED100's cap) or less.
100mm of aperture is capable of splitting double stars down to about 1.1 arcseconds separation - whereas 52mm only gives resolving power of around 2.3 arcsec.
Or to put it another way - you'd struggle to split the fairly bright 'Epsilon Lyra' (the Double-double) into it's 4 components with 52mm, same for Castor, Alnitak, Porrima, Epsilon Bootes..... and you wouldn't be able to see the Hadley Rille on the Moon, nor the Plato craterlets - whereas, I've 'done' all of those easily with an ED100

I'm doing a lot of double/multiple observing lately, and the ED100 is a briliant scope for it - it resolves right down to it's theoretical Dawes limit, and it's colour fidelity hasn't been significantly bettered by any frac I've ever looked through.

Admittedly, I could split all but the tightest doubles with a similar-sized achro, but the views are much nicer in the ED

Personally though - I couldn't justify the huge difference in price from ED optics, to a premium triplet made by - say - Televue for example.
The slight gain in performance, for me, wouldn't be worth the enormous price-jump.

ED optics.....
90+% of the performance of a premium triplet apo
For about 25% of the price

Great stuff, Carlos. Makes me want to add one of these these scopes to my collection (which is still n=1 at this point). I would love to have a fine refractor of this size just for doubles and planets. Someday.

[RussL]

I can say that my new 120ST f5 does show a lot of color on bright objects (unless I use an aperture mask), and high power is a bit soft, but for richfield astronomy at low power it is a winner. Sometimes, though, it works pretty darn good on planets when it's a good night. I have considered getting an Orion 90mm f10.1 achro to supplement it. I agree with Carlos that it's all about the intended use of a scope that matters. Oh, and even though I have an 8" SCT and 6" Newtonian, I have become addicted to refractors and the type of images they produce.