80ED got beat by 80mm achromat on Saturn?

[heliumstar]

Is it possible? Do you think it is possible?

[Anthonyexmouth]

need a few more details than that. 

[Galen Gilmore]

What specific scopes are you referring to? Maybe the achromat has a higher f/ratio, or maybe you didn't give the 80ED sufficient time to cool down?

[Alien 13]

I would think so if its a long achromat, after all so is the ED 80.

Alan

[Ben the Ignorant]

Nope, I happen to own an 80mm f/7.5 achro and two 80mm apos, a doublet and a triplet. Both apos are carefully centered with their factory screws, the achro has aftermarket centering screws to reach the same precise adjustment, and there is no way it will outperform the others in any regard.

The only point in favor of the achro is its slightly whiter image when my triplet (and other FPL-53 triplets) adds a faint yellowish tinge to what it's aimed at. Besides that the apos are superior in sharpness, resolution and contrast. Lateral color and edge aberrations are minimal, and of course, the amount of on-axis false color is no contest.

The crown of false color is about three or four times fainter and narrower in the semi-apo, and simply non-existent in the triplet up to 274x. Still, the achro is a bargain and a travel scope you won't be afraid to bring to hazardous places because it costs only 115€.

[heliumstar]

The scopes are Starwave 80ED and Vixen A80M. The eyepieces are Vixen SSW 3.5mm and Baader Morpheus 4.5mm with 2x BST Barlow. Same time cool down - aprox. an hour outside.

Cassini division and even a hint of belts visible on Vixen duo while ED mushy. Surprisingly on Jupiter they provide the same mushy view ( seeing and low in the sky ).

It just shows that no matter the technical specifications what matters is what you see with your eyes. Both scopes are great though!

[Anthonyexmouth]

2 minutes ago, heliumstar said:

The scopes are Starwave 80ED and Vixen A80M. The eyepieces are Vixen SSW 3.5mm and Baader Morpheus 4.5mm with 2x BST Barlow. Same time cool down - aprox. an hour outside.

Cassini divison and even a hint of belts visible on Vixen duo while ED mushy. Surprisingly on Jupiter they provide the same mushy view ( seeing and low in the sky ).

It just shows that no matter the technical specifications what matters is what you see with your eyes. Both scopes are great though!

well theres the answer then. the vixen is something like f10/11 i think. the starwave is a much wider field. 

[heliumstar]

Should it matter at practically the same magnification?

[John]

How does the 80ED star test ?

I would expect both scopes to put up a similar performance at 150x - 200x.

 

[Ben the Ignorant]

Vixen has very high standards of glass figuring and polishing, chinese scopes a little less so, especially the older ones. In that case the advantage of ED glass could be offset by more sharpness, but that's about the only way a japanese achro can outclass a chinese apo.

Has to be a Vixen, Mizar or some top-class vintage american achro. But at the same figuring/polishing level of quality, ED glass wins.

Of all the Vixen refractor reviews I've read, only one mentioned spherical aberration, and I have personally never seen troublesome spherical aberration in a Vixen lens.

[heliumstar]

John, they do put out similar performance. If anything the star test to me on Starwave looks better - more consistent in and out of focus but I never used green filter to test it so not really sure. On moon for example the Starwave is crisper to my eye. I just can't explain the Saturn.....in Vixen it just looks better and the 'ball' is really pronounced 3d like - like I have a playing marble in front of me while on Starwave it's flat.

[Anthonyexmouth]

5 minutes ago, heliumstar said:

Should it matter at practically the same magnification?

if you put the same eyepiece in both scopes the vixen will offer about 80% more magnification than the starwave

[heliumstar]

Anthony, I used 3.5mm in Vixen and 4.5mm with 2x barlow in Starwave. This comes at 260x and 247x. Pretty close. The main thing I actually take out of this is that on Saturn A80M can take 260x while Starwave cannot.

[Anthonyexmouth]

2 minutes ago, heliumstar said:

Anthony, I used 3.5mm in Vixen and 4.5mm with 2x barlow in Starwave. This comes at 260x and 247x. Pretty close. The main thing I actually take out of this is that on Saturn A80M can take 260x while Starwave cannot.

i wouldnt be pushing an 80mm f6ish past about 150x  and the vixen only a little past that anyway. x250ish is too much i think

[John]

7 minutes ago, heliumstar said:

Anthony, I used 3.5mm in Vixen and 4.5mm with 2x barlow in Starwave. This comes at 260x and 247x. Pretty close. The main thing I actually take out of this is that on Saturn A80M can take 260x while Starwave cannot.

Well beyond the useful magnfication of either scope I'd have thought, even on Saturn ?

 

 

[johninderby]

Long focal length scopes have a greater depth of field which can improve planetary views as the whole disk can be in sharp focus. Some of the classic long fl achros were figured to very high standards and can deliver great planetary views.

Bit different with modern scopes though where achos tend to be the cheaper scopes and aren't made to the same standards as APOs which often gives many observers the mistaken opinion that APOs are always better than achros for planetary use as they may never have had a chance to observe with one of the classic achros.

Case in point my Carton 100 f13 saw off my FLT 98 for visual planetary use. Just gave better views. Yes the FLT was a better all rounder but couln’t match the Carton  at it’s specialty.

[heliumstar]

Anthony : I totally agree. The sweet spot I found actually is 4.5mm eyepiece which gives around 120x. With this Starwave is crisp, crisp, crisp! See below comment for Vixen though....imo the achromat easily takes higher magnification without degradation. You would be surprised.

John: I regularly use 3.5mm on A80M for Moon, Saturn and Jupiter. It takes it like a champ. This is purely subjective though. Others might not find the image as pleasing.

[Stu]

Interesting results. I've had high quality 85mm apos before and found they ran out of steam at around x200 I guess. My floaters certainly call time above that!!

One question, how good is the Barlow? It's the main difference between the two setups and a poor Barlow can trash the image.

[John]

I know that Vixen do make very good objectives - I've owned a few !

Never owned an Altair though.

 

[heliumstar]

5 minutes ago, Stu said:

Interesting results. I've had high quality 85mm apos before and found they ran out of steam at around x200 I guess. My floaters certainly call time above that!!

One question, how good is the Barlow? It's the main difference between the two setups and a poor Barlow can trash the image.

Good catch Stu The barlow might be the culprit with such high magnification. When I barlow 14mm Morpheus and then use 7mm Vixen SSW the image is completely the same. So barlow should be fine but not sure since the magnification is really pushing it.

 

John : Altair is a very nice telescope. Well built and the focuser is just perfect. Better than on Vixen! If I only had to keep one it would be the shorty Much more convenient to live with in these busy times...

[John]

If either of them give you crisp, sharp, contrasty Jupiter views at 240x then they are simply amazing performers for an 80mm aperture

 

[heliumstar]

John, unfortunately no Jupiter is harder on both than Saturn.

[Ben the Ignorant]

2 hours ago, John said:

If either of them give you crisp, sharp, contrasty Jupiter views at 240x then they are simply amazing performers for an 80mm aperture

 

My 80mm triplet can do it (4mm TS and Ultima 2x Barlow) but only when turbulence is nil, meaning it happened only twice since I own it. Otherwise 204x is the max but not fully exploited because of the residual turbulence that's always there when conditions are not super-perfect.

[SIDO]

Achromats are a hard to beat design from the standpoint of a refractor, just look at all the technology expense and centuries it took not to mention the broad cost comparison that still exists even today. A quality well tuned achromat at or above the Sidgwick standard is a way understated scope due to the higher quality of much more expensive and current designs even though in some cases they only barely succeed to best some better achromatic examples. Love to here this truth come out in the wash occasionally, they are so still relevant ?

[Stu]

A good, long focal length achromatic refractor can be an excellent option, with certain limitations. I’ve owned two of the original Japanese Vixen 80mm f11s, and have looked through a few of the 102mm F11 clones and they give very satisfying and sharp views, particularly of planets, the moon and doubles.

The reason I don’t have one now is that I enjoy my widefield views (aswell as planetary, lunar etc) and also do much observing away from home so a shorter focal length scope suits these applications better, and an apo doublet is what is needed to achieve this.

Horses for courses still though, these are all lovely scopes.