New Antares 5.7mm 70 degrees FOV and its W70 series

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VinSnr
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New Antares 5.7mm 70 degrees FOV and its W70 series

Postby VinSnr » Mon Oct 06, 2003 2:04 am

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When Harlequin Astronomics first annouced this series of eyepieces, I was astounded. Simply because they look good and the price seems too low for 70 degrees eyepieces. Maybe they are from China, I am not sure, but all the while the impression is that Antares gets their goods from Japan. Anyway, since their price is pretty low and I love "value" eyepieces, I placed an order for the 5.7mm. I just sold off the 7mm Nagler, and was desperate for a high power eyepiece for collimation purposes. (and it doesn't make sense to use Nagler for only collimation)

So I was at Samuel's house today to collect my order. I saw a Megrez by the window side and a series of these new Antares eyepieces. I am familiar with the performance of the more expensive wide field eyepieces ( I had the 13.8 Meade SWA as well as the 19mm Axiom) and Samuel has a Pentax 7mm SMC is his dry cabinet. Seems like a perfect setting to make a comparison of this new Antares series with the Pentax 7mm SMC (cost three times more!) and those other SWAs that I have used before.

Now a little about the 5.7mm. First of all, it has a really large eye lens. In fact, its eyelens is even bigger than the 7mm Nagler. Look below

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If you have use Plossl before..you will know that at 5-6mm fl, their eyelens is even smaller than a pea. So with such huge eyelens, will its eye relief be comfortable? I will tell that later. Now notice that it has a green multi-coatings at the top of the lens. The rubber eyeguard can be folded down.

Now talking about the 7mm Nagler, the height of this eyepiece is as big as the 7mm Nagler too.

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Seriously, I expected it to be a pretty small eyepeice. While not as huge as the Pentax, it's still pretty big for a 5.7mm. But its weigth should not throw those sensitive dob off balance.

The top of the eyepiece has a very comfortable rubber grip.

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Ok..so how does it performs compared to the Pentax 7mm? But before that, how do you actually test eyepieces during daytime? Here is the tip. Point the scope to any HDB flats that has a window grill. The window grill has those square chequered gratings which is very good to test for edge distortions. If the edge distortion is bad, the grills will appear bended at the edge of the FOV.

Sharpness-wise, both the 5.7mm Antares and the Pentax 7mm was almost a horserace. FOV is almost the same for both eyepieces. However, the Pentax won on edge sharpness. The Antares 5.7 however, is sharp to about 80% FOV. The last 20% of the FOV was distorted, but not really as bad as I expected it to be. I have seen worse. But because stars are not straight lines like the window grill, the edge distortion should be more forgiving on stars. Do note that using window grills to test is as severe as using a flashlight pointing onto your mirror.

There is another slight flaw on the 5.7mm. It's very demanding on the eye position. You can easily run into kidney bean effect if your eyes are not place correctly. Unfortunately even though it has a huge eyelens, you still have to place your eyes pretty near to eliminate those kidney bean effect. The Pentax however, was easier on the eyes.

I then checked out the rest of the series. It was found that

1) As the fl gets larger, the eyepiece becomes easier on the eye position without much kidney bean effect

2) As the fl gets larger, the edge sharpness gets better. Using the 19mm, I didn't see any edge distortion at all. I was really impressed with the longer fl eyepieces. I think the 19mm can easily rival the 19mm Axiom with much less money.

Overall, I think this series is pretty impressive for the money. If you are on a shoe-string budget, but you want huge FOV with looks that can be brag at, you might want to take a look at this series. I won't really recommend the shorter fl series unless you are like me, buying it for testing work like star testing and collimation. Or you just want something better than your short fl Plossl. In that case, the shorter fl W70 series does make a good upgrade without robbing the bank.

However, for those longer fl series (14mm and above), I would say grab it if you can find one at Samuel's price. The 19mm is especially impressive for the price. I think Samuel should raise the price for the 19mm and treat all of us to some coffee.

Any questions, just post in this thread.

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harlequin2902
 
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Postby harlequin2902 » Mon Oct 06, 2003 8:43 am

There is another slight flaw on the 5.7mm. It's very demanding on the eye position. You can easily run into kidney bean effect if your eyes are not place correctly. Unfortunately even though it has a huge eyelens, you still have to place your eyes pretty near to eliminate those kidney bean effect. The Pentax however, was easier on the eyes.


Hi Vin,

Do you think an optional pupil guide or an optional higher eyecup will help solve the problem a little ?

Thanks.
Samuel Ng

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VinSnr
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Postby VinSnr » Mon Oct 06, 2003 10:11 am

Hi Vin,

Do you think an optional pupil guide or an optional higher eyecup will help solve the problem a little ?

Thanks.


I doubt so. The kidney bean effect is inherent to the design. It's like some panoptics and radians. In fact, I suspect it's quite hard to be kidney-bean free when the fl is short and the FOV is wide. The 3mm radian is far worse in kidney bean effect.


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