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Spec-Chum

Stock 50 degree 25mm MA vs 2” 70 degree 24mm vs 60 degree 25mm BST

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Both the 24mm 2” EP and the 25mm BST were from Skies the limit on Ebay:

http://www.ebay.co.u...=item589421b374

http://www.ebay.co.u...=item256730210f

As per my sig, my scope is an fast-ish F6 so is fairly demanding on eyepieces, but not overly so. If there is a flaw, it’ll more then likely show it.

For these tests I didn’t bother with any DSOs apart from the Dumbbell as, really, it’s not what I would use them for but though it would be nice to gaze at least one DSO.

So, anyway, here is what I found on the Dumbbell nebula. For what it’s worth, I didn’t use my UHC filter as I only have the 1.25” version, so would have to use the 2” unfiltered anyway.

First up was the 25mm MA which showed a smallish, greyish, er, something. It was quite hard to see anything really; you could tell there was something there, but if you didn’t know what you were looking for you’d quite easily scan straight past it. I think it’s fair to say contrast is a little lacking on the MA but still, I could see the nebula, so that’s always a bonus.

Score: 6 / 10

Next I tried BST. Now we’re talking. M27 was obviously still small but now stood out like a sore thumb against the sky. I can quite clearly make out its shape and the extra 10 degrees FOV was very pleasing also. I’ve heard the term “spacewalk” for this, I wouldn’t go that far, but it was nice. It was no surprise to not see any colour, but the brightness and contrast were fantastic. Overall, a very notable improvement over the stock MA. I’m very impressed.

Score: 9 / 10

Next up was the big feller. Impressive! M27 quite prominent; not as bright or contrasty as the BST but certainly a step up over the MA but the 70 degree Field of View made this more of the “spacewalk” I’ve read about. Overall I liked it; but the overall “pop” of the BST view just edged it for me as FOV is not really important for looking at this kind of object.

Score: 8 / 10

Final test was, to my mind, the most important; Edge to Edge sharpness. What’s the point of having a massive FOV if only half of it is useful?

To test the edges I used The Double Cluster in Perseus as at 24mm and 25mm as I knew there would be stars right to the edge (and beyond) the FOV on all 3.

First up again was the 25mm MA which managed to frame most of both clusters in its Field of View, and gave a pleasant, if not spectacular view. Stars were pin sharp and well defined in the middle, but tailed off into little comma’s towards the outer edge; a common attribute and expected but it’s fair to say they actually hold up pretty well until about the last 10% or so of the FOV, but when you’ve only got 50 degree to play with to start with, that makes quite a difference. Overall, I liked my 25mm MA here and I’m often puzzled as to why people are always so keen to upgrade it.

Score: 7 / 10

Next again was the BST. This is where the extra FOV shone. With the 2 clusters centred there were masses of stars around the edge that just weren’t there on the 50 degree MA. 10 degrees doesn’t sound like a massive amount, but boy do you notice it in this kind of scenario!

The stars in the centre were pin sharp as expected, so I decided to slowly drift the clusters towards the edge. At about 5% to go I noticed the comma effect, but it was fair less pronounced than on the MA and even at the very edge you could still resolve individual stars in the clusters. Yes they were not pin points anymore, but you could tell what they were. The MA was just a bit of a blur at this area of the FOV. The image as a whole was again was a lot brighter than the MA. Awesome stuff!

Score: 9 / 10

Now for the 70 degree monster. First impressions were again fantastic. The 2 clusters were centred and I could see what seemed like the rest of the visible universe around them! I was in awe!

Stars in the centre matched the BST in their sharpness, but once again I noticed the image to be quite a bit darker then the BST; about on par, if a little brighter than with the MA.

Moving the clusters to the edge of view was where the disappointment set it. Yes, the 70 degree FOV is certainly impressive at first but once object start getting say 10 – 15% from the edge the commas turn into smudges, the commas themselves start a little further in still; I literally couldn’t make out any individual stars anywhere near the edge. After swapping back and forth between this and the BST and studying the edges for a while I concluded you can actually see a more useable FOV in the BST despite the 10 degree disadvantage. The MA is beaten by both on the usable FOV, however.

Score: 7 / 10

Summary

25mm BST – Very bright and contrasty image. Does suffer from comma’s and seagulling at the edge, but certainly not a major distraction. A 60 degree 25mm for £41 will always raise a few eyebrows, but does it perform? Oh yes.

Highly recommended.

24mm 2”

Now, you may think after reading my critique above I’m going to slate this one. Nope.

We really must remember I’m reviewing a sub £40 70 degree 2” EP here and on that score I liked it and thinks it’s a bargain.

Yes, the image was quite dark compared to the BST (I really don’t think we can blame that on the 24mm vs 25mm), yes the image starts off nice and sharp and rather quickly deteriorates as you get closer to the edge but you must also consider it’s plus points as in it’s cheap as chips and I’m comparing it against a BST which is arguably the best eyepiece you can buy for under £50. It’s a huge step up from the supplied MA and well worth the asking price of £39 for the “spacewalk” feeling alone.

My personal choice here would be the BST, but if, for whatever reason, you must have a 2” SWA EP I can wholeheartedly recommend this one and challenge anyone to better it for the price.

Edited by Spec-Chum
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Thats an excellent and interesting report. Thanks very much for posting it. It's great to see some real world comparisons of affordable eyepieces which addresses just the sort of questions that folks are thinking about as they consider their first eyepiece upgrades.

Nice piece :smiley:

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Great post, really interesting.

Not everyone can afford high end stuff so it is nice to see comparisons in a range open to most of us.

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Nice report. The BSTs seem to be really great value for money EPs. My impression is that the 70 deg SWAs are Erfle designs, and these are notorious for astigmatism (like the one in my finder, but, hey, that is just a finder EP)..

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Thanks Michael. I must stress again tho, I was impressed with the 2" ep and the astigmatism only was a major distraction under scrutiny. The BST won it for me tho, and that's the one I've decided to keep.

For the record, I've managed to twist Alan's arm to also send me his 80 degree ep too, so I'll post how that fares, but that's obviously not ine same budget range.

I'll post a review once it gets here...

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The edge sharpness is often only an issue under scrutiny. However, once you have noticed it (or have had it pointed out to you (people can really hate that :D)), you start disliking the EP (at least I did). Looking through a top-notch EP is a very risky business, you will want more! My rule is essentially this: upgrade if and when you start noticing the limitations of your kit, but no sooner.

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I've recently got a 12mm BST which is 60 degrees and love it! Reviews like this helped push me in that direction. Really only had a chance to use it as of last night and really looks the part! Compared to the 10mm stock EP that came with my 130P it is much nicer when looking at Jupiter......but you would expect that! When I decide to up my mag in the future, I'll definitely think BST.

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Happy to help!

As it happens I've also got my hands on this: http://www.ebay.co.u...=item588faef567

I managed to use it last week and was very impressed, I'll post a full review later...

I used to have the Japanese eyepiece that the above were cloned from - the KK Widescan III. That delivered an 84 degree FoV so the chinese have cut that down a little in their versions. The Moonfish 30mm 80 degree eyepieces are the same thing as Skies the Limit are selling there.

I'll be interested in your views on how it performs in your F/6.

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It certainly is, yes. It won a S@N best buy award in 2006 too beating a Tele Vue 31mm Nagler Type 5 by 1% overall (85 vs 86).

Obvioulsy the Nagler won on performance and quality, but the price/performance ratio of the Moonfish was undeniable...

Edited by Spec-Chum

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Yes I read that review too !.

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Excellent and well written report, I agree with what John said, it is nice to see someone taking the time to review a more affordable option.

Alan.

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+ 1 for the 25mm BST, an excellent eyepiece, at an incredible price, even at £47 now, though I acquired all mine at the old price and I am dead pleased with them.

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Part of the "problem" of the BST's are that they are so good. People ask about eyepieces and saying go buy a BST seems too simple. When I first had mine I lent then to a friend before I had a chance to use them, getting them back took some time.

When I first used them Jupiter was small (not much magnification on the scope I used) but it was clear and crisp.

I eventually bought the complete set, when I did this they were still £41 a piece so even better.

When someone asks about a more expensive eyepiece it is difficult to say buy this £120 eyepiece when you are pretty sure that the BST will perform as well, possibly better.

One small point, it was reckoned that the 25mm BST was the last able of the bunch, if that gets 9/10 the performance of the rest should really impress. :grin: :grin: :grin:

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