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My honest review of the 52 degree series from Explore Scientific.


Tyler

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I’ve had the opportunity to try out some of Explore Scientific’s new line of 52° eyepieces.  I must say I am always blown away by what Explore Scientific is doing as a company.

These eyepieces are of excellent quality and the optical performance is quite amazing indeed.  These eyepieces are great for planetary views, bringing in detail with the moon that I haven’t seen in a while.  Mars is also fantastic!  Seeing the ice cap on Mars was truly remarkable.

The detail I am able to acquire with all of the longer focal length eyepieces in this series is truly astounding.  I can easily split Albireo with these eyepieces as well as Polaris A and Polaris B.

Using the 40mm and the 30mm eyepieces with my Orion ST120, I was able to fit the entirety of the Pleiades inside the field of view and experienced only slight distortion towards the edge of the FOV.  Observing these beautiful bright stars is simply breathtaking.  Using these eyepieces to star hop, I did not have to worry about light scatter on either of them.  I could just sit there and take in everything the view had to offer with no worries at all. Moving over to M33, I could see the central core brightening within a nice slanted cloudy patch of light. The NGC’s 869 and 884 (Double Cluster) is sharp will a little bit of distortion towards the outer edge.  Compared to a GSO SuperView 30mm eyepiece, the Explore Scientific 52° 30mm seems to offer more depth of field.

The 25mm eyepiece had no problem finding and displaying M1 (Crab Nebula) with good contrast compared to a generic Plössl of the same focal length. The Explore Scientific eyepiece lets in more darkness (better contrast) and it has the advantage for sure over the Plössl, even in an f/5 scope.  I did note a little bit of distortion at the edge of the field, but I had to go looking for it.  While observing M1, it was not noticed. If I were to choose a jewel amongst the 52° series that I have evaluated so far, the 25mm would be a close second.

The 20mm eyepiece in this 52° series had no notable distortion at the edge of the field. While observing the brighter stars of the Pleiades, I was able to discern the soft and subtle glow of nebulosity.  Swapping out for a 20mm Plössl, a similar view was had, but the edge of field distortion in this fast scope was much more noticeable.  The Explore Scientific eyepiece was much better corrected for this fast refractor.  Swinging over to M42 (Orion Nebula), nice contrast was offered despite the lower altitude of this object.  Four of the Trapezium stars could be easily picked out.  This eyepiece offered sharp stars from center to edge.

The 52° 15mm, when compared to a GSO Plössl of the same focal length, has much better eye relief and offered a more immersive visual experience.  The field of view with this eyepiece is very well corrected for my fast scope.  An attempt at Mars was made, but with this planet rapidly receding and getting much smaller, the view was not especially remarkable here.  Poor seeing conditions were also impactful with the planet.  Moving up to M31, (Andromeda Galaxy), the 52° 15mm was definitely superior to the GSO 15mm.  Again, excellent contrast and immersive viewing experience.  The field stop on the Plössl was quite noticeable, whereas the 52° was smooth and the field stop did not interfere with the light path.  Sliding southward to the Cetus/Eridanus area, comet 46P/Wirtanen clawed its way through the worsening transparency and was easily seen.  The 52° again offered better contrast vs. the Plössl.  M42 presented a fine view as well.  Moving to M45 (Pleiades), the pinpoint stars, even to the edge, was amazing.  In Auriga, M37 displayed a fine sprinkling of diamond dust with a brighter red star nested in the center.  Back to M1, this small little cloudy patch of light was easily picked out despite the worsening sky conditions.  In my honest opinion, the 52° 15mm is hands-down the crown jewel in this series that I have tried so far.  It has little to no distortion at the edge, and stars remain as sharp pinpoints across the entirety of the field of view, an excellent eyepiece.

These eyepieces all come inside Explore Scientific’s great boxes.  Inside of each box, the eyepiece is held warmly in a little soft black velvet pouch for added protection, a nice touch.

While looking through these eyepieces at the scope, I did not experience any eye-strain.  They offered a clear view of what I was looking at with nice contrast and no noticeable light scatter.  The 52° AFOV was expansive enough to hold an object for observing finer detail even when using a manual alt/az mount.

The 6.5mm brings out all the beauty in the Double Cluster.  The contrast was great and I can easily make out the copper color of the red stars.  I compared this eyepiece to a 6mm Fujiyama KK HD Orthoscopic eyepiece with a slightly narrower apparent field of view, as well as a 6mm Baader Classic Ortho.  The KK 6mm has a sharper image and the center to edge is definitely noticeable in the KK and the BCO.  The 6.5mm does show a lot of contrast in the nebulosity, but, moving to the ES 52° 4.5mm, the contrast is diminished, and even more so with the 3mm.

In my opinion, the 3mm would be great for planetary and lunar on nights of excellent seeing conditions with the scope that was used for this review.  While observing the Orion Nebula (M42), I can make out the 4 main stars of the Trapezium Cluster and its very well corrected and also very nice to edge.

Using the Orion ST120, the 6.5mm performed very well.  On M42, the four brighter stars of the Trapezium Cluster popped out really well and the center to edge was amazing as well.  The 3mm and the 6.5mm in the ST120 are great eyepieces.  The 3mm can split Polaris which I found amazing being the first time that I’ve seen the secondary star of this pair.  M31 (Andromeda Galaxy) through the 6.5mm showed contrast that just pops in the center which I found to be very nice.  The 4.5mm makes it so much sweeter as it picked up some dust lanes with no problem.  Back to M42, I can make out a fifth star in the Trapezium Cluster which is exciting.

In my opinion, the 52° series is a great set to have in one’s collection or if just starting out in this great hobby.  The eye relief is quite adequate in my experience.  I did not have to hug the eyepiece to see the objects and I typically wear glasses when I am able to bring out the telescope for nightly viewing.  I feel that one of the best aspects of these eyepieces is the minimal maintenance required with them.  Cleaning (when required) is very easy since they are waterproof.  The removable eyecup allows for easier cleaning also.  The anti-fogging coating is a winner too in my book.  What is not to love about these eyepieces?

They would be excellent as a beginner set if you are just starting out in the hobby, or even if you are an experienced astronomer looking to enhance the eyepiece collection you can’t go wrong.

 

40mm:  Great for star hopping and seeing open clusters and larger deep sky objects, such as M45 (Pleiades) and M31 (Andromeda Galaxy).

Exit pupil:  8mm

Eye Relief:  27mm

Eyepiece Barrel Size:  2"

Eyepiece:  Fixed 

Apparent Field of View:  52°

Field Stop Diameter:  35mm

Focal Length:  40mm

 

30mm:  Star hopping and zooming in on the Double Cluster along with a closer look at M45 (Pleiades) and M31 (Andromeda Galaxy) and could almost split Polaris.

Eye Relief:  20mm

Eyepiece Barrel Size:  1.25"

Eyepiece:  Fixed

Apparent Field of View:  52°

Field Stop Diameter:  26.2mm

Focal Length:  30mm

 

25mm:  M34 fits in the eyepiece rather nicely and make the sky a little darker, increasing contrast, which is great. Being able to gaze M35 or NGC 2099 is amazing.

Eye Relief:  16mm

Eyepiece Barrel Size:  1.25"

Eyepiece Fixed

Apparent Field of View:  52°

Field Stop Diameter:  21.8mm

Focal Length:  25mm

 

20mm:  Brings in more contrast.

Eye Relief:  15mm

Eyepiece Barrel Size:  1.25"

Eyepiece:  Fixed

Apparent Field of View:  52°

Field Stop Diameter:  19.4mm

Focal Length:  20mm

 

15mm:  Offers the best picture of M34, the best open cluster in Perseus.  I could count the stars in M36 in Auriga with all the great detail this eyepiece offered.

Eye Relief:  16mm

Eyepiece Barrel Size:  1.25"

Eyepiece:  Fixed

Apparent Field of View:  52°

Field Stop Diameter:  19.4mm

Focal Length:  15mm

 

3mm: good detail in the Trapezium cluster and corrected to edge. Polaris can be split

Barrel Size: 1.25"

Focal Length:3mm

Apparent Field of View: 52°

Eye Relief: 15mm

Field Stop: 5mm

 

4.5mm: Brings in more contrast in the Andromeda Galaxy.

Barrel Size: 1.25"

Focal Length: 4.5mm

Apparent Field of View: 52°

Eye Relief: 15mm

Field Stop: 15.5mm

 

6.5mm: Andromeda galaxy has great detail the contrast just pops

Barrel Size: 1.25"

Focal Length: 6.5mm

Apparent Field of View: 52°

Eye Relief: 15.9mm

Field Stop: 17.4mm

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Thanks for your thoughts on these eyepieces and welcome to the forum :smiley:

I have not seen very much reported on Explore Scientific's 52 degree range so it's good to have some 1st hand feedback.

 

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I interesting addition to the range. Useful eye relief through the range too. Also, good to see quality through the range. I’ve found that the 68° range go from OK to really quite good.

I’m assuming the the scope is f5? 

Paul

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3 hours ago, Tyler said:

The KK 6mm has a sharper image and the center to edge is definitely noticeable in the KK and the BCO.

Can you provide additional info on center field sharpness form these (maybe in another scope better suited to this instead of F/5 achromat - did you get a chance to try them out in a different scope)?

At 52 degrees I would consider these to be aimed at planets, and sharpness is something that can make all the difference. If these are not sharp eyepieces, don't see much value on them over BST Starguider range for example.

If sharpness is very good compared to most eyepieces then they could be cheaper alternative to Vixen SLV range.

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I’m not sure that we can assume that these are aimed at purely planetary work. The lower cost of these designs make them comfortable “all rounders” for a lot of people. BCO’s were mentioned by the OP. They are cracking planetary  eyepieces, being noticeably sharper and with better transmission that the Starguiders. However, an evening of general viewing with a set of BCO’s can be a bit wearing (eye relief at the shorter end and lack of adjustable eye cups making eye placement trickier). So I’d rather charge around the sky with a set of Starguiders (even at sub f5) for general observing. Despite the BCO having ‘better, optics.

From the OP’s language, ES 52° seem to be easy to use, comfy and pretty sharp across the field.

Paul

 

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2 minutes ago, Paul73 said:

I’m not sure that we can assume that these are aimed at purely planetary work. The lower cost of these designs make them comfortable “all rounders” for a lot of people. BCO’s were mentioned by the OP. They are cracking planetary  eyepieces, being noticeably sharper and with better transmission that the Starguiders. However, an evening of general viewing with a set of BCO’s can be a bit wearing (eye relief at the shorter end and lack of adjustable eye cups making eye placement trickier). So I’d rather charge around the sky with a set of Starguiders (even at sub f5) for general observing. Despite the BCO having ‘better, optics.

From the OP’s language, ES 52° seem to be easy to use, comfy and pretty sharp across the field.

Paul

 

Quite agree - we have decent planetary eyepieces - sharp and even good eye relief like Vixen SLV in 50 degrees bracket.

For general purpose all rounders - we have Starguiders, right? having 60 degree FOV and very good eye relief.

If ES52 eyepieces are not sharper than Starguiders - what would be the point? I mean they have nice / quality build, but for general all rounders I think most people would prefer 60 degrees to 52 at the same price point (or even cheaper).

I think I could settle for 50 degrees now days (although I seem to prefer 60-70 range) if it meant great sharpness and comfortable eye relief. Maybe it's just me, but I tend to think that most eyepieces below 10mm are mostly for high power work where one wants good sharpness - and this is where eye relief starts to be important, otherwise we have very good plossls in higher focal lengths that have 50 degree afov and are very reasonably priced.

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Thank you for the review, Tyler! Well done. If I didn't have plenty eyepieces already, I would consider an ES 52° to fill my 52° needs, based on this review.

Also saw the ES video. That could have been better. The fearmongering about how other eyepieces suffer from internal fogging ("some of you may not have experienced this this, but many of you have...") never fails to put me off.

 

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12 minutes ago, Ruud said:

Also saw the ES video. That could have been better. The fearmongering about how other eyepieces suffer from internal fogging ("some of you may not have experienced this this, but many of you have...") never fails to put me off....

 

I agree. I have never had an eyepiece internally fogged in 30+ years of observing with dozens of different eyepieces. Most of my eyepieces during that time were not gas purged or water resistant.

 

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Yes. Outperforming the likes of Starguiders, which cost a bit less, would be the first hurdle. Next up would be taking down the likes of the likes of the excellent, similarly priced, Vixen SLV range. For me the Starguiders run out of steam at much below f5, which is a BIG ask for a £50ish eyepiece.

Am I the only one who is totally confused by the ES range? 52°,68°,70°,82°,92°,100° and yes, even a couple at 120°!!!! I’m definitely a fan of their products, but it doesn’t come across as a cohearant lineup. Although, Televue seem to have a similar number of lines (but each seems to have a defined niche).

Paul

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1 minute ago, John said:

I agree. I have never had an eyepiece internally fogged in 30+ years of observing with dozens of different eyepieces. Most of my eyepieces during that time were not gas purged or water resistant.

 

Agreed. 

I am not in the habit of observing in the rain or washing my eyepiece under a tap!

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2 hours ago, vlaiv said:

Can you provide additional info on center field sharpness form these (maybe in another scope better suited to this instead of F/5 achromat - did you get a chance to try them out in a different scope)?

At 52 degrees I would consider these to be aimed at planets, and sharpness is something that can make all the difference. If these are not sharp eyepieces, don't see much value on them over BST Starguider range for example.

If sharpness is very good compared to most eyepieces then they could be cheaper alternative to Vixen SLV range.

Unfortunately all I have is the Orion st120

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10 minutes ago, Paul73 said:

Yes. Outperforming the likes of Starguiders, which cost a bit less, would be the first hurdle. Next up would be taking down the likes of the likes of the excellent, similarly priced, Vixen SLV range. For me the Starguiders run out of steam at much below f5, which is a BIG ask for a £50ish eyepiece.

Am I the only one who is totally confused by the ES range? 52°,68°,70°,82°,92°,100° and yes, even a couple at 120°!!!! I’m definitely a fan of their products, but it doesn’t come across as a cohearant lineup. Although, Televue seem to have a similar number of lines (but each seems to have a defined niche).

Paul

Don't they have 62 degrees line as well - marketed as LER but fell short in that regard?

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11 minutes ago, vlaiv said:

Don't they have 62 degrees line as well - marketed as LER but fell short in that regard?

Yes, there is a range of ES 62's as well:

https://www.firstlightoptics.com/explore-scientific-eyepieces/explore-scientific-62-series-ler-eyepieces.html

They seem to have all the bases covered plus have introduced some of their own !

 

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3 hours ago, vlaiv said:

Can you provide additional info on center field sharpness form these (maybe in another scope better suited to this instead of F/5 achromat - did you get a chance to try them out in a different scope)?

At 52 degrees I would consider these to be aimed at planets, and sharpness is something that can make all the difference. If these are not sharp eyepieces, don't see much value on them over BST Starguider range for example.

If sharpness is very good compared to most eyepieces then they could be cheaper alternative to Vixen SLV range.

I would consider them equal to or better than BST Starguiders.  Of course i didn’t have a good planet to point them at.  ?

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17 hours ago, Paul73 said:

Am I the only one who is totally confused by the ES range? 52°,68°,70°,82°,92°,100° and yes, even a couple at 120°!!!! I’m definitely a fan of their products, but it doesn’t come across as a cohearant lineup. Although, Televue seem to have a similar number of lines (but each seems to have a defined niche).

Paul

I'm not sure about their reasoning, but I think they're trying to be like car companies.  They want models to appeal to a wide variety of shoppers at varying price points.  And yes, you skipped over the 62° lineup.  They even have the giant 3" 30mm 100°.

What's most maddening to me is that they have yet to add any other 120° or 92° offerings.  Are they done with one and two focal lengths for them, respectively?  What about a 3" 100° to max-out the available field in that size like the 30mm 82° does for 2"?  Maybe a 3" 120° instead to keep down the exit pupil?

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