Astrolux S42 Flashlight Review


With the continuing popularity of the Astrolux S41, an updated was developed: The S42.  This light is essentially iterative, but adds micro-USB charging.  And the Nichia emitter (which I have here) is 219c instead of 219b.  Possibly most importantly, a new user interface! Let’s see how this S42 stacks up!

Official Specs and Features

(The product page will have to serve as the official page, since I don’t know that Astrolux has an official site. Sorry!)  That link above is a referral link!


There are a number of versions of this light.  There’s the one I’m reviewing, the Nichia 219c, and a Cree XP-G3 version too.  Then there’s a version called the S42s, which has a stainless body where mine is aluminum, and has a copper heatsink.  That one’s available with both emitters, too.  There’s a version in stainless that’s been heat treated so it’s rainbow colored, too.

Unfortunately, and inexplicably, the best performing possibility isn’t available from Astrolux: a copper heatsink aluminum body version.

Basically all of these are available in both 18350 and 18650 format (with an extension tube for the 18650).

I’d be remiss not to mention the Manker version of this light, which is similar but different:  Available in a copper head/aluminum body and with a different UI, and a slightly different build around the charge port.  That one’s called the Manker E14 II.


This light costs $45.95.  It’s currently on sale for $23.95!

Short Review

The output on this light with the Nichia 219c’s is impressive and incredible.  The UI is hard to understand and get accustomed to, and some build quibbles that have been fixed after I got my review unit.

Long Review

What’s Included

  • Astrolux S42
  • Lanyard
  • Pocket clip
  • Glass breaker
  • Lanyard
  • Spare O-rings (2)
  • Manual


Note: the extension tube for 18650 cells is not included.


Here’s a photo album of this light, a runtime, a chargetime, and some beamshots.

Package and Manual

The s42 arrives in a slip fit cardboard box.  It’s extra nice because the top has cutouts so a user can grab the bottom (instead of just waiting for the halves to fall apart).  There’s not much printing – just a brand name.  There is a descriptive sticker, however, with the light and emitter info.


Inside the box, the light and goodies are held in place by a big of PE foam.

The manual has the needful information, including specs and a UI diagram and the mode/runtime information.  It’s a fine manual, though nothing special.  I’ll talk more about the UI diagram later….


Build Quality and Disassembly

This light is on par with other Astrolux lights.  I have no real complaints about the light on the whole, but a few niggles that I just don’t care for.  The rubber boot that covers the charge port just does not work.  (Note: there’s a fix for this, and BangGood will ship you one for free:  I have not received mine yet, however.)  There has also been an issue with the extension tube meant to work with 18650 cells.  I didn’t receive one of those anyway, so I can’t comment about that.  I believe the tube was too short or long and wasn’t allowing good contact with the 18650.  This too has been fixed, and I think all new lights are shipping with the right parts.

Otherwise, the light is nice quality.


The threads are nicely lubed and seem to have a bit of a flat (not pointed) edge, which I like.  And the knurling on this light is my favorite kind of knurling (diamond, with a flat top).


Disassembly with the S42 is easy.  Most parts just unscrew, including the bezel.  It’s thus fairly easy to get at the emiters, but why would you want to?  If you bought the right mode, that is. 🙂


Here’s the cell tube, for 18350 cells.  If I had the cell tube for the 18650 cells, I’d put the picture here:


The tail end has a large threaded opening – approximately 1/2″ I’d guess.  This is fit for an included part:  a glass breaker (or murder point, but you call it what you want to call it).  The murder point screws into this opening.  Truth is, the murder point screws into a stainless adapter that screws into this 1/2″ opening.  So you can have a normal tripod mount too, if you chose to not protect yourself with the murder point.




77mm x 27mm (length x head diameter) (18350 size)
102mm x 27mm(length x head diameter) (18650 size)

Here are some photos of the S42 with items you know and love.




As mentioned above, there’s the screw in threaded 1/4″ adapter, which fits into the 1/2″ threaded opening in the tailcap.

There’s also a deep carry pocket clip.  It’s kind of reversible, but then the mouth of the clip hangs down too far on the 18350 version.


And a final option, a lanyard.  The lanyard fits on the tailcap, in a small hole.  Also below you can observe the 1/4″ adapter for tripods.



The Astrolux S42 in my configuration is suited to 18350 cells of any variety.  The extension tube works with 18650 cells, of any variety.  Below are two runtime tests with an 800 mAh Efest unprotected flat top.  Stepdown is dramatic and quick (less than a minute to 25% output).


The S42 also has the ability to charge cells, with the micro-USB port on the side of the light.  You can see the problem with the rubber boot meant for covering the port: it just basically flops loosely, and doesn’t stay in it’s place.  There is a fix, and if you order this light right now, you should get that fix from the start.


The charge time is below.  It’s a pretty solid >0.5A after a bit of a rocky start.


Termination at 3.02V from Turbo. Runtime 2 (also tubro) shutoff was 3.28V.

User Interface and Operation

To operate the light, there’s a single side e-switch.  It’s a nice sized rubber button with a copper color ring.  That’s kind of where the good points about the UI end…

The UI here is the real sticking point.  There’s no good way to describe it…. except to just say it’s not very good.

Glance back up at the manual.  The UI looks fairly simple but note to yourself…. how does one turn the light off?  Well, if you read it like I do, then turning the light off requires going through turbo.  That’s not actual fact, but it stands as a bastion of the UI itself.  It’s unclear, it’s fiddly, it’s fussy, and it’s not a fun UI to mess around with.

There are two mode groups available.  Group 1 is the more complex, and group 2 is a simple four mode option.  There are two ways to switch modes: short press or long press.  In either group, short pressing the button will change modes.  Long pressing will get Turbo (G1 only).  While in Turbo, a short press will cycle: Tactical Strobe, Battery Check, and Bike Flash.  In both groups, the modes cycle Low to High.  In my experience, one must just play finger gymnastics to get light to turn off.  Like my Facebook friend’s new relationship status: It’s Complicated.


So don’t really buy this for the UI.  If you need four Nichia 219c emitters?  This is not a horrible way to get them.  If you can flash UI’s?  Buy this light.  If you’re just curious about 219c tint, this is a great way to see it.

One more note: the light can be electronically locked out by long pressing from off.  Long press again to get out of lockout.

The switch is also an indicating switch – useful when charging.  The manual doesn’t go into much detail about what all this indicating switch can do, except to say it’s a “breathing” mode that displays battery voltage.



Mode Mode Claimed Output (lm) Claimed Runtime Mode Measured Lux Measured Amps
Moon 1 2.9d 20 0.006
Low 16  1.3d 275 0.068
Middle 1 125  6h 1768 0.214
Middle 2 210  2h 2760 0.320
High 1 475  1h 3770 0.452
High 2 630  0.4h 5800 0.810
Turbo 1630  0.39h 18000 3.02

LED and Beam

I opted for the same emitters you should opt for, the Nichia 219c.  There’s a Cree version available too, the XP-G3.  There are four emitters in this light – a “quad.”  The 219c is a fantastic tint and beam….



Here the light is turned on, low.


The beam itself is quite diffuse, and smooth from center to the outer edge.  I typically like a little more spot in my beam profile, but this one’s just fine.

Tint vs BLF-348

Rare is the light that makes the BLF-348 look off…. The 219c’s are just so clean white…

Beamshots, Runtime, and Lux Measurements

Astrolux S42
Emitter Nichia 219c
Emitter Notes 5000K
Cell 18350
Runtime 18350
Chargetime 18350
Beamshots [0.3″, f/8, ISO 100, 5000k] 18350
LVP? Yes
Claimed Lumens (lm) 2023
Lux (Measured) 100
At (m) 4.768
Candela (Calculated) in cd 2273.38
Throw (Calculated) (m) 95.36
Throw (Claimed) (m) 168

Random Comparisons and Competitive Options….

At this point I have to mention the Emisar D4.  It is new since I got the S42, but absolutely worht mentioning.  Also a quad, also available with 4x219c, but has a ramping UI that one might love or hate.  But it’s around twice the price of this S42.


What I like

  • Quad Nichia 219c
  • Build quality is good
  • I love a TIR.  I love a quad or triple…. I just love me some emitters!

What I don’t like

  • Charge port cover
  • UI is really not good
  • The murder point is a little excessive, in my opinion.

Parting Shot



  • This light was provided by for review. I was not paid to write this review.
  • This content originally appeared at  Please visit there for the best experience!
  • Whether or not I have a coupon for this light, I do have a bunch of coupons!!  Have a look at my spreadsheet for those coupons.

Comments are closed.

Create a website or blog at

Up ↑

%d bloggers like this: