First Light Report – Explore Scientific 305mm Ultralight Dobsonian.

New kit...!

New kit…!

What is it about astro gear that it lends itself to snap decisions in regards to buying and selling…!?

I made just such a decision the other day.  First a bit of background…  From when I started in astronomy at 8 years old, until December 2012, all of my astronomy was good old fashioned manual-style.  I only discovered the joys of goto and driven mounts when I bought my HEQ5 pro, so at time of writing, just over two years ago.

Since getting that, I’ll freely admit that 90% of my astronomical shenanigans have been centred around imaging.  I love imaging – there’s nothing like the feeling of processing data and effectively ‘seeing the unseeable’.  I’m in no hurry to give it up!  However, at the same time, my participation in the visual side of astronomy has been patchy at best, and has suffered due to my concentration on the imaging side.  Just so happens that my recent little visual session with the newly-acquired 70ED (which I talk about here), really brought back to me the joys of visual.  I think the stripped-down experience that it afforded, with the lack of electronics and alignment, made me realise what I’ve been missing for the last few years.

The other day I was perusing the astro classifieds, and noticed an Explore Scientific 12″ (305mm) Ultralight Dobsonian up for sale.  These are very interesting scopes, in that they’re designed to pack down small, and be very easy to transport.  The thing that’s always put me off getting anything of the Dob variety that’s over 8″ was the sheer size and difficulty storing that I have.  We live in a small house, with very little room to store my kit.  The astro kit itself is stored, all boxed up, in the cupboard under the stairs.  Even my 200p Sky-Watcher Skyliner base is too big to store there, and to be frank, the base weighs a ton, and it’s awkward as hell to carry any distance.  I also recently borrowed the society 14″ Orion Dob, which whilst being a formidable light bucket, is about the least transportable thing I’ve ever had to, well, transport.

This is why the Explore Scientific Dob caught my eye.  I’ve been following the progress of a few people who’ve bought them.  There have been multiple reports of supply problems, meaning getting hold of them is kind of like obtaining the proverbial rocking horse poo – i.e. not easy.  This is especially the case outside Europe.  The Explore Scientific website page that describes this scope can be found here…

When one came up on the classifieds for a reasonable price, I decided to effectively trade my Celestron C8 for the chance to buy it.  I’ve not been getting on well with my C8 for imaging.  It’s a fantastic scope, but the focal length is so considerable (even when reduced), that using it on a mobile setup has proven to be very challenging, and frustrating to the point where guiding and focusing challenges have meant that, in recent times, Ive been much more likely to reach for one of the two refractors I have for imaging rather than the C8.  As a visual scope, it offers little over my Newtonian – in fact the contrast and FOV are actually lower on the C8.  It’s for these reasons I thought it was a good idea to switch.  That way, I’d get the chance to grab the other thing I’d always wanted – a light bucket dob, whilst still having something I could successfully store and transport with ease.  The seller was on his way down to Kent anyway, so delivered it for me too, which was a nice bonus!

So… first impressions?

Well, it certainly lives up to it’s name.  Whilst not being ‘light’ in relation to a small refractor or something similar, it’s definitely light when compared to a standard Dobsonian design of a similar size.  It’s lovely and rigid once put together, and moves very smoothly, making nudging to keep an object in the field of view very easy.  It’s 100% aluminium (apart from some of the bolts that you use to put it together), so  is remarkably light.  The heaviest part is by far the mirror itself.  Take that out and it would be truly ‘ultralight’.  Unfortunately, the mirror is kind of a pre-requisite to getting anything constructive done with it :).

In Storage…

It weighs in at just under 30 kilos all-in, and breaks down into several parts for storage and transportation.  You can leave it partially assembled if you like, which I do.  I leave the bearings on the side, and leave the mirror box mounted in the rocker box, just with the lid closed to protect the mirror.  The photo to the left shows it in my small cupboard under the stairs, along with various other astro kit (oh, and some shoes…).  The scope itself simply consists of the front most boxes with the secondary cage on top, and the trusses behind.

Assembly is a cinch. It takes around 5-10 minutes for one person to assemble – less if you have another pair of hands.  Collimation of the scope (which needs to really be done every time you build it), can only be described as a dream come true when you’ve dealt with other Newtonians.  There are a three large secondary collimation screws, topped with large hand-turning knobs, so aligning that is very straightforward.  This is followed by collimation of the primary, which is done with a special, meter-long aluminium tool – effectively a long allen key.  This locks into the top of the inward-facing collimation screws, providing a way to collimate the scope whilst looking through the eyepiece – something I’ve never seen on a Newt before.

This collimation takes a couple of minutes with a cheshire or laser collimator, and is, I would say, almost more of a killer feature on this scope than the ‘ultralight’ bit.  Being able to collimate a scope of this size easily, on your own, is a breath of fresh air!

Lovely R+P Focuser

Lovely R+P Focuser

The focuser on this thing is a joy to behold.  It’s buttery-smooth (especially considering its a rack-and-pinion and not a Crayford), and has no slop, wobble or anything like that.  It also has a 1:10 fine focuser, and is the first newtonian I’ve used that does.

The setup is coupled with a Telrad finder – which I was going to accompany with an optical finderscope but I’m starting to wonder whether I actually need to.  The Telrad made finding everything so easy that I’m not sure the optical finder is necessary.  I’ll see over the next few sessions…

Lets get down to it… what is it like, and how does it perform once assembled? That is, in the end, why we have these things isn’t it?  Well, I’m happy to say, I wasn’t disappointed.  I’ve never had anything over an 8″ reflector in the past, so you have to bear in mind I’m coming from the point of view of a lower-aperture user historically.  That aside, I’m glad to say that the views from this beast were stunning.  First ‘proper’ light was from the SEKAS dark site near Canterbury.  This is what I’d describe as a medium-dark site – i.e. it’s a lot better then being in the middle of the city, but unless the atmosphere is particularly clear, you still get a lot of residual sky glow from the surrounding urban conurbations.

I decided to do a bit of an object bagging session to test out the limits of what the scope could achieve.  The objects I ended up viewing, and how they looked were as follows:-

[unordered_list style=”green-dot”]

  • Comet C2014 Q2 (Lovejoy) – At near full brightness, comet Lovejoy was showing off a wonderful tail in my 25mm Tal EP.  The head of the comet showed an expanse of corona, with detail being evident in the tail with averted vision.
  • M42 (the Orion Nebula), M43 and NGC1977 (Running Man Nebula) – An easy one to start (well, M42 and M43 anyway) – a wonderful set of objects in the sword of Orion.  All showed up well without filtration, though looked even more spectacular when viewed via  an OIII filter.  M42, a permanent favourite, showed the most incredible filamented structure, and appeared much wider and more expansive than any time I’ve seen it in the past.  I observed the Running Man for the first time visually. Very faint, but definitely there.
  • Caldwell 49 (The Rosette Nebula)  – Onto something a lot more challenging.  Happy to say that I observed this one for the first time ever visually via OIII filtration.  The FOV with the 25mm EP only captured the central cluster and a little of the surrounding nebulosity, but the darkening towards the centre of the nebula was very obvious.  Panning around revealed a textured ring that gave up more detail the longer you observed.  I saw very faint hints of the filaments and bok globules that permeate through the whole of this huge gem.  I’ll be returning to this with a UHC filter, as that is supposed to be even better.
  • M35, M36, M37 and M38The four clusters in and around Auriga.  Ok – so M35 is in Gemini, I know, but they’re all in the same patch of sky.  All showed a multitude of stars, with M37 (my favourite of them) showing off particularly well in 12″ of aperture, giving away more stars than I’ve ever managed to see in the past.
  • M81 and M82 – The galaxy pair in Ursa Major – A visual favorite.  Both showed detail, with M82 in particular displaying it;s central dust lane very well.  A fellow SEKA member even managed to pick this pair up in a pair of binoculars for the first time ever!
  • M44 – The Beehive Cluster – Stunning as always.  An easily visible naked eye fuzzy that looks great in binoculars, and twinkled away beautifully in the dob.
  • M31 – The Andromeda Galaxy – Quite low in the sky by the time I got to it, M31 didn’t give up too much detail tonight – more likely due to it being caught in the haze above Canterbury than anything else.   A tiny hint of dust lanes but nothing more.  I’ll return to this one in the future.
  • M51 – The Whirlpool Galaxy – A double galaxy (wonderfully dubbed the ‘cat and mouse’ by a fellow SEKAS member) that I’d never before observed visually (tried in the past with the 8″ skyliner, but had no luck).  Showed up a small amount of structure with averted vision.
  • M45 – The Pleiades – Twinkled away as usual in the wide field.  Was absolutely sure I could detect a few wisps of nebulosity around the brighter members with the OIII filter.
  • The ‘Leo Trio’ (the M66 Group) – This triplet of galaxies (consisting of M65, M66 and NGC3628) in Leo all showed well, with some signs of detail being evident throughout.
  • M95 and M96  – Another two Spiral Galaxies in Leo.  Both of these I actually came across by accident when searching for the Trio.
  • Jupiter – Old planetary favourite climbed into the sky over the course of the evening.  Looked great right down to 8mm, with detail evident in the belts.  Unfortunately no shadow transits or great red spot to check out, but still a great view.  Short spells of good seeing made 4mm worth the effort, though these were few and far between. Mostly used my 8mm BST EP for this one.  A blue filter shoed up the bands even more clearly, and accidentally leaving the OIII filter on (which gives the FOV a green tinge), also enhanced them in a similar way![/unordered_list]

As you can see – quite a prolific night in the sense of volume of objects observed.  I’ve never before managed to see such a wide variety of objects in one sitting.

Conclusions?  Well, first impressions are great.  The views I got through this scope verged, at times, on the ‘photographic’, especially when it came to certain nebulae viewed via OIII.  The aperture of this scope really makes OIII viewing a joy, and I’ll be using filtering a lot more in future, as the difference on some objects is truly astounding.

The scope itself seems good, and I am happy to say it assembles an disassembles as well and easily you’d imagine, with collimation being a small part of it, rather than the chore it often becomes.

In use, the scope is smooth and well balanced, and I found very little problem in locating everything I looked for with just the use of a Telrad and reasonably wide-field eyepiece.  I’m really looking forward to getting back out there with this one and carrying on my new odyssey around the sky.  It’s opened up a whole new window on the universe for me, and I can only say that I’m as happy as you could be with a purchase.  Can’t wait for the next clear night!

 A Note on Filters

Final image

The Rosette – Visible with an OIII Filter – not quite like this though!

This was the first and only time I’ve ever used filtration for visual use.  I can safely say that it won’t be the last.  A fellow SEKAS member was good enough to loan me an OIII filter to try on the nebulae I was observing, and the difference it made blew me away.  It makes the background inky black, whilst still allowing the structure of the nebulae to show through.  The contrast is so enhanced on M42 that you see probably about 50% more nebulosity than you do without it, and the view overall is infinitely more satisfying.  I have a UHC filter on order, and will also be picking up my own OIII filter to compliment it, as each objects places it’s own demands for filtration, depending on the light it emits or reflects.   The OIII even allowed me to observe the Rosette (Caldwell 49) for the first time ever (see an image I took previously to the left).  I’m looking forward to making more ‘discoveries’ like that in future.

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13 Responses

  1. Mike says:


    Nice enjoyable review thank you.
    Though I have no plans to purchase a Dob I can quite relate to your yearn to get back to basics.
    I started on the imaging path about a year ago and have found it to be a mix of frustration and much excitement.
    Having just started guiding as I am often taking upwards of an hour to just get everything setup for imaging.

    My results have been mixed though I have recently purchased a William Optics Star 71 Astrograph so I am hoping to start to get some more pleasing result. In fact I gave it a test last week and greatly enjoyed looking at the whole of the Double cluster and the Pleiades due to its wide field view.
    What I have found is that the imaging can certainly become an obsession and just simply looking at the stars is a welcome relief. In fact last Saturday I took my C8 to a friends house and enjoyed an evening of showing them the delights of the night sky!

    • Adam says:

      Hi Mike,

      I think a lot of imagers who came from a visual background are often pleasantly surprised when they put some time into the visual side again. I absolutely love imaging, but I think that I’m now getting a bit of balance back in my astro life. The visual is definitely going to help balance out the imaging frustration factor, though now I’m not trying to use the C8 for imaging, i think I may have less of the frustration ahead!



  2. Russell Williams says:

    Hi Adam,

    I’m pleased to see you’re enjoying my old scope so much. 🙂

    It’s a clever piece of design, as whilst the build is quite basic, all the bits you actually interface with – collimation, focuser, nudging – are all done so well with no shortcuts. The collimation as you note, is simply genius.

    I’d only have added that it’s surprising how quick the ES Dob self damps after a nudge, or a focus. It’s far quicker to settle than my old SW FlexTube 300p. Whilst that had shorter trusses, everything hanging on the end was much heavier and harder to damp.

    As a recommendation; keep an eye on the classifieds for a good 24mm SWA (68-72deg aFOV). That will pretty much fit in most extended objects and makes a good finder EP for those things too dull to find in either the Telrad, or an optical finder. A TV Panoptic or Meade/ES/Maxvision clone all work really well, as they’re better corrected for astigmatism than most and usefully, stay in an easy to balance 1.25″ format.

    Keep enjoying it and feel smug to know you could pay an awful lot more and see nothing extra!

  3. Georg says:

    Hello Adam

    First,excuse my not so good english !
    Before one week,I received my 10 ” explore scientific dobson
    You wrote,that the whole dobson is Alu-made ???
    I can’t believe it, because by my dobson the side-plates from the
    mirrorbox and the rockerbox are not alu,and all sides are made
    with cheap sheet metall,and a little rusty when I received my dobson !!
    Try with a magnet,if your boxes are really full Alu !!
    An answer woult be verry nice.


    • Adam says:

      Hi Georg,

      Interestingly enough, it seems you may be right about the steel sides. I’m surprised, as the whole construction is quite light, and I was always under the impression it was sheet aluminium too. I’ll keep an eye on the rust situation – but I don’t seem to have any steel rust as of yet…

      I may contact ES about it to get clarification…

  4. MAC says:

    I recently purchase the ultra light 10″ version, it is really enjoyable instrument.
    Here come the “but”, I wonder if any of you fellows have had difficultys with principal mirror.
    The mirror in my telescope in not attached (or not attached correctly) and it moves when the ts is tilted. As result collimation is lost.
    Can someone tell me how was the mirror attached when your Explore Scientific Ultra Light Dobsonian 254mmm TS was purchased ?
    Thanks in advance for your help.

    • Adam says:

      Hi Mac,

      I always collimate with the scope at about 45 degrees. Some of them seem to come with straps that hold the mirror in (just glued on to the side of the mirror), and some come with nothing holding the mirror in. I’vee experienced both and have no preference really. There are two ‘wheels’ and a top bit that holds the mirror still. You can pack out the gap between the mirror and top bit with a folded pice of material or something, and that seems to help. To be honest though, I’ve never found it a big issue.

  5. Russell Williams says:

    Mac, I’d point the scope vertical and then grab hold of the wheels that support the mirror and see if they, or their carriage is loose. On my first example, a good whack in transit courtesy of the courier had partially broken one carriages, allowing the mirror to shift with changes in position of the scope.

  6. Emad says:

    Hey Adam, this is Emad from SGL 🙂

    I hope things are going well for you, mate!

    Fantastic review – I thinking about getting a 12″ Dob after about 2 years of no observing due to personal circumstances. As you know I observe from my back garden, and my main concern is the light intrusion considering the ES dob is an open truss. Don’t get me wrong, I’m no stranger to ES and perhaps amongst the first to test their products 3 or 4 years ago – I ended up being a big fat fan. Wouldn’t the scope, without a shroud, suffer from stray light coming? Also, since the mirror is not far down, does it stay dry in humid conditions?

    Also, how long does it take to take put it together…approximately?


    • Adam says:

      Hi Emad! Good to hear from you!

      Potentially, if you do have light sources nearby, then yes, you can get a bit of a loss of contrast. I find it most when I’m trying to observe with the moon up (but not actually observing the moon!). I use a long length of 4-way black stretch fabric tube to stretch over it if I absolutely have to. To be honest, I don’t use the 12″ as much when the moon is around, as even though it does give great lunar views, my other scopes are also pretty good for that. I tend to save the dob for deep sky and occasionally some quick and dirty planetary observing.

      As for dew – yes, it can get a little dewy, but I don’t find its that bad in general. The secondary is more of an issue, and I deal with that with a 12v hairdryer or even just by holding my had on the back of it for a minute or so. If it’s extra dewy, and the primary does start to dew up, then the shroud can help with that too. Never really had massive issues with the primary though, like i said. lastly, there are a couple of fans which you can power off batteries, or via a 12v power pack, which keep the air around the primary moving, which does again help.

      To set up, i’ve managed to get it all put together and collimated in about 6-7 minutes before – basically not long! At a leisurely pace, about 10-12 mins I suppose! If you have a second pair of hands with you, then even quicker… As I’ve said, the collimation method on the primary for these is absolute genius!

      • Emad says:

        Thanks, mate!

        I had the SW 12″ Flextube for a while, perhaps I had it when you came to see me, and I loved the views it delivered. The combination of the scope weight and me being lazy meant that over time my observation activities gradually dwindled. My impression is that the ES can be carried few meters into the garden as one bulk without having to separate the base as the case for the SW Flextube. Can you lift the ES Dob and move it into your garden without having to disassembling it? I understand perhaps it needs to be done with surgical accuracy; but is it doable in principle?

        I’m also considering a 6″ refractor on an alt-az mount as a quicker to set up alternative. We’ll see.

        • Adam says:

          You can carry it as one, though the only way to work out if you’re comfortable with it is to try it. However, it’s so easy to dismount from the rocker box that even that would only add about 20-30 secs on getting it in and out. I haven’t done it too many times as I don’t usually leave it set up, even at home, as I don’t have the room…

  7. Peter Hess says:

    Thanks for this nice review. I first looked out for an Orion 14″ but they are way too heavy for me to carry around (I have severe limitations due to health problems). I’m using a Meade LX90 and am looking for something with a wider field of view and easy to use and manipulate. It’s your fantastic book about the use of Dobs that makes me look for one of these.
    I don’t care much about goto’s, since I use my full-automatic LX90 for imaging. The DOB will be used to initiate my 10 year old girl to setting up and using a telescope. She is very interested in astronomy, but I know that buying mediocre and cheap stuff will discourage her. That’s why I look for a good and lightweight DOB. Easy collimation seems to be the big bonus on this telescope, and I probably will go for the 400mm.
    Thanks again for this and so many other useful and well-written reviews and books.
    By the way, did you ever think of having them translated in French? There are many people out there who would love this!

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