145 replies to this topic

[pippo]

Hi,

at the RCE, the astro-exposition in Paris France, one of the vendor presented the new 18" f/4 light-Dob of Skywatcher:

I attach a photo taken from the net.

The expected price in Europe is around 4000 euros.

 

I was impressed by the sens of solidity of the structure. It looks much much  better than the other Dobs from Chinese companies and than the smaller models from SW. The new explore-scientific dobs (explore-scientific presented a 20" prototype) looked like toys in comparison....

The mirror (Pyrex) has a structure similar to that of the primary of the Celestron SC (see the attached figure).

I hope the the optical quality matches the mechanical one...any one has already tried one of these on the sky?

I hope that they will come soon with a 20" and with faster focal ratios.

 

Francesco

Attached Thumbnails

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Edited by pippo, 10 November 2014 - 03:00 PM.

[Shneor]

Looks a lot like my 22", but sparser bearings for sure!

[areyoukiddingme]

Makes me wonder whether the slow release of the explore scientific dobs has something to do with anticipated competition with these. . .

[dr.who]

I have seen it, played with it, and briefly looked through it at the SIA Expo in Los Angeles. Skywatcher USA was there and this scope was on display and used at the outreach star party afterwards. I only had a brief look because the line was quite long with non-astronomers and I didnt want to take away from the outreach end of things. 

 

I will say this about the views and mechanicals after swinging it around and looking through a 31 Nagler (I believe it was a 31 Nag but I may be remembering it wrong)... It's a gorgeous scope! It floats when you move it, it cools quick, and views in it are very very nice. In my mind it's a game changer for the high end UC/UL Dob market. 

 

 

 

 

[pippo]

On the large diameters there is no competition (from a mechanical point of view, I did not test the optics)! At least if one compares the actual 18" SW and the ES 20" prototype. Actually (if the optics are as good as the mechanics) the 18" SW can compete with high-end Dobsons, as Apollo pointed out.

 

The 18" SW is solid as rock, without being heavy, and smooth in the movements. It will be commercialized in France starting next week (the vendor Optique Unterlinden received already 5 scopes)

 

The 16" ES is already distributed in France. It looks to me a little too light already for a 16".

 

The ES 20" is just a prototype. The prototype is a just a scale-up of the 16" model. This is not good to me. Testing the movements and the stability of the 20"-ES-prototype  at the Paris-expo  I got the impression that the structure is too light to keep collimation for these diameters and the movements were not smooth at all. They have to rethink the 20" from scratch as SW did if they want to go beyond a 16".

 

On the contrary the SW is so robust that it could easily be scaled up to 20-24" or to shorter focal ratio than f/4. I hope that they will take this way.

If they come out with a 20" with a f3.6 or even better a f/3.3 with good optics, I will buy it immediately!

 

Notice that the 6 truss-bars of the 18" SW can be spitted in two, to reduce the bar-lenghts for transportation.

 

If I have to suggest a simple mechanical improvement to SW, I would add the possibility to attach (just during transportation) two wheels at the end of the altitude bearings (on the back-side) to easily transport the mounted-tube (see the schematic wheels location in red in the attached figure). Given the solidity and rigidity of the structure, this modification would allow a single person to move quickly the Dobson without the need of mounting and unmounting the tube-structure. If I buy it, I will solder two attachments for the wheels, to move the Dobson mounted from the house to the garden. 

 

 

Attached Thumbnails

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Edited by pippo, 11 November 2014 - 06:49 AM.

[skyward_eyes]

There are a few small adjustments we asked the factory to make before we officially introduce the 18" in the US. It is however, very close to release. The 18" will also have a GoTo/tracking option in the future which is currently being worked on. The 18" is an f/4.15 making the eyepiece easy to get to, but for best performance we recommend a coma corrector. I have tested it with a Paracorr 2 and 31 Nagler and the views are pin point to the edge. 

 

For those asking for larger. We already have plans for a 20" f/3.9 which will follow once the 18" is released. We are also interested in larger but there are no plans currently to pass 20". Once the 20" is released we will have a better idea if its worth moving into the larger size such as 22" or 24". But that is another ball game at those sizes.

Edited by skyward_eyes, 11 November 2014 - 09:18 AM.

[Pinbout]

when you had the 18 at NEAF it had a sandwich mirror, in the pic above it looks cast.

 

what will the production mirror be?

[skyward_eyes]

The old sandwich mirror has been done away with. It was a proof of concept and only a handful of them exist. Sky-Watcher USA has two of these sandwich mirror, one coated and one uncoated, they remain in storage for historical reference. The 18" will use a new sandwich style mirror but instead of cylinders it will use glass ribs to separate the two pieces of glass. You will see these in the production models. The one in the picture and our current prototype uses a cast mirror for testing. 

[pippo]

The old sandwich mirror has been done away with. It was a proof of concept and only a handful of them exist. Sky-Watcher USA has two of these sandwich mirror, one coated and one uncoated, they remain in storage for historical reference. The 18" will use a new sandwich style mirror but instead of cylinders it will use glass ribs to separate the two pieces of glass. You will see these in the production models. The one in the picture and our current prototype uses a cast mirror for testing. 

This is strange,

the scope commercialized in Europe has a casted mirror like the one in the picture (and like the sw 14" model) and not a sandwitch mirror.

Edited by pippo, 11 November 2014 - 05:04 PM.

[skyward_eyes]

To my knowledge there are no public pictures of the new mirror. 

[Pinbout]

That sounds like a norman mirror, he had a 36" blank a couple of years ago at NEAF

Edited by Pinbout, 11 November 2014 - 07:20 PM.

[skyward_eyes]

These are very similar, expect it is produced by Sky-Watcher. 

[Howie Glatter]

> To my knowledge there are no public pictures of the new mirror.

 

I saw the new mirror at the factory in China. It appears to be fused from plate, with radial triangular ribs at the back. I'd call it a ribbed conical. I cautioned David Shen that the glass type of the plate and ribs must be the same, preferably from the same melt. He smiled, and it was clear he already knew this. I believe the ribs are cut from the same plate.

Edited by Howie Glatter, 11 November 2014 - 09:11 PM.

[hrgreen]

Is the size and weight of the mirror box configured for transport available?  If I can handle it alone, I'm interested.

 

Hal

[pippo]

At the RCE-show in Paris, the model presented was not a prototype but the one put on the market. The mirror was of the same kind used in the retractable 14 sw model  since many years.  Unfortunately I did not take a photo of it...

[pippo]

I gave for granted that the mirror and the ribs were casted togather, and not glued. I did not examine the mirror with attention to distinguish the two cases. I hope that is casted and not glued. There are many examples of large glued mirrors  degredating their performancing in time. I would never buy a glued mirror.

 

Is the mirror in the SW 14" Dobson a single cast or are the ribs glued to a conical back? Anyone with a 14" can give us some more detalied information?

Edited by pippo, 12 November 2014 - 03:08 AM.

[areyoukiddingme]

Is the information on the solidity of the mechanics speculation, or based on some good evidence? Pushing the thing about is obviously better than nothing, but has anyone tried seeing what a collimator does when the scope is moved in altitude?

 

I have two scopes with 3 truss arrangements, and they are anything but solid!

[pippo]

Is the information on the solidity of the mechanics speculation, or based on some good evidence? Pushing the thing about is obviously better than nothing, but has anyone tried seeing what a collimator does when the scope is moved in altitude?

 

I have two scopes with 3 truss arrangements, and they are anything but solid!

The 18" has 6 truss and not 3 as the 14" model.

I just moved around the scope at the Paris-show getting this impression of solidity. It should be tested with a laser collimation in use to verify more seriusly its mechanical solidity. As soon as will be available by a vendor in Paris (where I live) I will test this...

[skyward_eyes]

The primary mirrors on the 14" and 16" as well as the displayed 18" scopes are casted. They are a solid piece if glass produced at the factory.

 

The new 18" primary is a sandwich style mirror using glass ribs. The glass is fused together in a oven, there is no glue used.

 

As to collimating the scope holds it quite well. I am a dob user myself so I am aware of what need to be taken note of. I was able to use the scope throughout the evening without any noticeable shift in collimation. The views are bright and detailed, about what you'd expect from a scope this size. It is a very nice scope.

 

current the heaviest portion is the rocker/mirror box weighing in at 75lbs. We have asked the factory to work on a wheel system to make it easier to move. I have yet to hear back from them on this. The scope will have a shroud as well, Sky-Watcher USA has a sample on this for our 18". The shroud has ribs in it to help keep it out of the light path.

Edited by skyward_eyes, 12 November 2014 - 09:18 AM.

[pippo]

Thanks,

it would be great if the wheels would allow to move the tube alone without the base.

A system that allows one to move separately the tube and the base is much more efficient than that used for the 14" SW model (that goes under the base).

 

Probably two wheels as I schematically represented in red in my picture above can make the job... If this suggestion can be forwarded to SW is good...

Edited by pippo, 12 November 2014 - 10:29 AM.

[pippo]

I did not get if 75lbs is the weight of the mounted tube + mirror

[skyward_eyes]

The entire telescope is 147lbs. The heaviest single component is mirror/rocker box at 75lbs. This does not include the ground board which is a separate piece. 

[havasman]

This series appears to present a very attractive set of options in the higher-end medium Dob market. I hope they get it right with good rigidity, quality mirrors, effective DSC/Go-To/Tracking implementation and useful wheels for loading/unloading. If they do and are as cost effective as they should be, I'm in for a 16 or 18. If they blow it, it's just market clutter.

Three truss construction is not encouraging.

[Mike B]

...We already have plans for a 20" f/3.9 which will follow once the 18" is released.

 

That sounds quite enticing!

[yaroslav_s]

Here is the presentation of 18" SkyWatcher Dob in Kyiv, Ukraine.

Sorry, but there are no English subs.

Anyway, for the general impression of the product this video is OK.

 

https://www.youtube....ZY7fzo4WN6o48mA