Skywatcher 16 !!!

[DJ N]

Interesting........... just came across this........

http://www.photoimaging.com.au/pages/currentpage.taf?record_ID=46861

Just when I was thinking the 14 incher would be nice!!:eyepop:

[Raybot (Ray)]

Whoa ! thanks for sharing

[NorthernLight]

hey, that looks like an alternative to the meade lightbridge. I like the idea to just 3 clamps, push it in and store it away. do they also make a non goto version, sure they do, don´t they?
somebody an idea on the introduction price?

[kustard]

I'm thinking of something in the 14-16" range for my next scope and this might do the trick :)

*dreams*

[mic_m]

Thanks for the heads up.

While a new telescope is always exiting news, I can see some issues with the design of the SW 16.

I have serious doubts about the rigidity of the strut design over a conventional truss like the LB or the Orion XX series. Especially given the problems that many owners appear to have encountered with tube and strut flexure in the parallel strut design of the GSO 16. Hopefully this SW will not be a “flextube”. Time will tell.

Trusses are an inherently rigid configuration; a triangle cannot shift or collapse. Trusses are well proven in telescope design (and more largely in engineering in general).

I suspect that the decision to go with the strut design over a truss is marketing related; because Orion’s equivalent Synta manufactured telescope will likely be using a truss. What a shame.

With a large telescope it is often beneficial to be able to disassemble the telescope structure for transport. However it appears that one will have to move the LTA, UTA and connecting struts in one go, as is the case with the smaller models. That could be quite a challenge; the SW 16 looks like a heavy telescope.

Indeed, the SW 16 LTA looks to be far larger than the LTA of the LB 16, as does the base; based on the fact that SW and Meade (GSO) use similar material to construct their telescopes, it stands to reason that the 16” SW will be not only larger than the LB 16 but heavier too. Further, based on the specs for the SW 14 its tube weight is as heavy as the LB 16 LTA – 26kg (the LB 16’s heaviest component). Assuming that the SW 16 will be heavier than the SW 14, it follows that SW 16 will be somewhat heavier than the LB 16.

Its interesting to note that while Orion reduced the size of the LTA between the XX12 and XX14 models it looks as if SW has actually increased the size of the LTA, it seems to keep the length of the connecting struts short (to help minimise strut flexure perhaps).

I was hoping for a SW telescope that would be lighter and more compact than the LB 16. However, it is clear that many of the impediments that have prevented people purchasing a LB 16 (size and weight) are very much existent within the SW 16 design.

I think that companies like SW really need to start listening to what their customers want if they want successful products. While the SW 16 appears to have a collapsible base and a duel speed focuser, which is very positive, it also appears to be unnecessarily large and heavy.

[robz]

Tend to agree with you here Michael.

Three thin tubes coupled to an even thinner, flimsy looking lower half flange looks like trouble.

It's bad enough that these thin mirrors are usually not supported sufficiently in their cells, let alone a flexing mast at the top end.:rolleyes:

I hate to slag a yet to be used or seen scope, but this collapsible three strut stuff has to stop.

[chris lewis]

One positive aspect of these types of designs is the ability to use a binoviewer just by reducing the focal length via the strut lengths. Of course the added weight could induce more flex.

Chris

[Sylvain]

I agree with Michael and Robert on this one.
The principle of extension tubes definitely does not look sound to me when it comes to rigidity.
It sure is looks good in terms of marketing, but engineering wise this does not make much sense to me for a product where flexibility is critical. Very sceptical.

[noswonky]

I have the 12 inch version of this scope and I find it to be close to the weight limit of what one person can move and assemble. It's also too big to fit easily in a medium size vehicle. The base is too tall to stand upright in a typical station wagon - have to lie it down - which may put stress on the azimuth bearing.

I'm upgrading my vehicle to a compact SUV just so that I can transport the scope. Only an SUV has a high enough ceiling to transport the base standing upright!

I think the 16 inch will need a LARGE SUV and 2 people to transport it.

As for the rigidity of the collapsible strut design, the 12 seems very rigid. The struts are quite thick which makes up for the inherent weakness of a parallel strut design. It also adds to the weight. Obviously the 16 is going to be less rigid but it still could be rigid enough.

[Kevnool]

I suppose someone will purchase this and hopefully do a review concerning all the points you have all raised.

Me being a 16"er all i can tell you is its going to be heavy and will flex.

Then comes the mods to stop flex.

All the best with this one.

Cheers Kev.

[Rickster]

Hey all,
Just received my SW 14" flex tube goto Dob. I have to say, the quality and design are excellent! Very impressive and money well spent. I have only been able to briefly use it, but optics are very good and I am looking forward for a nice clear night. Not sure what flex you are talking about as this telescope is very rigid. The design has been well thought out, which makes for a large portable unit, but It is on the limit of portability. The 16" will be a handfull I'm sure!

Cheers
Rick

[mental4astro]

Rick, the way 'flex' manifests itself in a scope is when you first aim the scope to zenith, and the optics are collimated & stars are pinpoint, you then drop the scope to view something close to the horizon, does the image of the stars distort from pinpoint to 'comet' like. This shows that the alignment of the optics has been compromised in the shift of position.

This might indicate flex in the OTA, but also and not exclusive of a weak primary mirror cell, or a weak secondary/spider arrangement, or movement in the mount, or movement in any other component or combination.

Congrats on the scope, though. Nice light bucket you've got yourself.

[Rickster]

As I said, I havent had a chance to really suss it out as yet, but I will see if any flex occurs as you mention. From what I have seen, it seems to be of a very rigid and a solid construction.

Rick

[Louwai]

I've got the 12" version of this.
The only down side that I can see is that the scope must ALWAYS be driven to position.
It does not have releasable clutches, so at no time can you "Push-To".
The scope is 100% GO-TO.


I also agree with the comments about transport. I'm lucky & am able to transport it in the trailer with my SDM. But if I didn;t have the trailer, I'd have to transport the tube in the boot & the base in the back seat laying on it's side.
Quite inconvenient.

[Rickster]

Hi,
This is not the case with the 14". You can hand position it as there are encoders within the drive units. This means once you have done the initial setup, you can move it anywhere and it stays calibrated. There is no clutch.

Cheers
Rick

[CraigS]

This is very interesting. SkyWatcher's description page for the 10 inch collapsible goto (http://www.skywatchertelescope.net/swtinc/product.php?id=171&class1=1&class2=106) says "The patented dual encoder design allows the telescope to be moved manually whenever the user wishes - but with no need for re-alignment!"

Until now, I had thought that this statement did not rule out that the scope might have to be manually driven using the auto-tracking control handset, (rather than hand-moved).

This is big news !!! Thanks Rickster !!

Cheers

[Satchmo]

There has to be a clutch otherwise the scope couldn't be driven, and also hand pushed. Sounds like they have a slip clutch there which would need adjustment occasionally so the adjustment of it would be in the manual.
I'm keen to hear from actual owners of the scope.

[CraigS]

So, I too would also like to hear from the actual owners about the navigation/clutch issue.

A close follow up question would then seem to be about the pointing accuracy.
For example is there any RA to Dec axis non-orthogonality evident ?
Are you using three star alignment and do you find this enough to maintain accurate alignment during an observing session ?

Cheers & Rgds

[Louwai]

I should be more specific I suppose Mark.

My 12" SW collapsable Truss definately does not have releasable clutches. It is not able to be used as "Push-to" in the usual way. Free movement..
If the scope is "pushed" then one must push quite slowly & with some force as you are spinning the drive motors, & at far higher revs than standard "drive" speed.
When Ron from Sirius Optics gave me the run-down on how to use the scope he specifically said not to push it, but to manually drive it with the hand ctrl when I was not usuing it as GO-TO.

So, in my way of thinking, my 12" is not a scope that is capable of "Push-To".

Cheers, Bryan

[noswonky]

Well that's very strange indeed!

I have the 12" SW Collapsible also. Mine is Auto Tracking (not go-to).
It does not have the problem you describe. It can be pushed around to point at targets just like a regular (non-motorised) dob. You can even do this while it's tracking and it just continues tracking the new target.

I normally push it for large distance slewing and use the motors for fine adjustments or star-hopping.

It does have an issue with some looseness or 'play' in the azimuth axis. A few others have mentioned this but I haven't yet seen anyone claim to have solved it. Someone said that you can 'tighten the gears' etc. But how do you get access to them???? Has anyone actually done it?

[CraigS]

From Noswonky:


Rob288 (from NZ) on 1st August in this link (http://www.iceinspace.com.au/forum/showthread.php?t=63781) said the following about a SW 12 inch Goto:



That's the closest I've heard of anyone addressing/resolving this problem.

Cheers & Rgds

[noswonky]

Further to that, see this video on Skywatcher's YouTube Channel which refers to the goto version of the scope...

http://www.youtube.com/watch?v=XW8nRe_-LyE

At 1:26 it says:

"The patented dual-encoder design allows you to manually move the telescope anytime and to anywhere you wish - with no need for re-allignment. Slewing to an object on the opposite side of the night sky no longer feels like watching a pot boil. Simply push the tube close to the object and let the computer do the rest of the work."

[CraigS]

Hmm .. Peter;

So now I'm wondering how much power one night's observing might take ? I'd love to get out of having to manage the charging & transportation of that battery pack. Do you reckon you could scale down the power supply if you stick to 'push to' for long distance slewing ?

Cheers

[Louwai]

Peter,
Haven't looked at the link. (can't access youtube from work).
I hear what you are saying, but I'd need to look at the specs of the individual scopes to make an informed comment / comparison.
I am only making comment on the actual scope that I have. (which is the unit that I recently won in the Qld Astrofest raffle)

My 12" has drive motors which are permenantly locked in. Manually pushing the scope will force the motors to spin. As the motors are designed for tracking, the gearing is very high & so the scope is reasonably stiff to manually push due to the resistance from the motors. If you push fast, the motors literally scream as they are spinning so fast.

The instructions which came with the scope advise to use the hand ctrl & drive the scope when needing to move manually, even to the alignment stars during initial alignment.

So from what I know about my 12" & from what you have said about yours, it seems that we may be trying to compare 2 different models of the same base unit.

Cheers, B

[Louwai]

The 12" that I have came with a battery pack to hold 8 x 'D' size batteries. Although I have not used this battery pack, I'm assuming that it would give at least 3 to 4hrs of motor use.

Also I found that the scope didn't actually come with a power cord that could be used with a std cig lighter socket. The ONLY power cord was that which was attached to the battery pack noted above.
I happened to have another cord which is suitable & can be used from a cig socket.

B

(my mistake - Yes 'D' size batteries)

[noswonky]

I've only had the auto-tracking scope about a month, so I'm not yet sure how much power it uses.

It came with a battery pack which takes 8 'D' size batteries (producing 12V) and I'm using heavy duty batteries.

I've probably run it on one set of batteries for at least 8 hours (possibly more) in total - tracking most of that time - and the batteries still seemed ok. However, I don't use the motors for slewing more than a few degrees.

I did change the batteries after that to avoid them going flat during a star party, so I'm not sure how much power they had left.

But my feeling is that it doesn't seem to use much power. I would expect the go-to version to use more power due to the more sophisticated hand controller and the greater use of motorised slewing.

[CraigS]

Thanks Peter.

So, the next question, (not for you 'cause this is a 'goto' question), would be does the SkyScan (SS) controller get feedback from the encoders in the Autotracking mechanism ?

If yes, then you could still push the scope to the approximate position and then use the SS to do the fine adjustments (thereby saving battery power).

Also, I think I read in the SS technical manual that the SS controller remembers the position if the power is removed (without the need for re-alignment). From memory, I think this feature only works if you park the scope in the vertical position before disconnecting the power (??). - I'll have to read up on that again.

Interesting.

Cheers & Rgds.

[noswonky]

In the case of the auto-tracker, it remembers your latitude setting when powered off - so you only have to set latitude once, not once per observing session.

The alignment at the start of a session involves simply pointing the scope at the northern horizon (ie zero degrees azimuth and zero degrees elevation) and powering it off and on. How you find north is up to the user.

[Steffen]

But that's the difference, for mere tracking the scope just needs to be aligned (the tracking computer needs to know which way the mount is oriented), it doesn't need to know where it's pointing right now, like a goto mount does. EDIT Sorry, strike that, I forgot for a moment that Dobs are alt-az… :screwy:

I never quite understood why encoders in goto mounts are always put into (or near) the motors?? They should be placed near the pivots, like you'd find with DSCs. That way it wouldn't matter if the tube gets unclutched from the motors, the computer would always know where it's pointing.

To take this slightly off-topic, I found a curious behaviour with my new HEQ5Pro mount. Without proper polar alignment of the mount I can still perform a 3-star align and goto accuracy would be quite good. However, tracking gets worse with sloppier polar alignment. It appears that while the computer takes the actual mount orientation into account for goto it will track by simply turning in RA at the siderial rate. If that's the case it seems like an odd limitation of the software… :shrug:

Cheers
Steffen.

[CraigS]

Hi Steffen;

i) Would that suggest that the Goto software doesn't get involved in the tracking (??) but only gets involved in the pointing (??) (Am I reading you right here ?)

ii) I believe, (read somewhere), that on a GEM, non-orthogonality between the Dec and Optical axes is quite common but analysis using three stars only
is not adequate to compensate for RA to Dec non-orthogonality. Some GEM controllers apparently only offer three star alignment to compensate for this error.

Perhaps what you're pointing out maybe answered by (i) or (ii) above.
Not sure, though.
Interesting.

Cheers & Rgds

[Steffen]

That appears to be the case. I can use goto to slew to an object, watch it drift out of the field and then get it back by simply pressing enter again on the hand controller to initiate a new goto to the same object.

This indicates to me that the "intelligence" gathered during alignment is available to the goto function but disregarded for the purpose of tracking. Weird.



Isn't that what's known as "cone error"? I believe some scope control software can detect and compensate for cone error, not sure about SynScan at the moment. Gotta read the manual when I get home ;)

Cheers
Steffen.

[CraigS]

Or the controller simply isn't compensating for a systematic pointing error which only manifests itself as the scope moves. (?) (As opposed to during the alignment process).


Perhaps this error correction is only 'crude' and is based solely on calculations based on the three star alignment at the outset (?).

- Don't know .. but we'd have to delve into the software to find out !

Cheers & Rgds