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Throwing in the Towel on the Sky-Watcher 10" Flextube

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#1 Eddgie

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Posted 05 December 2020 - 11:33 AM

I have tried and tried to make peace with my decision to buy this scope, but I am done trying to make it better..

 

I bought the Flextube becuase I wanted to be able to use my .73 focal reducer/coma corrector and I saw the Flextube as a "short cut" to getting there. An added bonus was that I was able to reach focus with binoviewers using a 1.7x GPC and even at native focal length (no GPC) though this cost about half inch of aperture, which is not an unacceptable compromise to me.

 

The latest problem was a new neighbor that likes security lights on at night, and this necessitated the fabrication of a Kydex light shroud  and this added even more weight. 

 

XQE_01351.JPG

 

 

What started as a telescope that was supposed to be light has now wound up with a telescope that has gained five pounds of added weight (and this is using just a laser finder!) 

The real problems with this scope that I have struggled to overcome have been around movement. The azimuth motion on this scope was poor out of the box and while PTFE pads improved this, overall, it was just a modest improvement, and azimuth motion remains stiff and in particular, when working near zenith, the scope becomes difficult to move.

 

Likewise, altitude motion is very balance dependent. Even slight imbalance requires that the friction clutch be utilized, and this clutch has kind of a fiber material, which does not have good friction behavior, making high power tracking of planets difficult. 

 

I was hard headed and thought I could overcome some of these issues, and I threw a lot of money into the scope (new focuser for light path intrusion, encoder kit, though some of this might transfer forward, in particular the Nexus II but probably the azimuth encoder, though I may still have to buy a new kit), but in the end, every time I use it, I curse the problems inherent to the design. 

 

I was initially leaning towards the Apertura or SkyLine dobs because of the closed tubes and the superior azimuth and altitude setup, but again, I was seduced by the easy of converting the Flextube to my needs (and indeed, it was easy to set it up for the focal reducer).  With the Apertura, I would have needed to raise the mirror to reach focus with the reducer (and this would have not been so difficult) and perhaps oversize the secondary mirror a bit.  I know raising the mirror would have induced balance problems but the Apertura has an altitude bearing that allows for CG modification and even if I ran out of range, it would have been very simple to drill new mounting holes higher on the tube.  The Flextube does not allow this kind of bearing movement because the molded bearing plate is placed as high on the tube as it can be, so moving the CG further to the front is out of the question.

 

So, after a couple of months of trying to be happy with it, I have come to believe that the instrument is simply never going to be what I had hoped it would be. 

I had thought about going with a custom dob, but these tend to be open truss scopes, and now that I have this new neighbor that likes security lights, I think closed is a better option. 

 

I wanted to love the Flextube, and indeed, it does allow for binoviewer and focal reducer use, but I struggle to even like it a lot.

This is not a telescope I can recommend to anyone, even if they have a special requirement like using a binoviewer.  The balance and poor bearing design conspire together to make this an unsatisfying telescope to use. 

 

Now I have to decide whether just to live with it and curse it when I am doing high power work, or start over. I dread the thought of starting over, but I do find that the current setup aggravates me more than I care to admit.

So, something of a rant, and forgive me for that, but I am just tired of trying to make this scope something it can't be.  

 

 

 

 

 

 


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#2 ICit2

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Posted 05 December 2020 - 11:51 AM

Hey Eddgie;

 

I've read some of your posts in the past and I know you're no newbie to the hobby. So, if a guy with your experience can't make it work the way you wanted, then maybe it is time to cut your losses.  I know on occasion there's nights that turn out to be a bust.  That's par for the course.  But having a bad feeling before you even setup is not what this is about.  It's about having fun while improving your game. Right?

 

Best of luck.

Richard


Edited by ICit2, 05 December 2020 - 11:52 AM.

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#3 JGass

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Posted 05 December 2020 - 12:01 PM

Hey Ed,

How did the optics perform?

Jim

#4 Grounddweller

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Posted 05 December 2020 - 12:09 PM

Sorry to hear of your plight with this scope. I owned one for several years before moving away from a semi-rural area and while I had it I enjoyed the views a great deal. BUT... you are right about the base, friction controls and balance issues. This scope is a great concept and the collapsable tubing is an awesome convenience, it even held collimation well despite the constant sliding. However it is a very basic setup and does not have the capability of absorbing a lot of ancillary equipment and continue to function well. I had some great views of M1 & M57 under some Bortles 4 skies with it and even without a coma corrector basic plossls seemed to give clear views. But that is the extent of its capabilities, enjoy it for some competent views but not for specialized work.

 

Steve


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#5 rowdy388

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Posted 05 December 2020 - 12:12 PM

Have you considered replacing the dob mount with a high end kit dob mount? Seems like a reasonable solution as long as the OTA components

are acceptable.


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#6 vtornado

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Posted 05 December 2020 - 12:26 PM

I bought my 300  flextube as a surplus tube only and built the mount for it.

I used a dreaded lazy susan bearing for azimuth.  I had problems with stiction with traditional methods.

I have always felt it is a lot easier to increase friction than decrease it.

A small square of carpeting works like a charm between the ground board and az board.

I am struggling with the altitude.  Yeah it works, but it is a bit wonky.  The trunions are just too small on the scope.

I have them running a vee notch covered with ldpe.

I am using a doughnut magnet to help with altitude balance.  If I ever get a big block of time (ha ha)

I will replace the trunions with march larger ones.


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#7 MellonLake

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Posted 05 December 2020 - 12:40 PM

I had a hell of a time with my XT10 for a long time. I finally zip tied a 5lb soft scuba weight to bottom end of the tube (long zip ties around the tube holding the weight where it would hit the rocker box front board).  It made one hell of a difference in the altitude movement.  I lubed up the altitude bearing with some soap and now it runs really smooth and the tube is balanced in all positions really well (even with the crappy XT10 springs).  I can even use it without the tensioning springs.  I think if there was any less stiction it would be difficult to use.  

 

For the Azimuth bearing I used the CD mod (put a stack of CDs under the position of the centre post), this took a bit of weight off of the Azimuth pads and with the addition of some soap it is very smooth and similar force to the altitude (although I think it could still be better). 

 

I view planets at 240X a good amount and can easily shift the view to allow the planet to drift across without loosing the planet. 

 

As you noted balance is key.  The addition of a 5lb weight really really helped me.      


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#8 cookjaiii

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Posted 05 December 2020 - 02:28 PM

Thanks for your candid review.  I have looked longingly at this design for years but never quite got it into the shopping cart.  



#9 junomike

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Posted 05 December 2020 - 03:00 PM

Eddgie, sorry to hear it's not going to work out. 

Before my SW 12 Synscan I modded a standard SW 12 Base  which also had poor AZ movement.  Like vtornado I found a lazy susan was a great answer. I, added a break as the movement was too smooth. I'm sure you've seen it but if not have a glance as it really does work.

A similar felt "brake" on the Alt might be something to consider as well.



#10 SteveG

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Posted 05 December 2020 - 03:52 PM

Very sorry to hear! My GSO uses a Lazy Susan Az bearing, and I find it perfect and very easy to use at Zenith.

 

Like yours, mine is top heavy too - by a lot! I'm contemplating having an aluminum tube cut for the upper tube assembly only.


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#11 coopman

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Posted 05 December 2020 - 04:39 PM

Perhaps get an Astrogoods tube cradle with 12" dia. alt. bearings.  Rebuild the mount to accommodate this.  Pics are on Mark's website.  I have a set ordered for my 8" Dob.  There is currently a 6 week backlog of orders he is working through. 


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#12 doug mc

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Posted 05 December 2020 - 06:08 PM

A few years ago I moved from Synta dobs to a GSO 8. The smooth operation ot the GSO was marvelous.



#13 Eddgie

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Posted 05 December 2020 - 06:45 PM

Hey Ed,

How did the optics perform?

Jim

The optics are pretty decent.  Good views of Mars and moon. I have no issues with the performance. 

 

I would also say that to be fair, the Flextube does what it is marketed for, which is to allow you go be flexible with the configuration.  It did indeed make it very easy to get my binoviewer and my focal redcucer to work.  It is just not a smooth telescope to operate and having to throw on a lot of counterweight further burdens the bearings and Teflon glides. This is my biggest complaint.  I could perhaps make a new custom base to solve the azimuth problem, but the altitude bearing design is poor and I am just done messing with it. 

 

The Apertura bearing system looks superior.  I don't know that it is superior, but it looks superior. The thing where the sides curve on the SW when the friction clutch is used is just horrible, and the clutch itself does not allow for smooth movement even when there is minor imbalance.   

Even out of the box, with just the factory finder on it, this thing was almost completely incapable of handling binoviewers. I had to have the friction set so high that the scope would barely move in altitude.  Had to dump the finder, but mostly I use laser, and really, I only do that to get to my alignment star for the digital circles, which I use for everything else.  I love digital circles and Sky Safari.

 

Another fair point.  In the binoviewer detent, it does actually balance well with binoviewers, but this comes at about .8" of aperture loss. Why use a 9" scope when you can use a 10" scope. 



#14 Jon Isaacs

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Posted 05 December 2020 - 07:31 PM

Ed:

 

Sorry to hear you weren't able to get the scope to live up to its potential..

 

About all I can suggest in a last ditch effort to make it work are bar soap for the bearings and HarborFrelght lifting magnets for balance..

 

This one weighs 2 lbs

 

https://www.harborfr...pull-36904.html

 

This one weighs 5 lbs

 

https://www.harborfr...pull-36905.html

 

I keep some around just to rebalance when swapping finders and stuff.  My big Dob has a balance ratio of about 5.5:1. If I add one pound to the top, I need to add 5.5 lbs on the bottom.  The large bearings handle the eyepiece swaps but it must be balanced.

 

Jon



#15 Spacedude4040

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Posted 06 December 2020 - 08:24 AM

Eddgie, 

Go old school on it!  Rebuild the base with Formica and Teflon and add proper Alt bearings. You may have to add a little weight to the optical tube for balance but I bet you could save the same amount of weight on the new base.

The beauty of this is you have a working scope while you are making the new base so no rush in do so.

Mike


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#16 Will_S

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Posted 06 December 2020 - 08:40 AM

Perhaps get an Astrogoods tube cradle with 12" dia. alt. bearings.  Rebuild the mount to accommodate this.  Pics are on Mark's website.  I have a set ordered for my 8" Dob.  There is currently a 6 week backlog of orders he is working through. 

That's roughly what I did, although I'm not sure a cradle would be compatible with the struts being extended/collapsed.

 

I just had Mark make trunnions that bolted on over the existing ones, offset a bit so that it was properly balanced rather than nose-heavy. I then ended up making it very slightly nose-heavy again by adding a 10:1 focuser upgrade, heavier eyepiece extension tube, and heavier finder bracket. It's really only an issue with my heaviest eyepiece, but I broke down and got a 1.25 lb magnetic "platemate" that lets me fine tune the balance. In practice I seem to have found a single spot for the weight that yields acceptable balance for all my eyepieces and at all aiming altitudes, so maybe a slightly different offset on the trunnions would eliminate the need for the weight, but it's nice to know that if I ever want to add heavier accessories it shouldn't pose a problem.

 

I'm quite happy with the scope on its upgraded mount, but I gave away the particleboard abomination of a stock mount as was my plan from day one. I'm sorry to hear it's not really working out for Edgie.

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#17 vdog

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Posted 06 December 2020 - 10:26 AM

Sorry to hear you're not having any success with that scope.

 

I can relate.  My SW 10" would still sink even with the clutch locked down as tight as I could get it.  I kept going back and back to Harbor Freight for more plate magnets.  Finally, I ended up hanging a 2.5 lb plate weight off the back end with a bungee cord.  Combined with about 3 lbs. more of magnets, this finally did the trick. 



#18 Old Rookie

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Posted 06 December 2020 - 11:16 AM

That's bad news about your SW.  I can relate since I have one also.  However, other than being heavier than I would like, it's turned into a decent dob.  There's a couple of things I did that have worked pretty well.

 

1.  Azimuth Motion:  I replaced the original pads with 3/16" pads.  In addition, I added the lazy susan bearing with the metal plates.  The end result was that I have smooth motion with no wobble.  The formica on the bottom is not really the proper material for  az motion.  The lazy susan bearings have kept things smooth and carry most of the weight while the pads prevent any wobble.

 

2.  Altitude Motion:  The original friction material on the altitude bearing is almost like a brake pad.  I used FRP on the opposite side that makes contact with the plastic of the bearing while allowing that friction material to sit inside.  In other words, I've bypassed that material entirely.

 

3.  I also moved the side bearings up the tube.  That is, I took them off, moved the bearing up the tube, drilled new holes and removed plastic material at the top of the bearing so I could reattach them.  This moves some weight towards the bottom of the tube without adding weight.  I removed about an inch from the bearing, could have removed another half an inch.   I still use weight but I don't have to add as much.  I've also attached a weight system on opposite underside of the tube that has 4lbs.  And one more movable weight.  

 

At the top I have a Moonlight focuser, GSO RACI finder and a Telrad.  I typically use a GSO coma corrector.  This whole thing balances pretty well without any input from the altitude tension brake most of the time.  I only use that when I use my 35mm Panoptic.  

 

You might find some of these ideas handy.


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#19 doug mc

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Posted 06 December 2020 - 05:49 PM

Find someone near you with a GSO 10inch and try it out if you can.  I am confident you will be surprised how much better they are.



#20 GeneT

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Posted 06 December 2020 - 07:45 PM

Eddgie, I know you carefully thought through all the specs and parameters before buying the Sky-Watcher. You made modifications that should have fixed the issues--but they didn't. All of us have gotten caught up in similar situations. I think you should just start over. You could make someone a good deal on the telescope. Your neighbors and their security lights are their own problem. Aren't those problems apart from the telescope, though? I don't know if movement lights going on and off would help. However, most people I know aren't very considerate when it comes to how they light up their property and for the most part aren't open to discussion.  



#21 Eddgie

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Posted 09 December 2020 - 10:58 AM

 

 

2.  Altitude Motion:  The original friction material on the altitude bearing is almost like a brake pad.  I used FRP on the opposite side that makes contact with the plastic of the bearing while allowing that friction material to sit inside.  In other words, I've bypassed that material entirely.

 

 

I have very seriously considered doing this mod but when I did the math on it, it suggested that it would not really do much to eliminate the counterweight though it might reduce it by a pound and a half, but that simply might not be enough to make it worth doing for me.



#22 Eddgie

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Posted 09 December 2020 - 11:13 AM

I tried the Rockler bearing but found it to be lighter, but not as smooth as the original nylon pads, which have since been replaced with true PTFE pads (I think the originals are nylon).

 

I am just not interested in rebuilding the base at this time. 

 

The scope is working. It is actually more or less OK for the image intensifier because here, I rarely use more than 80x, and the the scope is more or less balanced for the image intensifier, focal reducer, and filter wheel.

 

When I bought the scope, I was not really using binoviewers for anything by planets and in truth, I was not really doing that much planetary observing anymore, but the more I used the binoviewers with this scope, I forgot how much I enjoyed using binoviewers, and this is where it is very disappointing.  Tracking at high power is tedious.  

Again, I don't use it that much for binoviewers, and since it does work decently well for image intensified astronomy, by throwing in the towel, I am simply saying that I am unlikely to invest more time and money in this scope.

 

I have not decided whether I will replace it with an Apertura.  That scope might even require some modification (move the mirror up with longer screws) and it is still a physically larger telescope, but next time Jupiter and Saturn come back, I will consider at that time whether I want to move to the Apertura.  

 

I am just done messing with the scope as it is. Already spent too much time and energy and while it is better than it was, I do not think it is possible to make it "great" and have suspended all efforts to improve further.  Just annoying that the design is so poor to start with. Should not need this much effort to make it acceptable, and from where I sit, impossible to make it excellent without a total rebuild. 



#23 Woj2007

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Posted 09 December 2020 - 11:38 AM

The real problems with this scope that I have struggled to overcome have been around movement. The azimuth motion on this scope was poor out of the box and while PTFE pads improved this, overall, it was just a modest improvement, and azimuth motion remains stiff and in particular, when working near zenith, the scope becomes difficult to move.

 

Eddgie, sorry to hear about the inconveniences. Still, the problems seem to be in the 'mount'.

So, if you don't mind tinkering, and would like to invest a little more time in the scope, this is what I see could be done: 

1) Building your own rocker box, and exhanging tube side handles for tube rings with wooden circles attached + teflon pads, as others have suggested. Balance could be achieved by some regulated / sliding counterweight (yes, even more pounds:)

 

2) If money is no object, buying the go-to upgrade for Skywatchers. Then tracking might be smoother.


Edited by Woj2007, 09 December 2020 - 06:10 PM.


#24 Waynosworld

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Posted 09 December 2020 - 09:33 PM

I also am sorry to hear about your issues, I also understand that someone that has been around telescopes as long as you appear to have been getting frustrated with brands that used to be good jumping onto the pump them out standards and using band aids to fix short comings.

 

I myself just acquired a 10" Apertura AD10 F/4.9 telescope(used), it has short comings itself, the very first thing I figured out had to do with the mount and them friction clutches and the "U" shape they rest in, for a scope that was used maybe ten times in 3 years they had already opened up(the "U" slots), so when I used a Meade focal extender/8.8mm UWA eyepiece I had to crank on the friction knobs to take the weight, well when tracking Orions Nebula on its rise into the sky I would lift on the tube and when I let go it would settle where it was before, so I had to lift farther until I felt the friction give and let go and hope I could still see Orions Nebula or find it again, this was very annoying, I gave up because the 90 degree finder was almost useless as I could not tell which star was in the finder, I ordered a Telrad last night, anyway the next day I looked really close at the friction clutches, lifted on the tube and watched what happened, the "U" shaped friction blocks that rested in the "U" shaped slots were moving in the slots, the clutch was not giving, but they had to be that tight to take the weight of the focal extender/eyepiece combo, I took a break to think about it.

 

That evening I put a thumb tack on both sides into the front side of the "U" slot, this fixed the sloppiness of the "U" slot, but now I have to push the "U" shaped friction blocks into the "U" slots, I am sure over time it will get easier to install and remove the telescope from the mount, but right now I need to put my toes on each side of the mount and pull hard to remove the telescope from the mount.

 

I also adjusted the center of gravity of the OTA, I had to move the center of gravity within 5mm of all the way away from the primary mirror and now it balances with my 6mm Radian and my 6.7mm Meade UWA, but I had to move the center of gravity all the way away from the mirror to support my 4.4mm combo and it is still sort of hard to lift the front of the telescope so I would have to use weights. on the mirror end of the telescope.

 

My 6.7mm eyepiece with a barlow lens screwed onto it

011.JPG

 

My 6mm Radian eyepiece.

010.JPG

 

And my 4.4mm combo, a 2" focal extender/8.8mm eyepiece which weighs quite a bit and likely would be close to what you use, keeping in mind that the tube center of gravity is moved all the way away from the primary mirror and still needs weights depending on the angle of the telescope.

009.JPG

 

The tube is too light, I suppose I could use weights for the 4.4mm combo, but whenever I remove an eyepiece the telescope moves unless I start cranking on them friction knobs and then it starts getting hard to move as the mount turns so easily that when I move the scope it wants to turn instead of lift when trying to lift and turn at the same time.

 

My Starsplitter does not have these issues, but it weighs 3 or 4 times as much and when I put the 4.4mm combo on it I throw a hunk of steel on the box as a counterweight and it does not move when I put the weight on it before adding the 4.4mm combo, but it does move if I put the eyepiece combo in first.



#25 Eddgie

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Posted 10 December 2020 - 07:54 AM

Interesting to hear that the Apertura has altitude issues as well.  For the Aperatura to work well for me, I would need to move the mirror up in the tube and inch or two, and that would no doubt aggrevate the problem.  I had expected that I could re-mount the altitude bearing plates on the sides of the tube to offset that.  I would prefer the tube to be a little tail heavy because I could tweak that with a little sliding balance weight near the focuser.

 

I know that balance is always an issue with Dobs, but the Flextube is very limited in the kinds of fixes.  The disappointing thing in the case of the Flextube is that the reviews I read really did not say that much about the balance.

 

Another scope I had been interested in was the Explore Scientific Firstlight.  I liked that it mounted in rings that would allow an "infinite" range of adjustment and it uses a more modern large bearing. Maybe a scope I have to look closer at in the future. 




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