16” GSO DOB “mirror SPRINGs” + other Mods!

[Davekyn]

Has anyone here replaced the much talked about "weak springs" in the mirror cell?

Where did you source your springs and how did you replace them?

What mods can be done to Strengthen the Struts?

Shroud attachment ... any comments?

Here is a Link I found that highlights all the weak spots of the 16" GSO scope:
www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/2753248/Main/2748206 (http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/2753248/Main/2748206)

I'm not sure what the reference to removing the silicon is about, or how that would effect the scope. Could anyone explain this...has this something to do with correcting the space between mirror and cell ?

I'd also like to talk about any other mods you may have made to strengthen and make this scope "useable" Other than the springs being inadequate and something about the spacing of mirror and cell being slightly out...plus the rocker box being weak ... what else needs "fixing!"

Perhaps this explains the price has drop..I guess the day they sell a Dob that works out of the Box...there would be outrage. :)

[Calibos]

The price drop is probably about clearing stock. This model has been discontinued afaik.

In terms of the rockerbox and cell mods then you should aim your searches at the 16" lightbridge which is the same cell and similarly constructed base. The LB16 would have a vastly larger user base so there are a lot more mod discusions.

Heavier duty springs on the Collimation bolts to prevent the mirror going out of collimation when changing altitude. tbh though after getting a new set for my LB16, I think the OEM springs are fine as long as you compress them more. ie. tighten all 3 all the way back. Loosen one a turn and then never touch that collimation knob again. Collimate your primary with the other two and only the other two for ever more. This prevents you gradually over several collimations letting the primary creep up on the bolts to a point where the springs aren't compressed enough to provide enough resistance for stable collimation. You only need 2 collimation bolts to collimate the primary. What I gather is that the springs were definately underpowered on the smaller GSO models and everyone just assumed the 16" models were as bad. They are not. GSO did upgrade the springs for the 16" versions.

If you are replacing the springs then its just a case of loosening all the bolts and popping one out and replacing it before moving onto the next.

Heres what a German guy called Deister did to his GSO 16" with metal cable and turnbuckle.

GSO String Strut mod ('http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3155224/Main/3151775')

This kind of mod would also solve Shroud attachment issues.

The GSO's use silicone between the edge of the mirror and the rim of the mirror cell for edge support. The thickness of the GSO 16" mirrors means the mirror is more tolerant of less than perfect edge support like this and most people don't have a problem caused by the silicone edge support. Where it is a problem for most people however is when the mirror needs a bath. You can't remove the mirror from the cell without cutting the silicone. Some people fearful of disrupting their silicone edge support strip all other hardware from the cell and wash the mirror still stuck to the cell. Others decide to kill two birds with one stone and get rid of the silicone to make it ewasy to remove the mirror and implement a better edge support system. This is drilling 2 threaded holes on the bottom of the cell rim at the mirrors centre of gravity 90 degrees apart and using a nylon bolt through those holes to hold the mirror.

Now, I think you might find the following thread interesting.

GSO Collapsible Strut conversion (http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/5028653/page/0/view/collapsed/sb/5/o/all/fpart/1)

This was a guy who converted his solid tube Zhummel(GSO) to a Strut system like a Skywatcher Flextube using Moonlite Truss hardware. After reading the thread I realised that although to some it might seem like a step backwards for me with a truss lightbridge in terms of flexure, I nevertheless could see very many Pro's and few cons other than flexure if I were to do a similar conversion to my Lightbridge. Neither of us would need to go through a load of Dremel cutting discs like he had to to cut out the middle section of his Solid tube. :D

IMHO while I did have to think about a conversion from Truss to 3 Strut for a while before making my mind up, for you it could be a no brainer. You already have to think about a cable string mod to remove flexure anyway. You could even use your old struts to make the outriggers for a wheel system similar to what this guy did, so its not like your old struts would go to waste :D

You would now have a scope that didn't dominate the space it was in set up when collapsed into R2D2 configuration :D but with no assembly required to use. Just extend the UTA. Just wheel it out with the built in handtruck system. BTW one can safely trim off the circle baseboard and groundboard to make it fit through doors.

With a collapsible strut conversion one might then question whether one should have bought the 16" Skywatcher Flextube. Don't worry, you still made the right choice. The SW FT is a behemoth. The Rockerbox sides are nearly a foot taller than our scopes. The Lower OTA is longer and heavier than ours. The UTA cannot be removed for lifting or transport like ours could with the Moonlite truss hardware. The fact that the Non Goto version of the SW FT uses the same parts as the Goto means that both versions rides higher than ours (to clear their azimuth motor) and thus puts the EP out of reach at zenith of all but the 6'4" brigade. ie. EP height is a good 5 inches higher than ours despite the fact that the scope is the same apeture and focal length as ours.

Finally have a look here where I asked Dobstuff guy Dennis Steele about the string mod.

String Mod discussion (http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Board/reflectors/Number/4908618/page/1/view/collapsed/sb/5/o/all/fpart/2)

Feel free to barrage me with further questions if need be. :D

[Calibos]

Ah, just noticed you decided on a 12" GSO in the end......or have I just thrown the cat amongst the pigeons in your head again :D

Hey, why not get an LB 16, do what I am going to do, then when the savings recover get a servocat/argo goto system for it. Do some boundary layer fan mods and you've got a DSO and planet killer.

Put it this way. I only ever saw the planets as white discs with some grey detail with my 12". ie White Jupiter with 2 dark grey bands and on occasion some fainter grey detail, White Saturn and rings with some faint grey cloudbands, White Mars with some faint grey features like Syrtis major. I always wonder how anyone was seeing the White polar caps on a white disc!!

Anyway, although the 16" was a noticable but not huge jump with regard to DSO's, it seems it crossed a threashold for me seeing colour in the planets. Salmon Mars with white Polar caps!. Creamy Saturn and creamy Jupiter with brown bands etc.

For me, the apeture jump to 16" was as much about managability as anything else. I could fit the 16" truss broken down in my car where I couldn't fit my solid tube 12".

[Davekyn]

Awesome Keith ... Due to time constraints ... even with all this rain ... I am pushed for time and will definitely respond as soon as I can. LOL with ... "or have I just thrown the cat amongst the pigeons in your head again :D"

Thank You for taking the time yourself...I will be back!

[Davekyn]

Keith...I am going to be honest here and tell you that although I could collimate my 12” Dob previously...I never knew which of the 6 screws I was suppose to turn in order to collimate, and at times ran into trouble with some screws either having no more turn left in them when tightening , or about to drop out when loosening them.
I know that the springs are the Lock Screws and that having them set properly is the way to go? ... But I think I cheated and started turning those instead of the other three (with out springs)
Perhaps this is wrong ... I get confused very easily with such things...especially with verbal descriptions...none the less I am re-reading and then reading again...Back to reading now...

I am getting a 12” Dob and I will explain why in a second...I also intend to replace the springs in the 12” Model as well (however that sounds encouraging about the 16” version...it does effect SALES for those who don’t want to buy stuff then fix it)...BUT...first I obviously need to keep rereading what you have said...it sounds like excellent advice and what I need to know...BUT...I am still confused...one second while I still process....010101010100011001100111 01011101111010101110111001001010101 01110010101001010100110010011010101 10001010101000110000100110100101011 100011010100001010...:
Actually...no offense...but my head hurts...The two following links are awesome and what a good job that fellow did on his Dob.......................I will try to work out what to do with the springs and collimation procedure later. I just wish someone would start selling these things so that we don’t have to go through all this effort...and there if the only way to get around such things is to buy an obsession to avoid such things...then I will just give up...No I won’t...that’s why I am asking...Just exhausted with trying to make the right call.
YES...I went back to the 12” Dob...
As stated...no one seems to sell a DOB that works out of the box so I need money left over to address those issues...Bunning’s is getting too expensive and everything else as well...BUT...once the penny drops, I don’t mind doing what has to be done.
With the left over money I intend to get some choice eye pieces this time around...I also need filters as I know what a difference to my visual enjoyment these can make...Mostly UHC...Never really thought much about the OIII ... but then I never go to try that out properly... I want to build a cupboard with some of the left over money to store my scope in as well as due control and...well there is a host of things and I am sure I won’t get them all...However if I buy the 16” scope...the freight will be ridiculous and I will be left with bugger all.............
Transport...I can appreciate what you say there, however when I drop my back seat in the Hyundi Elantra sedan...It’s not so much a problem with the 12” at all going in from the boot end and coming at the back seat...I can just fit the rocker box in to one side of the extend solid tube and way I go...The 16” inch rocker box is a no go and even if I can mod it ... I really don’t want to at this stage and I also don’t want to have to cart all the pieces around...Of course the collapsible idea would be great, BUT still too big...I do have a 4WD with a TRAY BACK which would be better than a trailer...I intend to make a transport Box with foam and all that.............
The Views..................well, to be honest and I am not the first to say this...”But no one is really raving about it online”...a statement that came up on cloudy nights and I have to agree! There is all the usual mod talk and so on, but no one is really giving any descriptive view or adding any real detailed information about the actual VIEWS ... I did find one in here where someone said “I bought a 16” dob, then listed the all the targets and that was it..............That kind of said it all to me.......I mean these guys obviously have a lot of equipment and have a lot to compare with ... but the only obs I am reading a purely clinical and dry ... It’s the same all over the web ... hard to find good reviews with many of the scopes available out there ... the best obs I have read come from 12” Dobs and maybe some other affordable and widely used refractors ... particularly some large Achro’s...I guess when I came across that statement at cloudy nights about the lack of obserevational content with regard to the 16” other than its weak point and “I own One” LOL...just kidding...well...I don’t think it’s going to be worth it ... so many times I hear ... If only you can get that little scope out to a dark site!!! ... I think the price difference and the quality I will get from my solid tube dob, makes the 16” way over priced and over rated. I don’t have enough money regardless of price drops...given my situation I really am better off with the 12”...................I also believe there are less wow moments recorded with a 16” Dob, because once the reality of transport hits most people, they don’t use it as much as they wished they could...that even happens with a 12” for many folk. Having said that ... If I was fortunate enough ... I would find a way.
Thanks again for your assistance ... your information is just what I need to get the most out whatever dob I do buy. It was really good to also hear you talk about planetary views like that with your experience...I think slow dobs suck on the planets full stop...my only struggle now it to keep focused on good gear for my DSO’s .......or get a cheap 127Mak...and settle for the plossles.......actually after I get my Binos replaced.....I will only have enough to search the net for good eye pieces, so scratch the Mak.....

[Davekyn]

Keith...I just spent a bit of time with a friend who also did not know if the springs were used to lock in place or not...can't find it now, but somewhere in cloudy nights...we went over a description there as well and now understand what it is that your saying about collimation.

One question though ... Lets say I have taken the mirror and cell out for a clean and now have to put it back in ... at which point do I line up the collimation bolts (springs) ...

We got to talking about how the weight of the mirror would increase at the bottom half as the scope moved through its arc ... and wondered about how this would play on the arrangement of tight and semi tight springs...We played through two arrangements in our head with the 1st being; the tighter spring (to be left untouched) dead center on the lower half of the mirror facing the front Board of the rocker box, when scope fully erect and the two springs with give in them, evenly spread on the opposite side. The 2nd arrangement just in reverse with the two collimation bolts evenly spread across the center point of the lower mirror and the tight spring dead center opposite to that.

Is there at all a preferred way to position the cell when fitting it and the mirror back into the scope?