GSO 12" RC Dissambly.

[ollypenrice]

A mighty impressive thread and kudos to Doug, Marco and Rob for their expertise and perseverance. I think that the point about learning and understanding is well made. I've spent time tinkering with motorbikes, karts, bicycles and other bits and bobs but maybe I already spend enough time around telescopes and prefer a change of tinkering topics. I think I might enjoy it if I had an optical bench. The thread has made me feel pretty guilty, though, about what I might call my 'sliced white bread' attitude to telescopes and my preference for 'plug and play.'

Well done, gents. Any updates? I wonder who, in France, you were dealing with, Rob?

Olly

[Jussi_K]

I have been looking at getting a GSO based 12inch RC but have been put off by the issues people are having with astigmatism and collimation.

I have a question for Doug and Marco - have you achieved those beautiful round stars by simply replacing/adding cork to the mirror cell? I appreciate there is a need to separate the focusser from the cell, but there is a relatively simple solution for that issue already out there. If you can truly overcome the incredibly poor design for virtually no outlay it entirely changes the viability of these scopes.

I looked at the images of a stripped down 12 inch and was horrified at the mirror cell 'design' It looked to me that it might be possible to put  triangles for a 9 point support in the triangular gaps in the cell thus adding  about 3mm to the thickness of the cell and moving the mirror higher in it's cell by about 5mm. Unless there is scope to move the secondary at least 5mm further up the tube it may be that this wouldn't work and I'd be into building a complete new tube or truss.

Incidently, these scopes have been available for some time with solid tubes - does anyone have any experience of these?

Ian B 

Hello Ian B

I bought 12" GSO RC about 3 months ago.

Im been able to take collimation to the level that satisfies me for now (see attached images). Im not done yet a full imaging session, just couple test shots around the sky, just to see does the collimation hold. I have the Carbon fiber version. Camera behind scope is SBIG 8300M and there is AP 0.67X focal reducer. Distance from Sensor to the reducer is 72.5mm, I haven't calculated how much does it actually reduce focal length.

My scope is entirely factory settings, nothing altered.

[silentrunning]

Once I got things to an acceptable level - by taking the measures described in this thread - the scope has remained remarkably constant collimation wise. Having said that it now needs a retweak but that's not bad for 6 months or so.

A few more images are at

http://www.bbc.co.uk/news/uk-25604696

Doug

[ollypenrice]

Once I got things to an acceptable level - by taking the measures described in this thread - the scope has remained remarkably constant collimation wise. Having said that it now needs a retweak but that's not bad for 6 months or so.

A few more images are at

http://www.bbc.co.uk/news/uk-25604696

Doug

The link took me to videos of cliffs falling into the sea... Don't get seawater on yuor mirror!!!

Olly

[silentrunning]

DOH!

That link should have been 

http://www.astrobin.com/users/silentrunning/

when can I start editing my posts??!!

Doug

[astronomer2002]

Thankyou all for the updates. I can see that some scopes work pretty well without any adaptations. It makes the issue more difficult to resolve. If I could find a good priced second hand metal tubed version I'd probably buy-to-try and rework the cell if necessary. 

It's a real quandary I'm in. I have a observatory housed 14 inch RCX400 which is visually fantastic, but the mechanics make imaging even more of a lottery than with the lighter 12inch LX200.

I purchased a MX mount last summer to solve that issue with the Intention of getting a GSO based RC 12inch for imaging. Following this thread and others I have considered dismounting the Meade OTA but at a predicted 60lbs it might be a bit much for the MX. I also don't know if the Meade will produce as good an image as the RC. I have to say that with a AP reducer the Meade gives a flat field on an APS sized chip, which is about the biggest I can ever see me using, so the issue is purely down to star sizes the two OTA's will produce. The star sizes with the Meade are certainly larger than I am seeing in images here, but seeing and guiding performance is such a big part of astrophotography I am reluctant to conclude it is purely down to optical quality. As I have already said I was astounded with the visual performance of this Meade scope (I had to check it really said Meade on the side). I have never been remotely as pleased with initial viewing through a scope as this RCX400 - no wonder Meade stopped making them. It also yields nearly as contrasty planetary images as the C14, which was a real surprise and something a true RC won't do. I know the scope solution depends on the application, but I am looking for an imaging scope that will give me  1500-2500mm focal length range and have the C14 on a MI250 for planets.

I'd like a truss tubed version of a RC, but given the high number of negative comments from those who actually use low cost GSO based instruments I will probably punt for a s/h solid tubed one and evaluate the issues for myself at the lowest outlay possible - if I can ever find one.  

Ian B

[astronomer2002]

OK - I am convinced. 

I need a 12 inch GSO even if I need to do work on the mirror cell and focuser attachment.

Now the big question - does any one know of somebody looking to sell or a disgruntled user who might want to sell? 

I haven't seen these on Astrobuysell and my wanted ad got one genuine offer - that was immediately rescinded.

There seems to be no stockist in the UK and Ian King is reluctant to talk about his venture into GSO RC's, which is why I had concerns in the first place. Buying from Germany looks like the only new purchase option, which I am reluctant to do because of the distance.  

[Jussi_K]

OK - I am convinced. 

I need a 12 inch GSO even if I need to do work on the mirror cell and focuser attachment.

Now the big question - does any one know of somebody looking to sell or a disgruntled user who might want to sell? 

I haven't seen these on Astrobuysell and my wanted ad got one genuine offer - that was immediately rescinded.

There seems to be no stockist in the UK and Ian King is reluctant to talk about his venture into GSO RC's, which is why I had concerns in the first place. Buying from Germany looks like the only new purchase option, which I am reluctant to do because of the distance.  

I live in Finland and got my GSO RC 12" from Germany, no problems at all.

[astronomer2002]

First one is a 100% crop of the second image.

Marco,

The stars in those images look perfect to me.

It sounds like to get this improvement all you had to do was replace the cork installed by GSO with larger pieces, presumably centred on the 70% zone. Is that correct?

Whilst I fully agree with your conclusion regarding hanging the focuser and imaging train off the mirror cell did you see any difference in your images when you did this? From your earlier posts it appears the overriding issue you had was a pinched and inadequately supported main  mirror.

I am still agonising over this acquisition.  Last night I tried my SXV-M25C out for the first time on my RCX (I usually use a 9mm sized chip)- and the images were sharp to the edge which means the field is flat to 29mm dia at least. However, with periodic slop of 40 arc seconds (made worse as the changes are sudden) I can not guide out the errors adequately even using an AO unit. With no guiding 1 in 3  40 second exposures yield round stars. I love the optical quality of the Meade but the mount is just inadequate for imaging. 

[RobH]

Hi all.....I got my scope back from Astromeca in France, after having a new 18 point mirror cell built, and everything checked on an optical bench, and Ian King dropped it off for me in Mid November.

Despite the awful weather, I’ve managed a few nights here and there to test it and finally everything seems fine....no astigmatism and the scope is easy to collimate, and holds collimation too, which wasn’t the case before, even when I’d sorted out most of the astigmatism.

The astigmatism was being caused by the lack of a decent mirror cell (the original only being a 3 point suspension), the way the baffle was attached, and the mirror clamps.

With my own testing, I had determined that the secondary holder needed to be made adjustable, as when using a glatter collimator (and checking that all else was correctly adjusted), the laser didn’t line up with the centre spot on the seconday. I had the secondary holder rebuilt to allow lateral motion and after getting the scope back, Astromeca had indeed made the same adjustments I had also made.

First light is here.....

http://stargazerslounge.com/topic/205083-ngc-891first-light-with-the-fully-functioning-12-inch-rc/

Here are pics of the new cell and the secondary.....

[silentrunning]

Great news Rob - NGC891 is astonishing.

Any chance you can send some images of the secondary and what mods have been done to allow lateral movement to it?

Doug

[alpal]

Hi Rob,

This is a great thread.

I like those primary mirror holder  parts which allow adjustment.

Are they custom made or off the shelf parts?

cheers

Allan

[derrickf]

Hi Rob,

it looks like you may have cracked it.

I'm interested to know how the total investment you have made in getting the scope to this stage would compare to the cost of a similarly performing OTA from a "higher end" manufacturer - a Planewave 12" at approximately £10k  for example.

Regards

Derrick

[alpal]

Hi Rob - again -

I am using an 8" custom built Newt.

I thought I had all my problems licked until I downloaded CCD inspector
& then realised that something is moving causing the
curvature, tilt & collimation to change slightly over an imaging session most

likely due to the different angle of the scope at different times.

I thought I had my RCC coma corrector spacing pretty close -
but it's not according to CCD inspector.

Luckily I have a Varilock spacer so I can adjust that.

How stable is your system now if you look at a whole set of frames taken over a night using CCD inspector?

I know CCD inspector is supposed to be used for a part of the sky where there are just stars

but I feel that the sub frames on any night should all be similar no matter what the target.

cheers

Allan

[RobH]

Hi Rob,

it looks like you may have cracked it.

I'm interested to know how the total investment you have made in getting the scope to this stage would compare to the cost of a similarly performing OTA from a "higher end" manufacturer - a Planewave 12" at approximately £10k  for example.

Regards

Derrick

Hard to say exactly Derrick as Ian King has borne some of the costs, but I'd say that I've saved 50% or thereabouts.

[RobH]

Hi Rob - again -

I am using an 8" custom built Newt.

I thought I had all my problems licked until I downloaded CCD inspector

& then realised that something is moving causing the

curvature, tilt & collimation to change slightly over an imaging session most

likely due to the different angle of the scope at different times.

I thought I had my RCC coma corrector spacing pretty close -

but it's not according to CCD inspector.

Luckily I have a Varilock spacer so I can adjust that.

How stable is your system now if you look at a whole set of frames taken over a night using CCD inspector?

I know CCD inspector is supposed to be used for a part of the sky where there are just stars

but I feel that the sub frames on any night should all be similar no matter what the target.

cheers

Allan

I'll run a nights worth of subs through CCD inspector anb have a look Allan. It seems rock solid now though, from the look of the data when stacking.

[alpal]

I'll run a nights worth of subs through CCD inspector anb have a look Allan. It seems rock solid now though, from the look of the data when stacking.

Thanks Rob,

I'll be interested to hear the results.

cheers

Allan

[marcoverstraaten]

Superb Rob!
So how is the main mirror hold down on its position? Just by the center baffle?

Is this a commercial available upgrade kit or is it custom made?

[Jussi_K]

Superb Rob!

So how is the main mirror hold down on its position? Just by the center baffle?

Is this a commercial available upgrade kit or is it custom made?

By the look of pics RobH posted, the upgrade kit is from Skymeca.

I asked that kit from them, and they said it would cost 1350 euros!!!

Well its seems that upgrade is not necessary for my scope. It seems to hold collimation well and I like the quality of pictures it produces for me. 

[astronomer2002]

I finally made up my mind and a 12 inch GSO RC with a truss tube is on it's way. I am under no illusion that it's going to work out of the packing case, but this thread has given me the confidence to know there will be a solution to any mechanical issues.

Has anyone reading this thread got one of the GSO truss mounter RC's? There's probably going to be a whole new saga associated with this version, however, since the base cost is 1/3 of other manufacturers 12 inch RC's I guess it will be a popular option.

Looking at Rob's images of his upgraded cell  it appears the cell has gone altogether and the mirror is now supported by the tube end casting, only being held in place laterally and longitudinally by the central baffle, which in turn appears to be screwed into the old base casting. I am a bit surprised as this means the mirror can experience slight distortion as you adjust the collimation since the mirror is effectively clamped to the base casting.  I guess it works extremely well given the images Rob has taken so maybe the prime issue has always been the three 'point' suspension of the mirror. I am planning to rework the GSO cell to incorporate 9 point suspension for the mirror and detach the focusing mount from the back of it. I never had a problem with my old 12 inch Newtonian once I built a 9 point cell for it so I hope this will be sufficient.

Another thing I am not sure about is the need to adjust the secondary  laterally in it's cell. Surely if it's centre  isn't in line perfectly with the primary mirror's centre then the truss needs adjusting - or am I missing something? 

Ian B  

[silentrunning]

Hi Ian

In my experience with the metal tubed version some mechanism to lateral adjust the secondary will be vital for obtaining results likes Robs. I have not managed this on my scope yet but recognised it as a problem early on, the optical and mechanical axis are not aligned and I still have artefacts from this. I hope at some point to provide such a mechanism on the cheap - like the springs I used to support the mirror - but I don't expect to get close to Robs results. Having said that even with my basic attempts to improve things the scope is now performing beyond my expectations and Robs results clearly indicate just how good the optics are. Good luck with any mods you make and please keep us informed of progress.

[astronomer2002]

My GSO 12 inch Truss tubed RC finally arrived, just as the weather changed!

I got my RCX off the old pillar and installed a new one over the weekend. I installed my MX mount for the first time and, finally, the RC on Sunday evening.

As predictable my first hasty view through a non-collimated RC on a mount that was yet to be aligned was not as startling as my first view through my trusty RCX (why oh why did Meade put these beautiful optics in an over-complicated tube on a mount that works visually but isn't up to astro-photography).

The first thing you notice about the Truss tube is that there are no mirror covers.......

The second thing you notice is that the lack of a finder is because there is no provision for one.......

The third thing you notice is the back focus is so great even with a 2 inch extension and a star diagonal you can barely reach focus.........

These scopes weren't meant for visual observers but the lack of covers and no provision for attaching a finder (other than on the second Losmandy plate) makes you wonder whether any field testing was done.

OK, I thought - these will be 'optional extras'. Nope, you cannot get mirror covers or a finder bracket to suit.

For those that dared hope the mirror cell was different to the metal tubed versions I can report it isn't, so the mods will be necessary. At least the back plate of the truss tube is nice and flat so making an adapter to separate the focuser from the mirror cell will be easier.

As for my actual first view the stars were seagulls and Jupiter had an echo. Even so I could see the contrast and definition were much poorer than the old 10 inch f6.3 Meade LX200 I dug out to sell to help pay for this beast.  

At this point it is hard to see how this scope can produce the high definition images I have seen on this site. On the plus side I have a truss tubed RC at less cost that if I'd purchased GSO optics and constructed the truss myself.

Ian B  

[kirkster501]

The 12" GSO has given some truly spectacular results Ian.  Stick with it mate, even if there are few in the way of extras.

[RobH]

I'm really pleased with mine now.

Since having the new mirror cell made, I've not had to tweak the collimation at all.

Collimating with the new cell was very smooth and easy to do, and the scope, when it gets a chance, is giving some good sharp data.

[Jussi_K]

Hi 

Some updates about this scope and how it has performed in my hands for half an year for now.

Here are couple of pics with GSO 12" Carbon RC and 0.67X reducer. The scope itself is non -modded, just tried to collimate it.

Now its summertime and its like 2-3 months until next imaging session...

So there is time to make further adjustments.

Does anyone have any new pics about homemade mods to this scope?