View Full Version here: : GSO 12" truss Newtonian initial impressions

Paul Haese
28-06-2017, 05:51 PM
Monday I took delivery of a GSO Truss Newtonian through Bintel. I thought it might be worth advising people what I thought of my initial impressions.

First up, the price is very good for what you are getting and the delivery was very prompt.

Next the box for this thing is huge. I could just get it through our front door. The telescope is well supported by polystyrene packing and the box is two thicknesses of cardboard. See the photo

Whilst the scope is large it is easy to lift. In fact it is easier to lift than the 12" RC that GSO make. The build quality looks great. Everything is well machined and put together nicely. The back supporting plate is one piece and appears to be quite rigid. It has three fans which are placed 120 degrees apart. The primary is a conical mirror which will aid cooling. It appears to be adhered to the back plate. Collimation is done via three sets of screws with one moving the assembly and the other acting as the locking screw.

The back focus is about 180mm from the plate which supports the focusor (ignoring the focusor will aid in getting adapters sorted if you intend to use an Atlas). That plate seems to hold the focusor really well and helps stabilise the secondary assembly. The secondary assembly seems quite rigid with supporting poles inside the secondary cage. It will be interesting to see if it supports my STXL sometime in the future.

After some collimation I took an image of a water tower 5 km away from our home across the valley whilst the scope was sitting on a bench. The resolution is pretty reasonable I think, of course star testing and imaging will confirm my thoughts on the matter. See photo.

One thing I have noticed though is that the truss needs a shroud as light can be seen entering into the focusor from bottom of the secondary assembly. It's not a big problem and it can be alleviated really quickly.

Another thing GSO could do to improve this scope would be to install a secondary heater. I would expect the secondary will dew up quickly without a dew heater. Kendrick make a dew heater which I am expecting delivery of in next day or so which will sort that problem.

Those minor things aside I am expecting this scope to be as good as their RC's. Bang for buck is going to be high and I am looking forward to imaging with it. It will be a light bucket compared to RC and I am hoping it will perform every bit as good as that scope.

28-06-2017, 06:04 PM
Thats awesome Paul looking forward to hearing your opinion of it. Ive been looking at 12" newt options myself although ideally I would rather an f5 . The tube version of this seems to have a lot of structural issues and flexure so hoping this solves some of the issues otherwise my next options are a big jump price .

28-06-2017, 06:05 PM
Thank you for sharing your first impressions Paul. The telescope looks very impressive. I have been entertaining an idea of going a similar path (a fast Newtonian for imaging) so I will be following your journey with this beast :thumbsup:

28-06-2017, 06:38 PM
Looking really good Paul! The GSO optics have been top notch for quite some time, just been waiting on their mechanics to catch up :)

What corrector are you planning on using?

John K
29-06-2017, 07:35 AM
Hi Paul,

thanks for sharing your initial impressions. I was looking for feedback on this scope in this thread so what you have posted is useful,


- Just wondering if you can confirm the 180mm back focus (is that without a focuser?)

- What coma corrector do you plan to use?

- What are your initial impressions about the rigidity of the top cage assembly where the focuser is?

Clear skies.

John K.

Paul Haese
29-06-2017, 12:20 PM
Colin I have been an advocate for GSO optics ever since they were first sold here. I had one of the very first 8" RC's and despite all the negative talk about them I got some nice results.

I am awaiting a Baader MPCCIII. I will also consider a Wynn if that does not work.

John, that 180mm is what I measured to my sensor from the mounting plate, not including the focusor.

The top cage looks ok to me but imaging will soon tell me what is going on. I did not feel any loose components at all but taking a look at spiezzy's mods it could be on the cards. Time will tell.

29-06-2017, 01:40 PM
Awesome Paul....looking forward to seeing first light results.

29-06-2017, 03:52 PM
Lookin good Paul.

I received my 12" scope from Bintel yesterday over the ditch here in NZ. It's a beast! See image attached compared to my 10".

Pretty much agree with everything Paul has said. However I wish the front section was beefed up a little. eg as per the SkyVision or Hercules newt astrograph design.

I will be using my GPU corrector rather than my Baader MrkIII. I tend to get smaller tighter stars with the GPU.

Moonlite focuser is now attached with a adapter from Ron.

Images attached.

Cheers Dave

Paul Haese
29-06-2017, 09:39 PM
Dave, which adapter did you get to attach your focusor? I take it this your using a 2.5" focusor?

30-06-2017, 05:23 AM
Paul, yes, it's the 2.5" focuser.

I used the Moonlite Altair flange. Not sure if it is listed but he has them in stock.

It is use for the Altair astro version on the GSO truss newt.

30-06-2017, 05:52 AM
Hi Paul, which secondary dew heater did you purchase.

I'm struggling to find something the correct size.

Thanks Dave

Paul Haese
30-06-2017, 11:29 AM
Dave, did this have a straight fit or did you have to do some cutting? The flange kit looks bigger than the hole to me. See photo of my base plate?

The one I was initially sent did not fit but I believe the Kendrick R200SS does fit correctly or is very close to fitting correctly. I'll let you know how that goes.

30-06-2017, 12:20 PM
[QUOTE=Paul Haese;1319099]Dave, did this have a straight fit or did you have to do some cutting? The flange kit looks bigger than the hole to me. See photo of my base plate?

No cutting. The adapter is made for our GSO truss newt.
You remove the GSO ring with the four screw holes. The Moonlite adapter fits in the hole and has a screw ring which screws in from underneath and clamps the adapter in place. the top section of the Moonlite adapter is wider than the GSO focuser plate.

30-06-2017, 01:56 PM
Paul, I noticed that there are several tapped positions for the dovetail mounting plate but none inline with the focuser/imaging train. This causes an issue with balance. Your balance changes as you move across the sky through the zenith.

Seems a design issue. Probably need to shift the focusing plate/focusing position.

Paul Haese
30-06-2017, 04:52 PM
I rotated the entire secondary assembly and recollimated. All fine now. That puts the focusor in line with the RA shaft in the traditional park position. Took about half an hour to sort that.

30-06-2017, 05:54 PM
I would be interested to know exactly how you did that. Did you remove to top section from the truss and rotate ?

Paul Haese
30-06-2017, 06:03 PM
I undid the bolts from the truss which hold the cage in place and rotated. It all matches so rotation is easy.

Paul Haese
30-06-2017, 06:08 PM
Peter here is an image with some of the wiring nearing completion and the secondary assembly rotated.

For those interested I bought 20 meters of cable shielding from a firm here in Adelaide. Works well and provides a neat looking system.

I am waiting on the arrival of the focusor which I ordered today. Thanks Dave for the confirmation.

30-06-2017, 06:21 PM
Thanks Paul that looks great so when the scope is mounted the focuser pints down in home position ?
cheers Pete

30-06-2017, 06:22 PM
Thanks, I just popped out to the observatory and had a look.

I have some Bobs nobs and springs but I think I'll just use the GSO set in the mean time.

I'm rather impressed with the conical mirror. I wasn't expecting that. This means a simplified cell design. You would think GSO would advertise this as a point of difference.

Paul Haese
30-06-2017, 07:17 PM
Yep, that alleviates trying to balance the scope through different parts of the sky.

Yeah Jim is not great at getting the word out. Luckily he has the likes of me on his side.

I have not bothered with Bob's knobs yet on any GSO scope. I have them on my C14 but not on the GSO gear. The secondary adjustment screws look a little flimsy to me but I'll see how they go before I go changing things.

30-06-2017, 07:29 PM
thanks again Paul I will do that with mine so just undo the 2 bolts on either side of the truss bracket that are screwed into the fist secondary plate and rotate then screw it back together again
cheers Pete

Paul Haese
30-06-2017, 08:30 PM
Yeah all 8 bolts on all the trusses first then rotate. ;) I figure that is what you meant.

07-07-2017, 06:20 PM
hi Paul
well I did as you have done with the front secondary cell support and wow what a difference it made with balancing works like a charm while I had the front cell off I changed the aluminium sleeves I installed for bracing for carbon fibre
thanks again Paul for mentioning that about swinging the cell around
cheers Pete

Paul Haese
16-07-2017, 08:44 PM

I installed the Moonlite focusor with an Altair adapter and have the motor hooked up to a Robofocus control unit. The motor works well with the Robofocus software and manual controls.

Both cameras feed into a MHP which will directly connect to the FitPC. MHP and FitPC will ride on the same D bar. I need to tidy up the wiring a bit more yet.

I have also installed a dew heater on the secondary. I tested that tonight too and that works well. It gets quite warm on full power with the MHP contols, so I till try it on 3/4 first and that should be enough to eliminate dew. I will probably do something about the red insulation tape, I just need to work on eliminating the sideways movement of the cabling.

So nearly time for first light.

16-07-2017, 08:59 PM
Having been watching out for reviews on these. Will be very interested to hear how it holds up Paul. So nice to have the speed of Newt optics.

17-07-2017, 08:19 AM
Hello Paul,

I think it's a remarkable image at 5km. The handrail around the top of the tower is 50mm in diameter (2 arc seconds) which gives a sense of scale. As a test of resolution the guy wires, which are many times smaller probably 6 or 8mm in diameter(0.25 - 0.33 arc seconds) are well resolved and give or take the accuracy of the 5km, are right up there with (slightly better than) the manufacturer specified resolution and probably right at the diffraction limit.


21-07-2017, 02:31 PM
Here is an image of the conical mirror.

The scope seems to be holding focus quite well with small temperature shifts.

I have done a few 5min test exposures and all is well.

I havent tested how well the scope holds collimation with the weight of my QSI683 camera when I do a meridian flip. It is fine with just with a 2" laser collimator.


24-07-2017, 10:44 AM
This diagram shows the extended baffled tube idea.
I found it in some Hubble diagrams.
I put it here because I can't seem to send it via PM.


24-07-2017, 11:01 AM
They call them " stray light baffles".

Paul Haese
31-07-2017, 04:16 PM
Commissioning commenced over the weekend. Scope and camera are installed with FitPC riding on the scopes back. Moonlite focuser is driven by the Robofocus controller I had.

I had to run cables reverse through the mount to communicate with the weather station and the roof controller. For those interested I ran a Ethernet cable through the mount down onto a Ethernet over power module and that communicates directly with the router.

The Mount Hub Pro powers the computer, camera, dew heaters and focuser. In other words everything on the scope.

So far all appears to work. Now for V curves and some collimation testing. Pictures tell the story.

Cable management needs a little fine tuning but this is ok for now. Nice to have a large scope that does not have a balance issue.

31-07-2017, 04:54 PM
Very nice installation Paul. For what its worth, Kendrick Astro used to supply thin copper tape with their RC secondary heaters. The copper tape was thin but wide (thus equivalent cross sectional area to wires) and adhesive on one side so it would stick to the secondary vanes. Worked very well for me on my small RC, with no noticable thickening of a secondary diffraction spike. Blackened with a marker pen you could hardly see it. I guess they changed away from it for a reason.
RS-online here in Australia carries a range of adhesive copper tape:

http://au.rs-online.com/web/c/adhesives-sealants-tapes/tapes/copper-tapes/?cm_mmc=AU-PPC-_-google-_-1_AU_EN_G_Tapes_BMM-_-Copper_Tapes&mkwid=sYRFRzSeY_dt|pcrid|1089446558 70|pkw|%2Bcopper%20%2Btapes|pmt|b|p rd|

I think Jaycar has the stuff as well. You would want the type with the non conducting adhesive obviously.

Paul Haese
31-07-2017, 05:09 PM
Kendrick still supply the copper strips. At this stage I am seeing how effective the heater is before installing the copper strips. The tape I used is the same as that I used on my RC and it was not evident in the diffraction spikes on the images that I had a heater cable installed. It's something I'll consider if the spikes look odd though.

Thanks for the feed back.

Paul Haese
13-08-2017, 11:15 AM
Commissioning continues -

After sorting a minor astigmatic issue with the secondary; commissioning has resumed. Sync into existing pointing model, V curves and guiding sorted (guide camera needed to be lowered to gain focus).

I have decided that the MPCC is probably not going to cut the mustard long term for me. I think the stars look a little soft in the centre of the image, but detail seems reasonable.

I have found that collimating the scope is certainly finicky and I am currently waiting on the GPU CC and a couple of adapters to alleviate any slack I have in the compression ring which is currently holding the camera in place. Using cats eye collimation gear shows good collimation without the camera in place but once the camera is on board the collimation seems to change. Now that could be the secondary cage not providing enough support or it could be the compression ring on the focuser draw tube. For now I'll go with the later. There appears to be a little movement upon tightening the compression ring. Slews across the sky seem to maintain a consistent collimation.

An f4 is really quick at gathering photons and I can see the attraction. The image attached shows the lagoon with 4 minute subs at 28 minutes integration. No flats applied as I need to get collimation sorted first and then I'll do flats. If you look hard you can see the warts near the bottom of the image. Overall though my OCD is happy with the current results.

13-08-2017, 11:31 AM
I'd seen some comparisons between coma correctors a little while back and the MPCC faired better than the GSO one. It not as good as the Paracorr Type II or the other one you're looking at.

13-08-2017, 11:34 AM
hi there Paul
that image looks pretty darn good I think if you are having any issues with collimation it will be the top secondary cage being not braced enough since my mod on my 10" version I have diminished 99% of the flexure in the front cage and when I point the scope in any direction in the sky it seems to hold collimation very well I have also added compression springs under the secondary mirror adjustment screws which make it a lot more precise in adjustment
cheers Pete

Paul Haese
10-09-2017, 10:08 AM

I am now approaching final completion of commissioning.

Everything is now screw threaded into position and I have installed shims to adjust for tilt.

I am using the GPU coma corrector which gives superior star sizes and detail sharpness over the Baader. However, the GPU is very sensitive to tilt.

I had to also pay particular attention to the focuser being aligned with the optical centre of the scope. It was slightly out and that combine with tilt made it difficult to find the exact problem.

There is still some slight slop coming from the focuser via the draw tube. It needs some final tweaking to prevent slop from one side of the meridian to the other. Gravity can be a pain in the you know what.

You'll find a few images of the corners of last nights run in the moon light. So ignore the gradients. Flats need adjustment too since my fiddling with collimation.

Paul Haese
10-09-2017, 05:38 PM
One more lot of frames taken about 85 degrees up and with slight better corner stars.

It looks to me that my bottom left stars are now slightly over corrected rather than being under corrected before.

10-09-2017, 06:00 PM
Gotta be happy with that!

That scope is going to produce some corker images.

Looking forward to first light!


16-09-2017, 02:46 PM
I also used CCD Inspector which would help show which way it was out as well.

CCD Inspector is good but if I got a good result from manually correcting tilt I would find it was senior to what CCD Inspector would say as occasionally it would not give the same answer twice on the same image. But if you know how your camera is oriented with regards to the images then it does give an idea as to which way the camera needs to be packed out. Its another tool. It can also be helpful to use it to know when to stop!


16-09-2017, 04:53 PM

Through my investigations I've found that CCD Inspector can be very helpful, but one needs to take at least 10 dithered subs (20 is better), and calibrate them before making measurements. Stars need to be sufficiently exposed too (not too short, not too long). Then results given by CCD Inspector are very precise each time. It allowed me to fine-tune tilt in my imaging train and now PI reports eccentricity in my subs just under 0.29, which equates to 96% round stars across the entire frame.

Paul - the stars are really good now, but I feel that like me, you won't stop until you will get star shapes at least 95% perfect :)

16-09-2017, 05:20 PM
That's very interesting Suavi. Thanks for explaining the value of multiple subs and dithering for CCDI

Paul Haese
16-09-2017, 05:22 PM
After our conversation last week I went back and worked out where things where things needed packing out. I am not really a fan of CCD Inspector but use it more out of curiosity really. I need to install my Atlas to get a workable solution here and that means taking a few measurements on my next visit to the observatory. Using the Atlas will solve the sag problem which I believe is causing 90 per cent of the problem with the stars. I never had this problem with the FSQ or the TSA holding up the QSI. So I doubt that the QSI is not square to the optical axis which means it is the focuser not being able to hold up the camera. It might only be a few microns but its enough to cause imperfection.

Yes Suavi, you know me rather well. I hate losing even a few pixels off the images so I will work a bit more to solve the actual problems. This should provide a clear path for others to follow. :)

16-09-2017, 06:01 PM
[QUOTE=Paul Haese;1335769]After our conversation last week I went back and worked out where things where things needed packing out. I am not really a fan of CCD Inspector but use it more out of curiosity really. I need to install my Atlas to get a workable solution here and that means taking a few measurements on my next visit to the observatory. Using the Atlas will solve the sag problem which I believe is causing 90 per cent of the problem with the stars. I never had this problem with the FSQ or the TSA holding up the QSI. So I doubt that the QSI is not square to the optical axis which means it is the focuser not being able to hold up the camera. It might only be a few microns but its enough to cause imperfection.

Well that is the next level in the problem of tilt/flexure. unfortunately not as easy to fix. I found little things for my system helped. I know all your adapters are strong but for me I replaced any that were not thick metal and that helped. In my case my filter wheel is heavily cantilevered and I think it was causing flex. I have it oriented upside down. Not sure if that is any use to your setup though. But I would consider any cantilevered effect. The QSI seems fairly symmetrical though. But does a Newt require the camera to be pointing down to the ground? Like rotating the tube so the camera points down?


Paul Haese
09-10-2017, 09:01 PM
Time for an update.

After beefing up the secondary cage I found star shapes were still moving a little bit. Not the huge amount prior to the secondary cage fix but just enough to disturb the star shapes. So I kept looking. I began to suspect that the movement was coming from the draw tube of the Moonlite focuser. I am now reasonably sure that this is the case after an experiment I conducted over the weekend. I clamped down the focuser to my work bench making sure that the laser light would go through one of the peg holes and then I clamped the laser into the focuser. I moved the focuser down until the draw tube was around the focus position of the scope. I had previously tightened the tension of the draw tube as far as I dare go. I turned the laser on and then applied pressure to the focuser. Not excessive but enough finger pressure to see the laser dot seen in the attached image move just a little either left or right or up or down. That might be enough to cause misshapen stars. The stiffness I have it now might actually be ok to hold the camera in the same position throughout the sky and I might actually conduct the experiment whilst I am waiting on the last adapter for the Atlas. I suspect though this will not be the case.

25-10-2017, 06:25 PM
How'd you go Paul? Have you verified whether the focuser can now hold your camera in the same position throughout the sky? Have you received the adapters for the Atlas yet and if so, did that solve your problem? I'm still intending to get the LiteCrawler for my ONTC, but have concerns that using such a heavy focuser will introduce new issues...

Paul Haese
25-10-2017, 09:27 PM
Hi Lee,

"funny thing happened along the way".

To start, yes I now have the Atlas focusor on board with the adapters. I got the first lot of adapters about a month ago. Everything fit as it nearly always does with Precise Parts (I've only ever had one issue and they fixed it free of charge), but somewhere in the mad calculations for back focus I neglected to allow for a 5mm adapter plate on the front of the QSI. Those that don't know, the Atlas has a draw tube length of 10mm and hence why it can carry do much weight. I thought I had allowed for the adapter, but not being able to reach focus would suggest otherwise. So; after ordering another adapter (the smaller of the previous ones) I received it earlier this week (despite it being in the country since last Wednesday :lol:, well done Australia Post) and started doing some V curves on Monday night.

From what I could see focus was consistent across the field but it looked a little out of collimation. Today, I drove to the observatory, fixed collimation, did a few other chores and now I am waiting for the sky to be clear. That has happened a few times whilst I was without the correct adapter, but not at present.

The Atlas is lighter than the Moonlite focuser and seems to have sorted the problem of draw tube flex. More testing will tell me if I have solved the problem of tilt etc and I will get back and tell everyone as soon as possible. :)

26-10-2017, 03:59 PM
Hi Lee, I ordered the "LiteCrawler" earlier in the week. Time will tell if I made the correct decision. I will let you know how I get on. I have strengthen the top cage of the GSO 12" considerably with carbon tubes.

Paul Haese
29-10-2017, 01:15 PM
Another Update

After two imaging runs I think I can confirm that most of the tilt and flex remaining was coming from the Moonlite focuser. I put a stack of 10 subs together of the better seeing I got on both nights.

The first image is the top left hand corner, second is top right hand corner, then bottom left, the bottom right and finally centre of field.

There is still some errant tilt/movement in the right hand corner, but nothing extreme. So using the Atlas has worked.

I have been reliably informed the best place to chase the last lot of movement is in the bracing on the secondary cage assembly and to provide a counter balance for the secondary on the spider. The bracing is an easy one to address but the counter balance will be more difficult.

I think generally, though the scope looks ok for general imaging for now with some minor sorting to be undertaken, including a small moment of inertia around the secondary cage.

Joshua Bunn
29-10-2017, 03:42 PM
Hi Paul. Been good following your progress. On an unrelated note, what is this target in the middle frame?


Paul Haese
30-10-2017, 08:50 AM
Hi Josh,

that is GCVS R Aqr, located in Aquarius. It's an interest star system.

31-10-2017, 06:22 PM
That's looking pretty damned good to me, Paul! Glad to hear the Atlas solved the majority of your issues... as great as it is to get new gear, it's frequently a colossal pain in the nether region. Looks like you've now solved the bulk of it so hopefully now you can sit back, relax and enjoy your new gear.

Very interested to hear how you get on with it, Dave. It's probably a couple of months yet before I order mine, so I'm keen to hear any bits of wisdom you may pick up in your experience with it.

Paul Haese
02-11-2017, 11:21 AM
Thanks Lee, here is a test image (http://paulhaese.net/NGC104.html)I am doing on 47 Tuc. There is still some movement, though not much. I am pretty certain this is coming from either the cage which needs diagonal bracing or it is coming from the secondary assembly which might need a counter weight.

Overall though I am more pleased with how things are now and I can deal with some errant star shapes. The image of 47 Tuc has nothing doing to the star shapes. There is some guide error and flex/tilt.

Dave and Lee, you'll be interested to hear that I have ordered a Moonlite Nightcrawler (heavy) for the RC. I'll let everyone know how that goes. I am hoping it will be the ticket to replace the Atlas.

03-11-2017, 11:15 AM
Looking forward to your Nitecrawler report Paul. Hopefully I will have my light version in a week or so.

I agree with your secondary/spider assessment. The components are rather underdone. I rather like the Hercules scope secondary implementation http://www.telescopeshercules.com/htn300?lightbox=imageo7o

Joshua Bunn
03-11-2017, 09:48 PM
Thanks for that Paul.
Yeah I bought the nightcrawler 35 for my settup to... it is a heavy piece of gear but it is solid.