46 replies to this topic

[TareqPhoto]

Totally understandable. I remember how tentative I was when I first drilled a hole in my 8" Newt for its secondary dew heater wire, I was having heart palpitations.  However, I guess once I got past that, I stopped worrying, and bought this OTA with the full intention of "Frankensteining" it if necessary.

 

It's a shame that was needed to get the most from it, but I can totally understand why this Newt was built like this. It was to allow plenty of in-travel for DSLR users. Unfortunately, that makes it less than optimal when using a coma corrector and cooled camera.

 

The fact that the spider and focuser are so far down the tube is curious, though. It's almost as if they intended to allow users to do this kind of mod. The previous version didn't have this, and users ended up needing to do things like add extra tube to the back end of the OTA.

 

 

 

What is the "blocked" collimation? Perhaps you could make a post about this and we could try to assist?

Mine can focus not a problem, i tested only once on Veil Nebula and it was in focus, with the stock focuser, i was planning to change all Newt focusers i have, i did with my 8" F/5 first, and not yet with 6" as i don't know which affordable good focuser to buy for it.

 

I called it a blocked collimation because i explained it so many times in another sites or groups or topics that with the secondary mirror and maybe spider vanes whenever i use the screws or the knobs [Bob's knobs after i installed them] i can't keep collimation or make it proper, to explain it more, there are three knobs, only two from any direction is only working, so whenever i adjust two of them, once i use the third for fine tune it ruins the other two knobs adjustments, this never happen with my 8" Newt, using exactly the same collimator, so i think either the secondary has a problem or its holder or something else i can't think of.

 

This scope is amazing once it will work, and if i buy a reducer for it i can go faster then i can have nice data, sure i will face issues with it until it is done, but i will never modify it with drills or cutting.

[TareqPhoto]

I dont know if "Frankensteining" is the right word.

The GSO 6-inch F4 is very poor mechanically, and I never really used mine because of this. The GSO CC actually increases focal length (to 687mm in my case), so the imaging train is an extra 87 mm out. And at low latitudes because the focuser is so far back from the front, the train has to be on top when mounted, which is a pain from the torque and balancing pov.

If it were possible, it would have been sold by now.

It's actually encouraging to see these kinds of mods working, and personally am looking forward to trying it out during the rains.

Of course, this is fine as a Newt is a simple design - doing this on a triplet or an RC would be a different story

Sent from my SM-S908E using Tapatalk

I will use it as it is, be it F4 or F5 or F8 i don't care, it is the fault of GSO not me to advertise it as F/4 or 6", maybe it is for visual more than for imaging, so i will do just the modifications that don't require me to cut shave drill anything, main mods i will do is to flock it inside and change the focuser and use very dark material or a cloth to the back for light leaking, then i will use it as it is, and if i buy that Starizona reducer to go to F3 then i can say it might be as F3.2 or F3.4 which is not bad anyway, anything but not drill or change the length of the tube or change the place of the focuser.

[AaronH]

I called it a blocked collimation because i explained it so many times in another sites or groups or topics that with the secondary mirror and maybe spider vanes whenever i use the screws or the knobs [Bob's knobs after i installed them] i can't keep collimation or make it proper, to explain it more, there are three knobs, only two from any direction is only working, so whenever i adjust two of them, once i use the third for fine tune it ruins the other two knobs adjustments, this never happen with my 8" Newt, using exactly the same collimator, so i think either the secondary has a problem or its holder or something else i can't think of.

The three screws just push against the secondary holder. There shouldn't be too much that can go wrong here. You loosen one or two off by a fraction of a turn, then tighten one on the other side until they're all tight again.

 

It may be that the divots in the secondary holder are causing issues. Maybe the screws are somehow catching on the edge of those divots?

 

Personally, I find the divots to be a problem, purely because they prevent free rotation of the secondary holder to ensure the primary reflection is centred. So I add a "fender washer" like the below on top of the secondary holder (between the holder and the spring) to allow free rotation. It may be that this helps your secondary adjustment issue, because then you'll just have three screws pushing against a flat washer to tilt it, which should remove any complexity from the equation.

 

Edited by AaronH, 02 April 2023 - 08:27 AM.

[TareqPhoto]

The three screws just push against the secondary holder. There shouldn't be too much that can go wrong here. You loosen one or two off by a fraction of a turn, then tighten one on the other side until they're all tight again.

 

It may be that the divots in the secondary holder are causing issues. Maybe the screws are somehow catching on the edge of those divots?

 

Personally, I find the divots to be a problem, purely because they prevent free rotation of the secondary holder to ensure the primary reflection is centred. So I add a "fender washer" like the below on top of the secondary holder (between the holder and the spring) to allow free rotation. It may be that this helps your secondary adjustment issue, because then you'll just have three screws pushing against a flat washer to tilt it, which should remove any complexity from the equation.

 

FenderWasher.jpg

It could be that, i was excited, but then i got busy and disappointed about it and left it for the time, now i think i must fix it, i think it could be that the holder is too tight locked with the mirror and i have to loosen a bit, or maybe the opposite and it is too loose, maybe i must remove the entire setup of that secondary including the vanes and give it a better check up, my 8" didn't have issue out of the box, and others with this GSO 6" don't have the same issue as well, i feel that there is something wrong that prevent it from being proper collimated, but as i said, i got busy with other stuff and didn't bother to fix it long time ago in time.

[TareqPhoto]

I remember one thing, always the knobs reached maximum lock without getting very close to the center, i mean i need to squeeze it more to put the laser cursor to the center, but that will damage the mirror, so i just rotate until it is no more room and too tight to go further, when i use the other knob it is also the same, it moves the laser cursor further so i rotate until it is getting closer but never center, it is like the knobs aren't trying to get it to the center but only close to the center, and i lock one knob or two but the laser is still further and the third knob can't make it to get it back, and when i fix that third to use another knob to correct it won't correct, it just cancel the other locked fixed knob adjustment, so for me it kind of either i change the holder or change the knobs or change the secondary mirror itself to fix it.

[ValeRyo]

The fact that the spider and focuser are so far down the tube is curious, though. It's almost as if they intended to allow users to do this kind of mod. The previous version didn't have this, and users ended up needing to do things like add extra tube to the back end of the OTA.

 

This is mindblowing! How can I know if I need the extra lenght of the tube?

[AaronH]

I remember one thing, always the knobs reached maximum lock without getting very close to the center, i mean i need to squeeze it more to put the laser cursor to the center, but that will damage the mirror, so i just rotate until it is no more room and too tight to go further, when i use the other knob it is also the same, it moves the laser cursor further so i rotate until it is getting closer but never center, it is like the knobs aren't trying to get it to the center but only close to the center, and i lock one knob or two but the laser is still further and the third knob can't make it to get it back, and when i fix that third to use another knob to correct it won't correct, it just cancel the other locked fixed knob adjustment, so for me it kind of either i change the holder or change the knobs or change the secondary mirror itself to fix it.

 

Collimation adjustments shouldn't damage the mirror with any conventional secondary holder. The screws should only touch the metal holder, which is sturdy enough to handle any reasonable pressure. The glass should be (well and truly) nowhere near them.

 

However, it does seem like something is wrong if the secondary tilt adjustment screws aren't doing their job.

 

Have you ensured your secondary is perfectly centred under the focuser using a collimation cap or short sight tube? For this, you'll need to use the centre screw to move the mirror up and down the tube and your hand to rotate it to face the focuser. With the new-style GSO secondary holder, this rotation will be limited by the divots that the tilt adjustment screws sit in (which is why I add a fender washer - a tip I picked up over in the Reflectors forum here).

 

In reality, this initial centring under the focuser is the trickiest bit of secondary collimation (but you generally don't have to do it often). If the mirror is not perfectly under the focuser, you'll end up trying to tilt it too much via the collimation screws, which will lead to uneven illumination, and can even make it impossible to get perfect collimation from the screws if the initial alignment with the focuser is too far off.

 

AstroBaby's collimation guide has an excellent set of instructions for this. Step 2 is the critical part:

https://www.astro-ba...nian-reflector/

Edited by AaronH, 02 April 2023 - 06:47 PM.

[Mike in Rancho]

Yes, on the original (maybe improved now?) secondary holder, you are limited by both the dimples and the Y-shaped legs, though obviously that Y is built so that proper alignment will fall within its location.  But with either the original screws or Bob's knobs, the ends will grind into those dimples and also will not push in a predictable and repeatable manner, making collimation more a matter of pure luck than following proper procedure.  The big metal washer is almost a mandatory mod.  And adding milk or water jug washers to that will really improve smoothness of movement, and the secondary will actually do what it is supposed to do when you read collimation instructions.  The plastic I used was pretty thin, so I doubled it up and taped them together.

[TareqPhoto]

If some have images of how they did it for secondary mirror and what washers you are using it will be a big help, i might inspect my scope again and see what's wrong more critical soon, i won't live it non fixed for long time, i even will remove the secondary mirror to clean it [how to clean it properly?] and return it back, maybe that will fix the problem too suddenly, who knows, i just wasn't into imaging since long time ago, since 2020 precisely, that year i started to buy many items or gear and stopped imaging, but i found out that both of my Newt have light leaking from behind actually, will see if i can seal more around the focuser too.

 

Would like to replace the focuser from my GSO 6", so what are the recommendations for nice affordable one [not high end so expensive one]?

[calypsob]

My philosophy with these gso is that you buy it cheap expecting to ATM the heck out of it, knowing beforehand what it will require. You will likely use a coma corrector and focuser that cost 4x the scope, and thats ok because as you see above you can produce very nice results.

Edited by calypsob, 03 April 2023 - 11:13 AM.

[Mike in Rancho]

If some have images of how they did it for secondary mirror and what washers you are using it will be a big help, i might inspect my scope again and see what's wrong more critical soon, i won't live it non fixed for long time, i even will remove the secondary mirror to clean it [how to clean it properly?] and return it back, maybe that will fix the problem too suddenly, who knows, i just wasn't into imaging since long time ago, since 2020 precisely, that year i started to buy many items or gear and stopped imaging, but i found out that both of my Newt have light leaking from behind actually, will see if i can seal more around the focuser too.

 

Would like to replace the focuser from my GSO 6", so what are the recommendations for nice affordable one [not high end so expensive one]?

I do have one picture of this in the gallery.  Did this at around the same time I had everything apart to put a new centered Catseye hotspot on the primary.  Prior major mod was using ScopeStuff flocking paper on pretty much everything, and a sharpie or matte black camo paint on anything else.  I do use the stock focuser (as comes with the Orion, in case different) and, knock on wood, am not having the problems that others are.

 

Yes Newts, and maybe this one in particular, leak light like a sieve.  I use a neoprene sleeve (cut from cheap water socks, small, from Amazon) around the focuser as one side of the drawtube can leak, and for the rear I built a lined bucket with foam strips that I just slip over the back once the mirror is cooled down.  If you shine a flashlight at the back of the Newt and look down the OTA, you'll see what the potential problem is.

 

Apart from that, I collimate (full Catseye tri-pack) with the OTA angled at least somewhat upward.  Finally learned the hard way that if I collimate horizontally, a bit of mirror flop will take it out of alignment when in use.  But I have looked through my autocollimator and it holds perfectly everywhere I move the mount, just not horizontal.  That's okay, sky isn't that way anyhow.  Also I still do take directionally-matched flats.

 

In this pic you can see the Y shape of the stock holder and those troublesome dimples.  Big metal washer I happened to have in the garage, much like the image posted above by Aaron.  Then I made two layers of the water jug washer (you can probably see the scotch tape) for smooth turning of the Bob's knobs and reliable movement with very small turns.  Do note that without the dimples, rotation is not constrained.  I think that's a good thing, but you can end up way off so hold the mirror.  The Y legs are still a good ballpark of where to first start.  A good sight tube is very helpful here.

 

Finally as I mentioned in the earlier post, that little plastic sheath helps keep the spring under control.  Might have been cut further down to size once I started matching parts up, can't remember exactly.

 

Edited by Mike in Rancho, 03 April 2023 - 12:01 PM.

[TareqPhoto]

My philosophy with these gso is that you buy it cheap expecting to ATM the heck out of it, knowing beforehand what it will require. You will likely use a coma corrector and focuser that cost 4x the scope, and thats ok because as you see above you can produce very nice results.

That is true, and i accept that, because my Meade 8" F/5 was a discontinued item when i bought it but luckily i found it from one seller ready to sell it so i got it, it is an amazing scope, it is just needs to be modified, and that what i was doing since years, i couldn't afford to buy $800-2k Newt that time of any higher end brand or even better design, so i am not giving up the cheap one, and it is getting better every time i modify it which getting closer to a higher quality models, the point is that i can't pay $1k-3k at one run, but ready to pay that within years.

 

Someone bought GSO 6" F/4 according to my advice and he is happy with that scope a lot and produced nice results with it, so i am sure it can be fixed or used nicely, he didn't modify anything, mine could be nice, maybe i messed around with it first time and ruined something accidentally, i need to check it out and see, i just mentioned that i didn't play with it much yet as i got carried out or busy with other stuff and abandoned this and another scopes.

[TareqPhoto]

I do have one picture of this in the gallery.  Did this at around the same time I had everything apart to put a new centered Catseye hotspot on the primary.  Prior major mod was using ScopeStuff flocking paper on pretty much everything, and a sharpie or matte black camo paint on anything else.  I do use the stock focuser (as comes with the Orion, in case different) and, knock on wood, am not having the problems that others are.

 

Yes Newts, and maybe this one in particular, leak light like a sieve.  I use a neoprene sleeve (cut from cheap water socks, small, from Amazon) around the focuser as one side of the drawtube can leak, and for the rear I built a lined bucket with foam strips that I just slip over the back once the mirror is cooled down.  If you shine a flashlight at the back of the Newt and look down the OTA, you'll see what the potential problem is.

 

Apart from that, I collimate (full Catseye tri-pack) with the OTA angled at least somewhat upward.  Finally learned the hard way that if I collimate horizontally, a bit of mirror flop will take it out of alignment when in use.  But I have looked through my autocollimator and it holds perfectly everywhere I move the mount, just not horizontal.  That's okay, sky isn't that way anyhow.  Also I still do take directionally-matched flats.

 

In this pic you can see the Y shape of the stock holder and those troublesome dimples.  Big metal washer I happened to have in the garage, much like the image posted above by Aaron.  Then I made two layers of the water jug washer (you can probably see the scotch tape) for smooth turning of the Bob's knobs and reliable movement with very small turns.  Do note that without the dimples, rotation is not constrained.  I think that's a good thing, but you can end up way off so hold the mirror.  The Y legs are still a good ballpark of where to first start.  A good sight tube is very helpful here.

 

Finally as I mentioned in the earlier post, that little plastic sheath helps keep the spring under control.  Might have been cut further down to size once I started matching parts up, can't remember exactly.

 

That is great, nice tips, i will keep in mood this comment when i check out my GSO Newt.

 

As i can see from this pic that the user used Bob's knobs instead of screws, me too, i assume i chose the correct one for my Newt, i bought one set for my 8" which is working perfectly, and another set for 6" choosing the option for 6", i hope they sent the correct one then, in all cases, if i really truly want to use this 6" Newt then i must fix it, otherwise it will be a waste or pointless buying it for no use, but i don't regret at all, having a scope even with an issue by a nice good price is better than no scope at all, and if we had the budget for higher quality we could buy then, but not the case, and i saw many having this GSO 6" F/4 with success even without any modifications or changes, so it means it can be done, i won't give up.

 

Thank you very much for this 

[arbit]

My philosophy with these gso is that you buy it cheap expecting to ATM the heck out of it, knowing beforehand what it will require. You will likely use a coma corrector and focuser that cost 4x the scope, and thats ok because as you see above you can produce very nice results.

Pretty much.

The curious part is that their 6 inch RC costs a little more, but is _solid_. Mine holds collimation for months (no travel), and focus for days.

Clearly they can make a mechanically solid product close to that price point. Especially when you consider the RC mirrors are much more complex and likely much more expensive than a Newt.

So it seems to be a choice rather than necessary constraints for meeting the price point.

Sent from my SM-S908E using Tapatalk

[calypsob]

Pretty much.

The curious part is that their 6 inch RC costs a little more, but is _solid_. Mine holds collimation for months (no travel), and focus for days.

Clearly they can make a mechanically solid product close to that price point. Especially when you consider the RC mirrors are much more complex and likely much more expensive than a Newt.

So it seems to be a choice rather than necessary constraints for meeting the price point.

Sent from my SM-S908E using Tapatalk

An 6” RC is f9, so more forgiving in terms of focus, correction, and collimation. Gso rc’s are hard to collimate. Newtonians are easy to collimate, an f9 newtonian would be very easy to collimate. An f4 newtonian is tricky to collimate because the adjustment mechanisms on the gso are designed with cost cutting in mind, not performance. So its up to the user to find workarounds. As long as the newt mirror is ground reasonably well and the secondary is flat, you can make a gso newt work. Ive owned the 8” gso rc and it was a decent scope. You could see where they cut cost and because of this I added a moonlite focuser because the stock focuser slipped pretty bad with my camera.

Edited by calypsob, 04 April 2023 - 10:03 AM.

[calypsob]

I think there should be a gso newtonian mods sticky. If I have time tonight Id like to share an extensive list of my findings and learn what others have done.

Edited by calypsob, 04 April 2023 - 10:45 AM.

[Seven007]

Hi AaronH,
wow, congratulations to the improvement of your Newton.
I like to at some of your ideas to my skywatcher 150 PDS.

 

When you added the embroidery rings how critical was the size/diameter of the rings?
I have seen they come with one closed ring and one adustable ring.

Do you think it is possible to add the smaller ring inside the tube?

 

Best Regards
Sven

[AaronH]

When you added the embroidery rings how critical was the size/diameter of the rings?

I have seen they come with one closed ring and one adustable ring.

Do you think it is possible to add the smaller ring inside the tube?

 

You need to be reasonably close with the size, but it doesn't have to be perfect. If they're too small and can't close, then that would be an issue. However, a bit too large is fine. You can pad them.

 

The rings I bought were listed as 7.2". They're slightly too large, so I padded the inside with a few layers of thick foam tape. That did the job, and they're tight now when fully closed. If I had found 7" rings, they would probably have been perfect for the GSO 6" Newt and wouldn't have required any padding.

 

However, there's likely some variance between tube sizes from different manufacturers, so the same size may not be perfect for a Synta Newt.

 

The inside rings went into the craft box. With the 7.2" embroidery rings, they're a bit bigger than the tube, so aren't going to fit inside. It's unlikely any rings would have a fit that is millimetre-perfect enough for that to work.

 

And if anyone has an 8" GSO Newt, the 23cm rings I bought were a perfect fit. I put a layer of tape on the inside to avoid the tube getting scuffed, but they basically look like they were made for the OTA.

Edited by AaronH, 07 April 2023 - 08:28 PM.

[ValeRyo]

Just to update: I had the baffling printed and installed yesterday, after applying velour to the inner surface, I changed also the mirror clips with the 3d printed ones, with smaller indent on the mirror; also added plastic washers to the spiked of doom and no more movement due to size tolerances! I didn't change the cork as the mirror is able to rotate without big force, so I left it as it is. Reassembled everything and now need a good night to try it out!!!

 

A quick recap of modifications done:

- added primary baffling

- changed mirror clips form provided rubber ones to 3d printed ones with smaller indent

- added plastic washers to spikes of doom

- painted with blackboard paint the side of the primary and of the secondary mirror

- changed primary springs with stronger ones

- flocked the tube internals with self-adhesive black velour

- painted with blackboard paint the entrance of the tube

- changed secondary spring with stronger one

- changed secondary screws with set screws with cone point

 

Now, about the correct illumination of the field, this is the collimation I made yesterday after the assembly and that's through a Reego, is this alignment going to provide a well illuminated field?

 

Edited by ValeRyo, 13 April 2023 - 04:21 AM.

[ValeRyo]

Further Adjustments

I decided the secondary needed to be re-mounted. The astigmatism was just too bad to use it like this even temporarily.

 

So I grabbed an X-ACTO knife and proceeded to cut away the ludicrous amount of adhesive that bonded the secondary mirror to its holder. The mirror was really firmly held down from edge-to-edge, with no allowance for thermal expansion. Once I’d freed it, cleaned it up, and remounted it with three blobs of RTV silicone, the star test was satisfying. Astigmatism was now negligible.

 

I proceeded to do some more testing outside. After being bitten by the Tarantula Nebula, I decided SH2-308 would be a great, somewhat ambitious, choice of target. It was pretty high up in the sky, away from murk, and would allow me to assess whether there was any remaining eccentricity in my star shapes now that the secondary astigmatism had been addressed.

 

As the results rolled in, I could see the astigmatism was definitely gone, but I still wasn’t happy with the erratic FWHM I was seeing, and brighter stars still had some less than pleasing fan-like diffraction patterns. Stars were also more misshapen and eccentric than I’d like. That was the next thing that needed to be addressed. But what to do?

 

Aaron can you please tell me how you reattached the secondary? how did you ensure concentrity of primary, secondary and focuser?

[AaronH]

Aaron can you please tell me how you reattached the secondary? how did you ensure concentrity of primary, secondary and focuser?

I cleaned the mirror holder and the rear of the secondary mirror of any adhesive residue, then placed the secondary mirror face-down on a microfibre cloth (the kind you use for cleaning eyeglasses). I then placed three pea-sized blobs of RTV silicone about two-thirds of the way from the centre, placed three matchsticks in a "Y" shape in-between, and carefully lowered the holder onto the back to adhere it.

 

The weight of the holder provided enough pressure to bond, and the matchsticks gave adequate spacing between the holder and the mirror. I then left it for 12 hours to bond, removed the matchsticks, and then left it upright for another 12 hours before I cleaned off any residue, blackened the edges, and reinstalled it.

 

Here are some forum posts I referenced when doing this:

https://www.cloudyni...chment-methods/

https://www.cloudyni...ch-a-secondary/

 

I simply eyeballed the placement of the holder on the secondary, matching the same spacing as it had before I removed it (the holder is almost the same size as the secondary with this OTA, and there's just a small lip that protrudes). I'm sure I got it within a fraction of a millimetre that way. Any minor inaccuracy is going to disappear into irrelevance when compared to centring of the spider, which is much harder to get right to the millimetre. And if it's a fraction of a millimetre too high or low when compared to the original placement, then the holder can easily move up or down the tube using its centre screw.

 

Alignment of the primary, secondary and focuser is a task for collimation. Centring the secondary under the focuser, aligning the secondary mirror with the primary centre, and aligning the primary tilt, are all done using the usual tools (sight tube, laser, Cheshire/Tublug, etc.). These will cancel out any slight imperfections in the mounting.

Edited by AaronH, 01 May 2023 - 12:05 AM.

[ValeRyo]

this is a good question for all owners: how do you improve stiffness of the focuser? I still find tilting in my images due to camera weight that bends the focuser, how can this be solved or mitigated?

When I collimate with OCAL now I get a perfect collimation, but on the star test I get a very centered shadow area but in the image there's a bending that corresponds to the direction of gravity acting on the camera mostly due to the momentum difference of the OCAL, with gravity center at the end of the focuser tube and very lightweight, with the camera, much heavier and with gravity center out of the focuser tube