To make your system not flex one needs to tie it down.
A couple of images below shows that both the optic and camera just cannot move relative to each other, now?.
My differential flexure problems are almost non existent now.
The extra G clamps are for balancing weights.
Below is R G B L CCD Inspector images of the same area. It needs a slight adjustment to the left, about 0.2mm.
This involves removing one folded sheet of standard A4 paper I am using for shims for the lateral adjustment of the camera.
If it is not obvious I am using the side by side plates both left and right as outriggers to minimise lateral shift due to gravity as the mount
moves.
To put it simply the triangles that the stabilizing bars and turnbuckles form only have tension stresses. There is no bending moment that can induce movement anywhere laterally in the optic train as long as these tension stresses are far higher.
By making the whole lot quite robust the RH200 is now coupled to the camera no matter what all the bits between them decide to do. The real problem is the CFW
as it is quite heavy and has a very large bending moment that varies with mount position.
The problem is quite new as F3 has a critical focus zone of about 20 micron tops. This means that ANY flexure will lead to misalignment.
I thought flexure was only from guidescopes and it disappeared with OAG?
I guess I'm uncertain as to exactly what you've locked down here, would you please explain in more detail what you have done?
Cheers
Andy
Very good question!
With F3 an off axis guider would be next to useless if there was flexure between the optic and the camera.
For sure the star that was being guided on would not move relative to the optic depending or on where the off axis guider was mounted. If the camera was moving relative to the optic this is all a waste of time as the critical alignment needed with F3 would drift off!
Guide chips on cameras will fail also as the alignment will change with mount orientation.
Do we mount the guide scope on the camera or the optic?
This is a moot point as the slightest flexure between optic and sensor would again lose good alignment and result in distorted stars at some corner/s.
The problem with fast F3 optics is the very small critical focus zone. In the case of the RH200 it is less than 20 micron!
True, but I would NOT want to have to go to that much effort to make such expensive equipment work properly. Top range scope, top range camera, top range mount.
Is OS's assembly not adequate enough? I see more than yourself having flexure issues with OS large scopes - perhaps there is an underlying issue. Similarly, I see very few reports of issues with AP R-H scopes, or the Tak CCA250. Or is simply hanging THAT much FLI off the back causing no end of nightmare?
True, but I would NOT want to have to go to that much effort to make such expensive equipment work properly. Top range scope, top range camera, top range mount.
Is OS's assembly not adequate enough? I see more than yourself having flexure issues with OS large scopes - perhaps there is an underlying issue. Similarly, I see very few reports of issues with AP R-H scopes, or the Tak CCA250. Or is simply hanging THAT much FLI off the back causing no end of nightmare?
We are in a totally different paradigm. It does not matter who is at fault. It is up to up to us ALL to solve the problems.
I offer this as a community service not a lecture.
Fast anything will produce problems that are negligible terms in the infinite series that are the Fourier Series that describe a piecewise continuous function becoming far larger.
In my case the CFW is the main culprit. It is fine with slower systems. It just does not cut it with F3.
I want ten filters so I do not have to swap and introduce dust etc.
It is all a matter of balance. I chose the hard road as I like a challenge.
I feel sorry for all the smug safe participants in our hobby.
I image at f/3.8 Bart - I know the pitfalls, I just have not encountered so many issues to date. Perhaps I am lucky - don't know, and don't mind the status quo either. When something works, why ruin it.
It is all a matter of balance. I chose the hard road as I like a challenge.
I feel sorry for all the smug safe participants in our hobby.
Bert
Hi Bert, I thought I would just point out that the collective group of people you are insulting are a very small community that don't need this kind of elitest attitude. The fact of the matter is that the "new ground" you are breaking here in the form of surpassing manufacturer specifications is nothing to be proud of unless you are able to make it work to the level that it would inside the specs. As of yet I don't see it.
Personally I think you would be better off putting a 8300 chip on it. It would be within the specs, it would likely have integrated guiding, and if you really wanted to do these really large fields you could mosaic.
Finally I thought I would attach an image showing that the scope is still lacking. The second image is mine and while it was made with a safe smug f5 system on a eq5 it is deeper than your f3 and has more resolution.
Dear Peter,
I am sure Bert is aware that higher resolution is more easily
obtained with a longer focal length & a Newt. with a smaller obstruction.
He is not trying to do that.
He wants to be able to take large areas of the sky quickly at f3 to search for unseen structure.
If Bert can ever get his system to a dark site - maybe a robotic observatory -
he'll be able to do huge surveys of large areas of the sky in one night.
He's experimenting in uncharted territory & that is where new discoveries may be found.
I am fed up with the Melbourne weather & I see the future as a robotic system
in a place with better seeing & a greater abundance of clearer nights.
My Newt. is a bit too finicky for robotic work -
I really need something where the camera is at the back of the system
not hanging off the side.
Dear Peter,
I am sure Bert is aware that higher resolution is more easily
obtained with a longer focal length & a Newt. with a smaller obstruction.
cheers
Allan
I would be happier with this statement if I believed that those were the causes of his resolution related issues. The newt that took my image is 750mm focal length which is not much more than the rh200. Obviously pixel size will play a larger role. Forgetting this for a minute I suspect that a fsq with the same camera would perform better for both field curvature and on axis resolution.
As you like to point out Bert I am going to state the bleeding obvious.
You still have elongated stars in your high resolution images. You have not beaten flexure. Nor could you hope to do so when you are using a set of adjustable rings on your guide scope. Added to this is that you are imaging outside the imaging circle of the scope. From memory I think the RH200 has a 48mm circle and you are imaging at around 55mm or something like that disparity. I am probably wrong about the numbers but not the fact your sensor is well outside the circle. So to begin with your stars at the corners are not well corrected. Add flexure from the camera and guide scope and you are looking at odd shaped stars.
The weight of that camera on the back is well outside spec as I have spoken to OS myself about what size sensor they recommended. I was looking at one stage about buying one of the RH200 scopes and wanted to hear from OS what their thoughts were for what size camera and sensor would be suitable. It is possible to use a 11002 sensor but that is close to being on the edge of spec. Thought it depends on the weight of the camera itself as to whether that will work. An STL11002 seems to work ok because it is relatively light. An STXL on the other hand is heavier again and might cause flex. That is coming straight from Gino at OS.
I don't know why you bother to put up super high resolution images anyway. I have not seen a single one without deformed stars in them anyway. Your issues entirely relate to the points above and you will never fix the problem with that size camera sitting on the back. I am also including the filter wheel in my description of camera. You after all need that to use the sensor to its full potential and therefore need the filters.
While I applaud you having the guts to go and try this experiment, I reckon you would be better either getting a different scope that can handle the weight and image circle or get a new camera and sell that one. Good luck in that regard from one of the smug safe participants.
Now by way of example to press the point. I have included crops of top and bottom left, top and bottom right and centre of your helix image. I cannot see any place where your stars are round. Certainly approaching round in the centre, but not far out from the centre bad deformation starts.
This deformation has to be coming from flex either in the back of the scope or the guide scope or a combination of both. I would say to a lesser extent from the guide scope as there is still some deformation in the centre and then the rest is from either the image circle itself and the weight of the camera assembly.
Is the scope itself supported by rings? What about the dove tail on the main scope? Is that a D sized dovetail? No point in holding the camera in place if the scope can flex from the camera.
Your images show us faint stuff that nobody else can get to without a huge expenditure of time. The stars are not perfect all over, but so what - we know where they are and how bright, the rest is cosmetic. The nebulae that you chase are still beautiful, regardless of minor residual distortion.
Your images show us faint stuff that nobody else can get to without a huge expenditure of time. The stars are not perfect all over, but so what - we know where they are and how bright, the rest is cosmetic. The nebulae that you chase are still beautiful, regardless of minor residual distortion.
Don't get me wrong Ray, the reason I am being picky is because Berts post was excessively condecending towards pretty much all imagers, while claiming that all of his problems are sorted which they clearly aren't.
If Bert was happy with the performance of the scope for what he wants then he could have said that he was aware of residual error but didn't mind, and it would be a different story.
Hey, if Bert is happy that's all that matters isn't it Paul and Pete?...besides he clearly owns the Worlds sexiest production scope (once you look under its burka)
Satisfaction in imaging should be about much more than percieved optical or processing perfection or where you rank in the imaging world....there is certainly no argument that Bert is going deep with that little red number, regardless of his processing techniques.
I would be happier with this statement if I believed that those were the causes of his resolution related issues. The newt that took my image is 750mm focal length which is not much more than the rh200. Obviously pixel size will play a larger role. Forgetting this for a minute I suspect that a fsq with the same camera would perform better for both field curvature and on axis resolution.
Aren't you forgetting the unusually large 55% obstruction of the RH200
which is required for a large camera?
