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A couple of questions:
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| hey, will take a look |
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RH200 users, Here is a brief start on the how I attack the 4th order collimation of the the RH200. please excuse my spelling and typos. use my methodology at your own risk. it is possible to make the scope worse than when you started. You are working to find a a 4th order collimation solution. the safest solution is sending the scope to OS for factory collimation at very high cost. A systematic approach with disipline is needed. special tools (you need to make a simple set of custom tools that works with your image train installed). gather a set of metric allen wrenches for push pull tilt grub screws and the primary tilt bolts. Shorten the short section so you can access the adjustments with the focuser in place. I always try to collimate the complete image train and scope together. the adjustments are so fine that simply removing and reinstalling the image train will cause frustrating variability in measured tilt in the system. assemble the focuser and filter wheel (no filter installed). make sure that you use threaded connections or precision dove connections. intall a 2" ep reciever in the filter wheel. put a gladder laser collimator in and check if the return spot is exactly centered. If it is not adjust the tilt plate until the return is correct. place a circle or grid pattern on the Gladder and project a image onto a screen in front of the RH200. check for concentric patterns around the secondary shadow and that the corrector field stop is also concentric. if it is not then the optical axis is tilted. you will need to reset the optics to a know state (primary tilt) if it is ok then the factory collimation of the primary and corrector are probably still good and you only need to correct focuser tilt. If not then the collimation now is a very involved with 4 variables. primary tilt, corrector/secondary tilt, focuser tilt and corrector to primary spacing. they all interact with each other. also centering of primary and corrector. OK we start a complete collimation without the aid of a double pass interferometer. 1 assemble scope focuser and filter wheel with Gladder laser. 2 turn the scope face up and remove the tilt bolts (do not touch the tilt grub screws as they will allow approx corrector tilt when reassembling). mark the rotation of the corrector cell with a index mark. 3 lift out the corrector cell off the long grub screws with spring washers on them. some washers will want to stick inside the bore of the holes that match the long grub screws. they are in between the collimation grub screws and bolts. retrieve the washers and put them on the long grub screws so they don't get lost. place the corrector and cell (the retaining ring is still bolted in place) face down and protect it. do not jarr the secondary baffle as it is only glued in place and will easily get knocked off. 4 now is a good time to clean the corrector. ADJUST THE FOCUSER TILT: cut a piece of paper that covers the front of the ota. fold it corner to corner on both axis to find the exact center of the ota. tape it over the front of the ota. x harks the center. punch a pin hole in the center to help tou see the gladder laser. A turn on the gladder with the small spot adapter installed. B adjust the tilt of the back focuser tilt plate until the laser points at the optical center of the ota. ADJUST THE PRIMARY TILT: Take a screen and punch a accurate smooth 1/8" hole in it (a pie tin with a white sheet of paper will work). place the screen infront of the scope and shine a flashlight through the hole pointing at the scope. I have the scope horizontal at this point. I mount the pie tin on a camera tripod with tilt swivel. adjust the spacing and position so the image of the hole light is focused and covers the hole in the pie tin. you now have the optical axis of the primary identified. Turn on the gladder. the laser spot should hit the center of the pie tin hole. adjust the primary tilt (MARK ONE PRIMARY TILT SCREWS AND NEVER TOUCH IT AGAIN)Go ahead and adjust the pimary tilt until the focust image of the hole and laser both hit the center of the hole in the pie tin. not done yet... repeat the focuser tilt and primary tilt as tilting the primary will affect the light path of the laser through the correction lenses in the primary baffle tube. usually only 2 or three passed are needed. should take all night. Install the corrector cell and snug not tight!! the tilt bolts until the corrector cell is seated against the tilt grub screws. do not over tighten as the cell will flex and produce aberrations. congrats!!! focuser tilt primary tilt. the gladder return may not return to the gladder. make a not of where the return spot is just in case. if it does not return to center there may be non centered optics. since optics are all pretty much spherical small offset are tolerated. adjusting the centering of optics is not within the scope of this process. there is quite a bit if play in the side to side position of the corrector cell. you can make some adjustment of the gladder laser return by shimming the corrector cell. fine collimation will follow in the next post. Jim |
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No way I am up to doing this but thanks for posting. Shots without looking at magnified stars are acceptable. Peter |
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FINE COLLIMATION OG THE RH200 USE AT YOUR OWN RISK WHAT WORKS FOR ME MAY NOT WORK FOR YOU. these are only guide lines that I use and work for me. each person will and produce equal or better results using their own guide lines. It is more about consistency and keeping track of each change so you can see trends and backtrack if needed. ASSUMPTIONS: focuser primary corrector optical aligned to the OTA optical center. Does not mean all is good. The RH200 is a very fast scope with a large image circle. Very small adjustments make large changes in the manifestations of aberrations. ever temperature changes will affect your results. Scope should be thermally stabilized and close to the temp you plan to use your scope. skies need to be stable and the mount needs to be properly polar aligned and guiding must be an arc second or less. you will be looking at tiny stars images and ant tracking issues will be showing up and you could be adjusting collimation to compensate for tracking errors. imagine above 60 degrees if possible to allow fine focus repeatability. Choose a bright heavily populated star field (open clusters work well). try to use 5 second subs longer than that makes it more difficult due to atmospheric star distortion. lets begin: Setup and begin imaging using a IR cut filter. if seeing is not behaving try a red filter. use a imaging program like SKYX with a center and 4 corner display where you can change the amount of zoom. do not try to use CCD Inspector as it relies on FWHM calculations that mask aberrations and is affected by sky glow and star brightness being even across the field. You can use it t0 evaluate field illumination and focus. identify which tilt screws (there are 4 sets) correspond to each of the 4 corners. keep in mind that the RH200 uses a 4 point tilt not a 3 point. 3 point is easier as you can adjust any one of the 3 without having to compensate with the other 2. 4 point means you have to unlock all 4 locking grub screws and depend on the spring washers to keep it all tight. If you do not unlock the tilt grubs you will flex the tilt plate and the tilt will keep drifting around with temperature and time. Goal is to unlock the tilts and adjust the tilt individually one at a time until image corners are satisfactory (subjective). this may take multiple nights. Slowly begin locking the tilt adjustments in place. As you snug them up you will have to also tighten the tilt small amounts as lock does cause small amounts of flexure of the tilt plate. I things are good then you will be done. WHAT IF THE SCACING IS INCORRECT: Incorrect spacing will cause coma and other aberration to appear or get worse. \ NOTE NOT ALL rh200 are free of Trefoil (coma with wings or bulges in the extreem corners). Some are better than others and affected by spacing and tilt.If stars are radially from the center if the image field or circular the spacing should be adjusted. You have the option to either/or move the corrector and/or the primary position. you do this by the tilt adjustments all at the same time by equal amounts either in or out. you can put in the gladder and keeping the return spot in the same place. make an adjustment and check if the aberations improve. if not try the opposite directions. keep notes on you adjustments. note the RH200are not guaranteed to be aberration free but that the RMS star size meets the spec. (aberrations are typically small and process out easily. for APSC you should not see any aberrations. for 35mm you will notice some in the extreem corners. My scope has a very small amount of trefoil ( probably from stress in the optics mounting) that comes and goes with when temps get hot. If adjusting spacing gets messed up then you may need to start over from the beginning.I have had to do this multiple times when I get a scope has been recklessly adjusted. from the factory only SMALL ADJUSTMENTS ARE NEEDED THE CORRECTOR AND PRIMARY SHOULD NEVER BE TOUCHED OR TIGHTENED. CLEAR SKIES JIM |
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Peter It's kinda like learning brain surgery. a lot of learning. A Interferometer would make it all easier. I'm sure OS has special tools and optical benches to do this kind of work in maybe an hour or two. What you just read and the fine collimation is what I did with your scope. I took over a week to do. High end optical equipment is wonderful to use but fixing it is meticulous and time consuming. being high performance means we tend to notice the smallest things. Jim |
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I have a older non-carbon fiber RH200 version. Reading the above post, there seems to be confusion about the term Collimation. Some of the advice deals with tilt and some deals with optical collimation. Looking at your images, it appears the problem is camera chip tilt, not optical collimation. Two totally unrelated issues. To judge collimation I would need to see out of focus diffraction rings on a bright star. You can have excellent collimation and still have distorted corner stars. I have the Hotech CT laser collimator. I found it difficult to get squared on the scope optics. AND, unless it is, it will not work. Personally, I would not attempt to collimate the RH200. I bought mine used and the secondary baffle fell off. The Optical coatings also went chalky. I live in Pennsylvnia, US. It cost $2500 including shipping/customs. Do you live in Europe? I have not attempted to adjust the back plate on the scope. I first want to be sure the tilt is square in the camera first. Which I suggest anyone does first. I have been using a Gerd Naumann tilt adjuster for that on a Tak FSQ106ED. I also have the Baader tilt adjuster. There are homemade laser jigs that can aid in eliminating chip tilt. Using Gerd Naumann or Baader tilt adjuster is a great aid, because they adjust from the side. BUT, take up considerable back focus. Since the QHY camera do not have a built in tilt plate, I will have to transfer the adjustments from the Gerd Naumann to the camera, by putting shims in between the front plate and camera body. I am also using the Optec Leo focuser. I had panned to use the Pegasus Falcon rotator, but the bottom motor flange hit the focuser draw tube and would not set flat. Another post mentioned that star shape could be altered buy the camera chip being too close OR too far from the rear of the scope. This only applies when using a focal reducer and does not apply to the RH200. You just need to 105mm from back plate for focus. I have used the free ASTAP software to help adjust tilt, and it is a great aid. I found it easier to work with than CCDInspector. There is a great post on Astrobin concerning tilt and using ASTAP. I believe it is by Chris White. Another issue is, you seem to be using a full frame camera with 3.76nm pixels. Looking for answers to how large the imaging circle is for a RH200 I came up with one post saying 42mm and another 60mm. However the 60mm was for the newer AT version. Lynn K. |
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Recently taken with my scope at current settings. What do you think? The Foculynx controller for Optec Leo just went out, so I am out of business with it for a couple of weeks. https://www.astrobin.com/jfxdcw/B/ Peter |
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Hi Peter. Zooming in at full resolution, it appears your image is suffering from the same tilt issues as the poster. There are other star issues that be more software stacting problems, but not sure. Are your Chroma filters adjusted to F3? Looking at these images, makes me realize why I have procrastinated in tackling my RH200 tilt. And I'm only using a APS-C size chip. Also explains why there is such criticism of this scope and low resale of this highly complex sensitive scope. For me at present, It's much easier just to use the F3.6 FSQ. But, I too will be taking this on soon. I will be comparing it's prefromance to my Tak FSQ106ED at F3.6 and AP130GTX at f4.5. Which, Officina Stellare claims the RH200 will out perform. I am skeptical. I picked the RH200 up used for $2600. I thought I would give it a try, and could easily resale. That was untill the secondary baffle fell off and noticed the coating had turned to powder. 6 months and $2500+ later that changes any resale. The scope is now ungrungraded new primary and secondary baffels, better new Coatings, and perfectly collcollimat. After resolving tilt of a APC-C chip it should perform well. A note. Most early images I saw with the RH200 were done with the Sony ICX694 chip. Much smaller than even the APS-C, let alone full frame. Also larger more forgiving 4.5 pixels. The 3.76 pixel full frame will be a lot more challenging and demanding to resolve. That is true of any scope, not just the RH200. But F3 created other demands. Lynn K. |
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I was trying to use Nina Hocus Focus to get tilt measurements, but am running into problems with auto focus in Nina timing out. I had used it previously. Peter |
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Peter, have you tried ASTAP? it's a free download. It will either give you three point triangular format or an 8 point rectangular format. It gives you a FWHM reading for each of those points plus the center. When the FWHM reading vary by considerable amount, the rectangle will be distorted. After adjusting the 4 back plate screws, The goal is to get all FWHM readings fairly close. The rectangle them will appear fairly square. It also gives tilt and collimation percentages. You can use any acqusition software to take the images. I was using 10 sec. Subs with MaximDL. You just have to tell ASTAP which folder the images are being downloaded to. Lynn K. |
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I would trust what Jim says, he collimated 3 RH200 and rebuilt my CRC 312 so well that Officina Stellare was impressed. To collimate an astrograph of this caliber and speed you can't eyeball it, you need a process and it must be done from scratch (remove the corrector) unless you want OS to do it, that will cost $1200 + shipping. If you don't do it right it will be bad and inconistent, I use CCD Inspector and star field to correct for small errors but that's when the scope is almost perfect. I tried the same method you described Lynn and it didn't work..it was to far off. Peter you need share unprocessed images, the oversaturated stars cover any semblance of detail. Again, I have had Jim fix a few of my scopes, one came with the secondary fallen off it. He is very good because of this process and background, you can eyeball a tilt on a slow scope, also if a $11000 has a tilt plate...use that not some cheapo $100 tilt adjuster..it's a house of cards and it's pretty crazy to even consider it, titl is very easy to fix on the RH200 but you have to do 2 parts at a time (this is what Jim told me as well), check my images here, my RH200 MK1 (like Peters) is looking pretty damn impressive  Don't waste time and effort on a ferarri scopes with a 2 cent tool you will waste your time, if the scope has different star deformations across the fields it's clear sign it needs help, all the monkey tweaking in the world will not get it right! I tried for weeks. If you do get your scope collimated it will last for years, mine has 2 years since it was collimated with no issues what so ever. That's my 2cents ioan |
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Here is a link for an unprocessed image: https://www.dropbox.com/scl/fi/xxw2vh508xakgig72rj9e/IC-1318B_300sec_2x2_Ha_0001.fit?rlkey=fs1llobihjziietyv194zge44&dl=0 As I said, the Foculynx controller is at Optec for repair. Peter |
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Hi Ioan. You completely misunderstood my suggestions. I am talking about Camera chip tilt, NOT scope collimation. These are two totally separate issues. My suggestions have nothing to do with the scope optics or adjusting them. Yes a tilt adjuster would never resolve RH200 collimation issue My point is: if you have tilt in your camera chip, and I have never owned a camera that didn't, there will be distorted stars in the corners. I have a Astro Physics AP130GTX. I can guarantee that scope does not suffer from any mis-collimation OR any other optical issues. BUT, with a full frame, and even a APS-C, there will be distorted stars, until the camera chip is squared with the front of the camera. If you think these Chinese cameras have perfectly squared chip to camera front, despite there claims, you are mistaken. The reason I brought up the tilt and tilt adjusters, is that the posters images looked more like camera tilt problems to me, than collimation problems. I was suggesting he needs to address camera tilt first. In my opinion, that is what the RH200 back plate can be used for. I think it is a poor design to adjust collimation. I think that was your point also, and collimation is a more complex procedure. The $300+ tilt adjusters I recommended is for the sole purpose of adjusting the Camera tilt, NOT adjusting optics. I would never suggest using ASTAP to adjust optics. Certainly not the complex optics of the RH200. ASTAP is not designed to adjust optical collimation issues. It is designed to adjust camera tilt using a camera tilt adjuster. I hope this explains my comments. Lynn K. |
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Hi Ioan, I looked at some of your RH200 images, and they are excellent. No doubt your RH200 is very well adjusted. I only hope that Officina Stellare adjusted mine well enough and the trip back to the US didn't through it out. I am hoping I will only have to deal with my APS-c camera tilt. I also plane to use a Kodak KAF-16200 chip camera. At present, it has terrible tilt issues. Lynn K. |
