OK I have officially had it with this piece of crap.
I cannot for the life of me get the secondary mirror lined up under the focuser properly.
I adjust its position in the tube so that I can see a ROUND circle in the image, then tilt the secondary to get all three clips of the primary visible in the secondary mirror and the image then becomes OVAL shaped.
I back off the secondary allen key screws, adjust the position of the mirror to make it close to centre of the focuser and then when I try to tilt it again, it goes OVAL again.
I have tried Darryl's suggestion of snagging the secondary mirror and holding it in place while I adjust it up, but this doesnt work either.
For the life of me I cannot resolve it and am becoming extremely p'd off with this. Is anyone close to me available for me to bring it over and see if they can kick the tires and cast a more experienced eye over it?
Please?
Anyone?
Chris
Screwie - I hope what I'm thinking here is correct and that your ***** scope is redeemable!?! I have placed in bold, part of your quote (above) and need to ask you what you mean by this?
What do you mean by "I can see a round circle in the image" ? - you are not meant to be concerning yourself with any "images" (and by that I'm presuming you mean reflections) at this stage!
Rotating the secondary (mirror and holder) thus is to make the actual appearance of the actual mirror seem circular as you peer down the chesire/sight tube or film canister or with the naked eye etc! You are not meant to be looking at any reflected imagery, but at the real, actual edges of the sec mirror and how it is aligned within/inside the real bottom edges of the focusser tube. Do not get distracted or mesmerized into looking into, or at, any reflections for this procedure! The piece of white paper fixed inside the scope tube opposite and behind the sec mirror and holder helps some people here.
When this is achieved, the sec mirror will not only appear circular, it will also appear concentric within the actual bottom edge of the focusser tube (which is of course circular.)
A number of instructions also include a bit about trying to get some of the primary mirror visible in the secondary mirror's surface when doing the above: but as this complicates the procedure by having to worry about this when in fact it occurs automatically I do not suggest you concern yourself with it! (I'll make a comment about it further down in my post)
Suffice to say that when you achieve the above (and keep remembering as you do the above Screwie, do not look at the shiny surface of that sec, just the very real, touchable edges......do not look into any mirrors or reflections..... do not look into....!) you pinch up those 3 outer sec mirror screws to hold it in this position.
Then you adjust these 3 screws, going from to another until slowly and carefully you bring the circular image of the primary (and its three clips) into concenticity with the sec's surface. (for this part you are now looking into/onto that sec mirror surface!)
At this point the spider and sec (which is an actual reflection of this unit in the primary, reflected back off the secondary into your eye) will hopefully be somewhere on the circular image of the primary with clips mentioned in the preceding paragraph!
This is when you now turn to your primary and using its' adjustment screws centre that spider (mentioned in the paragraph above) within the whole darn lot! You will more than likely find that you'll have to go back to the sec mirror's 3 screws and fiddle with them again and then back to the primary's screws, a couple of iterations brings it all together: BUT MAKE SURE YOU FOLLOW THE ABOVE PROCESS AND DON'T TRY AND SHORT-CIRCUIT ANYTHING IN THE SEQUENCES DESCRIBED!
In my 5th paragraph I mentioned about not worrying too much about getting the primary mirror reflection on the sec mirror surface when rotating the sec and holder to get the sec concentric within the bottom of the focusser tube. If none of the primary is visible on the sec mirror surface after you've rotated the sec, and adjusting the sec's 3 screws doesn't bring the primary into view, then you've most probably thrown everything right out of whack Screwie: possibly when (as I think you said) you removed the spider and sec mirror assembly.
This will call for using a rule to adjust the nuts on the spider arms to get the centre point of the spider (and sec mirror) smack dab in the centre of the scope tube. Then, of course, winding the sec's central bolt/screw to get it centralized under the focusser and thence into the above procedures.....Lastly I presume that the primary mirror's adjusting screws are in an "equilibrium" mode and that one or two of them have not been jacked up and the other one slackened right off during your desperado attempts....!
Hope this helps, I've just about got keyboard RSI now Chris - but if none of what I've said makes sense or doesn't apply then hopefully you'll find someone: there must be an AA mob around your area!
If I wasn't struggling with welding up my pier Daniel, I really could justify that !!! When I got the material from the salvage yard I thought "***** of a stuff to weld, but at least this massive coating of zinc'll make it really corrosion-resistant."
I pride myself on decent (and decent looking) welds - but this'll be the ugliest (meaning, get out the bog-up) I've ever seen! I do hope poor old Screwie's making some progress though!
I will print that out and sit down and read it thoroughly to try and shake the cobwebs out of my head and hopefully, start all over again with your instructions.
I think you are right, I am confusing myself by looking at the wrong thing at the wrong time by reading too many guides and merging them into the quagmire that is my memory and coming unstuck in the process.
I appreciate the effort and the time you took to put that all in writing for me. It may just save the day. Kokatha man TO THE RESCUE!
I will let you know the outcome when I can clear the house of people, put on my thinking cap and salvage some pride.
Another way of saying that first bit Chris is to imagine you've taken the sec mirror and holder out of the scope and it's in one hand. In your other hand you've got a short length of 1&1/4 inch poly pipe which you hold up to your eye and look down at an angle of 90 degrees at the sec.
You twist/rotate the sec and holder in one hand whilst peering at it through the pipe (with the pipe a couple of inches off the sec mirror surface to avoid poking it and to simulate the "in situ" mode: by twisting/rotating the sec and holder it will arrive at a position of appearing circular as you peer at it through that bit of pipe - this is what you are aiming at as the first step in the collimation of the scope (after, of course, screwing its' central bolt/screw either way to make the sec and holder move up or down the scope tube and thus be centralized physically under the focusser tube if initially required!)
I could just as easily have said "imagine you are peering through that piece of polypipe perpendicularly down at an oval cardboard cut out that is fixed at 90 degrees (with regard to its' radial axis.) As I'm sure you realize, the sec holder has the sec mirror fixed to it at an angle of 45 degrees.
Don't think of it as a mirror, forget about any reflections etc, it's just an oval object that you want to make appear circular at the bottom of the focusser tube: and you achieve this by rotating it and its' holder whilst peering down the focusser tube with whatever - remembering that to rotate this shebang you need to have those 3 screws loosened: when it looks circular, pinch up those 3 screws and the sec mirror will stay in that position!
Post or pm if you can get to that stage, or if something is stalling you before you can achieve this! I had to go through this head-banging myself to arrive at my present understanding Screwie; and even though I've got a simple newtonian I'm a ***** perfectionist pain-in-the butt type that had to intimately understand what I was doing and really get on top of it - my star tests turn out spot on re diffraction rings now as a benefit.
I could just as easily have said "imagine you are peering through that piece of polypipe perpendicularly down at an oval cardboard cut out that is fixed at 90 degrees(with regard to its' radial axis.) As I'm sure you realize, the sec holder has the sec mirror fixed to it at an angle of 45 degrees.
This emboldened bit above should have read "45 degrees ( with regard to its' radial axis and the palm of your hand)"
I thought I would give google another shot at my problem and it turned up this from Andy's Shot Glass.
This guy had EXACTLY the same problem as me and a fellow poster told him this:
"Hate to tell you, but you got a problem there and no easy way around it. From what I found that is a Jones-Bird optical system. Spherical primary with a corrector lens in the focuser to correct the aberations of the mirror and increase the focal length of the optical system.
To collimate one of those can be a nightmare. I've heard of guys taking the corrector out and then getting a fairly decent collimation, then putting the lens unit back in. I dunno, tough call. I think your best option is to use it as is and try and do some collimating with a star test."
Now with the purchase of a new scope (even though I have looked and found a 10" Dob with 10:1 for only $599) pretty much out of the question for now, (why oh why didnt I buy this in the first place), I found out that our fella took out the "2x Barlow" thingy and had some success.
"This morning I popped the Jones-bird out of it. Turns out that the secondary isnt to close, the J-B has a collar or ring that narrows the view of the secondary thus not being able to see the outer edges of the primary. As the lasers beam returned to the focuser, that J-B was disbursing the beam so the best I could get it was red over the entire reticle. Not kiddin, once the J-B was out , had it collumated in 3 minutes. Put the J-B back in and we'll see how it does. "
Now my mirror is a paraboloid one, so it may not be exactly the same issue, but I am willing to give it a shot as I am armed with Darryl's excellent info and everyone else's ideas. I have checked out this lens previously and its just held in by a holding ring screwed in.
Unfortunately, some more digging turned up this, http://www.cloudynights.com/item.php?item_id=1105
which looks remarkably similar in design shape and size to mine, but mine has a 5 year warranty and a Skywatcher name on it so I am not throwing in the towel as yet.
Phew, this is turning out to be a project in its own right. Sounds like you've now got a good understanding of how the scope hangs together ... and some momentum up for adjusting/validating the collimation.
Taking out the secondary corrector lens didnt help. It is critical to make the 500mm tube focus the primary mirror's 1000mm FL towards the secondary mirror placement. Without it, its USELESS. Oh well.
So, I took the scope back to the place of purchase after calling them and asking if I could bring it in (after explaining all of the problems I have been having).
After trying and trying with a laser collimator (yes it WAS collimated) it seems that even once it was lined up with respect to the laser rebounding in the right place, a quick visual look through the focuser revealed optics WAY out of whack. If they cant fix it, there is something definitely wrong here.
The good news is: the scope is now back at the distributor for inspection of the lens / secondary mirror as there has always been some issues with the chromatic abberation and the focus as well as this doosy of an issue with trying to collimate it, so they are looking into where the problem may be and if luck is on my side, perhaps replaced under warranty.
Fingers crossed that they identify a fault somewhere in the optics that I cannot detect and it turns out that I am not going nuts after all.......here's hoping
Taking out the secondary corrector lens didnt help. It is critical to make the 500mm tube focus the primary mirror's 1000mm FL towards the secondary mirror placement. Without it, its USELESS. Oh well.
So, I took the scope back to the place of purchase after calling them and asking if I could bring it in (after explaining all of the problems I have been having).
After trying and trying with a laser collimator (yes it WAS collimated) it seems that even once it was lined up with respect to the laser rebounding in the right place, a quick visual look through the focuser revealed optics WAY out of whack. If they cant fix it, there is something definitely wrong here.
The good news is: the scope is now back at the distributor for inspection of the lens / secondary mirror as there has always been some issues with the chromatic abberation and the focus as well as this doosy of an issue with trying to collimate it, so they are looking into where the problem may be and if luck is on my side, perhaps replaced under warranty.
Fingers crossed that they identify a fault somewhere in the optics that I cannot detect and it turns out that I am not going nuts after all.......here's hoping
I will let you know the outcome.
Chris
If, even after laser collimation the view through the eyepiece was still out of whack, I'd say you have a badly ground primary mirror. It's not the right shape for the focal length of the scope.
I thought I might post a followup on the status of the scope.
I spoke with the shop today and it turns out the secondary mirror and the focuser needed to be replaced!
Essentially these two items were stopping it from being collimated properly.
I am hoping to pick it up tomorrow morning and with luck get it ready for a clear night of collimated observing. Here's hoping!
Hope you've finally got that sorted Chris. I've been keeping tabs on the thread with much sympathy. Still, if worst comes to worst, there's still those cheap 10" dobs.
Best of luck Chris. My first reflector was one of those Jones-Bird beasties and it gave me a few headaches too with colimation. Got it sorted out in the end, but bought a 150 Skywatcher and EQ5, then sold it on. (I did tell the new owner about the problems, but he was happy to deal with it)
My problem is this: I cannot seem to get the secondary mirror to line up with the focuser AND be round in shape AT THE SAME TIME.
This confusing situation usually indicates that either the focuser isn't mounted square, or the secondary spider is off centre with respect to the ota tube.
I notice the spider is a cast non adjustable unit. Perhaps its sledgehammer time.
Update - on my growing migraine. Get comfortable, its a long one...
Hi Again,
Yes its time to contemplate the line to the shop /distributor : "If you cant collimate this scope after replacing the secondary mirror and fixing the focuser tube (and charging me for it), then perhaps you should replace it with one that works or refund my money"......
I picked up the scope from the repair centre at the distributor and spoke at length to the guy who "collimated" it and he assured me after I looked into the focuser and saw mirrors half obscured, that all was in perfect collimation.........
He showed me a red LED mounted on a piece of board that he placed in the warehouse about 50-100m away that was used to collimate the scope and said this is the best way to do it. I was skeptical and it appears now with good reason.
The focuser tube was repaired as the excessive slop was caused by incorrect packing around it and this seems to be OK now. I brought the scope home after paying for the replacement of the secondary chipped mirror and the collimation and thought I would grab a look at the stars on Friday night.
Well.... Can anyone guess what happened?
Yes, as expected the star test showed up SERIOUS miscollimation to the point of not being able to get a pinpoint star at any point of focus and flaring of the star either side of what should have been focus which looked like a soap bubble enlongated on the right side. After resisting the urge to head to the shed and pick up the sledgehammer (seriously, I had to stop myself), I took it back inside with much cursing, and put my cheshire in again and shook my head again and cursed some more.
At least this time, I knew what I had to do and how to do it and tried to get some collimation happening.
I managed to take out the primary mirror cell from the end of the scope and correctly and accurately put a centre spot on it (using a foolscap hole reinforcement sticker) and then assembled everything back together. After a test on Saturday night on the moon and a few stars at dusk I was a little closer to correct, but found my star tests still showed up some issues, namely non concentric flaring off focus. Certainly a quick squizz at Saturn had me cursing some more as I could not achieve a focus at 200x at all and at 80x I had some ghosting.
Well today (Sunday) I pointed the scope out the window to the bright daylight sky and tweaked and tweaked and now think I have achieved as close a collimation that I possibly can.
I have ALL three primary mirror clips within view, a ROUND image of the primary, a concentric circle around the outside of the view of the primary (from the reflected 45 deg silvered bit of the cheshire) and concentric secondary reflection AS WELL as FINALLY getting the centre spot on the primary concentric to the whole thing. (something I havent been able to achieve before as it had no spot on the mirror and I can see why this could have been a missing jigsaw piece before) The crosshairs of the bottom of the cheshire line up EXACTLY with the secondary vanes and everything is as centred as can be expected. NOTHING looks out of whack, even the secondary's holder is not skewed or off to one side but is now centred within the view.
All that is left now is to hope these clouds disappear tonight and I can test the view AGAIN
I cannotpossibly conceive anything wrong in ANY respect with the mechanical alignment of the equipment. Every aspect of the optics are aligned along the centre of the view through the cheshire and all "looks" perfect. Certainly it all looks better than I have EVER seen even before I started this nightmare a month and a half ago.
I have reviewed every collimation document on the planet it seems and the instructions of the cheshire and the Skywatcher manual itself and have followed them all to the letter. I have done this so many times now I am thinking of starting a TAFE course and charging others for the priviledge.
I would have definitely expected that the scope was to come back from the distributor repaired to factory precision and it certainly wasnt, so I am going to be getting a refund for the collimation charge ($40) tomorrow. I will live with the secondary mirror charge ($20) as my tinkering caused the damage there.
If the star tests tonight (weather permitting) are unsuccessful, then I am going to be lobbying to the shop and the distributor to return the scope and the tripod and get a full refund because this is getting BEYOND ridiculous.
If ANYONE can find any flaws in my methods, please post a reply to this post urgently as I am of the belief that I have done everything exactly as it should be and if the collimation is still not working then I think I have a lemon. Plain and simple.
Wish me luck....if there is any left.
PS. I have plagiarised two of Don Pensack's collimation images from his guide to show you what I had before I had the primary mirror spot was put on (image 1) and what view I now have (ignore the laser triangle as I dont have one of those)
Hey Chris, I can knock you up a batch of 'angel paper" if you like. Just place said paper in the back of your primary's mirror cell and carefully replace the back of the scope. Then apply a sharp, hard blow to the back of the scope to launch the primary out of your newly made cannon!!!
I just had a quick star test and found my same "blue bottle" effect on the star out of focus - GRRRRRRRRR! Also, think of a bubble gum bubble with the whole thing taken out of your mouth - thats what it looks like....http://www.oarval.org/coma.gif without the rings of course (it just has one ring). Edit: It seems (after again researching what phenomena I am seeing) that I am suffering from coma and astigmatism, as the image is "flipping" 90 degrees from out of focus, to further in focus. It is yet to be seen if this can be corrected by minor tweaking of collimation as the clouds seem to have settled in for now.
If the clouds bugger off I am going to try and tweak the collimation on a tracked star using the motor drive and spend some time trying to perfect it. If it doesnt get any better, its going back.
Far out, surely it shouldnt be this friggin hard should it? By the way, I do know what a collimated image looks like, because my binoculars are spot on, and the scope originally was pretty close, except now, it seems it cant get back there, even with visually perfectly aligned optics???
Chris
Last edited by Screwdriverone; 12-05-2008 at 04:20 PM.
Reason: coma and astigmatism edit
OK I checked it again last night at 2am when the clouds buggered off and found the coma was so bad I couldnt even focus on Jupiter at zenith!. I could see the cloud bands just off focus but the double image ghosting was rendering the view unusable. Single star test? forget it! I even spent an hour outside at 2am collimating in the field and got no discernible improvement.
I have Quadruple checked the collimation and everything is concentric including the centre spot on the primary and the secondary reflection as well as the secondary vanes and the cheshire reflection in the focuser tube.
I spoke with the shop and the distributor and they have agreed to replace the entire OTA with a brand new one as they and I suspect that there is an issue with the Secondary corrector lens and /or the primary mirror.
After all the pain I have gone through with this, I am glad that the issue is not with my methods, but it still hasnt put me off what is essentially a good scope (minus the mount problem, the altitude setting problem and the collimation problem). I am therefore quite happy with this result.
I will be hopefully even more happy when I get my new beastie home, set it up and get some serious clear, in focus and coma free images of the good stuff I have been seeing through my binoculars for the last two months.
I will post a followup to this once I have the replacement, with some pictures of an in focus Jupiter, if the weather lets me.
Like I said some posts ago, I'll bet that your problem is a faulty primary mirror. It's not figured right for the scope and you have a case of "Hubble-itis". That would explain the astigmatism. You probably also have secondary problems too, and that made it even harder to try and collimate.
Hoooooray! A fixed scope thats ALSO now collimated!
Hi All,
Well, can anyone guess who is a happy chappy today?
Picked up my replacement OTA and while there I got them to fix the faulty Altitude scale on the EQ2 which was 5 degrees out of whack.
I checked the scope before I left the warehouse with my cheshire and it was pretty close. I also got my collimation charge refunded as discussed before.
I came home, put it all together and waited for the clouds to disappear and then took it out the back and had a play.
The collimation was still a bit crook and I thought I was done for, but then I focused on a bright star, tracked the EQ2 and wound the focuser right out as far as it could go and did some TINY adjustments to the alignment of the primary on the spider image in the EP.
This allowed me to see a similar image to the Cheshire image and was quite easy to see which way the primary needed to go.
After a few tries and some fine tuning, I wound it back to focus and found I had NO coma, NO chromatic abberations and almost "perfect" focus with fine point stars and details on Jupiter!
The old scope must have had some additional problems with the corrector lens as I everything the same with it and never got it this good!
So, with some actual focus ability I tracked Jupiter at 200x and tried a few AVI's with the Afocal adapter.
Visually the view has improved 100% and I am rapt with it now. The quality and ease of photos using the point and shoot digital camera is a bit of a pain though so I dont know how long I will stick with this method. After a bit the fog and dew closed in anyway so I packed it all up and headed in to watch some 20/20 cricket and process my avi files.
Here is a shot from one of the captures. Its not too bad compared to some of my other ones. Taken at 14:21 UT at 200x using Pentax Optio S7 at VGA mode stacked 555 frames in registax and sharpened in Gimp. Seeing 8/10 and transparency of about 4.5/5.
All in all, it has been a real pain, but at least now I am pretty much an expert at how to collimate and have learnt heaps about how everything fits together. I am just glad the dramas are over for now......
Thanks again for all the comments and support from those who read this thread, I appreciate it.
Cheers
Chris
Last edited by Screwdriverone; 14-05-2008 at 09:17 AM.
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