Can you collimate with a SLEDGEHAMMER?

[Screwdriverone]

Hi All,

I collimated my scope recently after purchasing a cheshire eyepiece and after the initial issues and learning, thought I had it pretty good after a quick view at some familiar subjects.

Seems I have jumped the gun. The other night I was looking at Saturn and Regulus and couldnt understand why everything looked like I was drunk (I wasnt) , even to the points right up to focus. I realised that my collimation had some issues and decided to fix it.

Well, that was 3 days ago and I have just about decided to get some fuel, some kindling and a few firestarters to make a nice, warm Newtonian Bonfire out the backyard to keep me warm while I use my binoculars instead. :mad2:

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.

I can adjust the secondary to look like it is lined up and circular, but then I put the Cheshire back in and adjust the tilt and it goes oval and I cant seem to fix it.

I have read everyone's and I mean everyone's instructions on collimation and have absorbed all I can on the subject. However, this doesnt help when you get an instruction that says: " Line up the secondary mirror so that it is in line with the focuser and then adjust the mirror's tilt so that you can see all three clips" and then goes to show you a pretty picture of what its supposed to look like! What happens if you CANT get it to look like that?

I have almost stripped the central phillips head metal off the screw head, I have turned it in and out so many times and have just about had enough of adjusting it this way and that, trying to get it closer to centre and then tilt and I have officially now lost the plot.

Can anyone please help me? I need a tip or some inside knowledge of how to do this easily. As I said, I thought I got it right the first time, I dont think I have busted anything, but now, I am ready to take a sledgehammer to it if I struggle over it any longer. Add to this the last two nights have been clear all night and well, you get my drift.

I would even be prepared to jump in my car with the POS (piece of s#$%) and take it to someone who obviously knows more about this than me if only I could get it back to some semblance of working order again. I live in Kellyville NSW so if anyone nearby can whack me upside the head with a piece of 4x2 and help me sort this out, then I would be forever in their debt.

Sorry for the rant. :sadeyes:

Chris

[erick]

I suspect they don't burn very well, so better give that thought a miss.

Last approach seems most productive. Get yourself and it to someone with a bit more experience and see what they discover. Try and do it on a clear evening so it can be tested immediately in the field.

[programmer]

Hi Chris

Do you have the cheshire in the focuser 'just enough' so that the secondary is just smaller than the entire field of view of the cheshire? Did you also have some white paper between the secondary and the primary to reduce reflections? Moving the mirror up and down the tube shouldn't affect the circular appearance, AFAIK. Also adjusting the tilt shouldn't affect it that much?

When you decided that the collimation was out, when viewing Saturn, did you do a star collimation test?

[Screwdriverone]

Hi Eric,

Thanks, i think this could be the best (and safest for my scope) option.

Hi Programmer,

Yeah, I have tried all that, the cheshire is pretty much OK anywhere in the tube, I dont have any problems seeing the difference between the reflections of the primary and the secondary / outside of the cheshire reflection.

The focuser has a bit of slop in it as it is R&P but I did test the collimation on Regulus, Betelgeuse, Sirius and a few others and found that I didnt have concentric round circles either side of focus but a squashed looking halo of the star that reminded me of a smoke ring in a very slight breeze. It was crooked and bent like a froot loop that has gone soggy on one side. (sorry, all I could think of)

I certainly didnt get a nice round image off focus like all the guides show you.

Chris

[programmer]

Erick's is sound advice. I guess I'm just asking to help with my own feeble collimation attempts (which I *think* I have got down pat).

Just to clarify.. the star collimation test you did is the one to check collimation, not the optics (i.e. the 'airy disc') test?

But, I guess you'd know if your collimation was out or not. As I said, I'm just curious.

[Kokatha man]

Hi Chris - that central bolt/screw moves the secondary up and down the tube: to get that (the sec) in the right position re the focusser tube is the first thing.

(1) slacken right off the 3 screws around that central one on the sec.

(2) look down the focusser tube with either "nothing*" - "the chesire sight tube" or "the ol' film canister with pin hole."

*using "nothing" but your eye requires getting your eyeball really centralized over the focusser tube!

(3) by turning the central sec mirror screw clockwise or anti, the sec mirror should be able to be centalized when you look down the focusser, thru whatever above method you've chosen. This means that when you then carefully grab the body of the sec with one hand and rotate it till it appears as if it's circular, it will appear concentric within the bottom of the focusser tube (or actually the sight tube/chesire, if you use one of these) - ie it will have an even gap all around its' perimeter in relation to the bottom walls/edge of the focusser tube (or sight/chesire tube.)

(4) holding it as steadily as you can in this position, twitch up the 3 surrounding screws of the sec till they all impinge slightly onto the back of the sec holder ,and this will hold the sec in aforesaid position: having someone to help, and/or "bob's knobs" helps immensely here.

(5) the above should have the sec centred and looking circular in the focusser tube (or chesire/sight tube) - the piece of white paper (A4) lightly taped onto the scope tube directly opposite the focusser tube (and thus behind the sec mirror, will assist the above process.)

(6) it's now time to start fiddling with the primary's screws to get everything aligned within each other!

Note: you do not touch/alter the central sec screw again after (3)

Cheers, Darryl.

[Screwdriverone]

Hi Darryl,

Thanks for the instructions, I have tried all this, but I have a slight discrepancy with what you have suggested as I have a secondary 2x barlow built in between the Secondary mirror and the primary mirror and this is held in by a sheath that shrouds the secondary mirror and basically passes behind the secondary and stops me from putting my hand in and holding the secondary while I tighten it all up.

The reason its there is because its a catadioptric short tube newt (500mm tube with 1000mm FL) so this is probably another reason for me to take to it with a baseball bat?

I have managed to get the secondary centred and round once when I first did the collimation but now try to line it up just back of centre so that when I turn the allen key screws the mirror tilts up towards the focuser tube and lines up nice and central. Unfortunately this is a hit and miss affair - hence the burred screw head as I have done it over and over and over and over.

I have even taken the secondary vane housing off from the end of the tube and adjusted it in my lap so that I can line up the secondary as close as I "think" is central to to opening of the shroud where the focuser should be once reassembled. After this, I put the secondary vane housing back on and what do you know, its NOWHERE near centred when looking down the cheshire.

I think I might take up tiddlywinks, its less stressful.

Chris

[Jeff]

Hi screwdriverone,

I did a quick google for "catadioptric short tube newt collimation" and got some interesting results ... its seems you're not alone. Looks like some potential "mounting/squareness" issues with the internal barlow mechanim according to the first 2 Google results.

http://en.allexperts.com/q/Astronomy-1360/schmidt-newtonian-telescope-1.htm

http://cs.astronomy.com/asycs/forums/p/19753/304750.aspx#304750

Hope this helps.

[Kokatha man]

Struth Screwie : I have never fiddled with one of those animals in my life!

So it it some sort of cowling/shroud - that is, a tube that the secondary is surrounded by, fixed on the vanes; with a cutaway/opening to allow the light to be reflected off the secondary and up into the focusser tube - with the part of this tube/cowling that extends towards the primary mirror holding the barlow?

And this cowling /cover/tube/shroud has an open end at the open end side of the scope tube to allow you to insert screwdrivers to adjust the central sec mirror screw and the 3 surrounding ones - but won't allow you to get your fingers/hand in to physically rotate the sec mirror?

Does this mean some sort of customized implement needs to be inserted from the open end of the scope down inside this shroud/cowling/sheath to grasp the sec mirror body so you can turn it as needed to get it circular looking? Could you make something up or use/modify some long tweezers or those kitchen tongs/snag holders etc?

Would like to see a piccy of the guts mate! Don't despair, where there's a will there's a way!!!

Regards, Darryl.

[Screwdriverone]

Hi Programmer,

Yes I focused in and out of focus on a bright star (or any star for that matter) and no, before you ask, it wasnt a binary or double star. Coming from far out of focus (focuser high in the tube) the image was a round donut with the four vanes visible which got smaller and smaller until I got closer to the focus point. At focus, or as close as I could see to it, the star appeared streaky or comet like with a "tail" off to the right and appeared like a piece of bird poo. Once I focused too far in, the star's image started to look like a thin smoke ring that kept getting bigger and bigger around the central part of where the star actually was. The problem is that smoke ring looks like it is dented on the right hand half as if it was being affected by a breeze and being pulled to the right as the focus goes further in the tube.

Additionally when focused, (only just remembered) the star or planet looks like the 3 colour pixels on an OLD colour TV where the red, blue and green images are slightly offset from each other, like when you move the individual colour channels around in Registax. It doesnt change with EP changes so I would assume this is a collimation issue with the streaky images and offset colours?

A final note, the scope was MUCH better than this before I collimated it. It may all come back to bite me on the ass.

Chris :doh:

[Screwdriverone]

Thanks Jeff,

reading up on this now. It seems from my reading that I have chromatic abberations which describe the shape and colour issues to a T. Check out this page to see what I mean about the shape and colour problems I am seeing. Maybe the adjustment of collimation has caused this. http://www.opticalres.com/gentsupp_f.html

Darryl,

Here are some pics down the focuser so you can see how bad things are at the moment, and in the front showing the secondary holder shroud and 2x barlow at the end towards the primary mirror.

Make sense now?

Chris

[Kokatha man]

Yes Chris - rather like I described, but such that you can't even use some sort of forceps directly to get hold of the sec mirror, cos of the vane assembly that the central screw and the 3 surrounding one are on - this blocks your access!

But necessity is the mother of invention: when I speak of forceps, in the jewellery trade (which I used to ply) we had long, bent spring loaded tweezers that I reckon you could insert from the open end of the scope tube and get around the obstacle to grasp whatever the sec mirror is mounted onto, hopefully to turn/rotate it.

This may sound silly and it may well be, just throwing ideas/possibilities for you to consider or work/bounce off!

Regards, Darryl.

[Screwdriverone]

Hi Darryl,

Yes, its EXACTLY as you described, now that i reread your post. I will give your idea a go, I think I have some long plastic (not as scratchy as metal ones) bent head tweezers my son had for a science kit on chemicals somewhere around here.

I have found the sledgehammer by the way. :P

Chris

[erick]

OK, with that information, I change my advice. Smash it up with the sledgehammer and throw it on the fire. When you feel better, go and buy a nice 6" GSO tube unit - full length without that embedded x2 barlow!

Edit: OK, better not smash it up, but while I haven't tried to collimate one myself, there have been a number of people in here saying it was difficult if not impossible to successfully collimate a reflector with that intermediate barlow. I think that a reasonable quality tube without this barlow is readily available, quite cheaply, and that problem would then be gone. Not sure how well your EQ2 would cope with the extra weight and length?

[Kokatha man]

Hoping you can get a purchase on that secondary mirror to rotate it Chris - if not, hoping you can get a purchase on another scope!!!!!

Just remember the old "where there's a will, there's a way" mantra as you struggle with it; we allways concede defeat too readily - which doesn't mean that there comes a time to do so sometimes!

And don't forget that if you can rectify it, it is a procedure that should not need to be done again. The other thought that comes to mind is with it being such a short tube, would removing the primary mirror and cell allow some manipulation from that end?

The primary is not necessary for the process in hand, and I know the shroud/cowling/tube/sheath has the barlow down the primary end, but....?
The other (quite possibly even more insane) suggestion is could you very accurately mark and cut small slits with a Dremel et al in the scope tube to allow radial adjustment/movement of the whole assembly (including the vanes) to achieve your objective?

This is most probably just before the sledgehammer process - but keep on "thinking outside the box" Screwie and something may evolve!

Best wishes, Darryl.

[renormalised]

Is the barlow removable??. If it is, try that. It may help.

Better than a sledgehammer, goto a hobbies store, buy a couple of H-500 model rocket engines, fit a nose cone and some fins to the scope, fit the engines to the inside of the scope and try to make it the first "orbital" amateur telescope. Park it up alongside the Hubble:D

[Screwdriverone]

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 :(

[GrahamL]

What happens when you line up the secondary best you can
and by eye tighten it all up ?.. while I don't know these scopes is it possible your trying to line up your secondary to a primary whos tilt is way off ?. ..primary to secondary .. not secondary to primary.

take care

[CoombellKid]

Yup I agree with Graham Primary to secondary in the final process. Using
your Cheshire tool (sloted all the way in your focuer) just consentrate on
making the secondary mirror fit nice and evenly in the FOV of the Cheshire.
Dont worry about the clips on the primary at this stage, because your
primary might not well aligned. Aligning the secondary with the Cheshire will
automatical setup your offset. Once you have that completed (could take a
lil fiddling) then move to your primary and adjust that.

regards,CS

[CoombellKid]

oooop's having now read most of this thread, I agree with Eric first suggestion in his last post.

regards,CS

[Kokatha man]

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!

Best of luck, Darryl.

[dannat]

After that Daryl, better give yourself a drink

[Kokatha man]

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!

Cheers, Darryl.

[Screwdriverone]

Thanks Darryl,

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.

Cheers

Chris

[Kokatha man]

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.

Cheers, Darryl.

[Kokatha man]

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)"

Cheers, Darryl.

[Screwdriverone]

Hmmmm, Look what I found!

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.

Wish me luck! I am GOING IN!

Chris

[Jeff]

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.

Good luck in the home stretch!

[Screwdriverone]

Ok, it doesnt seem to be me after all.

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

[renormalised]

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.

[Screwdriverone]

Hi All,

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!

(now just watch the clouds roll in :mad2: )

Cheers

Chris

[Dog Star]

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.;):thumbsup:

[Glenhuon]

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)

Cheers
Bill

[Starkler]

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.

[Screwdriverone]

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 :mad2:

I cannot possibly 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)

Cheers

Chris

[renormalised]

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!!!:P:D

[Screwdriverone]

Hmmm, Angel paper sounds good!

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

[Screwdriverone]

Hi Again,

Yes its me, the guy with the collimation problem.

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. :sad:

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.

Thanks for staying with my thread, phew....

Chris

[renormalised]

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.

[Screwdriverone]

Hi All,

Well, can anyone guess who is a happy chappy today? :D

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 :thumbsup:

Chris

[renormalised]

Glad everything's worked out and now you can actually use your scope. Plus, that's not too bad a piccie for a point and shoot setup!!!.

[Screwdriverone]

Thanks Renormalised,

I think this is about the limit of detail I can get with movie mode. I took some 7MP Jpegs which were overexposed but showed up some more details as well as 3 of the moons, so I think I will concentrate on trying to get as much out of this method as I can before sliding down the slippery prime focus slope with a webcam or DSLR.

Cheers

Chris

[programmer]

Well done, pity you had to get a lemon first up.. Nice pic.

[Screwdriverone]

Thanks Programmer,

Yes it was a pity, but everything is a learning curve!

The other good news is that all my eyepieces now give GREAT views, its surprising how much a little bit of focus and loss of abberations improves the view. I was impressed at the quality of even the standard plossl's that came with the scope and the 10mm 68 Deg wideview EP got me in nice and close for imaging, but I did use the ED 12.5mm to take this shot as its the duck's nuts of the family.

By the way, how is your Argo Navis going? Still have that new car feel to it?

Chris

[programmer]

Good to hear about your EP's.. I Must admit I'll never be able to go back after getting better EP's.. :eyepop:

Argo is going great, but being in Melbourne.... 'nuff said.

[Terry B]

Well done and good to see that you can now use the scope.
The sad thing is that someone else with a blossoming interest in astronomy will buy a similar scope. be very disappointed in the view, put it in a cupboard and never go back to astronomy.:shrug:

[Screwdriverone]

Hi Terry,

I was originally quite happy with the view through the scope, the problem started when I tried to collimate it.

The disadvantage of this scope is that it is very finicky when it comes to getting it spot on. The corrector lens is probably the issue as it magnifies everything by 2 to get the 1000mm FL out of a 500mm tube. I do still think that I definitely had something wrong with the original OTA though.

I now know that even when the cheshire is bang on for collimation and I also used a laser, looks can be deceiving and I am so glad that I learned (with lots of help from IISers) how to do a star test and tweak the final collimation from there. Even the new tube "looked" right and was really only about 1mm out in two directions from the TINY adjustments I made on the star test last night.

My advice from all this and from a beginner's perspective is to buy a 6-12" dob and enjoy the views. If there is an issue with collimation, it should be a doddle to fix on one of these scopes.

Chris

[Jeff]

Thank God!
:prey2:

[Screwdriverone]

HA HA HA HA HA HA HA! Jeff. :rofl::rofl::rofl::rofl:

Thanks for all your help too.

Made me laugh, you did!

Chris

[erick]

Good news Chris! Congrats!

Nice pic as well :)

[programmer]

I think we'll have to freeze this thread now that you're all happy! The title is a bit misleading now :lol:

[astro_nutt]

Hi Chris!
After following this thread, I can honestly say how great it is to have so many people offering to help out in one's crisis..
Enjoy the views!!