I've replaced my collimating screws on my 8" Meade LX200 and tried to do a collimation afterwards. Now when I go completely out of focus, I no longer get the traditional round circle with smaller black circle in it, I get the black circle and a sort of cut-off circle around it.
Looks like the image attached.
Now I can't get focus, everything's blurry! I can get close to a good focus, but not the same as before I 'bob knobbed' my Meade.
Does anyone know what I have done wrong? Do I need to send this somewhere to get serviced or is it completely stuffed? If it can be fixed with a service, does anyone know if there's someone in Canberra as shipping it somewhere is not appealing.
Not sure about rotating the secondary mirror, how would that happen? I'm guessing if you took all three screws out at the same time then there might be an issue, but I did it one at a time. Is there a way to tell if the secondary has moved from where it should be? The scope doesn't rattle when I shake it vigorously. Joking. JOKING!!!
On over-tightening, I tested it on a star earlier. I tightened the knobs until they were starting to feel hard to turn, then moved them in the opposite direction about three turns until they were in the middle of their travel (hopefully). Looked in the scope for my star again, found it and no difference to the shape, still looks like someone sliced off the side of my doughnut.
Should I try removing bob's knobs and putting the original screws back in? I'm guess that won't make much difference.
Well if you did them one at a time then it's fine. Nothing to worry about. Tightening them too hard can stress the glass which doesn't take much at all to deform star shapes. Cold also be a tube current at the time.
Woa! Surf's up Dude...but not in my tube. Actually, I understand what you mean by that. Could be right.
What happens though when I look at a nearby object is that it also doesn't focus. So, I used to be able to look at my neighbours barn about 1km away and use it to get the spotting scope lined up correctly.
Now I'm getting fuzzy things, not clear things. This is a tad worrying.
I doubt that you have ruined it but something has slipped while you were replacing the screws possibly.
It has a center pivot point ball under the secondary that may no longer be in the middle.
Loosening the screws could cause this to drop to one side if you did it with the scope on its side ( the safe way to do it just in case anything falls off inside ).
All three screws should be kept firm to stop this from happening.
It sound like you may have loosened thing too much.
Safest thing to do now is to remove the corrector plate and disassemble the adjuster and have a good look to make sure all is well and in position.
Don't be afraid to do this just take your time and as stated make sure you don't turn anything from its original location.
If you don't fancy doing it yourself by all means find someone you know has done this before to do it for you.
If you do it yourself just remember to make a small mark at the edge of the corrector plate and the tube ring so you know where to put it back, use a paint pen or similar and put a small dot on the glass edge and the ring.
With the corrector out support it with the secondary face down using soft cloth eg T shirt material and a couple of layers of tissues under the secondary mirror to protect it when the screws come out and then remove the three screws to check the position of the pivot ball and wave/cup washers. The wave washers are there to give some spring in the adjustment, they are cup shaped and should not all be facing the same way, the cups should face each other to give the flex needed.
You will see why the screws should never be loosened too much when doing this and when sure all is ok reassemble it all making sure there are no finger marks on the inside and the corrector goes back in the same place it came from and not turned at all.
Re-do the collimation check but do not loosen any of the screws more than a half turn at a time and tighten the opposite side screws by the same amount to keep all in place and prevent the parts from slipping out of place inside and then try your focus again.
Hope this helps.
PS if you want to try this yourself I do have some pictures somewhere of what it looks like inside, let me know and I'll post them for you.
Update: I removed the corrector plate but didn't go to the full extent of disassembly, just checked to see that everything was still present. Put it back in (after a 'blow' with my cleaner thingy) and it was a bit better. I'll go the whole way and make sure that the pivot ball and wave washers are ok.
However...then I did something really stupid and took the computer apart to replace the CR2032 because it wasn't holding time.
Now...circuit diagrams anyone? I think I've plugged something in the wrong place.
When handling optics and especially the mirrors it's a good idea to wear cotton or latex gloves - the slightest touch of your skin on an optical surface will leave an oily residue which has to be cleaned off.
Be careful with that corrector, they are matched to the mirror and if they break or crack it's pretty much curtains.
If your taking the corrector out mark its position as well, it will need to go back in the exact same way, otherwise you will have a lot of problems there as well.
1. Mark the position before taking it out
2. Wear cotton gloves as if handling photo's (I have a pair)
3. Ensure the surface and surround area is clean and well protected (I have a vacuum chamber and some new cotton wadding plus some soft-fall that I can use)
4. Don't break anything!
5. Take my time, not the positions of all components
6. Do this all at my own risk (insert limitations of liabilities for all participants, meade, the dog etc).
Provided you don't damage anything and there are rotational alignment marks between the components (they should already be there, but check) the worst case is that you'll have to take a bucket of parts to Bintel for reassembly. Assembly of schmidt cassegrains is quite simple once taken your first one apart though I haven't personally removed the secondary from it's holder.
However, it may just be that you've gotten lost with collimation and someone familiar with the process could fix it. Trying to collimate on a star can be confusing if the scope is a really long way out of collimation. One check you can perform is to look into the front of the ota in daylight from 6 or 8 feet away - you'll see a number of circles within circles - you can get the scope roughly collimated by adjusting the collimation screws until the pattern looks symetrical (ie. circles centred within each other). The screws only need to be firm; if a screw is too tight back off the other 2 rather than tightening that one.
Simon,
Be aware there are small cork like shims or spacers beween the edge of the corrector and and its cell. Do ensure you don't lose these and they go back in position.
Peter
1. Mark the position before taking it out
2. Wear cotton gloves as if handling photo's (I have a pair)
3. Ensure the surface and surround area is clean and well protected (I have a vacuum chamber and some new cotton wadding plus some soft-fall that I can use)
4. Don't break anything!
5. Take my time, not the positions of all components
6. Do this all at my own risk (insert limitations of liabilities for all participants, meade, the dog etc).
Here are the pictures keeping in mind that my scope is around 25 years old, newer units may well have changed.
One other thing I thought of, if you remove the secondary holder as shown here be careful not to turn the corrector over as it will come away from the center pieces and would be hard to tell which is the inside from the outside.
You can see how the cup washers fit on the center pivot this why you must never loosen the screws more than a turn before tightening the opposite side.
Fine adjustment is made with very small screw movements.
Simon,
Rule 1 Check with Don at Bintel.
Rule 2 Check with Don at Bintel.
Rule 3 Check with Don at Bintel.
You get the picture.
Mine is also an R model but I have never taken the corrector out, the Rs are about 5 years new so there is no chance any spacing shims would have rotted.
As I can see with a torch there is a dark grey looking foam along the edge but I can't see any spacing shims because of this. My previous Classic model definitely had them as I did take the corrector out several times. Doing a quick Google and looking up the R model shims on Cloudy Nights finds some references to them in this model. Some time ago Don explained the importance of putting these back in the same place.
And BEFORE you try to take apart the 2ndry I would also bring this up with Don, the R and ACF as I understand it have had major changes to what is in Kens images above. Just be very careful, talk to Don first as he does this almost every other week.
Infact going back over your initial post I have been exactly where you are after installing Bobs Knobs. Follow Tony's advice in post 13 above then you need a defocussed star that's not too bright. Start the collimation process with say a 20-25mm eyepiece and then make very very small adjustments to a knob then recentering the star using your hand control set to the very smallest movement. Then doing another very small adjustment and so on until you start to see an improvement. Once you get to this stage use a higher powered eyepiece and go over the whole process, again very very small turns and recenter using the Autostar. I would be doing this before attempting to pull things apart again.
Peter
Hmm, ok. Thanks for that. Stuck in the mire of assignment submission ATM for my masters, but will have time no doubt on the weekend.
I'll check with Don though, may just be easier to send the scope to them and ask for a complete service? I have the box etc so transport will not be an issue, just begging them to do it for me (and paying them of course).
Hmm, ok. Thanks for that. Stuck in the mire of assignment submission ATM for my masters, but will have time no doubt on the weekend.
I'll check with Don though, may just be easier to send the scope to them and ask for a complete service? I have the box etc so transport will not be an issue, just begging them to do it for me (and paying them of course).
hi simon,
yes i went down your road a few years ago on a 12"lx 90 i had,i didn't dare pull the corrector out but had trouble with bob's knob and collimation.ended up sending it to bintel.full service clean and update...i never looked back...
my advice send it and get a full service i will be done correct and be back running perfect again..
mozzie
Do I need to send this somewhere to get serviced or is it completely stuffed? 
If it can be fixed with a service, does anyone know if there's someone in Canberra as shipping it somewhere is not appealing. 
