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Old 11-11-2019, 01:24 PM
Nightingale
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Need Help with Collimation Meade lx90 ACF 12 inch

hi,


just received my meade lx90 12inch.. initially i thought my collimation was good but was unable to resolve the bands on jupiter clearly.. Then i was told that my collimation could be off. So i went back to my scope and there was possibly a teenie weenie off collimate.. so i decided to fiddle with the original collimation.. Now my collimation is completely out of whack.. have been attempting to get this right for the past 3 days (3 hours each day) with little success at perfect collimation. The big doughnut looks okay then when i get it into near focus (small doughnut), the doughnut skews.. never quite perfect.. Anyone in the Adelaide region could help me out with this? or if someone had a better method of trying to get all 3 collimation screws in the right place? i have trolled though various methods and none seem to be of help..
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Old 11-11-2019, 05:21 PM
poider (Peter)
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are you a member of the astronomical association of south Australia, They run monthly telescope clinics, you can even go if you are not a member
I had some collimation issues with my first Newtonian and took it there, they did very well
I don't know enough to help you out though but if you contact them they may help or give you some better contact
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Old 11-11-2019, 10:56 PM
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ngcles
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Hi Nightingale,

There are lots of things to love about a Schmidt-Cassegrainian telescope, but ease of collimation is not one of them. Generally, once collimated they hold it very well unless serious abused. Newtonains on the other hand while pretty easy to collimate, unless mounted permanently, require frequent adjustment.

Collimating a Schmidt-Cannegrainian is somewhat to much more difficult than a Newtonian. You need to do it on a star or other point source and examine the out of focus star images -- a laser is of practically no assistance. It is far more convenient to do it as a two-person operation with one gently adjusting the collimation screws, while the other examines the eyepiece image and provides directions to the other person.

If you don't have much experience with telescopes, I'd suggest getting it done professionally. There is a Meade dealer in Adelaide -- Adelaide Optical Centre, and I'm sure one of the staff there will have it done quickly, won't cost that much (in context) and you'll know it's right. You can also try other places as well, but this is a Meade dealership.

Best,

L.
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Old 12-11-2019, 12:45 AM
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ngcles
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https://starizona.com/tutorial/colli...dt-cassegrain/
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Old 12-11-2019, 08:16 AM
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Merlin66 (Ken)
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I used a 12" Meade SCT for many years.
A couple of comments:
The star must be re-positioned every time back to the centre of the field of view. You may need a cross wire eyepiece to verify position.

I found on a couple I tested, that the front correcting plate retaining screws had been tightened by the Incredible Hulk!!!! and caused some distortions.
Just check that these screws are finger tight no need to have have them over tight.

Always finish focusing with a anti-clock turn of the focus knob, this will keep the mirror "pushed" to the same side. There's a balance spring behind the mirror in the 12" SCT.

I fitted a mirror lock (as per the MAPUG site) to reduce mirror movement - I do spectroscopy.

I sounds like you're doing things correctly - don't panic
Ken
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Old 12-11-2019, 02:36 PM
morls (Stephen)
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Hi,
I've got a maksutov, and I think the collimation process is very similar?
Anyway, I have a bad habit of pulling things apart when I get them, and I did that with this mak. The collimation got waaay out when I replaced the stock screws, and so I had to do a lot of daylight adjustment to get it back in the ballpark, before I could think of star testing.
What really helped was setting up the scope on the mount during the day, and aiming it at a mirror 1-3m in front as I adjusted the screws on the visual back. I got the distance just right, so the circles of secondary, primary and baffle were really close. Doing it this way really helped me get a handle on what each adjustment did.
I also found it really useful to have the mount aligned when doing star testing. As another member has posted, the mirror shift makes this fine adjustment a bit of a pain. Using the hand controller the keep the star centred makes all the difference.
Good luck!
Stephen


p.s. what also helped was the realisation that I wouldn't break the scope through trying to collimate it. I just had to learn how to do it!
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Old 12-11-2019, 03:24 PM
gb44 (Glenn)
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Here is another tutorial;

http://www.astrophoto.fr/collim.html

The final adjustment is done at high power manification ( 5 or 9mm eyepiece?)and you need a night of great seeing.

Cheers
GlennB
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Old 12-11-2019, 11:35 PM
Nightingale
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I got cheesed off with the astronomical association of SA.. oh well, atleast with the secretary who replied to my email.. she said something along the lines of you have to wait for 4 weeks before we approve your membership.. Didn’t even approve online access.. got super cheesed off with that reply so i asked for a membership refund and bid them good riddance.. in terms of getting my scope somewhere else to get collimated - almost impossible.. i even had trouble lifting the scope off the floor onto the tripod.. now i lift the scope with the tripod attached - much easier not having to put the pivot on my waist.. and also collimation might go out of whack with transfers... so i would love if someone could get here and get it collimated for a fee.. might speak to Adelaide Optical over the wknd.. in the meantime, if any of you live in Adelaide and are expert collimators (including ASSA members) pls give me a buzz..
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Old 17-11-2019, 03:31 PM
crs (Colin)
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I have a 12 inch and 10 inch RC. I have had to buy an adjusting ring to allow the focuser to me moved separate to the main mirror. Even so they are hard hard work to adjust. I once had a Dob and it was simple...
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