Collimating SCT.

[JohnP]

umm.. Are the multiple images all seperate or is it one continual movement.... I guess if it is discrete images then the mount must be doing something evry so often to make image suddenly jump. I would expect that if something was slipping like mirror or focus etc then it would be a continual shift... Post an image the next time it happens? I think geting rid of any pec training etc. would be a good start. Also what happens if you turn off the DEC motor... like you say this shouldn't move anyway if your polar alignment is spot on..

John

[JohnP]

Did you use a fibre optic lamp?  If so thats a brilliant idea, have to get one.

Just make sure it's not one like I have got which continually changes colour & fades in & out (would make collimation a bit tricky to say the least...)

[Mike]

Just cut off one of the fibres and use that with a white light source.

[Ian]

has the society gone a bit kitsch? Perhaps to keep warm at DSC we could all get Afgan coats. Stay out of the mud with 12" platforms? Get into the Mud listening to "tiger feet" at full blast?

[Mac]

Have you ruled out mirror shift?

Yup, I've got a mirror lock on the scope which was locked.

Did you use a fibre optic lamp?  If so thats a brilliant idea, have to get one

I did try and use it as a star cluster with ccd colimator, but to no avail, the Light sources were a tad to large. (Not point sources).
But i used my home made one, which worked brilliantly

Are the multiple images all seperate or is it one continual movement

Its one continual movement, with the star staying stationarry in the four positions, you can see the trailing between the four star images.
It might have been wind, but i dont think it was windy last night.

I might make a video of the star with my old toucam, and see if i can replicate the movement,
If not then its probably the H9 and filter set moving.

But im going to have a look at the bearings and reset the data first.

[MarkS]

Mac,

Backlash compensation could cause part of the problem if you have PEC switched on - it would happen when the correction changes direction.  But it would affect only RA and not Dec

Backlash itself can cause problems if your scope and weights are not weighted slightly against the direction the scope is being driven.  Every so often it will drift ahead of the motor (up to the limit of gear backlash) - pulled by the weights instead of driven by the motor. But again it would affect only RA and not Dec

Again, slipping motors/gears would also only affect RA and not Dec.  Besides, you said it previously ran for a whole hour with no discernable problems.

Check though, that the handset wasn't set to Alt/Az instead of Polar.

My money is on some part of your optical train "settling" into position - this could affect both RA and Dec.

I suggest you take a whole train of 3min subs and then look for a pattern.

Mark

[MarkS]

Hi Dunc,

That's a very interesting collimation mask.  Where did you get the idea from?

I'm still scratching my head trying to work out how this works ...

Mark

[Mac]

Well having done a search for striping and rebuilding the lx200 drive,
it's apparent that they used to use plastic gears for the gear train,
pre 2004. But you can get the upgraded gear sets,
So im going to check mine, they should be metal, but who knows.
It was bought in 2004.

Any sugestions for the grease?
i was thinking of copper grease or would that be to thick?

I'm going to make that collimation mask, and compare the images
to see how out of collimation mine are, compared to aligning the rings.

[Ian]

depends what you're greasing Mac. For low pressure, low temperature I believe that white lithium grease is the way to go. Coppergrease is usually only used in high temperature environments.

[Mike]

I've used the white lithium grease on mine.

[JohnP]

yep white lithium grease...

[Mac]

well i've just ordered some white lithium grease from screwfix.
All i need to do now is check my gears.

[RobertM]

I have a whole tub of Castrol LM grease (white lithium) that you're welcome to borrow.  It was what was recommended and I used for my old G11 rebuild.

Let me know if you're interested.

[Mac]

Checked the gear set and they are plastic, so i've ordered the metals ones,
As for the white grease, it was only 4.88 so i've ordered it anyway, but thank you anyway.

[Rocket Pooch]

Mac,

I just ordered some

64 STRAND PMMA (PLASTIC) FIBRE OPTIC CABLE
2MTR LENGTH OF POLYMER FIBRE OPTIC
EACH OF THE 64 STRANDS IS 0.25mm DIAMETER

Hopefully one strand of this stuff with a super bright LED will do the job as well.

After I'm made the thing I should have 63 strands of the stuff left if anyone is interested?  20p per strand

Chris