Over previous years, i have spent more then my fair share of nights trying to get the collimation of my meade spot on.
Most nights i have had some success, but i then decided to go down the laser route.
After looking around for weeks I finally ordered an sct laser colminator (its now free to a good home).
After the said tool arived, i got to work getting the mirror aligned.
After spending about an hour I finally got the mirror collimated, as per the instructions.
On the night in question I found out that the scope was so far out of collimation, I had to start over
So i looked in to other ways of collimating the scope.
And came across various ways and means, but most of them were using the inter and outer focus rings.
Which is what i had been using anyway.
One web site started to mention about using the airy Disk as the final part of the collimation process.
so i decided to look in to this. Then i found out about using an artificial star to aid in the collimation process
Using either a 50 micron drilled hole, and another using a fibre optic.
Both of which were a tad expensive for what they were.
So i decided to make my own!
I ordered some 5mm Borate silica glass off of E-bay, and set to work on making my own star.
Hey presto, it only worked 1st attempt.
(http://www.macrhon.co.uk/website/oasphotos/fay/IMG_0686.jpg)
I know the picture is not great but will give you some idea of scale.
Drill bit is 1mm in diameter.
home made fibre 0.2mm ish as measured in photoshop.
the only bit that annoyed me was i broke off another 2 inches, which was probably about 5-10 times thinner again.
So im going to have another go and make another one,
Then to put it to the test.
However.......
This fibre 0.2mm when used with my scope at a distance of 20m (40 if i use a mirror and reflect around the garden)
will subtend an angle of 1 arc second.
Hopefuly I should be able to get the collimation of my scope spot on. :cheesy:
As i wont have any atmospheric distortions
Ill let you know how i get on collimating.
cool - if it works can I borrow it to collimate my MN... :-)
Good job, John
I'd be interested to know how you get on with this as most artificial star techniques require the 'star' to be a considerable distance away from the scope.
Well done Mac!
If it works you can borrow it,
As for the distance, i know that might be a problem, but the minimum distance my Meade will focus down to is about 50ft,
and the furthest point i can get from it is about 65ft,
so its going to be tight, however i can always place a mirror at the back of the garden and double the effective length to 120 ft.
Just trying to find my ultra bright LED's, dont fancy looking down the scope at a laser. :o
You can do a pretty accurate SCT collimation job indoors in 20 minutes or so and only one another helping hand required. Last time I did it and checked against a star it was well nigh spot on too.
Basically the process is to sit about 8-10 feet away in front of the scope, look with one eye at the centre and try and make all the secondary rings concentric in the primary with the collimation bolts (that's where the helping had comes in). You may be surprised but the accuracy needed to get them concentric is much less than 1/16th turn. It's always best to check with a point source like a star afterwards as you don't use the scope horizontally but I've always found the results very good. If short of a helping hand then I setup a mirror and look at the reflection of the secondary while adjusting the bolts. The main reason I do it this way is that there are very few nights where I can see the airy disc and concentric rings and there's nothing a decent distance away that I can use as a point source.
Warning - you may see concentric rings for a short while afterwards but they soon wear off ;)
Collimation of My Meade 10" Update.
Well kicking around the garden i remembered my meade just sitting there, so i decided to have a go at collimating it.
After removing the bird poo from inside!!! :o :o
Must have managed to get in somehow,
I decided to use the following,
(http://www.prezziesplus.co.uk/user/products/large/black-starlite-fibre-optic-.jpg)
set up in my bedroom and using CCd colimator, i set about collimating it
After about 10 mins the results i was getting were poor to say the least,
every new image would show the collimation off in some sort of random direction,
So i dug out the artificial star and set that up in the bedroom, and then used the defocused image to align the rings produced,
After about 25 mins of using the H9 as a live feed and tweeking the screws i managed to get the collimation as folllows.
(http://www.macrhon.co.uk/website/oasphotos/fay/collimation.gif)
Checking the circles with photoshop i would say they are spot on.
No flats :lol:
The bunnies are on the front of the optics.
Mac,
That looks very good, you should finish it off at high power just out of focus. I did the C9.25 a couple of days ago and after a bit of jiggery pokery, got the same result. The Baader laser collimator I originally used mucked it up a treat and was so far out that I couldn't even get proper focus on the moon. I would have expected the Baader unit to be good but it ended up being less than useless and is going back! As you say artificial stars are quite easy to make, in my case an LED torch and a piece of black card with a tiny fine needle hole was much better and cheaper.
That was real Poo in that scope? that stuff is really acidic and sticks like glue. Hope you got it all off!
Robert
Nice one Mac - that's a great image of the de-focused point source.
Mark
Looks good Mac - You should be all set for some great images now - collimated scope, new camera, guiding and pier... Looking forward to seeing some images.
John
Quotecollimated scope, new camera, guiding and pier
.
well thats a sore point at the moment,
Havent got guiding yet, but im still getting these weird and wonderfull images, and it's doing my head in.
(Havent got the image as i deleted it)
Tried last night to image the horse head,
Now i know that my polar alignment was nearly spot on, using a 15mm eyepeice the star drifted 1/4 of the view over a period of about an hour.
So over a period of 3 mins it shouldn't have been too bad.
but the scope is still shifting!!! or the camera is shifting!, something is not quite working and i've yet to suss it out,
I might have another play today in daylight to see if i can workout why it keep shifting,
Might strip the bearings down and give them a good service and regrease, see if that changes anything.
whilst imaging Alnitak for only 3 mins the final image had 4 images of the star!
So the camera/filter/telescope combination had shifted 4 times in 3 mins.
But the movement was in both RA & Dec, i could understand if the image had shifted in RA, as this would indicate that the worm gear was jamming / sticking,
but as for the Dec movement? There should be no movement in dec at all, as you only track in RA.
Going to think about this one. Will probably initilize the lx200 and get rid of any PEC training and start from scratch, that way i can eliminate everything.
and start by adding on by one, retraining the sensors, backlash, pec, ect.
By then i was cold and tired, so i packed everything away.
ps. i did also make sure there were no vibrations, as i set a dely of 1 min before i started, so i could go in and get a cuppa.
definitely sounds like the mount is doing something itself. Hopefully re-initialising the controller will help. I know I had fun with mine when the grub screws were a little loose on the drive pinions which made for erratic alignment and then tracking went off because the scope wasn't pointing where the controller though it was. Is there a way with your controller to see the alignment data? On mine, I can get info out of the controller such as polar alignment error and other parameters such as orthogonality and so on.
Does the controller have backlash compensation on? That has caused me issues in the past too.
Also, it's tracking at sidereal rate, not lunar I assume (not that that alone would account for dec drift).
Hi Mac,
I have had all these problems and more - last time out I did the calibrate motors, train drives (I strap a green laser to the top and do it in daylight - just get the spot back to the corner of the chimney 5 houses away), update PEC. I tend to leave the backlash compensation on the default 10% having tried other values. Then everything seemed to sort itself out as long as I didn't change the target. I think that on my LX90 the worm gear mounting blocks are a bit loose as there is a definite clunk when you nudge the OTA with the clutches locked down. It shouldn't be though as Telescope House virtually rebuilt it a couple of months ago (maybe therein lies the cause:-{ ) Maybe something you should check?
As for SCT collimation - I've got that cracked. Here is a description I put together:
http://www.decorateandplaster.co.uk/astronomy/collimation_mask.pdf (http://www.decorateandplaster.co.uk/astronomy/collimation_mask.pdf)
Have you ruled out mirror shift?
Mac,
Did you use a fibre optic lamp? If so thats a brilliant idea, have to get one.
Chris
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
QuoteDid 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...) :-)
Just cut off one of the fibres and use that with a white light source.
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?
QuoteHave you ruled out mirror shift?
Yup, I've got a mirror lock on the scope which was locked.
QuoteDid 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
QuoteAre 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.
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
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
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.
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.
I've used the white lithium grease on mine.
yep white lithium grease...
well i've just ordered some white lithium grease from screwfix.
All i need to do now is check my gears.
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.
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.
(http://www.screwfix.com/prods/71936/Van-Car-Accessories/Car-Lubricants/3-in-1-Oil-Pro-White-Lithium-Grease;jsessionid=XXSKHITLNPEGCCSTHZOCFGA)
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
Chris is that fibre-optic cable for data?
The reason I ask is it's usually sheathed with kevlar. it's a pain to cut, coz you can't easily without the right tools and if you try to break it with your hands it can cut like cheese wire.
That said, it'd be fun to play with as well :)
nope pvc
QuoteEACH OF THE 64 STRANDS IS 0.25mm DIAMETER
it will be interesting to see if you can pull the fibres out thinner with a little heat,
I've got some borat sillica glass, (glass blowers glass), which is what i used, as i said the fibre i was left with was about 0.2mm but the end piece broke off,
and was a lot thinner.
I used this at a distance of about 50ft ish.
I'm going to get some stiff card tomorrow and have a go at making that collimating mask,
I'll post the comparison results later.
Mac.
High Five...!!!! :lol:
Hi,
I also have made on using some 25nm fibre optic and a 9v battery, 1x48 ohm resister a switch and a supper bright led, works a treat, but I spent the last hour mucking about with my 6" primary, and now I need to optically collimate the primary again it was out, I very nearly got the collimation 100%.
But if you try really hard you can get your newt to do this.
(http://farm4.static.flickr.com/3349/3283038578_8783de2bb2_o.jpg)
Quote25nm fibre optic
:o :o :o :o :o :o
Thats *!£"%&&^% small.
are you sure thats the correct size!
the wavelength of light is between 400 & 800 nm
1mm = 1,000,000 nm
.01mm = 10,000 nm
I'd put money on it being 25 micron. The thinnest data carrying fibre I've worked with is 9 micron. And no, I don't have any I'm afraid, I wish I had...
ok ok 25 micron, still worked a treat though, you could actually see it like a little mag 4 star at the end of the garden, ahhhhhhhh,
Is this idea any good (laser diode from cheap LED laser pointer)
http://www.oldham-optical.co.uk/Red_Light_Source.htm
I suppose it depends on whether the light emitting bit of the LED is smaller than the 25microns you have already achieved. How does one find out?
Mark
The LED goes into a tube, the fibres go into the other end and then I have cut all but one of the fibres, the only light that comes out is from 1 fibre.
chris
Chris,
If you have any left - I'll buy a few fibres.
Mark
Chris 48 ohm at 9V works out at 9/48 or 0.1875Amps which is an awful lot of current for an LED - I would have limited the current to something like 20mA (as discussed) & so used a 400-500 ohm resistor...
Looks good though...
John
PS - Can't slag you off about your nm V's micro-meter slip up I screwed up the other day with Arcmins & ArcSecs.....
It would not even go on with a 500ohm one :-( they seriously chuck out light I almost blinded myself.
And my newt focuses to within 40 feet? Odd that.
Anyway, the said device prototype will be on display the weekend for all to laugh at! And I need a volunteer to help me collimate the primary on the 6".
Just checked the web site said 48ohm.
the max forward current is specified in the datasheet for the part. I had a quick look on maplins site for superbright LEDs and the max current was in the region of 0.1A. Don't forget when calculating the voltage across the resistor=battery voltage - forward voltage drop across the LED. The forward voltage drop can also be found on the datasheet for the part.
Alternatively, build a constant current supply...
Wow! - I never knew supbright LEDS drew that much current.... no wonder it's bright...
Don't forget your average Alkaline PP3 (9V battery) has a capacity of something like 500mAh so depending on how many hours it takes you to do your collimation battery may not last too long..... :-) :-)
John
I've got a 3W LED that draws 350mA and here's one (the white one) that can draw 1A http://www.jaycar.com.au/productView.asp?ID=ZD0442&keywords=bright+led&form=KEYWORD (http://www.jaycar.com.au/productView.asp?ID=ZD0442&keywords=bright+led&form=KEYWORD)
They need mounting on substantial heat sinks to prevent them from self-destructing.
Chris,
I thought you said "EACH OF THE 64 STRANDS IS 0.25mm DIAMETER". That means a diameter of 250 microns not 25microns.
Mac reckons he got 0.2 mm (200 microns) with his borate silicate glass (or whatever).
Last night I sawed the collimating lens off a cheap & nasty key-chain red diode laser. Ran it off 3V with a 4700ohm resistor in series to keep the power right down. This produced a pinprick light source which I measured photographically to be approx 0.08-0.1mm wide i.e. 70-100 microns. This is still slightly too large to act as an artificial star for collimating my C11 at 25metres (the length of my garden) - it subtends 0.7arcsec.
Mark
If i get a chance today, i'll have another go at making a nice very fine, glass fibre with the glass i've got,
I'll bring it tomorrow to high elms, and i'll bring in some glass for you to have a go with.
All you need is a blow torch to heat it up and you just pull it apart, the glass solidifies
in to a ver thin strand.
the .2mm strand i ended up with was a lot thinner, but the end piece broke off.
Mac.
QuoteI'll bring it tomorrow to high elms
Mac - remind me what's up tomorrow...... thks
do you want me to bring my blowtorch to dsc? my propane bottle will be there anyway...
QuoteI'll bring it tomorrow to high elms
Mac - remind me what's up tomorrow...... thks
sorry just me having a blond moment,
I thought the meeting was this thursday, :oops:
I'll bring some down on saturday then instead, as well as a pair of plyers and some gloves.
anyone got a micrometer?
Quote from: Mac on Feb 18, 2009, 13:48:39
anyone got a micrometer?
yup, shall I bring that too?
So if it's cloudy, at least we'll get some collimation practice. Sounds like we'll have a whole constellation of artificial stars!
Mark
Quoteanyone got a micrometer?
yup, shall I bring that too?
might as well, just to see how thin the fibres realy are,
Quote from: MarkS on Feb 16, 2009, 09:00:10
Chris,
If you have any left - I'll buy a few fibres.
Mark
I have 2 meters of the stuff, I will accept payment in beer please, not point in cashing in or it, it was very cheap...
Quote from: JohnP on Feb 16, 2009, 12:34:40
Wow! - I never knew supbright LEDS drew that much current.... no wonder it's bright...
Seriously you don't want to look into the end of one when its on.
8)