Collimating with a video camera tutorial with photos.

[Doc]

Just my type of kitchen table

Let me know how you get on.

[Starflyer]

Great idea Mick! I'm going to try this too, but with a slight twist

I'm imaging mostly with my 10" newt and a DSLR at the moment, currently I set the collimation with the Hotech and a cheshire eyepiece but it's always out a bit when I attach the DSLR.

I control the camera with Maxim and this has a cross-hair feature. I'm hoping I can insert the camera, collimate with your method but using the cross-hairs in Maxim and hopefully get a better imaging collimation, do you think this would work?

Cheers,

Ian

[Doc]

I agree here Ian with what you say. I always thought the Hotech was really a fantastic collimator and infact it is but I could never achieve really good collimation, it was near but not near enough.

After I collimated with the Handycam I tried my scope on the Trapezium and the E and F star was instantly visible, I tried a splitting a few binaries which I couldn't in the pass and even these were possible.

It is a lot more accurate way to do it because you are zooming into the desired accuracy with an electronic eye instead of your own eye I suppose.

I think your way with your DSLR and Maxim should work identical to mine and give you alot more accuracy.

Keep me imformed.

[TopHouse]

It's getting interesting!

OK, this is what I've done. Firstly, a piece of white card in the tube so that the primary is blocked off completely. Next, a piece of red card lying in the tube opposite the focusser to give some contrast, next, I removed the secondary completely, used a fine emery board to remove any slight burrs caused by the collimation screws iting into the metal of the secondary holder.

OK, so far so good, next, I loosened all three secondary collimation screws so that none of them stood proud of the secondary mating surfaces and then refitted the secondary, tightening the central screw all the way so that that everything was tight, next i used an allen key on the adjustment screws and tightened them so they JUST hit the steel holding the mirror. Next i took the first photo, this showed the mirror needed to move further down the tube, so, losened the central screw and tightened each of the colli adjustment screws by the SAME amount, then tightened central screw again. This centered the mirror top and bottom (second pic) BUT can you see the difference left and right? This now tells me that the focusser isn't square on the tube in that plane. More pics and posts as i progress.

NOTE, I'm feeling my way around this and if anyone comes up with any major flaws please jump in.

[Starflyer]

BUT can you see the difference left and right? This now tells me that the focusser isn't square on the tube in that plane.

It could be that the spider isn't holding the secondary central in the tube, set this up first with a rule (just measure the spider vane to tube distance) and then set the secondary position with the camera.

[TopHouse]

Forgot to mention I'd done that part already, all vanes are exact to center.

[Doc]

As Ian has said measure your left to right spider vane first. I'm glad this thread has sparked some good interest.

Sorry posted same time...

[TopHouse]

OK, yes it really has taken this long! adjusting the crayford was a total PITA. So, here's where I'm at now, picture one shows how it lies now, but it gives a slight optical illusion so the second one is with the green disks added in my graphics package, each green spot is obviously the same size. Now all i have to do is collimate the damn thing lol.

Oh, as an aside, i put the laser collimater in and used a makeup mirror down the tube to look where the beam was hitting the secondary prior to doing this and it was definitely off to one side.

Also, the pictures contrast is ramped right up to show everything better, also whilst i had the secondary off i black marker penned the edges.

[Doc]

Done with surgical precision one thinks...

[TopHouse]

Will upload some more pics in 5 mins, collimated it now, may be interesting pics

[TopHouse]

OK, done a normal laser collimation and taken a pic as before but obviously with the coloured paper removed, I can't understand though why the black 'center' is now very slightly down and over to the right.

Second show with a torch shone down the tube to show whats what, also shows the muck on my prmary. So, ideas on whats going on now anyone?

second pic shows the centre circle on primary.

[TopHouse]

As you can see, and as i've previously said, I never see my mirror clips.

[TopHouse]

So far have fully removed focuser, done the measuring and got the tube marked esaxtly opposite focuser center, lasered it and indeed the focuser was out originally, I'd used the focusser adjustment screws to get the secondary centered above, have now shimmed it with washers instead. Moral of the story so far, NEVER assume that a brand new OTA focuser is aligned properly.

[TopHouse]

FINALS

OK, these are taken with all measurements done, focuser having been removed and shimmed then laser centered to exact opposite side of OTA, secondary re-centered using camcorder method (not as perfect as last time but still a lot more precise than eyeballing i reckon) and finally, collimated primary so, in theory this 'should' be bang on, in practice, i don't know what more to look for or even if the pics show a perfect collimation so it's onto the experts lol. These photos taken with a piece of red card opposite focusser to highlight what's what.

Second picture i also added a green circle highlighting vignetted edge as it wasn't totally clear.

[TopHouse]

Little further info, some guides say to 'spot' the center of the secondary, I tried this and lazered it 'central' using a makeup mirror I adjusted the secondary so the laser hit dead center of the oval. This didn't actually centralise the mirror in the focuser though when camera checked, it did 'side to side' but not 'up and down' (up and down being along tube length axis) However I'm prepared to believe that skywatchers 'ovals' arent actually engineered precisely enough that 'dot centering' would do it.

Think I've wrote a book here!

When i next look at the moon with this, if i don't at least see a moon buggy and a flag i'll be gutted!

[astromerlin]

Following your thread with interest, great idea using the camera and checking centering with the green dots using a graphics package.

I'll give that a go myself this weekend, first I'll have to find a way to center the camera and fix to the focuser.

My current goal is to see Saturns Cassini division in my images.

Probably not all due to collimation though.

Cheers

John

[TopHouse]

I'm really really surprised there hasn't been a lot more interest in this thread.

[John]

I'm really really surprised there hasn't been a lot more interest in this thread.

Well I'm certainly following it with great interest - I have a 10" F/4.8 newtonian so that needs to be in good collimation to get the best from it.

I'm planning to have a go a barlowed laser collimation in the near future so I'll post a report on how that goes.

A few posts back Mick (Doc) mentioned seeing the E & F stars in the Trapezium clearly after video collimation of his 16". They are a good test of collimation in a newtonian I think.

[TopHouse]

As an addition to this and after putting a LOT of hours into trial and error, I'm going to stick my neck out and say that to achieve perfection and zen in the area of collimation, you NEED to center your focuser. However it's not the nightmare it sounds and I can explain how to do that practically perfectly if the demand is there, but you do need to have either a hotech collimater or a normal laser collimater with one of the orion precision self centering adapters. The only other tools needed are a decent square (one of the stanley sliding ones is ideal but not absolutely necessary) a pencil, a steel rule and some card.

My pics above show before and after focuser alignment if you follow the thread.

[Doc]

Mothering Sunday today so my experiment will have to wait. But Monday I'm going to try the method you explained in message #23 I cannot see how if you can achieve a perfect 1mm ring completely around the circumference of your secondary mirror then your focuser is not aligned correctly.

[Doc]

Well I'm certainly following it with great interest - I have a 10" F/4.8 newtonian so that needs to be in good collimation to get the best from it.

I'm planning to have a go a barlowed laser collimation in the near future so I'll post a report on how that goes.

A few posts back Mick (Doc) mentioned seeing the E & F stars in the Trapezium clearly after video collimation of his 16". They are a good test of collimation in a newtonian I think.

I think the main benefit here is that with a videocam you have loads of zoom available so you can reallly get this very precise.

I have never tried the barlowed method but have heard good remarkks about it so will look forward to your thread.

[Beyond_Vision]

A very interesting thread nice one Mick and Tophouse

Regards

Kevin

[harry page]

Hi

Interesting way of doing this !

I do not have a camcorder is this something you think could be done with a web cam ?

Harry

[TopHouse]

23 was more a thinking outloud, in practice, pre my alligning my focusser, which certainly was out, I 'thought' that if you aligned the secondary with the focuser 'out of flunter'. If you then shifted focus, either racking in or out, that the 'error' would change or 'show' but in practice it didnt.

SO

If the focuser is out 'across' the axis of the scope, it will show up, as mine does in post #29 BUT, if the focuser is out 'along' the axis of the scope you may never know because you would automatically assume the secondary needs to go up/down the tube, and if you do move the secondary, it will then 'hide' the fact that the focuser is out.

[TopHouse]

@Harry, definitely could be done with a webcam. Something I keep harping on about though is the orion centerer or similar, and I would say, if you use the camera method to obtain the precision that it certainly seems to give, you introduce a flaw if not using a centerer.

For clarification, here's the self centering eyepiece holder, probably the best 30 quid you would spend on astro gear :-

Orion Precision Eyepiece Centering Adaptor

My reason is this, if you have a 1.25 piece of kit, be it eyepiece, camera nose or whatever, firstly, they aren't to great tolerances anyway and you can have 2 eyepieces of the same make but one is looser in the EP holder than another. BUT using 2 screws in an 'approximate" 1.25 hole to secure an 'approximate' 1.25 piece of kit, every single time you remove that piece of kit and fit it again I say that the piece of kit is in a very slightly different position. Now if that 1.25 piece of kit is a laser collimater......

I seriously noticed a difference between fitting the collimater into a '2 screw" EP holder and the orion holder, not only that, but with the orion you can collimate your laser collimater too!

What you do is this, insert collimater into orion, tighten orion so it 'just' holds the collimater but allows you to rotate it without play, look down your tube at the laser dot on your primary, rotate the collimater, if the dot stays still it's collimated, if it draws small circles it's not.