Collimating with a video camera tutorial with photos.

[Doc]

Last night I collimated with a Sony Handycam video camera and I achieved the best collimation I have ever had. The E and F stars of the Trapezium just came into view instantly, stars were pinpoints and most bright ones had diffraction spikes.

Never thought of it before but it was so easy to do. I would imagine a bit hard to do at night, but during the day it was a breeze.

[Tim]

thats very interesting Mick. I have all the bits I need to fit my camera into a 2" focusser.

Did you follow a tutorial? I'd be interested to hear how you did it and what you did.

Cheers

Tim

[Dave Smith]

I would love to know how you did this during the day.

Dave

[Doc]

No I didn't follow any tutorial, this is what I did.

1. Fitted a crosshair reticle into a C Mount adapter.

2. Fitted this into the Sony Handycam.

3. Inserted handycan + Nosepiece into the focuser of the scope.

4. Pluged the Firewire lead into the laptop and the Handycam

5. Opened up WxAstrocapture software

6. Your live view instanly appears on your laptop.

7. Rotate camera until crosshairs are central.

8. By looking at image you can see if secondary mirror is centralised on primary.

9. You can now align the crosshairs right into the middle of your donut marking on your primary

10. Eventually everything will be exactly aligned. You can zoom in and make very small adjustments to get it spot on.

11. No need to worry about offset as this is automatically taken care off.

Thats about it, you now have a perfectly aligned mirror. I then star tested it and the secondary shadow was perfectly dead centre and slightly oval which it should be.

Actually slightly more accurate then the Hotech

[Rusty Strings]

Does this mean you can use any webcam, philips etc? or is there something specific about the sony?

John

[Doc]

I would imagine any cam would do John. I have the Sony so I tried that, good thing is you can zoom in and really align those crosshairs onto the middle of the donut.

[dobserver]

But does the Sony come in such a sexy box as the Hotech? lol

[Rusty Strings]

I'm liking this idea a lot. Is the C mount adaptor 1.25" in diameter also, the hotech expands into the focuser to ensure that it sits on the focal axis is this true of the nose piece or is there any play which may prevent the cam not looking down the centre of the optics?

[TopHouse]

Once again I suggest the orion precicion self centering eyepiece holder lol

Orion Precision Centering Adapter | Orion Telescopes

[Rusty Strings]

Another useful accessory for the wish list!

[Doc]

Once again I suggest the orion precicion self centering eyepiece holder lol

Orion Precision Centering Adapter | Orion Telescopes

With the 1.25 part of the hotech removed the 2" part does expand the same as the Orion you mention. So yes John the 2" adapter is centralised in the focuser and then you insert the C Adapter. Of course this is not centralised but if you wrap a piece of insulating tape around the nosepiece it becomes a very snug fit.

[Tim]

seems like a brilliant idea Mick, nicely done!

[Rusty Strings]

I'm going to give this a go. How difficult is it to locate the crosshair centrally on the C mount?

[Doc]

I'm going to try and step you through how to collimate with a standard video camera.

First of all I used a C Mount adapter with a crosshair reticle inserted into the nosepiece. This was attached to my Videocamera which is a Sony Handycam. (See #1)

I used the self centering device from the Hotech laser collimator in it's 2" format. This was inserted into my focuser and then the video camera and nosepiece was inserted into this. (See #2)

The wires were attached and I used WxAstrocapture to grab the frames and used the printscreen function to copy into Paint for this tutorial. At this stage the nosepiece is rotated so they are on the same axis plane as the spider vanes.

As you can see my collimation is way out. You can only see two of the three mirror clips. (See #3)

By undoing your three secondary screws you can rotate the mirror until all three clips are visible. Note that you must have as much of an even shadow around your secondary as possible. Try to centralise your secondary mirror if you can. Excuse the background blind and curtains. (See #4)

At this stage tighten the screws and make small adjustments until the cross hairs are aligned with the spider vanes, Keeping an eye on your mirror clips and how central your secondary is. (See#5)

This is the secondary now aligned, but you can see that the primary is not in line, so by turning the collimating screws at the primary mirror you can place the donut directly over the centre lines. The great thing about this is you can see via your monitor which way to turn the collimating screws. (See #6)

Eventually it should look like this with the crosshairs in line with the spider vanes and the donut on the primary mirror sitting over the centre of the cross hairs. (See #7)

This is now how your view should look, it could to with a tad more centralising but for this tutorial I think you get a good general idea of how the procedure is done. (See #8)

[albedo0.39]

Nice one Mick - certainly takes a lot of the pain out of the process !

[Doc]

Cheers Steve it gave me something to do while being off work

[TopHouse]

Where do i find one of those crosshair reticle thingys to have a play with this.

[TopHouse]

Another idea strikes me with this, could you also blank off the primary with a sheet of paper in the tube, then put something like a brown envelope oposite the focusser, use the camera zoom to get it right on the secondary and do a really precise focus tube/secondary alignment?

[Doc]

Another idea strikes me with this, could you also blank off the primary with a sheet of paper in the tube, then put something like a brown envelope oposite the focusser, use the camera zoom to get it right on the secondary and do a really precise focus tube/secondary alignment?

I got my reticule with my TAL Refractor many years ago. As for your idea above I'll give that a go next week and report back.

[TopHouse]

Just playing now Doc, but I need to explain better, if you put a longer nosepiece in, so that you get vignetting on the camcorder, then put it into the focuser, then zoom onto secondary so that the 'circle' being defined by the secondary almost fills the vignetted image, then you should be able to perfectly center the secondary, not only that, by then pulling back and forth on the focusser it 'should' show any focusser misalignment. I think!

[Doc]

You get alot of Vignetting with a standard nosepiece and most of these shots are zoomed in so they are pass that stage. Can you explain a little more on what you mean about seeing focuser missalignment

[Doc]

Thinking about it you are talking about squaring the focuser to the secondary. So yes if you zoom really close any missalignments really do show up and you can get this pretty close to spot on.

[TopHouse]

Yes, if you put a long enough nosepiece on so you get a vigneted circle in the viewfinder, then put the camcorder in the focusser, you will get a black screen with a circle in the middle (the vignet) now 'inside' that circle should be another circle that is the secondary presenting itself, so, what you now see is something like my picture. Where the grey mirror is centered in the vigneted view, if you did this with focusser all the way in, then surely if the focusser was not square, if you then pulled back on the OTA focusser, the mirror (grey) would drift withing the vignetted circle, and if it is dead square then all should stay the same. Or is there a really big hole in my theory i've overlooked.

[Doc]

I can see exactly what you mean and in my mind should work as long as the secondary casts a perfect circle which I think it does.

If it does work then it's an extremely accurate way of aligning your focuser.

I can zoom in far enough with a standard eyepiece I think if I cannot I'll try and rig something up and give it a go.

[TopHouse]

I'm having a play now but i cant find a lump of tube long enough to vignet small enough, I've got barlows in bits and allsorts here. Also what's really handy is to grab screeners or shoot stills with the camcorder and load them into a gfx package for pixel tight measurements. may get some pics up later of my attempts. My wife says our kitcen table looks like mad professors lab at the mo though!