Collimating with a video camera tutorial with photos.

[harry page]

Hi

I have the hotech laser collimator which has the 2" to 1 .25 adptor this does the same thing !

perhapes I will look into this and have a go

Harry

[TopHouse]

I've just ordered Protostar flocking for my OTA so when i've got all the bits off the tube I'll do a tutorial with pics on alligning focuser.

[Doc]

Hi

I have the hotech laser collimator which has the 2" to 1 .25 adptor this does the same thing !

perhapes I will look into this and have a go

Harry

I used the Hotech as well. I still needed to place one bit of insulating tape around the nosepiece before it fits into the Hotech as there is no clamping device on the 1.25" side of the hotech. But it is now an extremely tight fit so should be centered perfectly.

[Tim]

Following this with great interest, in fact I have had a go today. I dont have a crosshair piece to go in, but i do have the necessary adaptors to fit a handycam right into a 2" focusser. I played around on my GSO newt, which is a pig to collimate, and then had a look at my C9.25, finally the MN190.

The collimation was different with my chesire and with the camera, and as it cleared tonight by surprise I went back with the chesires option, a quick star test shows the collimation to be pretty good, if it had been part cloudy as they said i'd have tried the camcorders collimation out.

[Doc]

I spent a few hours on Sunday messing about with the video collimation method and I managed by extending the nosepiece to get a narrower field of view and by doing so managed to get the vignetting of the handycam to only about 1mm around the secondary except for a touch on the left hand side that is touching the secondary. (See photo in post #23)

So maybe my focuser is just out of true by a little bit but surely when zoomed in as much as I was the error must be very small.

I managed to get the crosshairs and donut exactly in the middle but then by zooming out I could see even though the mirror clips were all visible the secondary was just a tad out of true.

Anyway that night I star tested and had to tweak one primary screw about 1/2 a turn to get a perfect star test, is this to do with my slightly out of true focuser I'm not quite sure.

Strange thing is the Hotech Laser collimator doesn't read that my scope is collimated, it's not hitting the donut at all.

But the collimation was pretty damn good, all stars were pinpoints, Trapezium E & F were visible and I saw 15 new galaxies which I couldn't before.

So whats correct the video collimation or my Hotech collimator...

Don't get me wrong the Hotech laser collimation is pretty good, good enough for everyday viewing but even so if I have enough time I think the video collimation is more accurate.

[acey]

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.

Congratulations on this ingenious idea, but how is it any better than simply popping in a Cheshire? It seems that this is effectively what you're doing, except that you've replaced your own eye with a Handycam and a computer.

[Doc]

I agree Andrew it's basically the same principle but with a human eye a lot of errors can be obtained such as the positioning of the eye in regards to the crosshairs. Where you position your head can give slightly different results.

In my way the optical axis from the focuser down to the secondary is exactly 90° to the focuser and cannot wander from that.

Also the benefit of zooming in over 200% onto the crosshairs to position the donut exactly over the crosshairs.

Of course this depends on how accurate you want to be. Most times the Hotech or Cheshire are just fine and accurate enough, I was just bored with time off work so gave it a shot.

[TopHouse]

Also, with a cheshire or sight tube you will NEVER get the secondary as perfectly centered as you can this way. It also 'can' help with focuser centering and i think merlin made a statement, (the user on here, not the wizard) which i 100% agree with, he said something like, 'start at the end of the chain, focuser, secondary, primary, making sure each is perfect before moving onto the next'. The reason being, if the focuser is out, then you will make your secondary out to compensate, and so on.

I've got protostar flocking ordered so as i've said earlier, if the interest is there I'll do a thread with pics on focuser lineup later.

[Doc]

Anyway that night I star tested and had to tweak one primary screw about 1/2 a turn to get a perfect star test, is this to do with my slightly out of true focuser I'm not quite sure.

Strange thing is the Hotech Laser collimator doesn't read that my scope is collimated, it's not hitting the donut at all.

But the collimation was pretty damn good, all stars were pinpoints, Trapezium E & F were visible and I saw 15 new galaxies which I couldn't before.

So whats correct the video collimation or my Hotech collimator...

Any idea TopHouse on why I get such a difference between the Hotech and the handycam.

[astromerlin]

Congratulations on this ingenious idea, but how is it any better than simply popping in a Cheshire? It seems that this is effectively what you're doing, except that you've replaced your own eye with a Handycam and a computer.

Apart from other reasons mentioned, It's a good idea because if you are a bad back sufferer like me, continuously crouched over peering down a cheshire for long periods of time whilst the OTA is horizontal so you dont drop anything at the primary means you can do most of the first steps in collimating in comfort.

Yes if it just needs a tweak then use the cheshire but if your new to the game like me then you've probably got it so far out that you'll end up spending hours over it.

[George]

Great thread this

I'll be giving this a try with the QHY5 and either PHD or Maxim which have a built in crosshair. I wondering if this method will also work using the Canons live view?

[Doc]

Great thread this

I'll be giving this a try with the QHY5 and either PHD or Maxim which have a built in crosshair. I wondering if this method will also work using the Canons live view?

Give it a go George and let us know.

After using both methods...

The Hotech and this video collimation method, I can hand on heart say I have tighter stars and can see more finer detail when using the video collimation method.

What bugs me though is how far out it shows the Hotech. Even though I was really pleased and still am with the Hotech.

I suppose it all depends on how fanatical you are about precision.

[TopHouse]

Doc, if you put the hotech in so that it can just rotate, then look at it's reflection in the primary, does the dot move in circles or stay still?

Am tooing and frooing at the mo, got my EQ5 in bits now!

EDIT

EQ5 now rebuilt after full strip and regrease with 'proper' grease, now have a gliding mount.

[TopHouse]

Another discovery, because I've had the scope completely to bits today it's like starting completely from scratch, something else the camera will tell you. OK, the secondary is an oval at 45 degrees that 'should' present as a circle. The eye isn't so good at circles for some reason, it does squares great but circles are different. Anyway, if you load a still grab from the camcorder into a graphics package and draw a ring over the secondary, it will obviously confirm it's a circle, BUT, what if it's centered each side but is a little short top to bottom? It tells you that the mirror isn't at it's 45 and needs it's 'bottom' lifting a little, am just off back to it now to 'lift a bottom'.

[TopHouse]

OK, job done, scope back together, secondary centered to focuser almost PERFECTLY, and collimated, not only that I have a very interesting photo, once totally aligned, i pulled out my bits of paper from the tube and shone some light in to get a pic, but i got something strange. Now i could be totally wrong here but I 'think' what I have is the silver outside circle is possibly the secondary and right in the middle is my camcorder lens, and 'possibly' the 3 coloured flashes are the 3 ccd's (it's a 3ccd camera)

if that is the case, how centered is that!!!

Second pic is my 'pimped tube, and yes, there really is a secondary in there.

[Doc]

Pretty impressive stuff TopHouse, you have really took my idea one step further. If that is the case and you are soing the CCD's then as you say that must be very precise.

[Doc]

TopHouse would you like me to merge your other tutorial thread with this one so it doesn't get lost, if so just let me know.

[TopHouse]

Dunno, i did the focuser squaring as a seperate topic because I thought if people were'nt interested in camcorder collimation they should at least have their focuser squared. Thought the focuser squaring thing would be easier for people to spot if it was on it's own.

Am literally sitting at the window now waiting for it to go dark and clear, scope is all back together.

[Doc]

I agree.

Time will drag if you are just sitting around. How about making an artificial star

[TopHouse]

got some hydrogen?

[TopHouse]

OK, more experimantation and some results, which particular 'change' had the most effect on the final result I'm not sure but here goes, long winded but i think worth it.

For anyone who's been following this, last week I flocked my scope, the thing is though that the weather wasn't looking bad so I omited gluing the protostar overlaps and put the scope back together in case it turned out a decent night, which it didn't. The flocking is covered in another topic but briefly, it was a full tube flock, blacking of shoulders and back of secondary & spiders, flocking inside focuser tube and blacking outside of focuser tube.

So, yesterday, I stripped the tube again to glue the joints up as it was a really cloudy day i assumed the worst for the night. I also had a part made up for mr by an engineer friend, a 2mm thick stainless steel 'washer' 35mm diameter with a 6mm bore, this was to go between the secondary 'boss' and spider to stop the adjustment screw 'dig in'. I glued the tube up, added my 'washer' and made a start.

Observation 1

Doing a 'stealth tube' job makes a MASSIVE difference to how well your camcorder images down the focuser tube! I now had to use a torch almost all the time, shining it down the tube.

When assembling the spider and secondary with my new add on washer, I unscrewed all the adjustment grub screws until they were flush with the spiders secondary holder. I would then, using an allen key apply exactly the same number of turns to each one, the reason being, I had a lot of time and this was going to be not only an assembly of parts but a serious 'meddling and learning' session with some experimentation thrown in.

Also, before the secondary was fitted I double checked the centering of my focuser since I'd had the tube out for flocking & blacking, my focuser centering tut here :-

http://stargazerslounge.com/equipment-discussion/99623-centering-focuser-tutorial-focuser.html

So, with the camcorder attached to focuser, blocked off the primary with white card and with the OTA on the table with focuser pointing straight up I laid a piece of red card on the bottom of the tube under the focuser to give me some contrast.

I 'roughly' eyeballed the secondary central in the focuser in the up/down axis (nearer/further from primary) by holding the boss and adjusting ONLY the central screw. Next i turned in the adjustment grub screws by the same amount on each screw (counting turns) until I got some tension. What this gave me was a supported secondary but due to the hardness of the stainless washer i could still 'rotate' the secondary.

Now the human eye is usually quite good at spotting in straight lines, ie if something is square or level, but on circles and curves it isn't so good. because in effect i could now 'rotate' the secondary and watch it's effects in the camera viewfinder, I noticed that you can actually rotate the mirror quite a bit sde to side and it still presents itself as a decent circle, I replaced the camcorder with a collicap and the same was true.

FURTHER EXPERIMENTATION AND A DISCOVERY

I replaced the collicap with my laser collimater which I know is bang on collimation. (I'll also state at this point that all this is being done with a self centering eyepiece adapter fitted, so everything goes in and out like for like) Now, with the laser fitted, I removed the wite card blocking the primary and looking down the tube, the beam was almost bang on center in the vertical axis, which led to the discovery that rotating the secondary makes the red dot move only across the horizontal on the primary, only a little movement moved the 'dot' a LOT, so, I start to think, if only a slight movement of the secondary (rotational movement) has such a big effect on the position of the dot, then surely, the difference in movement available to what the eye percieves as a circle must also make a fairly big difference.

At this point I'm also shining a torch down the tube to further highlight the primary center ring. But what's that shadow in my red paper? the one that doesn't move or change shape if I rotate my secondary or move my torch?

The camcorder goes back in again and I discover that although I'm unsure what's creating this shadow it's a straight sided oval kind of shape, but it's EXACTLY the width of the secondary, if I rotate the secondary, I get to a point where the secondary touches each 'side' of the shadow, moving it the tiniest amount shows some shadow on the side of the secondary.

I took some photos to show what I mean, these show the shadow with the secondary at different point of rotation and then centered to show what I mean.

After the photos I'll add another post with the rest of the stuff so please avoid replying until the next post is up.

Note the my shadow isn't exactly 'verticle' but that's aused by the position of the camcorder, if i rotated the camcorder a little in the focuser, that shadow would be dead vertical, (or any other direction depending on camcorder rotation)

[TopHouse]

OK, so now I center the secondary using my 'mystery shadow' and replace the camcorder with the laser, the dot presents itself almost dead center in the primary!

So, I tighten everything up and tweak the collimation just a little using my laser collimater.

I backed this up using a barlowed collimation, also, for those not in the know, the normal articles describing barlow collimation and fitting a small screen with a hole to the bottom of the barlow is unnecesary if you have one of the laser collimaters with the 45 degree cutout and 'target'. The antares has it and i think the hotech does. Just use it in a barlow and the doughnut will project onto the target in your collimater.

So, as far as i knew, everything was practically perfect. As if by magic, the clouds parted and the stars came out. There was a lovely crescent moon too! However, conditions were far from perfect, the moon had a huge glowing corona from the humidity and it was a little misty but hell, I was gonna have a go!

I let the tube cool for around an hour, did a star collimation and no adjustment needed, all rings were concentric.

Looked at the moon and it was the best i'd ever seen it! Image was totally pin sharp, and I mean 'pin sharp'! detail was amazing at high mag. I tried a few other targets, Pleides etc, had a go at mars and saw detail almost instantly!

I waited for Saturn. Along it came and, that one totally blew me away, my wife is quite interested and comes out with me, so i called her outside to have a look, she agreed it was the sharpest and most detailed we had ever seen saturn, not only that but we could see definite colour, sort of a bluey greeney shade, and the stripes on the planet body as very subtle shades of this colour, the rings were pin sharp as was the gap between rings and body.

I assure you there is no poetic licence or exagerration in these descriptions, my wife verified my observations and was as surprised as me, couple this with the fact that conditions were far from perfect, the scope was literaly dripping with moisture at this point! (no, it wasn't drool!)

I'd managed to get some rings to attach my Finepix 5600 to my hyperion, I screwed it on and took a couple of photos, this is the first time I'd done this and they are slightly out of focus on the camera end, i haven't quite mastered that yet, but these are single exposure shots, no stacking, no photoshopping or anything. The one with the greeny blue hue is something like what we saw colour wise (definitely not sharpness wise) but to the eye the colour was more subtle.

Was it the flocking? Was it the 'super collimation'? Was it a combination of all? I have no idea, I just know i was one very happy puppy!

[Doc]

Well it seems your persistance paid off. I think it's a combination off everything you have done, from squaring the focuser through to flocking your tube. My tube is flocked with the same stuff as yours is and compared to my old Hardin dob the contrast is improved.

So did you find out what your mystery shadow was?

[TopHouse]

Nope, in fact i was wafting my arms and hands all over the place trying to track where it came from, wife was asking if i can do a rabbit!

[Jason D]

TopHouse, with all due respect, you are approaching collimation the wrong way. You are putting too much emphasis on mechanical alignment when collimation is all about optical alignment. Collimation consists of three main alignments:

1- Centering the secondary under the focuser – impacts field illumination

2- Aligning the focuser axis to strike the center of the primary mirror – impacts focal plane tilt at the eyepiece

3- Aligning the primary axis to coincide the focal point with the focuser axis – impacts focal plane shift at the eyepiece

Interestingly, the first two are not as critical for visual observation. Only the third alignment is the most critical. Image sharpness has little to do with the first two alignments but is significantly impacted by the third.

Jason