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Re: Advanced Newtonian Collimation Idea

PostPosted: Mon May 11, 2015 4:40 am
by MattW
Hi Dion.

Love the video, and what a great idea!

Just a few questions. I've carried out the mod of the Lifecam Cinema as best I can, given the instructions I have read are for modding the camera to be an astro cam, not a video cam with the lens retained etc

My first question is this: how can I be certain, when I put the camera back in the casing and restore it to as best its original state as I can, that the lens and chip alignment is square within the camera and therefore square in the adaptor looking down the eyepiece tube at the secondary mirror?

Also, how do you make the video zoom in and out like that in the video when you are lining up the centre of mire de collimation with the crosshairs in SharpCap?

I also notice that when you zoom in, the graphics seems to 'lay down' or tilt a little, to make lining up more simple. How do you do that, too?

Many thanks, andd keep up the great work on the site?


Re: Advanced Newtonian Collimation Idea

PostPosted: Mon May 18, 2015 4:34 pm
by Dion
Not getting much net time at the mo as have been in cyprus the last couple of weeks and am still there, currently in an internet cafe. It doesnt matter if the alignment within camera is right as you can center mir de colli on the focuser tube vignette if necessary, hence centering in the actual focuser tube, the zoom was simply using the zoom feature in sharpcap.

Re: Advanced Newtonian Collimation Idea

PostPosted: Mon Aug 10, 2015 7:47 pm
by astrotise
Hello. Thank you for this tutorial and all your other videos Dion.

I am wondering if I might be able to ask you (or anyone really) for some help.
I have been trying to collimate my skywatcher 150/750 but I can´t get it right. My images always comes out with skewed vinegretting
and "comet-stars".
After watching and following your tutorial I might have an idea what is wrong but I would love to double check
with you who knows this stuff (only had a ED80 before so I know nothing about collimation).

This is the result I get when trying to align the secondary.
*The primary is to the left on the images*

I have tried with a laser colimator before I found your tutorial Dion so I don´t know if I messed it up.
That something I will not rule out. :)

Anywhoozle my theory right now is that the secondary is to low, by quite abit aswell.
I did "meassure" the spider and as far as I can tell it is central (used astrobabys method).
Oh and since I couldn´t get hold of a Lifecam and Mod I had to modify my own webcam,
but after reading some replies here it shouldn´t matter if the webcam isn´t 100% aligned?

What would your initial thought be of this headache of mine? :)

Thank you so much


Re: Advanced Newtonian Collimation Idea

PostPosted: Mon Aug 10, 2015 9:23 pm
by Dion
Secondary looks a mile out, but line mir de collimation up with the vignette that your focuser is creating.

Re: Advanced Newtonian Collimation Idea

PostPosted: Mon Aug 10, 2015 9:48 pm
by astrotise
Thank you for the quick reply Dion. :)

I will try that. :)
Might this have been something that I did or?
I haven´t touched the spider vanes but I have done some (excessive?) tinkering with the secondary adjustment bolts.

Re: Advanced Newtonian Collimation Idea

PostPosted: Wed Aug 12, 2015 6:47 am
by astrotise
Actually solved my problem now. :)
And yes it was my fault (I think).
The screw the held the secondary in place was bent.

Re: Advanced Newtonian Collimation Idea

PostPosted: Wed Aug 12, 2015 9:02 pm
by Dion
Ooops, I actually replace mine with stainless countersunk hex screws from habit.

Re: Advanced Newtonian Collimation Idea

PostPosted: Mon Oct 09, 2017 8:25 pm
by allhoest
Thanks Dion for your tutorial.

I'm a solar imager, and I collimate during the day after having travelled to a place with good seeing. So, I have no reasonable way to make a star test. Your video raises ***such*** a hope for very fine collimation.

I have a D250mm solar truss Newton at f7 and observe at f28 to f35 with a barlow and/or a telecentric lenses:
Pic. Solar Newton ... _r-enh.jpg

To your video.
1° Webcam collimation
As mentioned also by others, my webcam is not collimated/centered. After having perfectly centered the webcam from a mechanical point of view, the vigneting of the focuser end is not centered.
With my f7 scope, my guess is that the sensor of the webcam must not be at the millimeter exactly centered.
The standard focuser is 31mm and the webcam external diameter is 29mm.
The mounting of the lifecam now is made with 2 set of 3 adjustment screws, so to collimate it. I’m not fully centered and the maximum error is (31-29)=2mm.
Pic webcam centered with home made sets (green and pink) of collimation screws. It shows a fe degrees of out of collimation. Terrible. ... enh_ar.jpg

Now, the vigneting of the focuser end can be centered. After adjustment, rotating the webcam does not introduce any offset regarding to the reticule.

Is the approach acceptable?

2° Tilt for aiming the primary center
From your video (18:00 and later) and after reading the post belonging to it, I understand that the tilt remains the most important adjustment to do.
In my case, I had this results, appealing for more adjustment than tilt.
Pic After moved the secondary into position, aiming the primary (Above the primary, this pictures shows a protection plate with a bolt in the middle) ... rcle_c.png

From the video, I understand that I should rotate also.
But, how to be sure that the primary cage and the secondary cage are reasonably centered?
Pic Hand made exaggerated view of a out of center truss system. ... cr-enh.jpg

After the tilt correction, do you recommend to slew or to rotate?
Or slew is the action we should avoid in any case.

3° Other error sources
With the alignment done (I did a tilt and a slew to aim the primary), when rotating the webcam assembly, the primary start offseting.
Pic After alignment, rotate the webcam by 180°

In one of the post, it is written: "To use you webcam method how do you fit a 1.25"" tube to the cam and know it's perfectly central?"
The answer: "if you have the reticule centered etc and you rotate the camera, if it stays on center with the primarp mirror spot then it's in"

3.1 Focuser
The axis of the focuser has been adjusted to be parallel to the top of the secondary cage
And in the other axis, to point over the center of the spider.
They are reasonably adjusted, because how to 100% adjust them?

3.2 Secondary at 45°
In my case, I mounted the secondary myself, with my 2 left hands.
It is not exactly at 45°.
Also, the mirror axis is probably not 100% on the axis of the secondary support.
Both introducing and other sources of error.
Pic. The secondary mirror is not erected at exactly 45° ... enh-Ar.jpg

3.2 Other errors…Spider
The video refers to the spider, and the secondary mirror support, which lies against it as the starting position.
But is this spider center part/secondary support well flat/parallel to the cage top?

I'm fighting with getting gooood collimation during the day.
Do you see short coming in my description?
How to stepwise eliminate/minimize error sources.
I'm not good in optics... Any help is appreciated.