Precise collimation of Vixen VC200L

[whzzz28]

So i've had my VC200L for three months now and have not been able to get it collimated. It is frustrating me to no tomorrow as i can collimate a Newtonian very easily, yet this thing escapes me.
I took it out the other night to see what it was like. Shocking is the best way to describe it i think.

Tonight i decided enough is enough and that i will spend the next few nights trying to get it collimated, or even better; perfectly collimated.

I have been following the instructions on Vixen's site but i can't help but feel that these visual methods are not very precise. I don't trust my eyes to know that the donut is perfectly centered when doing an out of focus star test, nor that the secondary baffle is evenly centered when adjusting the primary.

What are my options?
I have a glatter laser collimator (with barlow and hologram pieces) and have ordered the tuPlug + orion cheshire eyepiece to see how close i can get it. Mind you finding information on how to use a cheshire eyepiece is rather difficult for some reason.

Tonight i did an indoors test of the primary mirror. It was out, not too far, but far enough. I think it is close to being collimated now and i made sure the screws were done tight so it won't move (but not too tight).
I tried collimating the secondary using the C.2 method on the PDF (point telescope at even bright surface such as white wall or sky), but i am unable to see the dark ring, no matter how bright or dull the surface is or how far racked in or out the focuser is. Unless my idea of "centering eyepiece" is wrong and they mean a Cheshire eyepiece? I am using an orion eyepiece with crosshairs in it.

Does anyone else have any tips if you own a VC200L on what you have done to get great collimation?

Tomorrow, weather permitting, i will try and do an out-of-focus star collimation on the secondary.

Cheers.

[Tandum]

Nathan,
I could not collminate mine properly. IPonders has it now and he did it. Too much time on his hands I recon. These days I'd try and borrow a tak collmination scope. They are made for that sort of job.

[leinad]

Send me a PM with your email and I'll send you a guide I've sent to a few owners from the VC200L Yahoo group.

Collimation is a 3-step process to be correct
1. Focuser to secondary vane
2. Secondary to Focuser
3.Primary to Secondary

[BlackWidow]

I have a vixen 95 as a guide scope. Also could not collimate. Took it to a telescope tech we have in the astronomical society to have a look. He could not get it to collimate. We decided to open it up to find the prim mirror had its center hole on an angle so I't did not fit onto the light tube square. We had to file the light tube to get it to sit square and flat. Also had a look at the secondary that was also out. It was held in place with double sided tape that had a fold in it when fitted. That also had to be removed and re attached. The scope is better now, but not perfect. I purchased it new wen on holiday in the USA. I only use it as a guide scope and does the job. Very disappointed with the build quality for the price of the scope. I hope this is not also your problem. Good Luck..


Mardy

[BlackWidow]

I have a vixen 95 as a guide scope. Also could not collimate. Took it to a telescope tech we have in the astronomical society to have a look. He could not get it to collimate. We decided to open it up to find the prim mirror had its center hole on an angle so I't did not fit onto the light tube square. We had to file the light tube to get it to sit square and flat. Also had a look at the secondary that was also out. It was held in place with double sided tape that had a fold in it when fitted. That also had to be removed and re attached. The scope is better now, but not perfect. I purchased it new wen on holiday in the USA. I only use it as a guide scope and does the job. Very disappointed with the build quality for the price of the scope. I hope this is not also your problem. Good Luck..


Mardy

[garymck]

My VC200l was collimated as follows:

a friend turned up an adapter to screw a laser collimator directly to the focusing tube.

The secondary was completely removed (after carefully marking orientation and ensuring I did not lose the packing spacer between the secondary holder and the spider). The laser was then, after screwing in to the focuser tube, shone through the secondary support hole in the spider (a bit of tracing paper was fitted to the end of the scope to make the laser beam visible) - the focuser needed a tweak, enough to be noticeable,

The secondary was then replaced and adjusted such that the return beam hit the centre of the lasers 45 deg cutout.

This now means that the focuser and secondary are perfectly aligned. They should not need further work.

The primary can now be checked by looking up the focusing tube and centering the secondaries image by adjusting the primary.

Then look (easy with a ccd attached) at a centred defocused star - adjust until when the star is centred the rings are also centred.

At this point the scope has a roughly collimated primary and will still produce triangular stars.

According to CCD inspector the best I was ever able to get the primary using a star was to about 20 arc secs off line.

The using CCD inspector in collimation mode, adjust the primary progressively to improve collimation. You will find that once you hit about 3 ar secs of error, the triangular stars just disappear. Mine is collimated to about 1.8 arc secs, and stars are great right across the field. To get it this close you need to be adjusting the screws so that you are hardly moving them at all, otherwise they overshoot. Just lean on them....

This is the second VC200l I've had - I was an idiot and sold the first one - the current one ain't goin' nowhere!

If you get desperate, pm me and I'll lend you my laser adapter thingy and a collimated laser that is a heat fit to the adapter....

I also have an adapter for fitting a Takahashi collimation scope to the VC200l as well, though to use this fully the secondary mirror needs to be centre spotted - this needs a lathe to be accurate enough to use.

hope this helps,
cheers
Gary

[LewisM]

The VC200L I bought from an IIS member was CLOSE< but not close enough - there was definite asymmetric flare on stars. I tried to collimate it, I got frustrated. Traded it to Hugh (we all know Hugh :) )

Hugh, being the fitter/turner genius he is, got it collimated perfectly, and now reports the images are superb in it. I don't doubt it one bit!

[allan gould]

I had a VC200L and found that a laser collimator was no good really due to the optics in the draw tube. I don't know how many had the scope before me but I suspect quite a few as when the secondary was inspected there were various different alignment marks all around it. I then used the written method by Vixen to do the whole thing by eye. Followed it exactly and my collimation was then quite good but still slightly triangular stars. I then used Al's collimation aid on a bright star to do the final collimation.
Result: Perfectly round stars to the edge native or with the focal reducer. But like an idiot sold it which I regret to this day and may get another.

[garymck]

Hi Allan,

Exactly how I felt about the original vc200l I had.

That one, I originally collimated with a Takahashi collimation scope (after centre spotting the secondary). Because that was borrowed, a friend made up the fitting to screw the laser to the focuser so there was no slop at all. i actually have to heat the fitting up to get the laser in to it! The laser and the tak scope were exactly in agreement about how the secondary was collimated...so in that scope the internal optics had no effect on the lasers ability to achieve secondary collimation accurately. The same can be said of my current vc200l it all matches. The hardest thing about the primary is learning that adjustment moves are TINY. It is incredibly easy to overshoot and end up chasing your tail...

Cheers
Gary

[whzzz28]

Thanks for all the comments. Last weekend i tried again and had some success.
Collimation is still off, but not so far off that the scope was unusable.

There is still double diffraction spikes, so am i right to guess that the primary is off, or should i be looking at the secondary first?

I'm still waiting on my cheshire eyepiece from Bintel (order hasn't shipped yet... must be out of stock on something)

I tried using a laser collimator to check the secondary but didn't have much luck. I did confirm that the focuser was collimated almost perfectly, but when rotating the laser, the secondary was always off, thus i gave up on using the laser.
I followed the vixen documentation and got the primary aligned before the sun went down and then tried to get the secondary aligned with an out of focus star.