LX90 v's VC200L

[Rocket Pooch]

Hi,

Its cold tonight and I had both scopes out to see what the differences are.  Some comments as follows.

Collimation

LX90 dead easy, just place a mag star in the middle and use you're hand to see where the image is out of alignment by putting it in front of the collect plate and then loosen or tighten the opposite Allen key, Allen keys are fiddly, but you do not have to worry about dropping one on the primary.


VC200L same process as above, but longer arms are required and its very difficult to get airy disks, you don't get them, you get spiky disks due to the thickness of the secondary support.  Also if you drop an Allen key it's going to get expensive, there's nothing to stop it from hitting the primary.  Also you need baboon arms to do it properly.

Best for collimation LX90


Focusing

LX90 fiddly because of the mount and the mirror movement.

This is no contest the VC200L is in, focus or out of focus and there is no between, the big thick secondary supports ensure that the focus is easy to obtain, it you are out of focus on Saturn you get 2-4 Saturn's depending on how out of focus you are.

Winner VC200L


Image quality

In the centre of the field of view on Saturn the LX90 will win hands down, clear divisions and one band and an extreme clarity of image.  

The VC200L has better contrast and therefore, for example, the rings are easy to define but not as sharp as the LX90.  I could see three of the planets cloud bandings and the rings had contrast, but not as defined as the LX90.

On M42 the VC200L turns the trapezium stars into little crosses because they are bright, but the nebula extends very wide using a 26mm eyepiece and the stars at the edge of the field of view are quite good.  The LX90 has better definition and pinpoint stars, but the nebula is not as extended.  The VC200L better contrast and a flatter field.

Winner LX90 planetary, VC200L nebula and contrast related subjects.


Dew

LX90 dripping wet tonight, VC200L thick covering of ice all over but the mirror was clear.

Not sure about the comparison here, the LX90 I'm positive will give better planetary images, if only it did not have the focus and dew problems it would be excellent.  

The VC200L first impressions are ok, but I'm not positive its going to be as good as the LX on planets, but it does have a flat field and also obviously more contrast, tonight I could see three clear bands on Saturn and four changes in the ring contrast as well as the normal divisions, but it just seemed a little fuzzy, maybe the next 5% of collimation needs working on.  But VC200L no dew, dead light and no focus movement.


Watch this space for an imaging comparison soon.

Chris

[JohnP]

Interesting.. I'm guessing with all the visual you did last night you didn't get a chance to throw your ToUcam on.. sounds like when you perfect the collimation on the VC200L it's going to be a winner. I look forward to having a peak through it.

Cheers,  John

[Rocket Pooch]

Hi,

I'm not sure its going to be better than the LX90 as in the final results, but it is definately easier to focus and get the image on the CCD.  But the Vixen has really big secondary supports and the secondary itself must be in the area of 35%+ of primary width, on bright objects and stars you get big diffraction spikes, and I mean big.  Unlike the LX90 where it has no spikes and a smaller secondary.

But no dew even though it was foggy last night, I suppose the proof of its quality will be on Deep Sky and also Planetary images.  I have a mental picture of the LX performance on a lot of the DSO I can see, so it will be interesting to see the difference.

One thing though, no image shift big smily face on this front.

Anyway, if its not as good as the LX90, it will give me an excuse to get a 10" Meade OTA.  Or that 12" newt I was after

Mike you will be interested in this point, the EQ6 gives off a high leve of vibration, its apparent at F18+ on the Vixen and the vixen dovetail does not help things either,this seems to be due the the lack of load on the EQ6 by the Vixen VC200L.  I think this will go aware later when all the scopes are on the same mount and it actually has more than 6kg to bang around.  I noticed the vibration when I popped the web cam in to the VC to check the collimation.

A large focus knob is a must as well, the rack focusor is not delicate enough to get good focus easily.

This is just another observation, optically the ED80 is a lot better at double star splitting, observing star colours and contrast observation than both the LX or CV.  With a 5MM eyepiece 150x all the main stars within M42 could be resolved individually, I can do this with the LX at 133x but not the VC at 120x or 380x (probably the last 10% collimation), so for value for money and image quality the ED80 is a stunner, every star I looked at was the right colour and doubles we're split easily and the contrast was fab, if a little dim cimpaired to the LX90.  If they made a ED150 I'd probably go and buy it tomorrow and sell the LX and VC.

I forgot to say earlier that I looked at saturn at 380X, I beleive the limit for the CV should be about 400x so I was not far off the full potencial last night, it was very very still.  And icy.

Chris