[Paul Butler]

Hmmm, been playing with Astig on my NEC XG110, got the dots pretty round, not perfect but good enough for a first try.


One problem however, whilst looking at the astig screen (contrast set to max) I suddenly realised that none of my dots had a bright core, the outer edge of the dot is brighter than the inside! Thats not right is it - am I supposed to play with the 2 pole levers to get the bright spot (that appears when moving the dot grid around the screen with the levers) right in the middle of the dot?


If so, getting a round after getting the bright core centered is really difficult - I tried and failed a couple of times. (I can get everything back to the way it was easily enough having marked the plastic levers before hand - thanks John!).


I take it its a matter of practice getting it spot on.

Thanks,

Paul


[Edit - I took some pictures but the dots in the photos look solid which isn't what I'm seeing (which is more like a bright outer ring with a more faded inner core).

 

[gn2]

Swing your electronic focus the other way. The astig screen which comes on automatically defocusses in one direction only. To see the core best, you need to defocus the other way(I think). BUT the astig correction is for flare only, I think, so it won't affect the roundness of your core anyway. Put up the dot hatch and run your overall focus up, then down, one direction should make the core more apparent,

 

[KennyG]

Astig is the roundness of your dot...Flare is the halo around the core when underfocused (I think, I get them mixed up) Defocus in one direction for Astig (dot shape) then run focus in the opposite direction for flare adjustment.

 

[hificanuck]

Guys,I also get the halo with no central core. Am I correct in saying that when using the Astig adj. in the Ref. Menu the proj. automaticaly defocuses the dots but not reall in a helpfull way and you cannot defocus the other way and then go into the Astig. menu as it has no effect. When using the dot pattern, the only way to get the astig correct is to manually adjust the levers (yuck!!). Mine are siliconed in place, do you recommend removing the silicone to get better astig?


Alun

 

[KennyG]

Flare is not adjusted using the Astig menu selection.

When you setup the XG's mechanical dot shape you do it from the Focus menu...you adjust the focus in both the over, and under focused conditions to adjust both dot shape and flair with respect to the CPC magnets.

The electronic Astig adjustment is for fine tuning and zone adjustment of Astig only.

 

[Paul Butler]

Ok, I think I'm getting somewhere.


In the focus screen, underfocusing (reducing) focus produces the same display as the Astig Reference Adjust screen. Overfocusing (increasing) focus results in tight dots at about +35% on the focus bar and thereafter the halo increases in size.


The core appears more apparent when overfocusing but appears (at least in the red crt to be brightest at the top left of the halo.


I am right in assuming that;

a) My focus is out as ideally the dots should be tight at 0% (but this isn't a problem as such)? And


b) I need to adjust the 2 pole levers whilst overfocused to bring the bright spot into the center of the halo? (Whilst the halo is enlarged?)



Does Astig increase sharpness, the more accurate the dot, the less the halo, the sharper the display?


This Astig business is proving to be frustrating but hopefully worth the effort.

Thanks,

Paul

 

[gn2]

a.) Yes you could get better focus settings (closer to zero , or ideally zero) by carefully positioning your focus yoke when electronic focus is zeroed.

b.)Yes, adjust the 2 pole magnets to center the core in the flare, and to make the core as tight and round as possible, then adjust the 4 pole magnets to make the flare as circular as possible so when you focus the spot, the flair collapses evenly on all sides into the core, which should result in a focus point where there is NO flare left, only the perfectly focussed dot. When doing these adjustments, concentrate on the center of the screen, the rest of the screen is handled by the electonic controls.

Yes sharpness is astig. You really need to examine the need for it whenever the pj is moved to a new location because the earths magnetic influence will be different wherever you place the pj on it.

 

[Paul Butler]

Yes, I understand now, thanks Paul and to all others who responded.


Looks like I have some work ahead of me !

Paul

 

[stefuel]

It's pretty simple really. You must start with all parameters in the astig menu to the center then exit that menu and go to the focus menu. Put up a dot pattern and adjust one color at a time concerning only the most center dot on the screen. Turning your focus in one direction will give you a large blob that you adjust to be round. Turn the focus in the other direction gives you a halo with a bright core. You adjust the core to be centered within the halo. It is interactive so you will have to go back and forth a few times to get it correct. I think I've got that right...


Chip S.

 

[Paul Butler]

Thanks Chip.


Am I right in thinking that adjusting the bright core will mess up the raster centering? I assume that re-centering the rasters after fine tuning the bright core is ok? (Visions of going round in an endless circle !

Paul

 

[Gordon Fraser]

Paul,


Going round in circles is what you must do. The UP side is that if you persevere you will have a superior image to most who do not!


Gordon

 

[stefuel]

It's OK if you go around in circles, as long as your circles are round...


Chip S.

 

[Paul Butler]

By Jove I think I've done it!


Spent about an hour doing Astig this morning and its looking very good, not perfect perhaps and I'm sure some folks could do it better but it looks good to me and it will do until such time as I revisit it in the future.


It was easier than I thought it would be BUT I had the benefit of having read up on it here on this forum beforehand plus the input of folks in this and other threads.


As always, a word of warning to anyone trying this for the first time;


***DANGER***


THERE ARE LETHAL VOLTAGES IN THERE - BE VERY, VERY CAREFUL!!


My thanks to my fellow NEC'ers (and non NEC'ers!) for all their help!

Paul