Skywatcher 200PDS

[james_screech]

I recently bought a second hand 200PDS, I've noticed that the focuser has three sets of two screws around its base are they used to make adjustments in some way? I've searched online but have been unable to find any information. I was wondering, as my imaging flats have a large gradient across the field (one corner is 50% brighter than the opposite corner), if I need to adjust them someway. Collimation is OK, I've checked that. Any help / pointers / suggestions greatly appreciated.

 

James

[alacant]

2 hours ago, james_screech said:

Collimation is OK

Hi

AFAIK they are for squaring the focuser -which you don't need to do- so I'd leave them and go through the collimation again. I find that if the secondary is too far up or down the tube, the camera sensor isn't evenly illuminated. Shouldn't be a problem if you have the primary OK so don't waste a clear night by fixing it!

HTH and good luck.

[james_screech]

6 minutes ago, alacant said:

Hi

AFAIK they are for squaring the focuser -which you don't need to do- so I'd leave them and go through the collimation again. I find that if the secondary is too far up or down the tube, the camera sensor isn't evenly illuminated. Shouldn't be a problem if you have the primary OK so don't waste a clear night by fixing it!

HTH and good luck.

Thank's for that, I'll leave the screws alone then. I assume I can move the secondary can be moved up / down the tube with the three tilt collimation screws and the central screw? I'm new to reflectors, I've used mainly refractors and SCT's.

James

[alacant]

2 hours ago, james_screech said:

leave the screws alone

Hi. I didn't, until I read the myths that is. Before that I made a mess of collimation by adjusting the focuser. 

Yes. The central screw is used to adjust the secondary toward or away from the primary. Loosen the three adjusting screws first. Whilst you're there, centralise the spider by making all the vanes the same length. A pair of compasses or dividers makes this easier. 

HTH.

[james_screech]

Thank you for the suggestions, I'll give them a try tonight.

James