VCurve - what affects it?

Hi astro-friend,

We’ve had quite a few days with excellent weather here in Switzerland.

Yesterday, I wanted to add an additional V-Curve and I was a bit disappointed with the outcome; each time, I had one side of the curve “very good” and the other one not really.

What might be the main reason of that ? Seeing ? Backlash ? etc. ?

FYI, I did run some test with different star and had similar outcomes. Worth mentioning that usually I am getting very nice V-Curve.

Thanks for your kind support.


Hi Aygen,

If you don’t need it, don’t add Curves. The number of vcurves depends on their repeatability and on the resolution of the system.

The causes for what you indicate are usually:

  • focuser slippage or unscrew for temperature extreme change or loosening
  • backlash
  • cables retains not free to move
  • sensor not squared , threads not thighten
  • uncollimated instruments (intrafocal different from extrafocal)

Not seeing … seeing affect all !
Remove the last vcurve from the list, the one done in this message.

All the best

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Thank you, Leo, fo your swift input !

Make sense, will do as suggested.

All the best,

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