Off Axis guiding Rules...

[JohnP]

I think below data says it all - this was my alignment data for 3hrs of imaging last night - combination of 10 & 15 min subs..... look at total movement between first & last files....

Deep-Sky Auto-Process
Master Image: Tulip_Nebula_001.fit, Star1-> X:478.17, Y:154.06, Star2-> X:103.08, Y:342.36
Slave file 1: Tulip_Nebula_002.fit, dX = 0.09, dY = 0.02, Rotate = 0.00 Deg, Scale = 1.00
Slave file 2: Tulip_Nebula_003.fit, dX = 0.15, dY = 0.04, Rotate = 0.00 Deg, Scale = 1.00
Slave file 3: Tulip_Nebula_004.fit, dX = 0.23, dY = 0.10, Rotate = -0.01 Deg, Scale = 1.00
Slave file 4: Tulip_Nebula_005.fit, dX = 0.34, dY = 0.10, Rotate = 0.01 Deg, Scale = 1.00
Slave file 5: Tulip_Nebula_006.fit, dX = 0.40, dY = 0.25, Rotate = 0.01 Deg, Scale = 1.00
Slave file 6: Tulip_Nebula_007.fit, dX = 0.59, dY = 0.18, Rotate = 0.00 Deg, Scale = 1.00
Slave file 7: Tulip_Nebula_008.fit, dX = 0.74, dY = 0.26, Rotate = -0.01 Deg, Scale = 1.00
Slave file 8: Tulip_Nebula_009.fit, dX = 0.88, dY = 0.30, Rotate = -0.02 Deg, Scale = 1.00
Slave file 9: Tulip_Nebula_010.fit, dX = 1.09, dY = 0.37, Rotate = -0.02 Deg, Scale = 1.00
Slave file 10: Tulip_Nebula_011.fit, dX = 1.24, dY = 0.41, Rotate = -0.03 Deg, Scale = 1.00

[MarkS]

That's pretty spot on!  So which off-axis guider are you using?

Will you now introduce some deliberate dithering? 

Mark

[JohnP]

Will you now introduce some deliberate dithering?

... so let me get this straight after spending like the last year or two trying to sort out elongated stars due to shift/ flexure you now want me to intentionally move the scope between subs... I DON'T THINK SO...!!!!!!!!!! Issues I have are:

1. CCD only 640 X 480 (not many pixels to play with)
2. The guiding prog I am using doesn't support dithering & my guiding is working like a dream at moment so don't want to change...

Will dithering really make a big difference to noise?

John

[RobertM]

Will dithering really make a big difference to noise?

Not a big difference in your case but it should still be noticable.  On the otherhand if your guide s/w doesn't support it then decision made.

Dithering would benefit any CCD size but more so for noisy chips.

Robert

[Fay]

So wherre is your Tulip John?

[JohnP]

same place as my ic63 on my HDD....

[Fay]

What is HDD?

[RobertM]

 

[Fay]

Am I being blonde? 

[MarkS]

HDD is John's Hard Disk Drive.

But I still can't find these rules pertaining to off axis guiding ...

[JohnP]

Mark my OAG rule is easy...  It works so don't touch...!

[Rocket Pooch]

seems a less complicated way of explaining it John