X2 mono questions with Lodestar Live v11

[f15p5]

Hi,

Just got my x2 mono, had the X2c. Will I need different drivers or settings using Lodestar Live?

What is "max pixel displacement" what should I set it to?

Will be using with Ha filter. Any other suggested settings?

Thanks,

Richard

[f15p5]

Also where is the scaling function .75 being talked about?

Thanks,

Richard

[DoctorD]

Hi Richard

No need for different drivers, just tick the OSC box in Lodestar Live exposure tab. - the raw data form the chip is in the same format regardless of whether it's a OSC or mono.

Max Displacement is the maximum distance allowed for motion between two frames before the processing rejects the frame and does not try to stack it (I think - check with Paul81).

I set mine to about 10 as I'm not that accurate on polar alignment and I see some drift between frames.

I'm not sure what you mean by the 0.75 scaling function - could be the Colour modifier which is the only control that can be set to 0.75 as far as I'm aware.

HTH

Paul

[HiloDon]

Hi Richard,

I think the scaling function you are referring to is X^0.25. It's a selectable box where the default is Linear. The x^0.25 is useful when you have a large difference in brightness in an object like M42. Martin recently showed how it helps to bring out the Trapezium and still show some of the Nebulosity.

Hope this is what you meant.

Don

[f15p5]

Hi Don,

Yup, thats it.

Thanks!

Richard

[Paul81]

Hi Richard,

For you mono camera you don't want to check the OSC checkbox (only do that for colour Lodestars) - when checked, LL converts raw data from the camera to RGB using a CYMG bayer interpolation (otherwise for mono it just copies the mono pixel values into R, G and . The bayer interpolation uses multiple neighbouring pixels so you will end up inducing noise into your mono image.

As for max pixel displacement, this is the maximum pixel movement from the new frame (just downloaded) to the current 'key frame' that is allowed before LL forms a new key frame. Let me explain....

A key frame (after reseting the stack, the first image is always a key frame) is what all new images are aligned to. So LL downloads your first image A, then later downloads the new image B. Using the stars in the image, LL works out how to transform B so it aligns with A (and then combines the data). When it does this, it works out the average distance in pixels between a star in A to the same star in B - this is your 'Mean Pixel Displacement' on the stacking stats display.

It keeps doing this for all new images until the average displacement exceeds your threshold (i.e. all new images are aligned to the key frame image). The issue comes when your mount starts to drift - either due to polar alignment error, alt-az field rotation or mount inaccuracy. The more the object being observed drifts, the less image overlap there is between new images and the key frame. The less overlap, the less there is to stack, so you start getting little or no benefit. Also the image transformation will be more extreme so it has to work harder, the result of which is more noise.

To avoid this issue, you could keep aligning your live stack to the new image - the trouble is you keep re-transfroming the same data which will result in the image blurring.

LL answer to this conundrum is to when the displacement threshold is exceeded, for that image, LL transforms the live stack to match the new image, combines those, and then uses the new image as the new key frame (thus aligning new images to the one just downloaded).

So if the displacement threshold is exceeded, it doesn't discard data, but re-aligns the stack to the latest image, which will cause a little noise to occur, but reduces noise that would occur in the future.

So you need to select a value which generally means you get about 10 subs without inducing a new key frame, but at the same time don't get too much displacement. This all depends on your setup. I use 12 and this seems to fit the bill. Select a value too small and your images will have more noise.

Hope that helps? 

[DoctorD]

Hi Paul

Even more sophisticated than I thought!!

CS

Paul

[f15p5]

Hi Paul,

Thanks for the info. It was set to 1, I'll bump it up to 10 or 12 and try again.

Richard