Author Topic: I have a question about 'Drizzle'  (Read 312 times)

Offline indigo01

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I have a question about 'Drizzle'
« on: 2019 October 21 02:01:22 »
Hi all,

I am just starting to experiment with Drizzle. One thing I am not quite sure of is that once complete Drizzle Integration doubles the size of the image. At that point does one need to resize it down to smaller proportions or do you just use the larger size image?

Any suggestions would be appreciated.

Offline John_Gill

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Re: I have a question about 'Drizzle'
« Reply #1 on: 2019 October 21 03:59:56 »

When using DrizzleIntegration with the defaults, your image size will double.  I just use that image as the nebula should be a bit smoother.

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Offline airscottdenning

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Re: I have a question about 'Drizzle'
« Reply #2 on: 2019 October 22 15:15:22 »
A drizzled image has twice as many pixels in x and twice as many pixels in y, so it's 4x the size of the original (double-double)!

The reason we do this is because we have "under sampled" the sky -- we've used a camera with pixels bigger than the smallest the seeing would support, or equivalently we've imaged at a focal length too short to see the details of the object in the sky.

So quadrupling the number of pixels is a good thing!

Ideally it's the equivalent of imaging with 4x as many pixels half the size of the ones in our physical camera.

In practice, the smallest details we can see in the sky are often determined by seeing rather than the size of the camera pixels. In this (very common) case, drizzling an image in post-processing will NOT produce extra detail.

My experience has been that for short fast refractors or HyperStar with one-shot color or DSLR cameras, drizzling can produce dramatically better image detail. But for longer/slower scopes or with LRGB filters, it's not worth the effort.

Offline pfile

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Re: I have a question about 'Drizzle'
« Reply #3 on: 2019 October 22 16:22:01 »
just a minor point, you can do more than 2x drizzle - i think PI supports up to 10x but most people probably use 2x which is the default.