StarTools

Hi,

Subject title says it all really!

Now that I've started dithering to remove walking noise from my images, I thought best practice was then to drizzle in DSS.

However, I've come across numerous recommendations NOT to drizzle for StarTools.

I'm just curious: why is this?

That's all!

Thanks
Brendan

If your dataset would otherwise be undersampled (and all other requirements are met), you may very well want to drizzle!
The only recommendation is to not drizzle if there is no reason to. That is true for all software and not ST specific.

Where have you read drizzling is best practice if I may ask? That doesn't sound right at all!

Hi Ivo,

OK, maybe that was a gross oversimplification! I guess drizzling is good under certain circumstances - for example this page gives the main criteria for when it's worthwhile: https://www.astropixelprocessor.com/com ... o-cameras/

(Having said which, I still don't really understand what undersampling is).

So, I guess I need to do more research to find out when's best to do this.

Actually, while I'm typing - given that I have a focal length of 590mm and I'm using a Canon EOS1000D, would I benefit from drizzling after dithering, do you think?

Thanks
Brendan

Looks like this gives me my answer: https://astronomy.tools/calculators/ccd_suitability - I'm just about ok with good viewing.

So, no drizzle then!

If you do ever decide to drizzle, it is extremely important for your gear to be very precise in its sub-pixel movements; you'll want to be able to very precisely and evenly cover all sub-pixel values across your sub-frames. It requires a very good, very precise mount, with minimal tracking error.

If not done correctly, drizzling will cause correlated noise grain. Correlated noise (walking noise falls in the same category) is one of the worst types of noise you can have in AP, as it quickly becomes indistinguishable from small detail for algorithms and humans.

Brilliant. Thank you again Ivo.