No colour if I don't use wipe?

[BrendanC]

Hi all,

I've noticed this recently.

If I don't use the Wipe module, then when I come to the Colour module after using Contrast, HDR, Sharp and Decon, my image has no colour at all.

If I do use Wipe, it does have colour.

I'm not sure this used to happen.

Any ideas? I'm running v1.7.449beta. Perhaps I should roll back to a non-beta version?

Thanks, Brendan

[BrendanC]

Hmmm, doesn't do it now!

Just ran a test, checking the Colour module (and then Cancel) after each step, so opening the file, then bin, crop, contrast, HDR, sharp and decon. After each step, there was colour.

Strange.

I'll look out for it happening again and try to replicate it. In the meantime I'll leave this thread here in case anyone else notices this.

[BrendanC]

So it seems to be that, if I don't use Wipe, there is hardly any colour by the time I get to the Color module. I have to turn the saturation right up to get anything decent and that seems to clip some stars.

If I do use Wipe, there's much more colour information.

I guess this is because I Autodev after Wipe? So that the image has effectively been through two Autodev processes?

It's slightly frustrating because I now seem to have a choice: if I want good colour, I have to wipe; but sometimes my data is good enough not to need a wipe, in which case, I'd rather not use it.

Any takers?

[admin]

Hi Brendan,

Wipe is not optional, and you should always inspect the Color information when doing a Wipe (a popup dialog even reminds you of that). Wipe is an integral part of signal calibration. Without it, the channels will have almost always contain a bias.

Wipe is not detrimental to your signal and I cannot really think of a good reason to skip it.

If you are confused as to what is mandatory and what is optional, then this great workflow schematic by @hixx will be useful;

Notice the (M)andatory and (S)uggested designations.

Hope this helps!

[BrendanC]

Thank you, this does help. I was hoping not to have to wipe in instances where I thought the data didn't need it.

What I'm finding - and in fact have just found again, hence my returning to this post! - is that, without wipe, when I come to the Colour module, all the RGB channels are completely aligned and it's very difficult to bring any colour out. I've been checking my settings in DSS with regards to the 'Align RGB channels in image' setting, which I have turned off, so I was scratching my head quite a bit to understand this.

OK, so I'll go back to using Wipe then.

Thanks for clarifying, as always.

[BrendanC]

Quick question: why is Bin mandatory? I know it improves SNR but it also reduces the size of an image. What happens if I want my image to be as large as possible, for example if I want to print it?

[hixx]

Hi Brendan,
BIN is labelled as suggested NOT mandatory in the workflow...
It is only suggested if the pixel resolution exceeds the seeing limit (oversampling).
Please calculate your pixel resolution (in arsec) = ( Pixel Size (µm) / Telescope Focal Length (mm) ) X 206.265
If the result is equal or higher than the seeing limit, BIN may well be skipped
Please find calculators here: https://astronomy.tools/calculators/ccd


Regarding the color alignment...
Please check DSS for having selected "No White balance processing" under RAW/FITS and "No Background Calibration" under Stacking Parameters/Lights.
The background calibration is one of the reasons why Wipe is mandatory. The benifit from doing Background calibration not in DSS but under Wipe is that Tracking is switched on, so whatever factors are used for calibration are known to the tracking backbone and Noise may better be identified.

hope this helps,
jochen

[almcl]

I've been checking my settings in DSS with regards to the 'Align RGB channels in image' setting, which I have turned off,

The 'Align RGB channels in image' check box in DSS has nothing to do with colour balancing; it is about aligning the stars from the three different colour channels in the final image.

It used to be possible to use the lens module in StarTools to do this, but with the separation of colour and luminance data processing, it is no longer available.

[BrendanC]

Argh, my bad - of course, it says Bin is Suggested. Apologies.

I've checked DSS, No White Balancing and No Background Calibration are both switched on (strange way to design an interface but there you go...)

Quick additional question: I do have 'Set black point to 0' switched on. Presumably that's ok?