I would like more clarification as well. When I try background correction it is rarely satisfactory.

Peter

Posted by: 1CM69

Hi Mabula,

as the weather is bad I am taking time to learn more about APP & it's functions.

I am currently watching the video tutorial on Post Processing, Background & Star Colour Correction and was wondering if you could upload the widefield image that you used in the video so I could use it to work through the tutorial?

Also, on the first stage of removing LP from the image, is there a particular system that you use in order to place the boxes on the image, i.e. what exactly are you looking for in the image in order to determine the correct placement & measurement?

Regards..,

 

Kirk

@1cm69,

Hi Kirk,

I am about to release APP 1.057. Once released, I will focus on creating several new video tutorials and printable documentation in PDF format to address the questions that you have 😉 thoroughly.

But for now, some pointers, the light pollution correction needs to be done step by step. Start with placing 5 area select boxes and calculate. Then add a couple, calculate etc... remove red boxes if you are unsure if they are placed right. The key is to to do it step by step 😉

In the remove light pollution, correct vignetting & background calibration tools, you will need to select areas without any nebulosity or glow from a galaxy for instance. So the area must contain only sky background and stars. Stars, even a lot, are no problem.

Cheers, 

Mabula

Posted by: Peter

I would like more clarification as well. When I try background correction it is rarely satisfactory.

Peter

@petercpc,

Background calibration should never be problematic, so I think there might be some confusion about what the tool does and how you need to place the area select boxes.

It always works if you place just a couple of boxes on areas that only contain sky background and stars. Don't place the boxes on areas with nebulosity or glow of a galaxy/cluster.

The background calibration serves to get a perfect gray sky background without surpressing any nebulosity.

Does this clarify the tool and does it explain why it doesn't seem to work for you?

Kind regards,

Mabula

Well no. That is what I have been doing but I find that it does not give a standard colour over the image. There are still areas where the colour varies but I am guessing this is due to light pollution. I find AstroflatPro does give a good background and is a one step correction but I will persist with APP to see if I can get better results.

Peter

Posted by: Mabula Haverkamp - Admin

Posted by: 1CM69

Hi Mabula,

as the weather is bad I am taking time to learn more about APP & it's functions.

I am currently watching the video tutorial on Post Processing, Background & Star Colour Correction and was wondering if you could upload the widefield image that you used in the video so I could use it to work through the tutorial?

Also, on the first stage of removing LP from the image, is there a particular system that you use in order to place the boxes on the image, i.e. what exactly are you looking for in the image in order to determine the correct placement & measurement?

Regards..,

 

Kirk

@1cm69,

Hi Kirk,

I am about to release APP 1.057. Once released, I will focus on creating several new video tutorials and printable documentation in PDF format to address the questions that you have 😉 thoroughly.

But for now, some pointers, the light pollution correction needs to be done step by step. Start with placing 5 area select boxes and calculate. Then add a couple, calculate etc... remove red boxes if you are unsure if they are placed right. The key is to to do it step by step 😉

In the remove light pollution, correct vignetting & background calibration tools, you will need to select areas without any nebulosity or glow from a galaxy for instance. So the area must contain only sky background and stars. Stars, even a lot, are no problem.

Cheers, 

Mabula

 

OK, brilliant thanks Mabula

Posted by: Peter

Well no. That is what I have been doing but I find that it does not give a standard colour over the image. There are still areas where the colour varies but I am guessing this is due to light pollution. I find AstroflatPro does give a good background and is a one step correction but I will persist with APP to see if I can get better results.

Peter

Hi Peter,

So then I still think that there is a misunderstanding here, let me try to explain:

Background calibration will not correct any gradients. The proper way is to first use the remove light pollution tool to get a flat background. This corrects the unwanted gradients. But! light pollution correction / gradient correction  will not do background calibration.

Background calibration is however the most logical step to perform after gradient correction. Background calibration will only adjust the RGB channels linearly so the sky background become gray based on the area select boxes that you provide.

Performing background calibration before light pollution correction / gradient correction does not make sense, since the light pollution correction / gradient correction will always cause you to re-perform background calibration. This is because light pollution correction / gradient correction will change the values of sky backgroung over your entire field of view (since it is correcting it) and then the initial calculated background values lose their meaning.

I can however include the option to perform background calibration directly as part of light pollution correction / gradient correction. So then the background calirbation tool becomes more or less redundant and will save you some time.

Let me know if this is clear 😉

Cheers,

Mabula