Garish colours and red halos on bi colour image

[Craig123]

Hi all

I was pleased to put together my first image using ha and oiii but after looking closely and comparing with other images I can see I have red halos on stars and the blue looks a little out there.Ha mapped to red and oiii to blue and green in astro art. My question is (on a tight budget) would I benefit from getting a third NB filter.. Sii which might balance the image better or should I start thinking about pixinsight... or do I just need it all !. I just read up on the pixel math feature and it looks great. Iam just at the start of learning to process ds shots. Thank s in advance. 

Craig

[RolandKol]

ASTAP has similar pixel math option.

Give a try.

As per SII... Not sure... 

I started NB AP in Feb only...

SII need will mainly depend on the target.

And Most of the targets have very low SII amount....

My experience, SII was useless on Veil, Wizard and Crescent Nebula and ofcourse on Andromeda.

However, with Elephant nebula was a different story... Bicolour image was very noisy and colours looked odd... SII improved it drastically, - total noise smoothed out and colours became natural without any artificial adjustments....

In summary, lnstead of SIl, I would go for autofocuser   or LRGB filters.

[Craig123]

3 minutes ago, RolandKol said:

ASTAP has similar pixel math option.

Give a try.

As per SII... Not sure... 

I started NB AP in Feb only...

SII need will mainly depend on the target.

And Most of the targets have very low SII amount....

My experience, SII was useless on Veil, Wizard and Crescent Nebula and ofcourse on Andromeda.

However, with Elephant nebula was a different story... Bicolour image was very noisy and colours looked odd... SII improved it drastically, - total noise smoothed out and colours became natural without any artificial adjustments....

In summary, lnstead of SIl, I would go for autofocuser   or RGB filters.

Thanks. Funnily enough I was going to try Elephants trunk again next. I found a great image on Flickr of the Veil using ha oiii and Sii and processed with pixel math.What is Asatap btw?? 

[RolandKol]

ASTAP is .fits viewer and stacker like DSS, but it also has a separate pixel math option.

Just search it in this forum, - the developer always posti his soft updates here and even can advise how to use his app properly.

 

[Craig123]

OK. That's handy to know. Thanks

[carastro]

Can you re-post the image.

Carole 

[Craig123]

4 minutes ago, carastro said:

Can you re-post the image.

Carole 

[Craig123]

11 minutes ago, carastro said:

Can you re-post the image.

Carole 

Hi Carole. That's the image I was referring too. The top is how it came out of the stacking software and I took down the red levels on the 2nd picture with PS aswell as applying some curves. 

[carastro]

Filter/noise/reduce noise and drag the colour noise slider to the right will get rid of the red stars.

As an aside, I do find sometimes the star sizes will vary between filters, I guess depending on how much light they pass.  Sometimes I have to shrink some of the stars to match.

Carole 

[Craig123]

2 hours ago, carastro said:

Filter/noise/reduce noise and drag the colour noise slider to the right will get rid of the red stars.

As an aside, I do find sometimes the star sizes will vary between filters, I guess depending on how much light they pass.  Sometimes I have to shrink some of the stars to match.

Carole 

Thanks Carole. Much appreciated.So use the filter as a layer in ps so as to preserve the Ha in the Nebula ? 

Also what do you use to shrink stars..?

Craig

[jjosefsen]

I had a similar issue with my lrgb test recently. I haven't done a real lrgb project yet, but I did a focus test with a bahtinov mask on all filters, and there was a quite large shift in focus on my red filter.. Did you tune focus between filter change?

[Craig123]

Yep.. I was really meticulous refocusing with each filter and then checking it again every so often with fwhm. There was a big shift between baader Ha and Oiii filters. 

[jjosefsen]

11 minutes ago, Craig123 said:

Yep.. I was really meticulous refocusing with each filter and then checking it again every so often with fwhm. There was a big shift between baader Ha and Oiii filters. 

Ok.. interesting.. maybe it is a matter of star sizes as Carole suggested.

[wimvb]

What filters do you use, ie which linewidth? Narrower filters are generally better, but of course, more expensive. As far as software is concerned, PixInsight is totally worth the investment.

[Craig123]

13 minutes ago, wimvb said:

What filters do you use, ie which linewidth? Narrower filters are generally better, but of course, more expensive. As far as software is concerned, PixInsight is totally worth the investment.

They are 7nm for Ha and 8.5 for Oiii. 

I think pixinsight sounds great. No doubt I will get it one day. 

[wimvb]

Then I guess linewidth isn't the cause. If these were substantially different, that might be the reason for the halos.

[Craig123]

7 hours ago, carastro said:

Filter/noise/reduce noise and drag the colour noise slider to the right will get rid of the red stars.

As an aside, I do find sometimes the star sizes will vary between filters, I guess depending on how much light they pass.  Sometimes I have to shrink some of the stars to match.

Carole 

That worked pretty well Carole. ?