Eta Carina HST with 6RC

[miki63au]

Hello everyone


Long time no post... clear nights conflict with work/family commitments ... or equipment issues


Anyhow, after I decided to mod my GSO 6RC (replaced the focuser, reset secondary with Ronchi, collimate with Tak scope etc) here is a first 'presentable' pic of Eta Carina nebula. Many iteration before... all issues related to RC collimations. Not there yet me think. Pixel peeping prevented (to declare) perfection... Good fun



About 3h of HST palette Baader filters, CCDT @ 0.695x, Moravian 8300 @ -20degC


Happy Easter everyone
Mik

[Robert_T]

lovely, puts me in mind of a slice of opal. :-)

How are you processing? It would be good to try and tone down the purple halos on your stars there. They seem to be a side effect of the HST palette.

[miki63au]

Originally Posted by Robert_T

lovely, puts me in mind of a slice of opal. :-)

How are you processing? It would be good to try and tone down the purple halos on your stars there. They seem to be a side effect of the HST palette.

Thanks Robert,
yeah my processing skill is limited. Only PS. I don't know how to moderate the purple stars

[miki63au]

Did find in my PS has the 'Astronomy Tools' macro installed and has a violet halo reduce function. Here it is with a bit more OIII data added from last night.

[xa-coupe (Jeff)]

What a difference the extra data makes! Heaps more detail.

[Robert_T]

Originally Posted by miki63au

Thanks Robert,
yeah my processing skill is limited. Only PS. I don't know how to moderate the purple stars

if you have PS then you have all you need. Go to Filter menu, scroll down to Camera Raw Filter and select, then at right of the Camera Raw Window that comes up select Optics, and under that Defringe... then use the "purple" slide set ...set the purple hue slide to a similar colour to your Haloes and then it's simply a matter of adding a little amount 1 or 2 on the purple amount slider and watch those halos disappear...use sparingly as can create artefacts.

[miki63au]

Originally Posted by Robert_T

if you have PS then you have all you need. Go to Filter menu, scroll down to Camera Raw Filter and select, then at right of the Camera Raw Window that comes up select Optics, and under that Defringe... then use the "purple" slide set ...set the purple hue slide to a similar colour to your Haloes and then it's simply a matter of adding a little amount 1 or 2 on the purple amount slider and watch those halos disappear...use sparingly as can create artefacts.

Cheers Robert ... looking at PS, can't find 'Camera Raw Filter' however I've got Filters>Lens Correction > Custom> Chromatic Aberration sliders... looks much better ... all I need is more time to top up Ha and SII and perhaps Luminescence

(bought comp 2nd hand with PS installed, PS6 VS13.0)

[Andy01 (Andy)]

Nice image, cool colours.

Eliminating purple stars is easy - The general concept is to turn all the stars white with PhotoShop's colour noise reduction routine.

http://bf-astro.com/starColors.htm

PhotoShop's Reduce Colour Noise is used to gain this effect. On the Reduce Noise Basic Screen, set the filters "strength" to zero, "reduce colour noise" to 100% and "sharpen details" to zero and press OK. The noise reduction routine seems to identify the stars as colour noise and will set the stars to white. You may have to re-execute the filter a couple of times to get them really white. Press "Ctrl+F" to run the routine again.

Then the intensity of the white stars can be reduced by using PhotoShop's Image|Adjustments|Selective Colour routine. Select "White" in the colour drop down box. Then reduce the brightness of the white by moving the "Black" slider to the right, probably all the way, and click OK.

[AdamJL]

Love the reprocessed version. I would give a lot to have a massive focal length camera to image that core!

Great work, Mik

[miki63au]

Originally Posted by Andy01

Nice image, cool colours.

Eliminating purple stars is easy - The general concept is to turn all the stars white with PhotoShop's colour noise reduction routine.

http://bf-astro.com/starColors.htm

PhotoShop's Reduce Colour Noise is used to gain this effect. On the Reduce Noise Basic Screen, set the filters "strength" to zero, "reduce colour noise" to 100% and "sharpen details" to zero and press OK. The noise reduction routine seems to identify the stars as colour noise and will set the stars to white. You may have to re-execute the filter a couple of times to get them really white. Press "Ctrl+F" to run the routine again.

Then the intensity of the white stars can be reduced by using PhotoShop's Image|Adjustments|Selective Colour routine. Select "White" in the colour drop down box. Then reduce the brightness of the white by moving the "Black" slider to the right, probably all the way, and click OK.

Thanks Andy! Great tutorial ... tonight hopefully top up Ha and will play with PS.

[miki63au]

Originally Posted by AdamJL

Love the reprocessed version. I would give a lot to have a massive focal length camera to image that core!

Great work, Mik

Cheers Adam,
long focal length mean taxing on guiding. A few people imaged the Homunculus Nebula here. With good aperture and fast frame rate cmos it is doable

[multiweb (Marc)]

Originally Posted by miki63au

Did find in my PS has the 'Astronomy Tools' macro installed and has a violet halo reduce function. Here it is with a bit more OIII data added from last night.

The extra data did wonders to the color balance. That's the way to do it rather than replacing colors or changing ratios to taste. In a mapped SHO palette each object has a specific amount of Sii (red) Ha (green) and Oiii (blue). When the ratios are kept as per the raw data your stars will then have specific NB colors which is different from RGB stars. If your stars become purple it is because one of the color channels was streched more than the others. The correct way to balance a NB picture is to pick a background sky area devoid of nebulosity (doesn't matter if it has small stars) and use pixel math to get the same ADU across all channels. Then you have a good starting point. If you really want to get rid of the purple in your stars the most efficient way is to invert the picture (as purple will become green) and get rid of the green halos with HLVG in PS or SCNR in PI. Then invert again.

[Ryderscope (Rodney)]

That's a pretty smart image Mik. Presents our Carina very nicely indeed

[miki63au]

Thanks Marc, Rodney... so much more to learn, so little time 🙂