6 replies to this topic

[t.mihai147]

I am trying to fight light pollution and cold winter with initial steps in EAA for DSOs.

My setup is based on IMX585c camera and SVBony 7nm dual band filter (SV220). I have used AZ Mount and now Ragdoll 20 in AZ mode with 20s exposures stacked for 5-10 minutes when the DSOs are starting to get cleaner than initial capture. Sky is B7-B8.

I had great results from the beginning as I could immediately see some of the brightest nebulae (California, Rosette, Horse Head, Flame, Christmas tree, Heart and Soul, etc) in couple of minutes. I have used 300mm F4 tele lens and 8" F6 newton for different image scale.

I have also seen galaxies but for them I used no filter and a mono camera (IMX462m chip).

 

While I am happy with what I can see with such simple setup, I am comparing my EAA short exposures with some of more colorful pictures from more experienced users.

My own EAA captures are showing almost exclusively red targets, except the stars. Sometimes I can see very thin blue filaments in Crab nebula but that's it. How come the filter is dual band (Oiii and Ha) but I get almost only Ha signal in my exposures?

I have also tried different targets where the Oiii signal was predominant but I could not get any picture in the short exposure time allowed by AZ mount (20-30 sec max).

If I would try to use different filters with manual filter wheel my understanding is that SharpCap is not the right tool as it gets too complicated for EAA (due to different exposure parameters for different filters).

I do not want to go into complicated process of post processing implied by Astrophotography as my goal is to see in shortest possible time as many targets as possible (like in general public outreach events).

Do you have any advice for a simple EAA process that would show other bands apart from Ha? DO I need another filter or camera?

Thank you

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[t.mihai147]

Here it is another capture that I know should have also other signal apart from Ha in the Flame nebula

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Edited by t.mihai147, 11 January 2025 - 04:02 AM.

[BucketDave]

Generally, there is much more hydrogen in the universe than any other chemical. The same applies to the nebula that we see. They are mostly hydrogen but sometimes you get a bit of oxygen, nitrogen or sulphur as well. The pretty pictures people produce with lots if blue are because the blue light (oxygen) has been amplified in post-processing, relative to the hydrogen.

There is one type of object which does have more oxygen - planetry nebula (e.g. M27). Some supernovae also have significant quantities of oxygen (e.g. the Veil).

[zveck]

I think you have focus/collimation issues

[tcm2007]

The other colours usually come out in post processing - with the SV200 you can extract the B and G channels and use them as Oiii, trat the R as Ha and then recompose as though you had shot in narrowband. Doing it "live" with EAA would be tricky.

[t.mihai147]

I think I found the answer in above post plus the other entry here

https://www.cloudyni.../#entry13892384

 

Without post-processing it seems I cannot see too much except some planetary nebulae.

Thank you

 

I think you have focus/collimation issues

This is another aspect that is not related to my question. Manual focusing an objective lens is tricky, I know. But seeing the DSO is the main goal, even if the stars are not perfect.

[psienide]

Generally in most targets the Ha is going to overpower and stomp all over everything else. Without processing, your color image is just going to reflect that.

What I might suggest is using livestacking mode in a program that will allow you to easily view the individual channels.

In Siril you can do livestacking and tab through the R G B channels to see the individual data from each. Not as good as seeing the mix in the color image, but at least will allow you to view the individual signals from each band.