14 replies to this topic

[ATL Gator]

I think I'm slowly getting the hang of H-alpha imaging thanks to the great advice on this forum as well as the very helpful imaging tutorials by Marty/MalVeauX.

 

Here are two B&W images I captured today showing the sun (1) in "natural" light and (2) inverted. Both are composites -- separate exposures for the surface and proms -- as I haven't yet mastered the art of capturing everything in a single image. (When I exposure for the surface and try to bring out the proms in post-processing, they tend to come out looking noisy.) These images were captured using a ZWO ASI178MM camera attached to a double-stacked Lunt LS50. Transparency was good; seeing was average.

 

Settings were as follows:

• Exposure (surface): 6ms
• Gain (surface): 40
• Frames: 2000
• Exposure (proms): 6ms
• Gain (proms): 255
• Frames: 2000

I used SharpCap 3.2 for the capture and AS!3 to stack the best 20%. Sharpening in ImPPG and Photoshop.

 

Constructive feedback is very much appreciated!

Attached Thumbnails

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Edited by ATL Gator, 23 February 2021 - 07:28 PM.

[MalVeauX]

Fantastic discs Scott!

 

Very best,

[Jim Waters]

Real nice images and processing.

[peterm]

They look good Scott.  I have been using 80-90 gain for the surface for my single stack images. I think I will try 40 as you have when I try double stacking again.  

[PhotonJohn]

Great job on the proms Scott.

[dhkaiser]

Well done.

[rigel123]

Those look great Scott!  When you open your images in Photoshop does it open up the Camera Raw Box where you can adjust Clarity, Contrast etc?  I find Clarity helps to bring out proms in a single shot for both proms and surface for images done with a double stack.

[TheCrimson_King]

These are really good. They give me an aspirational goal for my 50 mm Lunt (single stack) & same sensor.

[chemman]

Beautiful images Scott!   

 

It was nice to see a relativly good amount of activity today.  My full disk was relativly easy to get more or less aligned with GOhttps://gong2.nso.ed...figs/hAlpha.cfgNG.  If at some point you decide to increase your magnification it sometimes is easy to navigate to features using GONG as a refrence map, at least for me anyhow.  

 

Chuck

[BYoesle]

Hi Scott,

 

Those are very good images.   You may just need a little adjustment for getting better prominence values to come up.

 

Be sure you're properly tuned with both etalons and have little to no double limb from photosphere parasitic continuum leaking through. This brightens the disc and makes bringing out prominences more difficult.

 

 

In my experience, while it is counter intuitive, your single image should generally have a little under-exposure. This is especially important for not oversaturating any active areas. Try no gain, as little gamma as possible, and keep your histogram values to the left rather than centered. Later in processing you can adjust the histogram or change highlights, mids, etc. to bring out more details:

 

Click for larger.

 

Experimentation has been key for me to see what works and what doesn't. 

[Hank Molesky]

I can see images are absolutely beautiful. I can only see you getting better at it.

[ATL Gator]

Those look great Scott!  When you open your images in Photoshop does it open up the Camera Raw Box where you can adjust Clarity, Contrast etc?  I find Clarity helps to bring out proms in a single shot for both proms and surface for images done with a double stack.

Thanks, Warren. I'll have to try that -- haven't had much luck with capturing both proms and surface detail in a single shot yet.

[ATL Gator]

These are really good. They give me an aspirational goal for my 50 mm Lunt (single stack) & same sensor.

Thanks -- I wasn't sure what to expect from an "entry level" H-alpha telescope (albeit an expensive one), but this little scope really has me impressed.

[ATL Gator]

Beautiful images Scott!   

 

It was nice to see a relativly good amount of activity today.  My full disk was relativly easy to get more or less aligned with GOhttps://gong2.nso.ed...figs/hAlpha.cfgNG.  If at some point you decide to increase your magnification it sometimes is easy to navigate to features using GONG as a refrence map, at least for me anyhow.  

 

Chuck

Thanks, Chuck. Good suggestion. I have experimented a little with a GSO 2x barlow but so far I haven't gotten very good results -- the images are larger but the resolution isn't any better. I'm guessing that the seeing here in ATL hasn't been steady enough to support imaging at a higher magnification with my set-up. I'm hoping for better results once the jet stream moves on and/or the sun is higher in the sky.

[ATL Gator]

Hi Scott,

 

Those are very good images.   You may just need a little adjustment for getting better prominence values to come up.

 

Be sure you're properly tuned with both etalons and have little to no double limb from photosphere parasitic continuum leaking through. This brightens the disc and makes bringing out prominences more difficult.

 

double stacking non-normalized.jpg

 

In my experience, while it is counter intuitive, your single image should generally have a little under-exposure. This is especially important for not oversaturating any active areas. Try no gain, as little gamma as possible, and keep your histogram values to the left rather than centered. Later in processing you can adjust the histogram or change highlights, mids, etc. to bring out more details:

 

Image capture settings.jpg

Click for larger.

 

Experimentation has been key for me to see what works and what doesn't. 

Thanks, Bob -- I appreciate the detailed suggestions. Your advice regarding underexposing the disk is helpful as I've been struggling with how to capture surface detail without blowing out the highlights in bright active regions like the one that was visible today.