White light/Wedge questions

[Ant-33]

Hi folks,

Many of you are very experienced and knowledgeable, and I know a lot of you use some pretty impressive gear – I'm pretty new to solar imaging, and I'd highly value some feedback on my early efforts.

I figured I'd get started with a Herschel Wedge. I chose the Lunt 1.25” wedge, and at the same time I got a polarising filter, a uv/ir cut filter and a Baader SC filter. Hopefully this will give me a good start. I began by using it with my Evostar 80ED on an AZ-EQ6 mount. For imaging I used a QHY5l-iic, and captured in .avi format. As it was a try-out I took a couple of short vids and turned to the processing. This one was 200 frames, and I used the best 30% in Registax, mostly with default settings, to give me a 16-bit tiff file, which I then processed in PS. All I did for processing was to make adjustments in levels and curves, treating R, G and B separately. Here's the result:

 

So, I have a lot of questions.

1. Am I on the right track with my approach to this? There is plenty I'd like to improve, but if that detail is real, I'd feel pretty pleased with this as a first effort – but I don't want to be misleading myself.

2. Having imaged using the SC filter, the starting point was, as expected, basically green. What I didn't expect was that when bringing out the details in PS processing, I'd bring out more orange and less green. Is this what you'd expect?

3. The surface detail shows pretty well in the centre of the Sun, but towards the edges it all flattens. Is the detail there in the data, but I've failed to extract it?

4. The two sunspots are okay – but I'd like to have got better detail if possible. Do you think better focus would help this? Better processing?

5. There are three shadows on the image – the most obvious one being the big round shadow just above the two sunspots. Is this a feature of the Sun or is it something in my imaging setup?

Thank you in advance for any advice/help you give.

Clear skies

Tony

[laudropb]

Hi Tony. I use the Lunt wedge and continuum filter, but can't really help with you questions as I do not do any photography. I am sure some of our experts will be along soon, but I can say that the shadows you have do not appear visually.

[Ant-33]

Just now, laudropb said:

Hi Tony. I use the Lunt wedge and continuum filter, but can't really help with you questions as I do not do any photography. I am sure some of our experts will be along soon, but I can say that the shadows you have do not appear visually.

Thanks for the reply - yes, I guessed it's more to do with my setup than real features, but it's nice to be sure

Cheers Tony

[Peter Drew]

Focus looks ok but the exposure doesn't look quite right although I'm not an imaging expert. The shadows are out of focus dust bunnies, most likely on the sensor.

[xtreemchaos]

hi mate, +1 for dust bunnys, you can get rid with a rocket blower, i get my best results with using my dslr, 1.5x barlow,lunt H wedge, and shooting in mono, i get the full disc, i use my ccd with closeups. charl.

[Ant-33]

18 minutes ago, Peter Drew said:

Focus looks ok but the exposure doesn't look quite right although I'm not an imaging expert. The shadows are out of focus dust bunnies, most likely on the sensor.

Thanks Peter - I didn't think of dust bunnies, but I'll clean up before my next session and see if it goes away. As for exposure, I think I need some trial and error - this was 15ms frames, but there's definitely scope for experimentation.

 

9 minutes ago, xtreemchaos said:

hi mate, +1 for dust bunnys, you can get rid with a rocket blower, i get my best results with using my dslr, 1.5x barlow,lunt H wedge, and shooting in mono, i get the full disc, i use my ccd with closeups. charl.

Hi - many thanks - yes, I'm planning to try with the dslr too, and a quick snap will show me what I need, if anything, by way of a barlow. I'll definitely be checking for those dust bunnies.

Cheers

Tony

[Stu]

I'm not an imager, other than the occasional attempt. What I'm confused about is the orange in the image. The Continuum filter is a narrow band filter so should only allow a frequency of light through that is green. Any time I have done imaging the results are a very pure green colour. I normally convert it to mono and go from there because it is basically a mono image anyway.

[Lowjiber]

Looks like you're off to a good start.

That's definitely a dust bunny.  I'm not familiar with that particular cam, but sometimes in a hurry you can move the image to another part of the chip to finish the capture session... then clean the dust bunny afterwards.

Thanks for sharing your first image.

Clear Skies

[Ant-33]

1 hour ago, Stu said:

I'm not an imager, other than the occasional attempt. What I'm confused about is the orange in the image. The Continuum filter is a narrow band filter so should only allow a frequency of light through that is green. Any time I have done imaging the results are a very pure green colour. I normally convert it to mono and go from there because it is basically a mono image anyway.

Yes, I had the same thought. If I look at the filter bandpass graph, it's all in the green part of the spectrum - so I too am confused about why there's so much red and blue in it. The image I started with before processing in PS was definitely green to look at, but that in itself doesn't mean there is no red or blue in the image - I'm just not sure how the red and blue got past the SC filter. Perhaps somebody will be able to explain.

[Ant-33]

1 hour ago, Lowjiber said:

Looks like you're off to a good start.

That's definitely a dust bunny.  I'm not familiar with that particular cam, but sometimes in a hurry you can move the image to another part of the chip to finish the capture session... then clean the dust bunny afterwards.

Thanks for sharing your first image.

Clear Skies

Thank you  Yes, I've taken a close look and there was a tiny bit of dust on the sensor, so I've used my photographer's lens-blower to get rid of it. I guess it's worth checking before using it as well.

Turning the camera is a good idea - but the shadow didn't show up until I'd processed the image, so it was too late for that. It's certainly something I'll keep an eye out for, though.

[michael.h.f.wilkinson]

With the Baader Solar Continuum filter I would just use the green band as a grey-scale image. You are most likely inflating any residual IR leakage by incorporating red. Having said that, there is a sunspot on the image, and some granulation, so it is a good start

[Ant-33]

4 minutes ago, michael.h.f.wilkinson said:

With the Baader Solar Continuum filter I would just use the green band as a grey-scale image. You are most likely inflating any residual IR leakage by incorporating red. Having said that, there is a sunspot on the image, and some granulation, so it is a good start

Thanks Michael. I suppose I'd expect there to be very little IR in it, since I had not only the SC filter, but the Baader uv/ir cut filter - but having said that, as you say, there could be some leakage, since no filter is perfect. I'll try reprocessing with only the green channel and see what I can get in terms of detail. Many thanks for the encouraging words.

[Drop Of Sun]

My first guess would have been IR leak but as you are using UV/IR cut maybe what is happening is that some of the green wavelength is being recorded on the red pixels too. e.g. see this curve (not specific to your sensor, but maybe gives an idea?):

Source: http://www.astrosurf.com/luxorion/photo-ir-uv3.htm

Looking at your image in Photoshop it looks to me like you have stretched the red channel a lot? I can see streaky lines, which look like low level sensor noise, which suggests to me the red signal was much weaker and you boosted it to match the green. I may be wrong, I am just guessing.

Using the green channel looks to be the solution!

The details you captured are looking good to me, you just need more practice and the rest will come, it's a great first image.

Once you have your nice detail from the green channel, my suggestion is try using Smart Sharpen to sharpen things up a touch. Your stacked image will usually be a bit blurry but should respond very well to sharpening. The stacked image is usually more blurry than your sharpest image in the capture, but stacking massively reduces the noise, letting you push sharpening quite a lot, more so than you could do with a single frame. Though sometimes a single frame can be very good!

The IR cut is probably a good idea, IR light can blur up an image taken with a refractor if the sensor records it.

The mark looks like a dust bunny to me too. One way to remove them is by recording a flat image, which you can then use with the stacking software to hopefully remove it. Roger did a nice solar tut here which also covers flat frames:

 

[Ant-33]

22 minutes ago, Drop Of Sun said:

My first guess would have been IR leak but as you are using UV/IR cut maybe what is happening is that some of the green wavelength is being recorded on the red pixels too. e.g. see this curve (not specific to your sensor, but maybe gives an idea?):

Source: http://www.astrosurf.com/luxorion/photo-ir-uv3.htm

Looking at your image in Photoshop it looks to me like you have stretched the red channel a lot? I can see streaky lines, which look like low level sensor noise, which suggests to me the red signal was much weaker and you boosted it to match the green. I may be wrong, I am just guessing.

Using the green channel looks to be the solution!

The details you captured are looking good to me, you just need more practice and the rest will come, it's a great first image.

Once you have your nice detail from the green channel, my suggestion is try using Smart Sharpen to sharpen things up a touch. Your stacked image will usually be a bit blurry but should respond very well to sharpening. The stacked image is usually more blurry than your sharpest image in the capture, but stacking massively reduces the noise, letting you push sharpening quite a lot, more so than you could do with a single frame. Though sometimes a single frame can be very good!

The IR cut is probably a good idea, IR light can blur up an image taken with a refractor if the sensor records it.

The mark looks like a dust bunny to me too. One way to remove them is by recording a flat image, which you can then use with the stacking software to hopefully remove it. Roger did a nice solar tut here which also covers flat frames:

 

Hi there - many thanks for your reply. I think I understand what you mean and what the graph is saying - it seems to suggest that the sensor will record some red on receipt of green photons - is that correct?

I've tried reprocessing using the green-only channel in monocrhome, and then doing the same exercise with levels and curves. I've also tried the smart-sharpen function, and oh boy! Yes, it does make a difference. As with all these adjustments it's hard to know how far to go, but I used 100% with a radius of about four pixels - that seemed to give the best result, although it's only a first stab. I've been trying to upload the result to flickr, but it's timing out, so I'll try again in a bit, and post the result. I think it's already a big improvement on what I posted above.

Many thanks for your suggestions and for the encouraging comments.

Cheers, Tony

[Ant-33]

1 hour ago, Drop Of Sun said:

The mark looks like a dust bunny to me too. One way to remove them is by recording a flat image, which you can then use with the stacking software to hopefully remove it. Roger did a nice solar tut here which also covers flat frames:

I just had a read of this, and it's an excellent tutorial - many thanks for the link.

[Ant-33]

So, I've taken on board the comments here - I've used the green channel only and converted it to monochrome, then played with levels and curves. I've also used smart-sharpen (works a treat), and here is the result:

 

Then I wondered what it would be like with some false colour, so I tried adding some, and ended up with this:

 

The dust bunnies are very evident in the picture, but I'm stuck with that. Otherwise, I'd appreciate any more feedback on how I'm doing.

Thanks so much to all who have given feedback to get me to this point! I think this is a great improvement on my first image at the beginning of the post. False colour isn't to everybody's taste, but to me it brings the image to life somewhat.

Clear skies

Tony

[Drop Of Sun]

Nice one, Tony. That's how I read the sensor graph, that the red will record some green light, though I am no expert on CCDs. Lots of sharp detail in your image! What I'd suggest is just more practice, and take a look at some high res pics takes with larger scopes, as it will give you a feel for the kind of structures you are imaging. In your iimage the structures are very fine and I feel knowing what it looks like in larger scopes can help guide you with the sharpening.

I'd suggest Alexandra's amazing white light images for inspiration! I hope they don't intimidate, as they are sensationally good!:

 

[Ant-33]

52 minutes ago, Drop Of Sun said:

Nice one, Tony. That's how I read the sensor graph, that the red will record some green light, though I am no expert on CCDs. Lots of sharp detail in your image! What I'd suggest is just more practice, and take a look at some high res pics takes with larger scopes, as it will give you a feel for the kind of structures you are imaging. In your iimage the structures are very fine and I feel knowing what it looks like in larger scopes can help guide you with the sharpening.

I'd suggest Alexandra's amazing white light images for inspiration! I hope they don't intimidate, as they are sensationally good!:

Wow! Now, he's done some sensational pictures. Curiously it doesn't intimidate me - rather it inspires me. I know my optical setup won't get that sort of resolution, but I think there's a lot I can hope to achieve with what I have. It's interesting that the white light setup allows for narrowband imaging - but that it really depends on the sensitivity of the camera in those parts of the spectrum. Plenty of food for thought.

Many thanks, Tony.