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Sunspots, in "white light"

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Paul Walker
(@pwalker)
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I received a text and email at 6:08 PM EDT alerting me to a solar flare that had been detect at 5:48 PM (M2.8 class solar flare at 14-Jul-2022 at 21:48:00 UTC).

10 minutes after the notice (30 minutes after the detection) I took the image below. I may or may not have gotten a picture of the flare. The 2 largest sunspots have light colored areas in the dark umbra region. I don't know whether it was one of those 2 or one of the smaller sunspot groups that produced the flare. I'm guessing it was the large spot to the lower right. I also don't know whether it was bright enough to see in white light (as opposed to Terri's H-alpha images) nor whether if it was visible whether it was still visible when I took the image.

2022-07-14  6:18 PM EDT
10in F/4 (1000mm fl) stopped down to 8" f/5 (due to using an 8" full aperture filter @ prime focus, 1/1250s @ iso200, Canon Rebel T7i camera with Baader coma corrector. Processing notes: crv-unshpR2,R2,R4-cb-cropped67%

Full resolution, cropped by 67%

 


   
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Terri Zittritsch
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Nice image Paul!   I like the 'clean-ness' of white light solar images.       I missed yesterdays imaging and could kick myself.  I was thinking of setting up right after work, and thought i'd go for a bike ride instead, and ended up doing neither. 🙁     What app do you use for solar flare alerts?

 

Terri


   
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Paul Walker
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Thanks Terri.

I signed up for alerts on https://www.spaceweatheralerts.com/.   It costs $50/yr but you can suspend or cancel any time.  They send both email and text notices.


   
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Paul Walker
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Here's a picture of the Sun with sunspots taken yesterday, Saturday, Sept. 2, 2022 from my backyard.
I continue to be surprised and pleased with the amount of detail I can see visually and image on the better days. The day before, Friday, was a day with poor seeing. Visually I have been using an 8" f/6 Orion SkyQuest Dobsonian telescope with a full aperture Orion glass solar filter. For imaging I have been using my 10" f/5.6 Newtonian with an 8" Baader ASTF 200 solar film filter which stops it down to f/7.
The images below are contrast enhanced using a histogram stretch (curves tool) and sharpened (using an unsharp mask tool).

10inF5.6, Canon T7i camera @ prime focus.
With Baader ASTF 200 (8") solar film filter.
1/800 sec @ iso 100

 
Here's a crop from the above full disk image.
On this image the smallest, medium to high contrast features, appear 2-3 pixels across.
At the camera's resolution of 0.52" (arc sec) per pixel this is 1" to 1.5" across for these features.
 
 
I also took images using a Barlow lens which gives me 2X the magnification of the prime focus shot. Here's a crop from that image.
This and the prime focus image were picked as being the best of 51 and 42 images taken respectively.
On this image the smallest, medium to high contrast features, that are visible on both images appear 3-4 pixels across.
At the camera's resolution of 0.26" (arc sec) per pixel with this setup this is 0.75" to 1.0" across for these features. This is closer to the actual resolution. This shows that the prime focus image in this case actually blurs and broadens the features slightly.
The images were taken 10 minutes apart so most the the visual differences are do to atmospheric distortion.
To give an idea of size:
Sun's mean diameter is 865,370 mi = ~30' (1800") of arc. So 1 arc sec (1") on the Sun = 480 miles.
1 px = 480mi / 0.26" = 125mi
This sunspot group spans about 520 px = 135” = 65,000 mi. or 27% the distance to the Moon
 
This post was modified 2 years ago 2 times by Paul Walker
This post was modified 1 year ago by Paul Walker

   
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Terri Zittritsch
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Nice additions Paul.   Great detail.. some nice deep shots.

 

 

Terri


   
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(@greg-erianne)
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Great images, Paul!  Geez, the size of those sunspots is absolutely amazing.  

I was waiting for the USPS to deliver a solar filter today, but was absolutely shocked when it didn't arrive -- NOT!  Would have liked to take a few shots myself.

Beautiful images...

Greg  


   
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Paul Walker
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2023-01-17  Naked Eye Sunspot.

I have been getting several email notifications of solar flares (small to medium ones).  With the Sun showing today I decided to check the sunspot situation on spaceweather.com. There I saw that were lots of spots and a message that one was big enough to see with the naked eye.  I pulled out a pair of solar viewing glasses and sure enough, I could see just see a spot in the lower left quadrant of the Sun.

After lunch I put an 8" full aperture white light solar filter on my 10" scope.  Even with the Sun so low in the South it was a beautiful sight.  The Sun was behind some clouds by the time I ate lunch and got set up.

Putting my camera on the scope I took some prime focus shots and some using a 1.5X Barlow (provides 2X with the camera).

Here is the prime focus shot and cropped image for more detail.  I superimposed a scaled image of Earth next to the large sunspot for comparison.  Note that even many of the smaller sunspots are much larger than the Earth.  I took 33 images and made a stacked the 15 best and a stack of all 33.  The 15 image stack came out sharper.

10" f/5.6 Newtonian stopped down to 8" f/6.9 with the solar filter.
Canon Rebel T7i DSLR, 1/800 sec @ iso100, stack of 15 out of 33 images.
Stacking done with AutoStakkert!3. With processing, this image has much more contrast than it had visually.
This image is at the full resolution of the camera on the 10" scope which is ~0.52"/pixel.  The smallest features are about 3 pixels wide or 1.6".  Not bad for the Winter Sun through clouds.

 
This post was modified 1 year ago 2 times by Paul Walker

   
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Terri Zittritsch
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Great images Paul...   I'm not getting notifications all of a sudden, or rather for the last month or so.      I've been looking at that ASTF film and you're showing that it works fantastically.    So this is at prime focal length 8" f6.x so around 1400mm with your DSLR.   I'd like to get one of those filters for my 7" refractor.    

 

Terri


   
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(@greg-erianne)
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I took some images of the sun today using a Baader ASTF Solar Filter for the first time. Lots of sunspots!  I haven't gone through all the images yet, but I was surprised I got fairly good results with a narrowband filter.  I tried a number of other filters but haven't had time to process all the images yet.

Askar 107PHQ Petzval Quadruplet (native 749mm fL; F/7) with a 0.7x reducer (524mm fL; F/4.9)
Baader 4" ASTF Solar Filter
ASI2600MC Pro (OSC camera)  -- Gain at 0; Exposures at 0.001s
ZWO AM5 mount with guiding via ASIAir Plus
Antlia dual narrowband filter (H-alpha/O-III) 
Image processed in Photoshop.

 

 

This post was modified 1 year ago 2 times by Greg Erianne

   
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Paul Walker
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Is this a single image or a stack?  And did you do any sharping or other contrast enhancement on it?  It looks a little "subdued" but copying onto my computer and checking it out more closely I see it has lot of detail.

Has it been suggested to use a narrow band deep sky filter on the Sun, or are you experimenting with it yourself?  

Paul


   
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(@greg-erianne)
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@pwalker This was just a single image, Paul.  I have so many different configurations I didn't stack them all (plus I only did about 5 images of each filter config).

I agree, it looked a bit subdued to me as well, but I was afraid if I made it too bright I'd lose the detail.  Maybe I should try it if you saw more detail!

No, I didn't see anything that said to use a narrowband filter so I was just trying it out (with the other filters I have) since I haven't done much solar imaging.

Greg

This post was modified 1 year ago by Greg Erianne

   
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(@greg-erianne)
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I was able to capture some images (videos) of the sun today. 

Unfortunately, I couldn't capture the entire sun even with a reducer in place since the highest resolution I could set on my ASI2600MC was 1920x1080 because I was running things through an ASIAir Plus (Raspberry Pi) which, apparently, limits the resolution for video.  Who knew?

Anyway, I think the images show how numerous sunspots are these days!

Askar 107PHQ Petzval Quadruplet (native 749mm fL; F/7) with a 0.7x reducer (524mm fL; F/4.9)
Baader 4" ASTF Solar Filter
ASI2600MC Pro (OSC camera) -- Gain at 0; Exposures at 0.015s; Resolution 1920x1080; 13 fps
ZWO AM5 mount with guiding via ASIAir Plus
Meade 13% Moon Filter
Videos processed in AS!3
Image processed in ImPPG and Photoshop.


   
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Paul Walker
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Oh yes, very nice detail and contrast.

I took some images yesterday, the day before that and on the 8th.  I haven't processed today's yet but I do have yesterday's.

2023-02-12 Sunspots 10inF5.6 prime focus, Canon Rebel T7i, still shots- 1/800 sec @ ISO 100.  I have been taking my solar and Moon images as high-quality JPG's rather than in RAW format partly to save space and partly because when stacking several images one will be hard pressed to tell the difference in the final result. Stacked 30 out of 164.  Stacked with AutoStakkert!3.

Normally I only do one round of wavelet sharpening in Registax.  However, it is not uncommon for me to do 2 rounds of unsharp mask sharping with Picture Window Pro 7 decided to do a maximum wavelet at the lowest level (smallest spacial resolution), save the image, open the saved image and to an 2nd round.  For those familiar with Registax wavelets you will probably understand at least part of my shortcut "code" where "w" stands for wavelets and the numbers following it are the slider settings for each of the 6 levels -- w100,1,1,1,1,1-w50d015,10,1,1,1,1  --  There is a dash between the 1st and 2nd rounds of wavelet application. For those not familiar, each level goes from -5 go 100 (1 is the default setting).  For each level one can change a denoise setting.  This is denoted as a "d" in my "code".  So in the 2nd round I set the first level wavelet to 50 with a denoise setting of 0.15.  It is very easy to overdo the wavelets.

 


   
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(@greg-erianne)
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@pwalker Beautiful image, Paul.   I tried ImPPG for the first time today instead of Registax. ImPPG uses deconvolution rather than wavelets and I seemed to better understand what it was doing since PixInsight uses deconvolution.  It's really a nice, simple application and easy to use once you play around with the controls a bit.

Greg


   
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Paul Walker
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Thanks.  I'll have to download and try ImPPG.  Deconvolution is one thing I don't have that I would like to have.

Paul


   
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