Six days with PST
Six days with PST
The skies were reasonably clear last week and the Sun's surface features were still rather uneventful so I took the opportunity to image with the PST double stacked. The objective was to consistently produce an acceptable full disk image with detail over at least most of the surface and devoid of the usual hot spot which required a lot of post processing to control.
I re-read the recent posts pertaining to PST imaging and searched through old ones. While most suggestions dealt with tuning between the etalons and adjusting tilt, which I found very difficult to determine on band with a blank sun, other suggestions mentioned placement of the disk in the field and rotating components. I would try them all. I had previously removed the black box from the PST and set it up for straight through imaging. All components could be rotated individually.
To make a short story longer picture this. The front etalon, the tilt mechanism, the main etalon, blocking filters, and camera. All can effect the image and all are interrelated. So, five degrees of freedom for a non optical engineer to contend with. After a while it was determined that the rotation between the front etalon and tilt mechanism was unnecessary as was the main etalon rotation in relation to the objective lens (optical tube). Both were tightened to their original positions. This simplified things a little.
Monitoring a high contrast, over exposed image on the computer screen, the solar disk was kept centered on the hot spot (sweet spot?). While making rotational adjustments to the double stack the spot could be moved closer to the center of the field. Minimum tilt was used to move the reflection just off field. Camera rotation helped as well. The PST eyepiece holder with the blocking filters still intact was rotated and the obnoxious glow off to one side of the disk was reduced somewhat. Progress.
Tuning the etalons on this double stacked PST was done by slowly rotating the main etalon counter clockwise in steps and adjusting the double stack to increase the intensity of the hot spot. Luckily there was a bright region near the limb to watch. Exposure was adjusted to maximize visibility. When contrast between the surface and the active region appeared the best, I centered the disk on the hot spot, lowered exposure and contrast, and hit record.
Unfortunately, these adjustments did not completely eliminate the brighter center produced by this PST and post processing was still required. I decided to use a flat frame to help with uniformity. A diffusing material was placed over the front of the scope and exposure time was increased along with gain to approximately match the original histogram. With this diffuser the exposure needed to be increased to 1 sec. That produced a noisy flat and was median filtered before applying. Minimum post processing was required for field illumination but now I notice Newton rings that I had not seen before.
The attached test images represent six days imaging with a double stacked PST. The last three images were flat corrected.
Phil
I re-read the recent posts pertaining to PST imaging and searched through old ones. While most suggestions dealt with tuning between the etalons and adjusting tilt, which I found very difficult to determine on band with a blank sun, other suggestions mentioned placement of the disk in the field and rotating components. I would try them all. I had previously removed the black box from the PST and set it up for straight through imaging. All components could be rotated individually.
To make a short story longer picture this. The front etalon, the tilt mechanism, the main etalon, blocking filters, and camera. All can effect the image and all are interrelated. So, five degrees of freedom for a non optical engineer to contend with. After a while it was determined that the rotation between the front etalon and tilt mechanism was unnecessary as was the main etalon rotation in relation to the objective lens (optical tube). Both were tightened to their original positions. This simplified things a little.
Monitoring a high contrast, over exposed image on the computer screen, the solar disk was kept centered on the hot spot (sweet spot?). While making rotational adjustments to the double stack the spot could be moved closer to the center of the field. Minimum tilt was used to move the reflection just off field. Camera rotation helped as well. The PST eyepiece holder with the blocking filters still intact was rotated and the obnoxious glow off to one side of the disk was reduced somewhat. Progress.
Tuning the etalons on this double stacked PST was done by slowly rotating the main etalon counter clockwise in steps and adjusting the double stack to increase the intensity of the hot spot. Luckily there was a bright region near the limb to watch. Exposure was adjusted to maximize visibility. When contrast between the surface and the active region appeared the best, I centered the disk on the hot spot, lowered exposure and contrast, and hit record.
Unfortunately, these adjustments did not completely eliminate the brighter center produced by this PST and post processing was still required. I decided to use a flat frame to help with uniformity. A diffusing material was placed over the front of the scope and exposure time was increased along with gain to approximately match the original histogram. With this diffuser the exposure needed to be increased to 1 sec. That produced a noisy flat and was median filtered before applying. Minimum post processing was required for field illumination but now I notice Newton rings that I had not seen before.
The attached test images represent six days imaging with a double stacked PST. The last three images were flat corrected.
Phil
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Re: Six days with PST
You got a nice set there Phil.
http://brierleyhillsolar.blogspot.co.uk/
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Re: Six days with PST
Pretty cool Phil, and good details are definitely seen! I think you have it dialed in as much as it can be.
Very best,
Very best,
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Re: Six days with PST
Really clean!
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Aeries D-ERF
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Mallincam .5x focal reducer (large format)
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Re: Six days with PST
Well done Phil, these are terrific you worked really hard to achieve the best possible results
Alexandra
Alexandra
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Re: Six days with PST
Great Imaging Phil. well done
Martin
Martin
H alpha : ,Skywatcher 120mm F8 open frame refractor, a tilted 2" 7nm H-alpha filter as a sub energy rejection filter, Baader TZ4 telecentric focal extender, Player One energy rejection filter, Combo Quark Chromosphere, Naked PST etalon for double stacking, ASI74mm camera
Re: Six days with PST
Thank you all for the kind comments.
Mark, your encouragement is always well received.
Marty, I much appreciate your practical solutions to problems. Most recently the cereal bag flat and source for the adapter to put this together.
Alexandra, the spectacular PST images you present really serve as a guide and a goal for us beginners.
And to all the other members here who provide knowledgeable and unpretentious advice, thanks.
So now, to gild the lily before retiring the PST, awaiting a more active Sun, here's the final take from October 6th.
Phil
.
Mark, your encouragement is always well received.
Marty, I much appreciate your practical solutions to problems. Most recently the cereal bag flat and source for the adapter to put this together.
Alexandra, the spectacular PST images you present really serve as a guide and a goal for us beginners.
And to all the other members here who provide knowledgeable and unpretentious advice, thanks.
So now, to gild the lily before retiring the PST, awaiting a more active Sun, here's the final take from October 6th.
Phil
.
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Re: Six days with PST
Excellent work, Phil.
Your persistence and hard work paid off. Lovely FDs
Stu
Your persistence and hard work paid off. Lovely FDs
Stu
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Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
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Re: Six days with PST
Superb series of full disk images Phil...excellent work
Brian
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Photos: https://www.flickr.com/photos/185395281@N08/albums
10'x15 Roll-off Roof Observatory
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Planetary Work - SBIG CFW10, ASI462MM
2.2m Diameter Dome
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Orion EON 130ED, f7 OTA for Day & Night Use
Ha Setup: Lunt LS80PT/LS75FHa/B1200Ha + Home Brew Lunt Double Stack/B1800Ha on the Orion OTA + Daystar Quantum
WL, G-Band & CaK Setup: Lunt Wedge & Lunt B1800CaK, Baader K-Line and Altair 2nm G-Band filter
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Re: Six days with PST
Nice images!
I’m jealous you got 6 days in a row to image.
I’m jealous you got 6 days in a row to image.
James
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Coming Soon: Solar Spectrum CaK II <1A filter
These pretzels are making me thirsty! (C.C.)
The Quark introduced me to this wonderful side of the hobby and the sun hasn’t disappointed yet.
Solar Equipment: Solar Spectrum RG-18 0.3A, Coronado Solarmax 90mm etalon Isle of Man SN-001, Tuscon SN-380 and Meade SM2, Lunt LS80 DS, Quark Chromosphere, Lunt 2" wedge, 2-Lunt CaK II 1200, Baader 3.8 and 5.0 solar film in 208mm cells, and 3D printed Sol'Ex SHG, Lunt 40mm
Coming Soon: Solar Spectrum CaK II <1A filter
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Re: Six days with PST
Phil:
Clean and sharp FD´s, the result of hard work tweaking the filters to their best position.
I don't know if you already got to the point that gives you the best adjustments with the scope pointing East, but when you go to the West side you loose the adjustment. Here you try to get the best adjustment possible E and W, or you try to image just on one side with the best adjustment possible, that is why I just image at home before lunch
Best regards,
Eric.
Clean and sharp FD´s, the result of hard work tweaking the filters to their best position.
I don't know if you already got to the point that gives you the best adjustments with the scope pointing East, but when you go to the West side you loose the adjustment. Here you try to get the best adjustment possible E and W, or you try to image just on one side with the best adjustment possible, that is why I just image at home before lunch
Best regards,
Eric.
Re: Six days with PST
Thanks Stu, Franco, Brian, and James. Six days in a row was exhausting, I had to take the next day off.
Eric, interesting info. I too image before lunch. Too many obstacles in the afternoon.
Phil
Eric, interesting info. I too image before lunch. Too many obstacles in the afternoon.
Phil