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Six days with PST

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Astrophil
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Six days with PST

Post by Astrophil » Tue Oct 08, 2019 5:58 pm

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

20191001_110836_acm.jpg
20191001_110836_acm.jpg (419.3 KiB) Viewed 162 times
20191002_095133_acm.jpg
20191002_095133_acm.jpg (408.53 KiB) Viewed 162 times
20191003_135633_acm.jpg
20191003_135633_acm.jpg (403.07 KiB) Viewed 162 times
20191004_121510_combo_cc.jpg
20191004_121510_combo_cc.jpg (618.34 KiB) Viewed 162 times
20191005_125217_combo.jpg
20191005_125217_combo.jpg (351.13 KiB) Viewed 162 times
20191006_101605_combo_afc.jpg
20191006_101605_combo_afc.jpg (407.35 KiB) Viewed 162 times

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marktownley
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Re: Six days with PST

Post by marktownley » Tue Oct 08, 2019 7:52 pm

You got a nice set there Phil.
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http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!

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Re: Six days with PST

Post by MalVeauX » Wed Oct 09, 2019 12:18 am

Pretty cool Phil, and good details are definitely seen! I think you have it dialed in as much as it can be.

Very best,

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Re: Six days with PST

Post by Starry Jack » Wed Oct 09, 2019 3:28 am

Really clean!
Explore Scientific 152mm f6.5 achromat
Aeries D-ERF
Quark Chromosphere f27 native, (f14 when focal reduced)
Mallincam .5x focal reducer (large format)
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Re: Six days with PST

Post by MAURITS » Wed Oct 09, 2019 7:36 am

Nice story Phil, well done.
Regards,
Maurits

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Montana
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Re: Six days with PST

Post by Montana » Wed Oct 09, 2019 9:14 am

Well done Phil, these are terrific :bow you worked really hard to achieve the best possible results :hamster:

Alexandra

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Re: Six days with PST

Post by Martin_S » Wed Oct 09, 2019 11:27 am

Great Imaging Phil. well done

Martin

Astrophil
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Re: Six days with PST

Post by Astrophil » Wed Oct 09, 2019 4:47 pm

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


.
20191006_100718_acm.jpg
20191006_100718_acm.jpg (387.04 KiB) Viewed 93 times

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Carbon60
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Re: Six days with PST

Post by Carbon60 » Wed Oct 09, 2019 6:09 pm

Excellent work, Phil.

Your persistence and hard work paid off. Lovely FDs

Stu
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Re: Six days with PST

Post by ffellah » Wed Oct 09, 2019 11:08 pm

Lovely results, Phil.

Franco

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Re: Six days with PST

Post by MapleRidge » Thu Oct 10, 2019 12:02 am

Superb series of full disk images Phil...excellent work :bow

Brian
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hopskipson
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Re: Six days with PST

Post by hopskipson » Fri Oct 11, 2019 12:19 pm

Nice images!

I’m jealous you got 6 days in a row to image.

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Re: Six days with PST

Post by eroel » Fri Oct 11, 2019 3:08 pm

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 :roll:
Best regards,
Eric.

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Re: Six days with PST

Post by Astrophil » Sat Oct 12, 2019 12:52 am

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

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