blocking filter chit chat chop chop - lets cut it out.

Frankenscope? Let's see it!***be advised that NOTHING in this forum has been safety tested and you are reading and using these posts at your own peril. blah, blah, blah... dont mess around with your eyesight when it comes to solar astronomy. Use appropriate filtration at all times...
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Re: blocking filter chit chat chop chop - lets cut it out.

Post by Montana »

Thanks :) What would happen if you used just one of these filters combined with your regular blocking filter, would this reduce the out of band stray light?

Alexandra


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by MalVeauX »

I look forward to the results! My weather is not cooperating, but I will attempt to stack a 1.7A with a standard 6A to see how that effects things, I have plenty of transmission to spare. I will report when my clouds go away!

Very best,


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by marktownley »

Thanks JAPP for your detailed post.

I know we've talked previously about the differences in Coronado blocking filters, all of mine are different. I've had some interesting initial results using a quark running at <f15 that gives an interesting increase in contrast when used with another eg front mounted etalon so I can see how your blocking filter design would be beneficial.

What is the clear diameter of these? They look 7-8mm i'm guessing?

Looking at the plots, I assume a bit of tilt to bring them blue would be beneficial too?

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Re: blocking filter chit chat chop chop - lets cut it out.

Post by Valery »

Been there, done this - several years ago with exactly the same Andover, but with 12.5mm filters - of the same size as front BF in a standard Quark.
Tried with Quarks. No gain at all, just makes a picture much dimmer and much less uniform than in original Quarks.
These filters were constructed for F/5 incoming light cone - to make them useable in Quarks installed in F/5-F/6 small refractors.

Better to spend money and efforts for coupling of the PST etalon with Quarks which I did then with a full success. For the same $500 I get a bandwidth of less than 0,25A double staked - with a very steep skirt of the tansmission curve. See attached picture how the dark filament is seen through such a DS system in a C11 telescope with a front mounted ARIES DERF.
Attachments
_2017 07 20 UT06h50m C11+ARIES DERF+DS QUARK + PST.png
_2017 07 20 UT06h50m C11+ARIES DERF+DS QUARK + PST.png (1.06 MiB) Viewed 5128 times
Last edited by Valery on Tue Feb 23, 2021 10:00 pm, edited 1 time in total.


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by christian viladrich »

Hello,
Years ago, I tested a Thousand Oaks 0.9 A as a complemetary filter with my DayStar 0.6A.
The "classic" Ha 0.9 A filter from TO was a stack etalon + various ITF/BF filters.
TO sent me the etalon part of it (i.e. without any additional filter).

The result was very interesting (left DayStar PE 0.6 A, right DayStar PE 0.6 + TO 0.9 A):

http://astrosurf.com/viladrich/astro/in ... TO09-a.jpg

http://astrosurf.com/viladrich/astro/in ... TO09-b.jpg

The 0.6 A + 0.9 A combination (right) gave similar results as the Ion 0.3 A(left) :

http://astrosurf.com/viladrich/astro/in ... TO09-a.jpg

Still, the main issue was the non uniformity of the TO 0.9A, and some banding due to the distance between CWL and Ha.
More info here:
http://astrosurf.com/viladrich/astro/in ... rast-2.htm

Andover filters are for sure more uniform and more up to the specs.

Having a 0.9A to 1.5 A etalon stacked on a "main" etalon is certainly a good idea. A 1.5 A + 0.6A combination results in a selectivity similar to a 0.3 simple stack etalon.


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by marktownley »

Different ways to achieve similar things in some respects!


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by marktownley »

Hey there Japp.

More questions from me; when Andover test these filters and produce the transmission curves above, what kind of beam is this done in? Converging, collimated or telecentric?

Thanks in advance.

Mark


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by MalVeauX »

Hello,

I'm trying to assemble a unit currently.

Do you think a 1.7A filter and a standard Coronado BF 5~6A filter will do this? Or does it need to be both filters near 1.7~1A after tilt?

I'm trying to currently assemble an ITF (maier I think), 1.7A filter in a tilt chamber of a sky bender, followed by a 5mm or 10mm typical Coronado blocking filter. If I can get this to assemble and work, I will have it follow a PST etalon in an imaging train.

My current challenge is being able to mount the 1.7A filter in the sky bender and have room to tilt.
DoubleBFBuild.jpg
DoubleBFBuild.jpg (130.2 KiB) Viewed 5125 times
Very best,


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by Valery »

Here the profiles of two Andover 12.5mm 0.1nm filters designed to work with F/5 telescopes (include both my SW F/5 100mm and 150mm.
Attachments
ANDOVER  #2.png
ANDOVER #2.png (1.15 MiB) Viewed 5046 times
ANDOVER  #1.png
ANDOVER #1.png (1.1 MiB) Viewed 5046 times


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by Stardust5858 »

I'm considering buy Lunt Cak module and currently own a baader k-line filter. I gather from other post's that the two can be used together for better contrast. I'm considering the straight through module. How does one go about putting the two together. Are the original Lunt interference filter replaced with the baader? Appreciate any advice.


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by marktownley »

Stardust5858 wrote: Wed Feb 24, 2021 9:14 pm I'm considering buy Lunt Cak module and currently own a baader k-line filter. I gather from other post's that the two can be used together for better contrast. I'm considering the straight through module. How does one go about putting the two together. Are the original Lunt interference filter replaced with the baader? Appreciate any advice.
My honest advice - hone your skill with capture and post processing first. Just adding a Baader K-line to a Lunt blocker isn't going to do a lot really. Walk before you try to run!


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by MalVeauX »

justapictureposter wrote: Wed Feb 24, 2021 2:15 am Marting : the two filter parts would fit in this blue fireball adapter to shorten its filter cell.

Just hold them in there with a standard 1.25' retaining ring from a color filter
https://agenaastro.com/blue-fireball-1- ... nsion.html
I'll order this and give it a shot!

Very best,


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by Valery »

justapictureposter wrote: Tue Feb 23, 2021 11:31 pm
These two filters seem very far off band and suspect this to be reason for the negative experience using them.
These filters were designed for F/5 cone and they stay on band in both my SW F/5 refractors.

I will try them again with more transparent Quark. Hope they will work better in a such combination.


However I still prefer a PST etalon installed right before the Quark etalon. I already showed the picture of how they do work together. Here can be seen more - a comparision of how the sun seen through such a double stack installed in C11 telescope equipped with a full size ARIES DERF vs how the sun is seen through IBIS imaging spectrograph on the Dunn Solar Telescope.


Valery
Attachments
_280mm ARIES vs DST IBIS.jpg
_280mm ARIES vs DST IBIS.jpg (602.36 KiB) Viewed 4935 times


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by Valery »

justapictureposter wrote: Thu Feb 25, 2021 2:39 pm
Using the aries d-erf is extremely awesome to everyone and I really do wish we all could have them, but its cost combined with a good rear mounted etalon like a solar spectrum and C11;


Would you be willing to perform a test on the solar limb using just your Pst etalon?

If your andover filters remove the double limb from the pst etalon, than it conclusively has a constructive effect.
1. All my achievements in the sun Ha imaging were done with PST etalons and with Quarks. So, even such modest etalons can work quite effectively with larger SCT and DERF. Effectively enough to justify a DERF and SCT purchase.

2. I don't have that PST etalon anylonger.


Valery


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by MalVeauX »

Hrm,

I tested some things today, just to see, knowing full well that without tilt and best placement that I would get issues. I got issues. But again they were expected.

I used ITF -> 1.7A BF (8mm) -> 6A BF (5mm) -> sensor; no tilt yet (lack of adapters)

The FOV of course was heavily vignetted and very dim. I had to crank exposure up via gain after hitting 10ms exposure time.
I tested this on a SM60II DS etalon front mounted on an ED80 and a PST etalon mod inserted in the focuser.
Using 1.1" IMX253 sensor for the tests.
I have no double limb in the test, but again, two etalons, so that's expected when tuned.
Lots of reflections all over the place.

This is not a good test. But it was interesting to try for the time being while I await some parts shipping in to introduce tilt on the 1.7A BF.

My biggest questions become:

1) How much softness will this basically cause, we're introducing something like 4 pieces of extra glass with the BF's, plus all other glass. Each one is introducing some SA right? So this many filters stacking up will likely degrade the image so much that high res is not possible?

2) Transmission being low means long exposures and more gain; so again, this makes high res probably not feasible?

Will report with more tests after I get the adapter in so I can use the skybender and tilt the BF to see if it helps any. I will test with a single etalon though, to try to see the effect on the double limb.

BFstack_test_notilt_IMX253_SM60IIPST.jpg
BFstack_test_notilt_IMX253_SM60IIPST.jpg (99.34 KiB) Viewed 5095 times
SM60_PST_DoubleStackBF_17A_6A.jpg
SM60_PST_DoubleStackBF_17A_6A.jpg (33.28 KiB) Viewed 5095 times
ED80_SM60II_PST_IMX253_2xBFStack.jpg
ED80_SM60II_PST_IMX253_2xBFStack.jpg (86.72 KiB) Viewed 5095 times

Very best,


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by MalVeauX »

Ok,

Keeping the ITF was one of the adapters, so if that's not needed, that solves a lot of issues. At that point, its just the tilt to remove reflections and play with bandpass a bit. Will update when I get it all in and can test again with the tilt introduced, and will remove the ITF. And I'll make sure to test with only a single etalon so we can see what the limb looks like. I'll do 1.7A + 6+ and just 6A on the same setup, same etalon, etc.

Very best,


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by MalVeauX »

Update,

I got the two adapters. A gender reversal 1.25" to be able to easily mount the ITF to the Skybender; and the shorter 1.25" cell (the link from above).

The new holding cell fits in and threads directly to the tilting plate internal to the Skybender. It bends without hitting the top piece that threads on to give it a 1.25" receiving nose. So it bends perfectly fine and has full clearance. I transplated the 1.7A BF into the new cell and put it internal into the skybender. It fits well and tilts fully now.

I installed the other blocking filter into the 1.25" receiving nose.
And the ITF is now simply optional, on or off, via the gender reversing adapter.

So this is the 1.7A blocking filter in the tilting chamber, first, then the 6A blocking filter nearest camera. But this could be oriented with any BF at this point with these cells and adapters to test. Plus its cool that its in a red Skybender. :beanie:

Full module:

Cell transplant:

17A_new_Cell_01.jpg
17A_new_Cell_01.jpg (37.12 KiB) Viewed 5054 times
17A_new_Cell_02.jpg
17A_new_Cell_02.jpg (32.69 KiB) Viewed 5054 times

Tilt now clears just fine:

Tilt_Success_SkyBender_01.jpg
Tilt_Success_SkyBender_01.jpg (33.33 KiB) Viewed 5054 times
Tilt_Success_SkyBender_02.jpg
Tilt_Success_SkyBender_02.jpg (31.6 KiB) Viewed 5054 times
Tilt_Success_SkyBender.jpg
Tilt_Success_SkyBender.jpg (30.63 KiB) Viewed 5054 times
ITF if needed (optional):

ITF_in_place_01.jpg
ITF_in_place_01.jpg (37.55 KiB) Viewed 5054 times
ITF_in_place_02.jpg
ITF_in_place_02.jpg (31.89 KiB) Viewed 5054 times

The two BF:

Two_BF.jpg
Two_BF.jpg (33.18 KiB) Viewed 5054 times

Full module without ITF:

Full_DS_BF_Skybender_Module.jpg
Full_DS_BF_Skybender_Module.jpg (25.44 KiB) Viewed 5054 times

Hopefully I can test this week weather permitting, storming again.

Very best,


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by AndiesHandyHandies »

Hi

I am using a 1.5A Omega Bob filter from one of his seconds pairs as a blocker with a PST which looks 0.75A from Daystars images. Will that be doing similar to what you are trying, and what will the resulting bandwidth be?

35nm Baader and Beloptic KG3 up front.

Cheers. Andrew.


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by MalVeauX »

Heya,

I have an update with tests of double stacking a 1.7A and 6A blocking filter set with a single etalon.

Setup:

PST Etalon with both F10 collimation lenses in place (front collimation lens is extended forward to achieve focus)
Skybender (inserted into PST etalon back adapter)
+ Apollo's 1.7A blocking filter (8mm) in tilt chamber
+ PST blocking filter (5mm) in eyepiece chamber

Scope is a 100mm F10 achromatic refractor.
D-ERF is an internal 2" Baader Red CCD-IR Block filter (threaded to front of nose of PST module)

Camera is IMX290 monochrome

FireCapture for data acqusition

Solarsetup_03042021.jpg
Solarsetup_03042021.jpg (86.76 KiB) Viewed 5001 times
DS_BF_Module_03042021.jpg
DS_BF_Module_03042021.jpg (89.25 KiB) Viewed 5001 times

I tested with the tilt chamber both flat and gently tilted. I have no means to give exact angle of tilt, but it doesn't matter since each filter is slightly different and no specific amount of tilt will agree with all filters. So that said, my procedure to tune them was to tune the PST etalon for max contrast on filament/plage area with best uniformity for the sweet spot with a single blocking filter. Then added the blocking filter double stack and gently tilted the chamber until the disc was as dark as I could get it, while being uniform and keeping high contrast on filament/plage area. Once dialed in, I left it parked there.

No Processing Results; Side by Side Comparison:

AR2807_HA_100mmF10_290MM_81frames_SingleBF_PSTetalon_03042021.jpg
AR2807_HA_100mmF10_290MM_81frames_SingleBF_PSTetalon_03042021.jpg (101.23 KiB) Viewed 5001 times
AR2806_HA_100mmF10_290MM_81frames_SingleBF_PSTetalon_Unprocessed_03042021.jpg
AR2806_HA_100mmF10_290MM_81frames_SingleBF_PSTetalon_Unprocessed_03042021.jpg (113 KiB) Viewed 5001 times
Filament_HA_100mmF10_290MM_81frames_SingleBF_PSTetalon_Unprocessed_03042021.jpg
Filament_HA_100mmF10_290MM_81frames_SingleBF_PSTetalon_Unprocessed_03042021.jpg (111.38 KiB) Viewed 5001 times

IMPPG Levels & Unsharp Mask Processing only; Side by Side Comparison:

AR2807_HA_100mmF10_290MM_81frames_SingleBF_PSTetalon_IMPPG_Processed_03042021.jpg
AR2807_HA_100mmF10_290MM_81frames_SingleBF_PSTetalon_IMPPG_Processed_03042021.jpg (214.37 KiB) Viewed 5001 times
AR2806_HA_100mmF10_290MM_81frames_SingleBF_PSTetalon_IMPPG_Processed_03042021.jpg
AR2806_HA_100mmF10_290MM_81frames_SingleBF_PSTetalon_IMPPG_Processed_03042021.jpg (208.38 KiB) Viewed 5001 times
Filament_HA_100mmF10_290MM_81frames_SingleBF_PSTetalon_IMPPG_Processed_03042021.jpg
Filament_HA_100mmF10_290MM_81frames_SingleBF_PSTetalon_IMPPG_Processed_03042021.jpg (167.4 KiB) Viewed 5001 times

Full Processing; Here's the results with the double stack 6A and 1.7A blocking filters, gently tilted:

Proms_HA_100mmF10_290MM_81frames_PSTEtalon_DoubleStackBF_BW_03042021.jpg
Proms_HA_100mmF10_290MM_81frames_PSTEtalon_DoubleStackBF_BW_03042021.jpg (95.84 KiB) Viewed 5001 times
Proms2_HA_100mmF10_290MM_81frames_PSTEtalon_DoubleStackBF_BW_03042021.jpg
Proms2_HA_100mmF10_290MM_81frames_PSTEtalon_DoubleStackBF_BW_03042021.jpg (109.43 KiB) Viewed 5001 times
Filament_HA_100mmF10_290MM_81frames_PSTetalon_DoubleStackBF_BW_03042021.jpg
Filament_HA_100mmF10_290MM_81frames_PSTetalon_DoubleStackBF_BW_03042021.jpg (191.19 KiB) Viewed 5001 times
AR2807_HA_100mmF10_290MM_81frames_PSTetalon_DoubleStackBF_BW_03042021.jpg
AR2807_HA_100mmF10_290MM_81frames_PSTetalon_DoubleStackBF_BW_03042021.jpg (190.26 KiB) Viewed 5001 times
AR2806_HA_100mmF10_290MM_81frames_PSTetalon_DoubleStackBF_BW_03042021.jpg
AR2806_HA_100mmF10_290MM_81frames_PSTetalon_DoubleStackBF_BW_03042021.jpg (208.11 KiB) Viewed 5001 times

FireCapture previews (with screen overlays) to see what I saw real time live stream:

FC_BFDS_AR_Plage_01_03042021.jpg
FC_BFDS_AR_Plage_01_03042021.jpg (99.38 KiB) Viewed 5001 times
FC_BFDS_AR_Plage_02_03042021.jpg
FC_BFDS_AR_Plage_02_03042021.jpg (96.54 KiB) Viewed 5001 times
FC_BFDS_Filament_01_03042021.jpg
FC_BFDS_Filament_01_03042021.jpg (110.2 KiB) Viewed 5001 times
FC_BFDS_PromLimb_01_03042021.jpg
FC_BFDS_PromLimb_01_03042021.jpg (94.72 KiB) Viewed 5001 times

Thoughts & Conclusions:

I think its pretty obvious that the 1.7A filter, when tuned with the system, helped with contrast on HA feature selectivity. This agrees with Christian's sets with the 1.5A filter he used on his tests. The filaments, plages and chromosphere network were higher contrast, significantly so. The double limb is still present, but its reduced in terms of the brightness difference of the spicule limb and limb prominences relative to the disc chromosphere network. So this system greatly reduces photosphere light further. Not quite to the degree of a double stack of etalons tuned on band together, but this is still quite close. I cannot give an accurate approximation of bandpass other than maybe it's around 0.6A~0.7A maybe but with high selectivity for HA line? Keep in mind this is a single PST etalon.

As you can see from my FC screen shots, the transmission was still high enough. The single etalon with two blocking filters was still able to image at 5ms or shorter, with minimal to no gain, to be able to maintain the full FPS speed of virtually any of the popular sensors with fast FPS. So the IMX290 for example was able to maintain the full 170 FPS in each session despite the transmission loss of using two blocking filters. I have tested double stacking two etalons with this same sensor in the past and while it's similar, this still has higher transmission in general by a little bit. So this would be an easier way to increase contrast on a single etalon high resolution system, so I will further test this on my 120mm, 150mm and 200mm when seeing permits.

I'm curious how much more contrast could be squeezed out of two 1.7A filters together, I think it would reduce the photosphere parasitic continuum just a bit more, perhaps not to the degree of a very good double stack, but enough to allow high resolution limb captures with better brightness relativity between the spicules and disc surface of chromosphere network. And of course, I think two 1A filters would probably replicate a double stack etalon system pretty close potentially. That said, 1.5~1.7A blocking filters stacked will probably get you rather close for a lot less cost and a much easier configuration requiring much less modding to achieve.

Very best,


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by MalVeauX »

justapictureposter wrote: Fri Mar 05, 2021 12:25 am win! So this pretty much confirms that it is indeed possible to improve a cheap etalon at the eyepiece with two of these andover filters in place of the standard blocker.

I will mail you a second one, then we can get a rock solid claim out there on this phenomena. Perhaps lunt, or daystar will listen up and realize they missed the boat here. 1 angstrom blocking filters are indeed the future way to proceed.

At just ~$500, this is a gamechanger from a second etalon; especially on a pst etalon. It may even be enough to change the market entirely.



The double limb has been suppressed by an impressive amount and a second filter is going to knock it down fully, i am convinced.

Great job Marty, seeing all this done in the red Skybender made a great impression!

You kept my dream alive and i am thankful you kept faith in me.

I will mail you that second filter, and my prediction is you will think twice before getting a new HA etalon for awhile.

Thank you for validating my claims.
Thanks, I agree, these are pretty solid as an option to take any single etalon to a better level of contrast and selectivity for HA line while keeping a high transmission without the ITF and just using a D-ERF. That was just an old 5mm PST blocking filter too, so a newer one that is 8mm like the second 1.7A filter will likely be brighter and have a larger FOV potential which allows for bigger sensors (like IMX174). Agreed that a 1.5A filter would be slightly better, and anything below 1.5A would probably be rather superb (with two of them stacked). Even if 1A couldn't be done. I think 1.2~1.5 x 2 stacked would be high contrast. The question is how much transmission is lost with the narrowing peak CWL on 656nm.

The Skybender was nice to use in this situation, I could real time tilt and see the transmission and bandpass change just like how it is real time to do it on the PST etalon itself. And at the rear of the scope where it's easy to reach. Very simple to do. I just wish I had a slightly bigger sweet spot, as my sweet spot shrinks with aperture and this was a 100mm aperture.

Thanks for the filter; I will put them both to the test after it arrives. I think it will be very close in eliminating the double limb.

Very simple concept to implement too, I think this is an excellent result Apollo. Awesome design! Maybe the Skybender was just waiting for this?

:bow :band

Very best,


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by marktownley »

Very interesting, very positive!


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by Montana »

I really wish I understood this, my PST definitely could do with a boost :)

Alexandra


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by MalVeauX »

Heya,

Another update, to make sure it wasn't just a good day or fluke. Did the tests again, but with a larger aperture in fair seeing conditions with a 120mm F10 scope and the PST etalon + double stacked 1.7A & 6A blocking filters in the Skybender on AR2806, AR2807 and the two prom areas. Limb supression was still pretty good. Contrast was very good. Tuning was not difficult and was able to find a fair balance.


Image

Image

Image

Image


Time Lapse of the Surge Prom:

01_2aligned_pipp.gif
01_2aligned_pipp.gif (908.62 KiB) Viewed 4925 times

(A colored version of this animation is now on the SpaceWeather front page for 3/5)

FireCapture real time:

FireCapture_AR2806_DS_BF_01.jpg
FireCapture_AR2806_DS_BF_01.jpg (97.77 KiB) Viewed 4925 times
Setup:

120mm F10 achromatic doublet (masked)
+ Baader Red CCD-IR Block Filter (2", D-ERF, Internal Sub Aperture)
+ Skybender with 1.7A blocking filter in tilt chamber + 6A blocking filter in eyepiece chamber
+ IMX290 Mono camera

Solarsetup_03052021.jpg
Solarsetup_03052021.jpg (61.81 KiB) Viewed 4925 times

Very best,


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by christian viladrich »

Excellent results Marty ! Thanks for sharing.This is in agreement with what I've found (with mica-spaced etalons).
Just wondering whether who could replace the whole BF by two stacked 1.7 A. You might just need to add an ITF (like Beloptik's one).

Well done Apollo. I don't think there is much to gain with a 1 A, given the associated technical difficulties. I hope to have a SHG ready in the coming month of so. I will then be able to measure 1 A filters. Then, discussions with manufactures will be easier (or more difficult ...).


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by MalVeauX »

christian viladrich wrote: Fri Mar 05, 2021 7:54 pm Excellent results Marty ! Thanks for sharing.This is in agreement with what I've found (with mica-spaced etalons).
Just wondering whether who could replace the whole BF by two stacked 1.7 A. You might just need to add an ITF (like Beloptik's one).

Well done Apollo. I don't think there is much to gain with a 1 A, given the associated technical difficulties. I hope to have a SHG ready in the coming month of so. I will then be able to measure 1 A filters. Then, discussions with manufactures will be easier (or more difficult ...).
Thanks, I was greatly interested based on your work with the 1.5A filter.

The goal is to remove the 6A filter from this setup and use two 1.7A filters stacked, one tilted (for reflections and to center the CWL on 656.3nm).

I started with an ITF, but removed it, it just lowered transmission (first tests above, very dim). The second tests (these last two) were with no ITF and the results were superior, and high transmission enough to image with no gain and still keep short exposure time to freeze seeing (5ms or less).

I think from here, ideally, 10mm~12mm 1.7A blocking filters in a shorter tilt chamber (a pancake skybender?) would be essentially a double stack for virtually any etalon setup and capable of full discs and for use with high res setups.

:bow

Very best,


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by MalVeauX »

That's brilliant Apollo, a 1 inch thick tilting chamber that can take 1.25" filters is golden for this.

Very best,


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by MalVeauX »

Heya,

Update.

I have the 2nd 1.7A filter. I stacked them both in the Skybender, one in the tilt chamber with just enough tilt to remove a reflection and keep highest contrast on features and diminish surface brightness. The 2nd 1.7A filter is secured to the camera nose with no tilt needed. This train follows a single PST etalon.

So the train is:

IMX290 sensor -> 1.7A BF -> Skybender with 1.7A BF tilted -> PST etalon -> 50mm D-ERF -> Focuser -> Telescope (120mm F10)

AR2808_HA_120mmF10_290MM_81frames_PSTEtalon_17ABFX2_UnprocVSProc_BW_03142021.jpg
AR2808_HA_120mmF10_290MM_81frames_PSTEtalon_17ABFX2_UnprocVSProc_BW_03142021.jpg (155.83 KiB) Viewed 2510 times
PromsLimb_HA_120mmF10_290MM_81frames_PSTEtalon_17ABFX2_UnprocVSProc_BW_03142021.jpg
PromsLimb_HA_120mmF10_290MM_81frames_PSTEtalon_17ABFX2_UnprocVSProc_BW_03142021.jpg (196.62 KiB) Viewed 2510 times
PromsLimb_02_HA_120mmF10_290MM_81frames_PSTEtalon_17ABFX2_UnprocVSProc_BW_03142021.jpg
PromsLimb_02_HA_120mmF10_290MM_81frames_PSTEtalon_17ABFX2_UnprocVSProc_BW_03142021.jpg (162.39 KiB) Viewed 2510 times
Conclusion & Thoughts:

I think there is an increase in contrast for sure, just judging from the unprocessed images, I was able to see dark filaments and a bright plage area. The double limb is virtually gone, except towards the edges where the bandpass rolls off but in this case its a nice thing to see because it shows how the two 1.7A filters stacked nearly eliminate the double limb compared to the edges where the effect isn't there, so you can see an obvious double limb. This is not optimized yet, so I still have a lot more fiddling to do for placement, tilt, tuning, etc. But so far, this is very promising. This is as close to a double stack as I've been able to get without two etalons and it's way less fussy than dealing with two etalons. It's not perfect, there's still a hint of double limb (and it comes out more depending on the processing you do). But it's very close. I suspect with a better etalon this would be even better (again this is just a PST etalon with a small sweet spot and only about 0.9A maybe?). A good 0.7A filter would probably have no double limb I wonder?

Transmission is good still, through the above imaging train, I imaged at 5ms exposure time for my histogram and no gain.

Seeing wasn't great today, but it was enough to allow the 120mm aperture to get close enough to good resolution to inspect features to see how the contrast is in better detail. I will test again on a better seeing day with a more optimal tuning setup when I have better time.

Very best,


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by AndiesHandyHandies »

Hi

Will this idea work for visual use?

Cheers. Andrew.


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by MalVeauX »

AndiesHandyHandies wrote: Mon Mar 15, 2021 9:42 am Hi

Will this idea work for visual use?

Cheers. Andrew.
Hi, yes, it's the same either way (visual or imaging). I used it visually to test as well and the view was dimmer as expected, just as a double stack etalon would be dimmer, but with high contrast and was still very pleasing to view through (8mm was plenty to pass the disc), but without needing a 2nd etalon.

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Re: blocking filter chit chat chop chop - lets cut it out.

Post by MAURITS »

Bravo for the inventive idea and all the tests about a second blocking filter.
I don't understand this difficult system, but I hope one day something like that can go in production ... 👍😀
Last edited by MAURITS on Mon Mar 15, 2021 4:10 pm, edited 1 time in total.


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by eroel »

Hi:
Thanks for a really interesting thread with a lot of experiences.
Best regards and keep well.
Eric.


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by AndiesHandyHandies »

MalVeauX wrote: Mon Mar 15, 2021 12:00 pm
AndiesHandyHandies wrote: Mon Mar 15, 2021 9:42 am Hi

Will this idea work for visual use?

Cheers. Andrew.
Hi, yes, it's the same either way (visual or imaging). I used it visually to test as well and the view was dimmer as expected, just as a double stack etalon would be dimmer, but with high contrast and was still very pleasing to view through (8mm was plenty to pass the disc), but without needing a 2nd etalon.

Very best,
Hi

I am using a 1.5A Omega filter from a seconds pair, Its a pretty good one, in my PST mod as the blocker and I nearly see the surface details as on Gong images with a x-polariser to dim down. My PST looks like 0.75A from Daystars site images. I am going to try the obviously seconds one instead. I have it up front in the collimated beam so I am hoping it will not show the cosmetic features as its in phase space.

Cheers. Andrew.


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Re: blocking filter chit chat chop chop - lets cut it out.

Post by mdwmark »

Hi Marty,
Your images are well processed but you are in the red wing. If you see high contrast at the tips( like the prominences images) , that is a good sign you need to move blue about .5ang. When you are in the center of the Ha line, the disk will look softer.
Mark W.


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