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Solar H-a from today 18/09/11

Photosbykev

By Photosbykev
in Imaging - Solar

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Photosbykev

Photosbykev

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After spending some time retuning the PST and cleaning the objective lens I then battled with high winds and not much sun to get a few images today. It is getting cold out there! lol. I think the next job will be to take the side off the PST and check the prism alignment and then make up a compression ring for the Powermate to stop it tilting slightly when I lock it into the PST eye piece socket, I will get rid of the newton rings properly.

20110918164121.jpg

20110918162017.jpg

20110918161321.jpg

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Photosbykev

Photosbykev

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Nice images Kev! Do like the colouration.

Careful with fiddling with the penta prism - you could turn it astigmatic very quickly, and believe me that will annoy the hell out of you...

If it's level with the underside of the eye piece that will do me :) If not I can put it all on an optical bench at work to align it.

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Photosbykev

Photosbykev

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Excellent images!

I personally would not go near touching the inside of the PST, your photos look perfect, if it isn't broke, don't try to fix it!

Alexandra

There is something not quite aligned which is causing the newton rings so I do need to do some investigating. I think is is the Powervue nosepiece being slightly smaller than the PST eye piece socket and being canted over when I lock the tube in place. If it is that then a skinny compression ring will cure it.

Opening up the PST doesn't worry me as I regularly have optical setups running on a bench with beam splitters / lens / optical shutters etc with class 4 lasers zipping around the optical paths.

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markt

markt

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Hiya Kev,

I completely agree regards the nosepeice of the powermate, however, IMHO I think with a compression ring you will reduce it but will not completely remove it - just my gut instinct... I've been down exactly the same route as you with the oversized ep holder on the BF10 and the naff nylon grubscrew. You may also want to consider using some electrical tape wrapped around the nosepeice of the powermate to produce a near interference fit. This was the most successful method I found, but, like I say, reduced but not completely removed newtons rings. YMMV.

I know i've said before but I think by ditching the quest for perfect tracking via guiding will improve things, allowing some drift will dither the image and remove the banding artefacts completely. Poor alignment is actually a positive in high res solar imaging.

Then there's the use of flats - this method will remove any banding artefacts aswell as dust motes and optical vigneting.

You sound like you're very experienced regards things of an optical nature, and in this case I would whole heartedly recommend some work on the PST. I do think there is something very slight going on with the optics, my gut feeling is it is a misalignment of the penta prism introducing slight astigmatism. However other things you may wish to consider looking into is whether the retaining ring on the objective is too tight, if it is this will pinch the objective and could be a cause... If you're really brave you could consider doing some work on the tilt mechanism for the etalon, and, with all these tweaks I think you will see much more uniformity across the image - i'm not saying your images are bad, not at all - they're very good, what I am saying is that any(bodies) Ha system can have improved performance by tweaking the mechanics of the system.

Keep the images coming Kev, been a pleasure to see how they've developed just in the short time i've been on this forum...

:glasses2:

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Photosbykev

Photosbykev

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Hiya Kev,

I completely agree regards the nosepeice of the powermate, however, IMHO I think with a compression ring you will reduce it but will not completely remove it - just my gut instinct... I've been down exactly the same route as you with the oversized ep holder on the BF10 and the naff nylon grubscrew. You may also want to consider using some electrical tape wrapped around the nosepeice of the powermate to produce a near interference fit. This was the most successful method I found, but, like I say, reduced but not completely removed newtons rings. YMMV.

I know i've said before but I think by ditching the quest for perfect tracking via guiding will improve things, allowing some drift will dither the image and remove the banding artefacts completely. Poor alignment is actually a positive in high res solar imaging.

Then there's the use of flats - this method will remove any banding artefacts aswell as dust motes and optical vigneting.

You sound like you're very experienced regards things of an optical nature, and in this case I would whole heartedly recommend some work on the PST. I do think there is something very slight going on with the optics, my gut feeling is it is a misalignment of the penta prism introducing slight astigmatism. However other things you may wish to consider looking into is whether the retaining ring on the objective is too tight, if it is this will pinch the objective and could be a cause... If you're really brave you could consider doing some work on the tilt mechanism for the etalon, and, with all these tweaks I think you will see much more uniformity across the image - i'm not saying your images are bad, not at all - they're very good, what I am saying is that any(bodies) Ha system can have improved performance by tweaking the mechanics of the system.

Keep the images coming Kev, been a pleasure to see how they've developed just in the short time i've been on this forum...

:glasses2:

The DSSR software I use for guiding does allow me to change the size of the feature search area before a correction is applied, at the moment in good calm conditions I set the search region to be very tight around a feature. I'll have a play with letting the scope drift a few pixels when I'm shooting mosaics also I do need to get back into shooting flats to flatten the image better but I don't allow dust to live very long lol.

Registax6 can use them but I'm not sure it can handle them if you batch process through Registax6. I have noticed that if I set up a gamma curve then Registax6 batch processing doesn't apply the gamma correction to the selected videos.

I'll take the investigation one step at a time, starting with the nose piece and move on from there if I need to. I'm happy with the images I'm getting but I can get better and I hate being in that position lol

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markt

markt

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The DSSR software I use for guiding does allow me to change the size of the feature search area before a correction is applied, at the moment in good calm conditions I set the search region to be very tight around a feature. I'll have a play with letting the scope drift a few pixels when I'm shooting mosaics also I do need to get back into shooting flats to flatten the image better but I don't allow dust to live very long lol.

Registax6 can use them but I'm not sure it can handle them if you batch process through Registax6. I have noticed that if I set up a gamma curve then Registax6 batch processing doesn't apply the gamma correction to the selected videos.

I'll take the investigation one step at a time, starting with the nose piece and move on from there if I need to. I'm happy with the images I'm getting but I can get better and I hate being in that position lol

I agree, small steps are the way forward...

When you set the amount you are going to drift by, a couple of pixels is going to make matters worse: You need to be drifting by atleast the width of the banding in pixels, and for maximum effectiveness the drift needs to be perpendicular to the banding (though this is easy enough to orientate). By drifting only a couple of pixels you will set up a contructive interference pattern and actually reinforce and accentuate the banding: If the drift is atleast the banding with the interference pattern will be destructive and will cancel out - which is the result you want :glasses2:

Sounds to me like your if your imaging is developing faster than your software (registax) will allow...

*cough cough* Avistack2 :rolleyes:

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Photosbykev

Photosbykev

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I've tried Avistack2 and find it fails during a batch process more than Registax6 does especially when doing the 'corner' tiles for a mosaic. If I can't find a way of making Registax6 do all of the adjustments I might go back to AV2.

The banding interference makes me all the more determined to resolve the problem at source which is always the best way rather than hiding the issue.

When I shoot timelapse animations the last thing I want is movement between or during video captures.

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markt

markt

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I've tried Avistack2 and find it fails during a batch process more than Registax6 does especially when doing the 'corner' tiles for a mosaic. If I can't find a way of making Registax6 do all of the adjustments I might go back to AV2.

The banding interference makes me all the more determined to resolve the problem at source which is always the best way rather than hiding the issue.

When I shoot timelapse animations the last thing I want is movement between or during video captures.

I can email you avistack settings if you want; these have been refined for solar :glasses2:

I personally think banding is a culmination of several (if not more) factors throughout the optical train, however will be interested to see how you get on with ridding of the blessed things.

Bit of movement shouldn't be an issue with a DMK41, you've got a huge chip to work on...

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Photosbykev

Photosbykev

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I can email you avistack settings if you want; these have been refined for solar :glasses2:

I personally think banding is a culmination of several (if not more) factors throughout the optical train, however will be interested to see how you get on with ridding of the blessed things.

Bit of movement shouldn't be an issue with a DMK41, you've got a huge chip to work on...

any help is welcome Mark, my email is kevin@photosbykev.com

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Merlin66

Merlin66

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Kev,

The newton ring/ banding issue has nothing to do with the penta prism (which by the way I think is pretty good at the moment) - It's interference between the powermate/ and the glass cover thickness on the CCD sensor. Nick H. did some studies a year or so ago with various camera combinations...

HTH

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Photosbykev

Photosbykev

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Kev,

The newton ring/ banding issue has nothing to do with the penta prism (which by the way I think is pretty good at the moment) - It's interference between the powermate/ and the glass cover thickness on the CCD sensor. Nick H. did some studies a year or so ago with various camera combinations...

HTH

Cheers Merlin, sounds like I need to delve a bit deeper and take a look a look at the camera/powermate as well :glasses2:

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markt

markt

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Yeah...

They seem to be more of an issue with the monochromatic imagers (ie Ha) than the usual stuff..

A narrowband monochromatic wavelength bouncing between 2 optical surfaces will setup a standing wave interference pattern, which is what we see as the banding. As there are no other wavelengths present I figure it will make the banding more obvious to the camera.

With broadband multiwavelength light the same standing wave patterns should still form, however there will be multiple bands (a function of the range of wavelengths present) all separated by different distances, therefore I presume will not be as easy to notice...

I'm currently experimenting with the use of a circular polariser situated between my 2 external etalons. This has had a positive effect in terms of removing the banding and reflection issues associated with double stacking, however this comes at a cost: The CP (I have) has poor transmission at 656nm resulting in reduced image brightness - though my soon to be new ERF should compensate somewhat for this. Sooo, i'm looking to source circular polarising material with excelent transmission at Ha wavelengths - this is my current hurdle... I wonder if a CP filter screwed into the nosepeice of the cam would get rid of the Newton ring banding???

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Merlin66

Merlin66

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I use a SM60 double stack external etalon set-up on the ED80.

With the T max tuners on each filter, I've never had a problem with newton rings (NR)..

IMHO it comes from the interference behind the blocking filter between the optics and the chip.

Do you get NR with a straight camera connection to the BF??

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