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Lunt CaK module testing 22nd April

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Lunt CaK module testing 22nd April

Post by Montana » Mon Apr 22, 2019 6:52 pm

This morning Stuart very kindly tested my Lunt CaK module. We used the same telescope, same settings, same processing in ASK3 and in ImPPG and here are the results. It is subtle but my module is definitely not quite right for high mag imaging. The question is, do I send it back to Teleskop Express but it is around 5 years old. Or do I fiddle with it, or send it to someone else to fiddle with and fix. The dilemma.
CaK test.jpg
CaK test.jpg (296.91 KiB) Viewed 1057 times
Stuart's
20190422_SG1_Reoriented.jpg
20190422_SG1_Reoriented.jpg (1.01 MiB) Viewed 1057 times
Mine
20190422_AH1.jpg
20190422_AH1.jpg (804.55 KiB) Viewed 1057 times
Stuart will be able to fill you on telescope details but it was definely at 2.5x and with the Basler camera.

Alexandra

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Re: Lunt CaK module testing 22nd April

Post by bart1805 » Mon Apr 22, 2019 7:01 pm

Did you try Stuart's Lunt nosepiece (the one with the tw bigger filters) with your B1800?

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Re: Lunt CaK module testing 22nd April

Post by MAURITS » Mon Apr 22, 2019 7:35 pm

Send it back Alexandra with a good explanation.
The people on Teleskop Express are very helpfull and they will test it out for you.
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Re: Lunt CaK module testing 22nd April

Post by christian viladrich » Mon Apr 22, 2019 8:25 pm

There is definitely a problem there. It is worth asking TS guys.
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Re: Lunt CaK module testing 22nd April

Post by MapleRidge » Tue Apr 23, 2019 1:05 am

Hi Alexandra...

Certainly worth a shot to see if you can get it checked, the comparison speaks for itself.

You have had the CaK module for several years, but don't recall other posts where you questioned it. Any chance something happened...physical (shock/impact) or any haze appearing on the filter elements? Just a few thoughts if it has changed over time.

My Ha blockers need to have one element replaced every few years as they get a hazy look and lead to a soft Ha image. My CaK has not been affected the same way, but not to say it couldn't have a similar effect.

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Re: Lunt CaK module testing 22nd April

Post by Montana » Tue Apr 23, 2019 6:58 am

Thanks guys.
Brian, I have always had my doubts since I purchased it as I have never got a good image out of it at all. I just I thought I was rubbish at taking CaK and everyone else was very experienced and good at it. In 2014 I did a comparison with Luca Valantini's homebrew CaK filter and the difference was night and day. So I just thought maybe that is how the Lunt is as you can't compare with a homebrew filter. I was kept being told my seeing wasn't good enough and try and try again. So after 5 years of blaming myself and the weather and I am slowly getting to grips with it :)

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Re: Lunt CaK module testing 22nd April

Post by krakatoa1883 » Wed Apr 24, 2019 7:31 am

Hello Alexandra

it seems that there could be a tilted element that put the light bundle out of collimation and blurs the details. On the other hand by looking at the same features present in both sets of images (yours and Stuart's) the filtering seems fine because the contrast is similar or even slightly better through your device. May be opening the module would easily reveal the faulty element.
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Re: Lunt CaK module testing 22nd April

Post by marktownley » Wed Apr 24, 2019 7:39 am

I think my advice would be to see what Telescope Service say on Germany and then if no joy there we attempt a dissection.
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Re: Lunt CaK module testing 22nd April

Post by Montana » Wed Apr 24, 2019 9:11 am

Thanks guys,
I wrote to Teleskop Service last night. I will await an answer then see what to do next I think. Wise words Mark.
On a positive, my Grasshopper 3 is on its way back from repair, fingers crossed it works when I get it in my hands.

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Re: Lunt CaK module testing 22nd April

Post by Bob Yoesle » Wed Apr 24, 2019 11:37 am

Hi Alexandra,

I noticed you called yours a "Lunt CaK wedge." I'm assuming that means it's the B1800 diagonal, and therefore the diagonal mirror itself might be a part of the problem. If you are beyond the Lunt 5 year warranty and end up stuck with it (and since you likely do only imaging for CaK anyway and the diagonal mirror may be superfluous), you could remove the filter portions from the diagonal mirror assembly and MacGyver it together as a straight through, which works better for imaging anyway. That would at least remove one possibility, and see how it works. It will also offer the ability to do a closer inspection for the ERF and blocking filter elements, or test them individually with alternative components. The Baader Blue CCD filter can be used as an ERF of sorts, and the Baader K line works as an intermediate pre-blocking filter.

For disassembly see: viewtopic.php?f=9&t=12203 and viewtopic.php?t=24511
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Re: Lunt CaK module testing 22nd April

Post by Valery » Wed Apr 24, 2019 11:43 am

I take Alexandra's image, cropped and further processed it.

Here is the result.

I don't see any faulty in the image.

Right click on the image and open it in a separate window to see it in a full resolution. You will see EXCELLENT image.


Valery
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Re: Lunt CaK module testing 22nd April

Post by marktownley » Wed Apr 24, 2019 12:24 pm

Useful links Bob, i'd forgot about them.
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Re: Lunt CaK module testing 22nd April

Post by christian viladrich » Wed Apr 24, 2019 12:37 pm

Thanks Bob, I'd completely forgot this one too !
It seems that one (or even both) of the ERF can be replaced with a EO394-10 nm in 50 mm diameter which much benefit.
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Re: Lunt CaK module testing 22nd April

Post by Montana » Wed Apr 24, 2019 2:31 pm

Very interesting Bob, mine is definitely not severe but the astigmatism is definitely causing big problems when using it on the TEC and the C11. It is not noticeable so much on the hubby's telescope. Mine is definitely a mild but annoying case.

Valery, there is definitely a problem with it, I have seen the difference and Stuart struggled to focus with mine as well.

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Re: Lunt CaK module testing 22nd April

Post by Valery » Wed Apr 24, 2019 2:46 pm

Montana wrote:
Wed Apr 24, 2019 2:31 pm

Valery, there is definitely a problem with it, I have seen the difference and Stuart struggled to focus with mine as well.

Alexandra
What the telescope has been used for testing for CaK filter?

If there is an astigmatism, the narrower the light cone, the less distorsion we will see.

But your image with harder processing there is no trace of astigmatism.


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Re: Lunt CaK module testing 22nd April

Post by Bob Yoesle » Wed Apr 24, 2019 5:35 pm

Hi Valery,

I don't think it is valid to apply processing to only one image and not the other to come to a conclusion that the questionable filter has no faults. Under the circumstances of using identical scopes, camera, and processing to obtain the images, the significant differences between the two are either due to changed seeing conditions, or the filter components/mechanics themselves. Indeed, there is also a bit of difference in brightness uniformity across the two images. I would have expected this more from the Lunt B600 than the B1800.

I honestly would say Alexandra's filter - while perhaps not completely FUBAR - needs to be returned to TS with the comparison images for potential repair or replacement. Even the best of companies can have a lemon slip through - I probably had the only bad Baader DERF in the world come to me, but the dealer tested it and found it indeed to be defective (my images were quite similar to Alexandra's) and quickly replaced it.

I would also include any previous images taken within the 5 year warranty period to demonstrate the problem existed from day one as Alexandra states. Hopefully Alexandra has some images taken with the TEC, as the C11 has some significant sphereochromatic issues at 394 nm to begin with, and this only complicates the situation.

Lunt Warranty: https://luntsolarsystems.com/warranty/

Christian - thanks for the reminder about the EO394-10 ;-)
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Re: Lunt CaK module testing 22nd April

Post by bart1805 » Wed Apr 24, 2019 5:50 pm

It could be that one or two of the pre-blocking filters are degraded. That is why I asked if you changed the two inch nosepieces, they screw of easily. If you want to make a straight through version (better for imaging as Bob suggested), this is how I did it:
viewtopic.php?f=9&t=25552

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Re: Lunt CaK module testing 22nd April

Post by marktownley » Wed Apr 24, 2019 6:28 pm

Valery wrote:
Wed Apr 24, 2019 11:43 am
I take Alexandra's image, cropped and further processed it.

Here is the result.

I don't see any faulty in the image.

Right click on the image and open it in a separate window to see it in a full resolution. You will see EXCELLENT image.


Valery
How do you account for the difference between Alexandras and Stus images then Valery?
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Re: Lunt CaK module testing 22nd April

Post by Valery » Thu Apr 25, 2019 1:33 am

marktownley wrote:
Wed Apr 24, 2019 6:28 pm
Valery wrote:
Wed Apr 24, 2019 11:43 am
I take Alexandra's image, cropped and further processed it.

Here is the result.

I don't see any faulty in the image.

Right click on the image and open it in a separate window to see it in a full resolution. You will see EXCELLENT image.


Valery
How do you account for the difference between Alexandras and Stus images then Valery?
If the telescope was the same, the focusing was the same and processing was the same, then only the seeing was the reason of the image difference. Deeper post processing shows this clearly.

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Re: Lunt CaK module testing 22nd April

Post by Carbon60 » Thu Apr 25, 2019 5:59 am

For information, the scope was a Tecnosky 125 (FPL53 glass).

There is definitely a significant difference at the point of use between the two modules. Mine was clearer and easier to focus and Alexandra's was much more difficult requiring significantly more time to get the 'sharpest' image on screen. Seeing was excellent; about the best I've experienced for a long time. We switched back and forth between modules a couple of times and the difference was constant, so I doubt seeing was the issue. The difference was 'chalk and cheese', as we say.

Subsequently I've reprocessed my image using less RL deconvolution and more UM sharpening with better results, but I cannot get the same out of Alexandra's image, no matter how I try. I'd love to know your processing method, Valery :)

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Re: Lunt CaK module testing 22nd April

Post by Montana » Thu Apr 25, 2019 7:17 am

I have been looking at my past images, to be honest nearly all of them I throw away. However there are a few decent ones I got which I saved and I can see that the smearing seems to be worse on one side than the other. One side is pretty much normal.

Alexandra

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Re: Lunt CaK module testing 22nd April

Post by robert » Thu Apr 25, 2019 10:32 am

Hi Alexandra

Really interesting.

I looked at your comparison images and aligned a part of Stuart's with yours. I think the y axis resolution is the same as Valery says but the x axis is smeared left to right by at least the minimum resolved image part.
CaK test copy.jpg
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I have aligned a part roughly in photoshop to illustrate what I am seeing. Must be fixable!

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Re: Lunt CaK module testing 22nd April

Post by marktownley » Thu Apr 25, 2019 10:40 am

That horizontal smear reeks to me of misaligned reflective surface in the module...
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Re: Lunt CaK module testing 22nd April

Post by Valery » Thu Apr 25, 2019 1:12 pm

The horizontal streaks were photographed with Alexandra's telescope. This may be coma (the most probable) or even high jet streams (I saw this on my images several times).

On the image taken with Stue's telescope there are _no any traces_ of asymmetrical images of spot-like details. So, no astigmatism at all.

The reason why Stue's CaK works well is the only one I can see: the 6mm aperture of the filter itself stops down the light cones from the objective. This greatly reduces spherical aberration of the telescope and produce very sharp images with larger of the focus depth. Alexandra's CaK is 1800 - 18mm in diameter and it does not reject the aperture of the telescope and telescope's native spherical aberration blurs the image.

Hope this helps.


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