white light comparison

Use this section to discuss "standard" Baader/Coronado/ Lunt SolarView/ Daystar, etc… filters, cameras and scopes. No mods, just questions/ answers and reviews.
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alpha76
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white light comparison

Post by alpha76 »

Good morning all

I would like to know if any of you have already compared the two filters

baader K-LINE

altair NUV
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ALTAIR NUV.JPG
ALTAIR NUV.JPG (37.58 KiB) Viewed 1190 times
KLINE.JPG
KLINE.JPG (29.48 KiB) Viewed 1190 times


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Re: white light comparison

Post by Montana »

Nope but it sounds interesting, I think the Baader is 8nm which is 80A wide. If it is 7nm then it is 70A wide, still too wide for the CaK band but better than the Baader.

My Baader has something wrong with it, I must look up how much this one costs, mmm much cheaper, I might give it a go.

Alexandra


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Re: white light comparison

Post by marktownley »

Nope. No comparison.

Personally I wouldn't waste my money with either.


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Re: white light comparison

Post by Montana »

No good for what Mark? bad quality optics or just wide band?

My Baader K line is permanently just out of focus, it works OK as a blocking filter for the PST at prime focus but when you use a 2x Barlow it is back to blurred. This one is 10A narrower and could be in focus and is much cheaper, that could be a win for me.

It will never give you a CaK view though when used with a Herschel wedge, it will still only enhance faculae in white light. We all know this :)

Alexandra


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Re: white light comparison

Post by alpha76 »

Montana wrote: Wed May 12, 2021 9:27 am Nope but it sounds interesting, I think the Baader is 8nm which is 80A wide. If it is 7nm then it is 70A wide, still too wide for the CaK band but better than the Baader.

My Baader has something wrong with it, I must look up how much this one costs, mmm much cheaper, I might give it a go.

Alexandra
thank you for your answer MONTANA

here is the link on the direct site

https://www.altairastro.com/altair-nuv- ... 6910-p.asp


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Re: white light comparison

Post by alpha76 »

I am very satisfied with my filter k-line baader with my tsa102 but I would have liked to compare them
to get an overview of the price / quality ratio compare to the baader
as a reminder in france the baader is at 295 € with astrosolar 3.8 A4 format included against 166.95 € for the NUV
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Sun_095516.jpg (819.12 KiB) Viewed 1153 times
sun_0925.jpg
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Re: white light comparison

Post by christian viladrich »

Hello Alexandra,
I was wondering about your blurred images with the K-line. Could it be more some reflection rather than actual blur ? Do you have this issue also without the Barlow lens ?


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Re: white light comparison

Post by Montana »

Thanks Christian. When I imaged with the TEC140 in WL the image was crystal clear, when I added the Baader K line it was like a fog. With the CaK from Lunt it is crystal clear again. I can't remember whether this test was with or without a barlow.

The PST is at prime focus and it works OK as a blocking filter but the images are not as sharp as when I used the old rusted blocking filters (which I removed) and swapped to the Baader K line. So I know something is wrong with the K line. This is without a Barlow and is much worse with a barlow.

Alexandra

Here is a link to how bad it is
https://www.flickr.com/photos/alexandra ... 8/sizes/k/


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Re: white light comparison

Post by MalVeauX »

Hi,

I use the Altair NUV 7nm 395nm filter. It's good quality with good transmission. It's ideally used for high res photosphere imaging if critically sampling but requires extraordinary seeing to do with any larger apertures since it's 58~59% higher angular resolution than typical red wavelengths. So 80~102mm aperture is significant with this wavelength of course, just like CaK. SCT mirrors are horrible with near UV with terrible spherical abberation which will require additional under-correctors to even begin to salvage the poor image. The ideal optic is a long focal-ratio newtonian or really long focal-ratio achromatic doublet with spacers to under-correct for the NUV wavelength to be diffraction limited. Custom newtonian mirror is the best way to go though, if this is your passion. The cost to make an SCT work for this, and work well, you might as well have just used a newtonian without all that fuss. And of course you can do this with photograde solar film with high transmission to keep it reasonable with cost and weight. That said, you can use a bigger long refractor super easily with a sub-aperture DERF or solar film for cheap and it will do quite well too if it's long focal ratio.

It's a good filter for high res solar if you have the seeing, photosphere anyways. But it's really a great Venus filter to image the lower cloud bands when Venus is in good position for imaging for you during the night with best seeing. The transmission is good for this since it's a dim image even though Venus is so bright in longer wavelength. So I have this filter primarily for getting the most resolution I can at the limits of seeing for photosphere and for imaging clouds on Venus.

I have yet to max out this filter's wavelength with my larger systems because the seeing requirement is steep. I need 0.6~0.7 arc-seconds to use my 120mm and 150mm apertures and get even close to this angular resoution but I do not get that kind of seeing often. I can use it at 100mm fairly well needing around 1 arc-second seeing. Still, I do not get this every day and this wavelength is heavily effected by atmospheric seeing. Same as Calcium basically. I do use this wavelength mostly to get the most resolution I can from smaller apertures where my seeing will handle it and get a higher resolution full disc when I can, from tiny apertures like 40mm to 60mm or so, and with long native focal ratio and using a big sensor. I like it for that. It's not tremendously different from a green or red wavelength image though.

So I'm not sure I would say to go this far for photosphere imaging unless you have superb seeing conditions, or unless you are also very interested in Venus cloud imaging, which it is good for.
AltairAstro_NUV_395nm_7nm_Filter_12072020.jpg
AltairAstro_NUV_395nm_7nm_Filter_12072020.jpg (205.53 KiB) Viewed 1106 times
150mm with frac, seeing simply didn't support it, but to give you an idea of convection cell size at this scale; 150mm F16 on 2.9um pixels:
AR2790_395nm_150mmF16_290MM_17frames_BW_12082020.jpg
AR2790_395nm_150mmF16_290MM_17frames_BW_12082020.jpg (453.27 KiB) Viewed 1106 times
Here's 60mm aperture at F16.7 on 3.45um pixels:
SolarDisc_395nm_60mmF16_IMX253_61frames_BW_02232021.jpg
SolarDisc_395nm_60mmF16_IMX253_61frames_BW_02232021.jpg (1.15 MiB) Viewed 1106 times
Otherwise, this is the kind of thing it's really useful for and well worth it for, Venus clouds:
Venus_150mmF16_RGB_UV_03292020.jpg
Venus_150mmF16_RGB_UV_03292020.jpg (51.26 KiB) Viewed 1105 times
Venus_RGB_UV_IR_200mmF12_IMX183_03132020.jpg
Venus_RGB_UV_IR_200mmF12_IMX183_03132020.jpg (53.73 KiB) Viewed 1105 times
Very best,


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