G band instead of Ca-k filter

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Re: G band instead of Ca-k filter

Post by DeepSolar64 » Thu Nov 26, 2020 4:27 pm

Does anyone make one to mount in an eyepiece, already mounted in a 1.25" cell? I am surprised Baader does not have one.


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Re: G band instead of Ca-k filter

Post by marktownley » Thu Nov 26, 2020 4:32 pm

DeepSolar64 wrote:
Thu Nov 26, 2020 4:27 pm
Does anyone make one to mount in an eyepiece, already mounted in a 1.25" cell? I am surprised Baader does not have one.
Nope, just us nerds on here aware of them.


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Re: G band instead of Ca-k filter

Post by MalVeauX » Thu Nov 26, 2020 7:47 pm

DeepSolar64 wrote:
Thu Nov 26, 2020 4:03 pm
Stardust5858 wrote:
Thu Nov 26, 2020 2:52 pm
DeepSolar64 wrote:
Thu Nov 26, 2020 3:29 am
Where would I find a 430nm filter and would it be of any real use visually? Would it benefit me in a similar way as a 540nm filter does? Obviously a true ultra-narrowband Gband filter would be better but I bet they are pricier too.
I found this one at:-
Edmund Scientific.
430nm CWL, 25mm Dia., Hard Coated OD 4.0 10nm Bandpass Filter
Do they make a 1.25" size? One that will screw into an eyepiece?
I have that filter, I mounted it into a 28mm holding cell (standard 1.25") which then threads to anything like a typical 1.25" filter.

That said, this is not a useful filter for visual, and frankly not that useful for imaging either. See above notes.

Stick to 540nm, or longer, for photosphere visual. Going any shorter wavelength, visually to see something meaningfully different than just the photosphere would be 396nm and even then only at around 5~6A or less. CaH basically. Shorter than that and you likely won't see anything due to yellowing of your cornea.

Very best,



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Re: G band instead of Ca-k filter

Post by DeepSolar64 » Thu Nov 26, 2020 10:10 pm

Thanks Marty,
I do already have a 540nm filter. I would like to have one of those Sodium Quarks to use with my Astro-Tech AT72EDII refractor.

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Re: G band instead of Ca-k filter

Post by DeepSolar64 » Thu Nov 26, 2020 10:11 pm

marktownley wrote:
Thu Nov 26, 2020 4:32 pm
DeepSolar64 wrote:
Thu Nov 26, 2020 4:27 pm
Does anyone make one to mount in an eyepiece, already mounted in a 1.25" cell? I am surprised Baader does not have one.
Nope, just us nerds on here aware of them.
:beanie: :lol:


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Re: G band instead of Ca-k filter

Post by christian viladrich » Sat Nov 28, 2020 3:09 pm

Hello,
Here is a comparison of a G-band 430-10 nm filter (Edmund Optics) and a 430-2nm filter (Andover Optics). The 2 nm FWHM filter provides more contrast on intergranular bright points.
Image

Image

The intergranular bright points (also called G-band bright spots) are also visible with a 395-5 nm filter or with Baader K-line filter :
Image

The minimum diameter required to observe the G-band bright spots is 200 mm (in best condition and only for the larger points) but this is definitely better with a 300 mm telescope (and excellent seeing).

The G-band filter is also my favourite for visual observation of granulation and sunspot with my Taka TOA 150. The contrast and resolution is increased compared to a continuum green filter.

You have to check Andover "surplus" for the 430-2 nm or a 396-5 nm filter.


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Re: G band instead of Ca-k filter

Post by Stardust5858 » Sat Nov 28, 2020 7:30 pm

Hi,
Would this be a good filter. 433.9nm 1.0nm 25mm

Andover Custom BP filter CWL 433.9nm/HBW 1.0nm/25.0mm dia.
433.9 / 1.0 - 59622
$154.05
Center Wavelength 433.9+0.2/-0 nm
Bandwidth 1.0+0.2/-0.2 nm
Transmission 40%





Blocking 1x10-4 avg. X-Ray to FIR
Size +0/-0.25mm
Thickness 7.0 +0/-nom mm
Effective refractive index (n*) -
Filter Type 2 (Click for profile)
CSV File (typical) N/A



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Re: G band instead of Ca-k filter

Post by christian viladrich » Sat Nov 28, 2020 10:13 pm

Unfortunately not. It should be 430.5 nm. The 433.9-1 nm is off G-band.


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Re: G band instead of Ca-k filter

Post by christian viladrich » Sat Nov 28, 2020 10:15 pm

This is the right filter :
Custom BP filter CWL 430.7nm/HBW 2.0nm/25.0mm
https://www.andovercorp.com/products/su ... s-filters/


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Re: G band instead of Ca-k filter

Post by Stardust5858 » Sat Nov 28, 2020 11:45 pm

christian viladrich wrote:
Sat Nov 28, 2020 10:13 pm
Unfortunately not. It should be 430.5 nm. The 433.9-1 nm is off G-band.
Thanks for your help



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Re: G band instead of Ca-k filter

Post by Stardust5858 » Sun Nov 29, 2020 9:28 am

Sorry for being a pain. Would this work, can't find an exact 430nm.

Andover Center Wavelength 430.7+0.4/-0.0 nm
Bandwidth 2.0+0.5/-0.5 nm
Transmission 45%
Blocking 1x10-4 avg. X-Ray to FIR
Size +0/-0.25mm
Thickness 9.5 +0/-nom mm



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Re: G band instead of Ca-k filter

Post by marktownley » Sun Nov 29, 2020 11:01 am

Have you tried plumbing in the shipping costs to the UK from Andover? They are likely to be more than you think. There's customs excise and everything on top too...

From what I can see they don't have stock for that filter.

Have you imaged at 540nm with a continuum filter?


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Re: G band instead of Ca-k filter

Post by Stardust5858 » Sun Nov 29, 2020 6:35 pm

marktownley wrote:
Sun Nov 29, 2020 11:01 am
Have you tried plumbing in the shipping costs to the UK from Andover? They are likely to be more than you think. There's customs excise and everything on top too...

From what I can see they don't have stock for that filter.

Have you imaged at 540nm with a continuum filter?
Yeah, I've thought about all the added cost too. I've a Lunt so only done ha. I'll probably add a Lunt Ca K next year, seems like the best way to go plus WL. Seems most seem to do these tri band observations. I've a white light filter for my birthday next week for my C11 and 80ed.



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Re: G band instead of Ca-k filter

Post by MalVeauX » Tue Dec 01, 2020 7:51 pm

Keep in mind what Christian pointed out, you need a big aperture and his seeing was sustained 0.7~0.8 arc-seconds, and as good as 0.3 arc-seconds. This isn't anyone's backyard seeing. This was at a specific location with exceptional seeing conditions. Professional observatory location class. G-band is really a fickle unicorn for most, simply due to the seeing requirements of such a short wavelength. For the same reason few people are able to image high resolution Calcium K (393nm) with enormous apertures.

Very best,



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Re: G band instead of Ca-k filter

Post by marktownley » Tue Dec 01, 2020 8:34 pm

MalVeauX wrote:
Tue Dec 01, 2020 7:51 pm
Keep in mind what Christian pointed out, you need a big aperture and his seeing was sustained 0.7~0.8 arc-seconds, and as good as 0.3 arc-seconds. This isn't anyone's backyard seeing. This was at a specific location with exceptional seeing conditions. Professional observatory location class. G-band is really a fickle unicorn for most, simply due to the seeing requirements of such a short wavelength. For the same reason few people are able to image high resolution Calcium K (393nm) with enormous apertures.

Very best,
100% agree with you here Marty.

Sage advice! :cool:


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Re: G band instead of Ca-k filter

Post by christian viladrich » Wed Dec 02, 2020 10:26 am

Stardust5858 wrote:
Sun Nov 29, 2020 9:28 am
Sorry for being a pain. Would this work, can't find an exact 430nm.

Andover Center Wavelength 430.7+0.4/-0.0 nm
Bandwidth 2.0+0.5/-0.5 nm
Transmission 45%
Blocking 1x10-4 avg. X-Ray to FIR
Size +0/-0.25mm
Thickness 9.5 +0/-nom mm
Sorry, I was not arround.
Yes, this is the one. Two pieces were still available a few days ago, but now none ...


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Re: G band instead of Ca-k filter

Post by christian viladrich » Wed Dec 02, 2020 10:27 am

MalVeauX wrote:
Tue Dec 01, 2020 7:51 pm
Keep in mind what Christian pointed out, you need a big aperture and his seeing was sustained 0.7~0.8 arc-seconds, and as good as 0.3 arc-seconds. This isn't anyone's backyard seeing. This was at a specific location with exceptional seeing conditions. Professional observatory location class. G-band is really a fickle unicorn for most, simply due to the seeing requirements of such a short wavelength. For the same reason few people are able to image high resolution Calcium K (393nm) with enormous apertures.

Very best,
This is completely true.


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Re: G band instead of Ca-k filter

Post by MalVeauX » Wed Dec 02, 2020 6:09 pm

Heya,

Just because it was asked, you can get filter mounts with threaded cells that will hold a 25mm filter.

https://www.ebay.com/itm/Eyepiece-Filte ... 236afeeb55

If you search eyepiece filter mount 28mm for 25mm filter you'll find lots of these out there.

I bought this exact one and it held my EO 430nm no problem.

But I still don't recommend the 430nm filter. :P

Very best,



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Re: G band instead of Ca-k filter

Post by DeepSolar64 » Thu Dec 03, 2020 5:53 am

MalVeauX wrote:
Wed Dec 02, 2020 6:09 pm
Heya,

Just because it was asked, you can get filter mounts with threaded cells that will hold a 25mm filter.

https://www.ebay.com/itm/Eyepiece-Filte ... 236afeeb55

If you search eyepiece filter mount 28mm for 25mm filter you'll find lots of these out there.

I bought this exact one and it held my EO 430nm no problem.

But I still don't recommend the 430nm filter. :P

Very best,

So you recommend the 540Nm filter?


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Re: G band instead of Ca-k filter

Post by MalVeauX » Thu Dec 03, 2020 1:21 pm

DeepSolar64 wrote:
Thu Dec 03, 2020 5:53 am
MalVeauX wrote:
Wed Dec 02, 2020 6:09 pm
Heya,

Just because it was asked, you can get filter mounts with threaded cells that will hold a 25mm filter.

https://www.ebay.com/itm/Eyepiece-Filte ... 236afeeb55

If you search eyepiece filter mount 28mm for 25mm filter you'll find lots of these out there.

I bought this exact one and it held my EO 430nm no problem.

But I still don't recommend the 430nm filter. :P

Very best,

So you recommend the 540Nm filter?
Yes, it's a good filter, it's as short wavelength (high angular resolution) as I would go, visually, unless you have exquisite seeing conditions. Even then, it's not needed, a polarized filter and something like a red filter will often be more useful simply because seeing will generally always be poor, and red will steady the seeing more than green will.

Very best,



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Re: G band instead of Ca-k filter

Post by DeepSolar64 » Fri Dec 04, 2020 4:52 pm

I hope in time to get a Sodium D line Quark for my AT72EDII refractor. With 72mm of aperture it shouldn't require an ERF but only a UV/IR cut filter.

http://www.daystarfilters.com/Quark/NaQuark.shtml


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Re: G band instead of Ca-k filter

Post by krakatoa1883 » Wed Dec 09, 2020 8:34 am

Stardust5858 wrote:
Sun Nov 29, 2020 9:28 am
Sorry for being a pain. Would this work, can't find an exact 430nm.

Andover Center Wavelength 430.7+0.4/-0.0 nm
Bandwidth 2.0+0.5/-0.5 nm
Transmission 45%
Blocking 1x10-4 avg. X-Ray to FIR
Size +0/-0.25mm
Thickness 9.5 +0/-nom mm
I have one purchased from the Andover dealer in Italy. It works fine, very sharp and contrasty. It requires plenty of light so I put it just behind the Baader wedge (on 100mm ED refractor) with no neutral filters inside. For using this filter seeing needs to be really good.


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Re: G band instead of Ca-k filter

Post by marktownley » Wed Dec 09, 2020 7:40 pm

krakatoa1883 wrote:
Wed Dec 09, 2020 8:34 am
For using this filter seeing needs to be really good.
And this is the key takeaway from this thread!


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Re: G band instead of Ca-k filter

Post by DeepSolar64 » Thu Dec 17, 2020 6:45 am

I might go for Gband if I had consistently better seeing. I don't, especially this time of year :(


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