Methane Filter for Jupiter

[stasman]

Hi,

I am new on this forum but have been reading threads for a bit of time now. Lots of information is very helpful.

However, I came up with a question of my own, and was not able to find an answer by searching the forum so far. Hopefully some of you might be able to help.

Which manufacturer's narrowband 890nm CH4 filter for Jupiter work would you recommended and why. These are not cheap so I would appreciate some information to make a good decision.

Thanks a lot for your help!

Stas

[Merlin66]

The methane bands out in the red and NIR are an interesting target.

Not many of the CCD cameras give good response efficiency this far into the red. I use a modified ( no filter) DSLR which can record the methane bands in the spectroscope, but honestly haven't tried filters or other CCD's in the NIR.

Who supplies these filters? Is there a transmission curve available?

Ken

[stasman]

Hi Ken,

Thank you for your interest. The reason why I am interested in 890nm is because that is where methane gas absorbs light the most, so you can do some interesting studies in that part of the spectrum. I would be using Flea 3 (ICX618) monochrome camera for this work. I was not able to find spectral sensitivity characteristics for ICX618, but I know that ICX424 is still sensitive that far into the red.

I know that Antonio Cidadao from Portugal is doing that type of work. But I am not sure what camera he is using.

Jupiter Impact | UCF Planetary Sciences Group

I also see CH4 photos on Christopher Go's web site. I know for a fact that he is using Flea3 for his work, as I am sure you know too, since I have read the Flea3 thread you have started :-). Although, I am not sure if he is taking 619, 727, or 890 nm images.

So far I was able to find 2 suppliers of these filters:

Hutech Filters and Accessories

These guys have it for 340 bucks.

Astronomy filters - Custom Scientific

And these guys have it for 495.

Was curious if there are any other options out there :-)

Thanks for the help!

[Merlin66]

I have the curves for the #424, it shows a relative efficiency at 890 of around 0.11. Based on a max of say 0.6 this would infer 0.066% efficiency at 890nm - not much!!

The DMK at 0.2 and the #425 at 0.25 relative look maybe a bit better.

I would have thought the 619, 727nm regions might be a better compromise of transmission/ CCD efficiency......

[stasman]

I agree with you on the 619, 727nm regions. Would be curious to find out which region Christopher Go is looking at.

Do you have spectral curve for ICX618 by any chance? I wonder is Sony has even made that available yet...

Thanks for your help :-)

[Merlin66]

Hutech Astronomical Products - BGR+L Filters

The type 4 G has a secondary bandwith in the 800nm which may be of interest...

I'll have a look for the #618 curves...

[Merlin66]

http://www.1stvision.com/cameras/sensor_specs/ICX618.pdf

What about this?

[stasman]

Thanks Ken!

According to that spectral sencitivity plot 619 is about 3 times more sensitive that 424 in that part of the spectrum. Not sure if that would be enough though.

Stas

[riklaunim]

Anthony Wesley did very good images in methane band with PGR Flea 3 / ICX618. With the old CCDs - ICX098 and ICX424 it's also doable but you will need better seeing and probably under-expose frames. As for filters - Baader did released methane filter some time ago, but as all CH4 filters - it's expensive.

Note: Emil did a mod of DMK - and changed the CCD from 098 to 618 and it does work - google for the mod.

[frewi808]

Planning to mod my ToUcam and the DFK21 with the ICX618ala, maybe one mono and one color.

[RobH]

Interesting that this thread has come up....I was considering a methane filter, but am more interested in a Helium filter (not He2), as this is nicey in the green I believe.

Cheers

Rob

[riklaunim]

There is few helium lines to choose

[RobH]

That one smack in the middle of the green is the one.

Proper RGB using Ha/He/OIII.

Any idea where to get one from?

Cheers

Rob

[riklaunim]

The yellowish He I ? Would be fragile to light pollution.

Start with:

Optical Filters and Instruments - Asahi Spectra USA Inc.

Optics, Imaging, and Photonics Technology - Edmund Optics