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Methane filters and night vision for planets

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#1 Gavster

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Posted 05 June 2019 - 02:57 PM

I have seen a few reports of people using methane filters with night vision for viewing planets.

Please could someone explain the benefits of doing this compared with normal glass viewing and what type of methane filter works best?

Thanks

Gavin



#2 Starman81

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Posted 05 June 2019 - 05:24 PM

I've been thinking about this lately after reading the S&T article about the GRS unraveling. See the picture in the article. The filter cited there was Methane 890nm. That would be pretty cool to see the 'flakes' forming off the GRS, but not sure if its feasible for visual, since they are small, fine features. Might require imaging (?). 



#3 Vondragonnoggin

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Posted 05 June 2019 - 06:20 PM

I've been thinking about this lately after reading the S&T article about the GRS unraveling. See the picture in the article. The filter cited there was Methane 890nm. That would be pretty cool to see the 'flakes' forming off the GRS, but not sure if its feasible for visual, since they are small, fine features. Might require imaging (?). 

Hmmm. This might be a good experiment for one of my gen 2 tubes. 

 

I think any planetary I try with a methane filter will be with one of my gen 2’s. I grazed across Saturn the other evening with my pvs-7 with a 3nm Ha in as I was scanning for other nebulae in the general region and was surprised to see division between rings and planet. I did not stay any length of time on it. I would hope the methane filter is considerably darker than a 3nm Ha filter or some tube damage will be imminent on prolonged study with it. The mx9644 gen 2 tubes I have are  inexpensive to purchase if something happens from objects too bright for them.

 

Just looked at the price of these. Think I’ll wait for more testers before I walk off that plank. 

 

The Baader is 8nm wide at 889nm

 

Gen 2+ might be too low a response at 889nm. Some gen 3’s even have sharp rolloff at 850nm. Extended Red, Enhanced Red, Extended IR would be better tubes for a Methane filter.

 

Photonis Intens 4G should be good to go for Methane:

 

https://www.ar15.com...own_/18-451412/

 

 

 

Interesting article on some spectral responses for intensifiers:

 

https://www.inframet...n metrology.pdf

 

 

 

This page has a response graph for different intensifiers GaAs, InGaAs, GaAsP, Enhanced Red GaAsP, MultiAlkali

 

http://www.hakuto.co...cts_d.php?p=193

 

 

 

Moshen also posted a graph and talks about GaAs tube responses and falloff (Thanks Moshen - always interesting info and discussions from you guys here)

 

https://www.cloudyni...tens/?p=8579489

 

 

 

Here is another graph on this page showing some different gen 2 and gen 3 type responses

 

https://www.lamberti...age-intensifier

 

 

 

 

Another showing Gen 2+ (S25 multiAlkali) and gen 3 GaAs

 

https://www.research..._fig3_257909095

 


Edited by Vondragonnoggin, 05 June 2019 - 07:06 PM.

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#4 slavicek

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Posted 05 June 2019 - 09:42 PM

I am planning to use the (recently purchased) Baader Methane filter with NV on Jupiter some time soon. I am curious about this too...

Hopefully I will have something interesting to report.



#5 jdbastro

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Posted 06 June 2019 - 12:20 AM

I have seen a few reports of people using methane filters with night vision for viewing planets.

Please could someone explain the benefits of doing this compared with normal glass viewing and what type of methane filter works best?

Thanks

Gavin

It gives you a 'different' looking view.

 

I tried this a couple years back with Gen 3 and a Photonis 4G tube.

 

Here are real-time video links:

 

Jupiter with Gen 3 unfilmed

Jupiter with Photonis 4G

 

Saturn with Gen 3 unfilmed

Saturn with Photonis 4G

 

Definitely worth a try.   wink.gif


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#6 Vondragonnoggin

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Posted 06 June 2019 - 12:58 AM

It gives you a 'different' looking view.

 

I tried this a couple years back with Gen 3 and a Photonis 4G tube.

 

Here are real-time video links:

 

Jupiter with Gen 3 unfilmed

Jupiter with Photonis 4G

 

Saturn with Gen 3 unfilmed

Saturn with Photonis 4G

 

Definitely worth a try.   wink.gif

The video looks cool, but any idea of scintillation difference in visual trying to get enough image scale to make out details vs the video presentation?

 

I think I’d have to use my mak’s native F/12 to get enough image scale and that looks darker than the narrowband Ha presentation. I would think visually scintillation is going to be pretty great.

 

Maybe not good for small apertures but better with a 10” or up to keep scintillation down and still get image scale.

 

I think it’s going to ace out my 6” or less scopes with too much scintillation.


Edited by Vondragonnoggin, 06 June 2019 - 01:03 AM.

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#7 Gavster

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Posted 06 June 2019 - 04:34 AM

It gives you a 'different' looking view.

 

I tried this a couple years back with Gen 3 and a Photonis 4G tube.

 

Here are real-time video links:

 

Jupiter with Gen 3 unfilmed

Jupiter with Photonis 4G

 

Saturn with Gen 3 unfilmed

Saturn with Photonis 4G

 

Definitely worth a try.   wink.gif

Thank you Jay. Given the brightness of Jupiter and Saturn do you think there is any risk of damaging the nv tube if you spend more than a few seconds on the planet? Or does the filter bring the brightness down to such a level it’s ok?

 

Re the filters I note that the chroma you use has 18nm bandwidth vs the baader which has 8nm bandwidth. Is the wider bandwidth of the chroma useful for reducing scintillation do you think?

 

Also given the wider spectral sensitivity of the photonis 4g than the l3 do you think the photonis has the advantage on this type of nv viewing? (I have both a photonis 4g and harder gen 3 so would be interested to hear if there was much difference between the two - from the your videos the differences seem marginal?)

 

I agree bigger aperture seems to make sense for this given the need to get 100x plus mag. I think I would try my c11 with my delite 18.2mm which would run at f10 and get over 100x mag so maybe not too much scintillation if I adjust the gain down.


Edited by Gavster, 06 June 2019 - 05:08 AM.

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#8 BJS

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Posted 06 June 2019 - 08:43 AM

I have used the zwo methane filter with my micro nv device.  I have observed both Jupiter and Saturn with a 25" f5 telescope.  The filter does reveal the red spot but it is hard to see details in it.  I think you may need very good seeing to be able to resolve details which is an issue here in nw ohio.  I have not been able to use it yet this year but I am also curious to see how it show the red spot.  From the images i have seen online using a methane filter, it may lend it self better to planetary imaging vs direct viewing.  Saturn is unreal btw....it looks like a negative image as the rings reflect much more than the planet does at that wavelength.  

 

The zwo filter has a bandpass of 20nm where as the baader filter is 8nm.....The zwo may be to wide for detailed observation.



#9 jdbastro

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Posted 07 June 2019 - 12:13 AM

Thank you Jay. Given the brightness of Jupiter and Saturn do you think there is any risk of damaging the nv tube if you spend more than a few seconds on the planet? Or does the filter bring the brightness down to such a level it’s ok?

 

Re the filters I note that the chroma you use has 18nm bandwidth vs the baader which has 8nm bandwidth. Is the wider bandwidth of the chroma useful for reducing scintillation do you think?

 

Also given the wider spectral sensitivity of the photonis 4g than the l3 do you think the photonis has the advantage on this type of nv viewing? (I have both a photonis 4g and harder gen 3 so would be interested to hear if there was much difference between the two - from the your videos the differences seem marginal?)

 

I agree bigger aperture seems to make sense for this given the need to get 100x plus mag. I think I would try my c11 with my delite 18.2mm which would run at f10 and get over 100x mag so maybe not too much scintillation if I adjust the gain down.

Risk of damage?  If you use a scope that is f10 or slower, I doubt there would be an issue.  My scope was operated at f12 (native), f24, and f48 (via barlows).

 

A wider filter certainly would help reduce scintillation.

 

The Photonis tubes show fewer sparkles in my videos.  The reason apparently is because the default gain on 4G tubes is set lower than it is on U.S. Gen 3 tubes.  None of my 18 mm tubes have manual gain.

 

In then methane band, I don't believe that 4G or Gen 3 tubes have an individual advantage.

 

So far, I have not attempted methane narrow band viewing with the afocal NV coupling method.  Only prime focus or barlow extended focus.


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#10 Gavster

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Posted 07 June 2019 - 02:25 AM

Risk of damage?  If you use a scope that is f10 or slower, I doubt there would be an issue.  My scope was operated at f12 (native), f24, and f48 (via barlows).

 

A wider filter certainly would help reduce scintillation.

 

The Photonis tubes show fewer sparkles in my videos.  The reason apparently is because the default gain on 4G tubes is set lower than it is on U.S. Gen 3 tubes.  None of my 18 mm tubes have manual gain.

 

In then methane band, I don't believe that 4G or Gen 3 tubes have an individual advantage.

 

So far, I have not attempted methane narrow band viewing with the afocal NV coupling method.  Only prime focus or barlow extended focus.

Is there any particular reason you haven’t gone for tubes with manual gain?



#11 Vondragonnoggin

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Posted 07 June 2019 - 06:24 AM

Risk of damage?  If you use a scope that is f10 or slower, I doubt there would be an issue.  My scope was operated at f12 (native), f24, and f48 (via barlows).

 

A wider filter certainly would help reduce scintillation.

 

The Photonis tubes show fewer sparkles in my videos.  The reason apparently is because the default gain on 4G tubes is set lower than it is on U.S. Gen 3 tubes.  None of my 18 mm tubes have manual gain.

 

In then methane band, I don't believe that 4G or Gen 3 tubes have an individual advantage.

 

So far, I have not attempted methane narrow band viewing with the afocal NV coupling method.  Only prime focus or barlow extended focus.

Wow that’s some long focal length on it. I can see how using focal length coupled with the narrow Methane notch should dim down the planet enough for extended observation with intensifiers. In the videos they didn’t look any brighter really than brightest M42 regions.

 

Ray (The Ardent) was saying it’s made the difference on seeing Neptune or not seeing it at all in his dob.




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