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#51 bdg

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Posted 10 June 2019 - 06:59 PM

thx - I will reach out to few vendors to check what they have, BTW it looks like I drove the OP away  :-)



#52 Vondragonnoggin

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Posted 10 June 2019 - 07:17 PM

thx - I will reach out to few vendors to check what they have, BTW it looks like I drove the OP away  :-)

He’s probably leisurely digesting information. My first thread asking about it had all kinds of folks jumping in. It was all good.

 

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#53 bdg

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Posted 10 June 2019 - 07:38 PM

has anyone tried to change the default EP from 27mm to something higher magnification, I presume the IIT diameter will act as the field stop if the tube size is 18mm will it work with wide afov EP's like XW 14 which has 17.6mm FS or Delite 15 with 16mm FS. 



#54 Jeff Morgan

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Posted 10 June 2019 - 08:30 PM

ditto! I ran the panasonic plasma @ 720p as my TV till 2015 and jumped on a Samsung 1080p Plasma and sold the 720p. I wouldn't have changed the Panasonic but Samsung plasma was the last Plasma TV ever made.

lol.gif

 

I did the same, grabbed the Samsung 64" at the end of 2014. Plasma is magnificent for movies and sports, about the only thing I use a TV for.

 

Hope it lasts forever grin.gif


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#55 Vondragonnoggin

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Posted 10 June 2019 - 10:15 PM

has anyone tried to change the default EP from 27mm to something higher magnification, I presume the IIT diameter will act as the field stop if the tube size is 18mm will it work with wide afov EP's like XW 14 which has 17.6mm FS or Delite 15 with 16mm FS. 

The oculars are proprietary and not interchangeable unless with a specific device with the same ocular threading. The current focal length was determined for best results with 1x lenses and supplied magnification lenses. Some years of research in the making of these. For the easiest devices to work with telescope use and still be able to change tubes easy, currently it’s going to be the pvs-7, pvs-14 (afocal use in telescope only - 1x, 3x, 5x lenses available), NVD Micro (c-mount), and Mod 3 (c-mount). I believe all but pvs-7 use the same ocular and threading. The pvs-7 oculars are tied in with the whole backplate of the device and the backplate is a field replaceable unit. Optimized for the 18mm tubes.

 

My advice would be to stick with the supplied ocular they are using in current devices.



#56 GOLGO13

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Posted 11 June 2019 - 08:32 AM

thx - I will reach out to few vendors to check what they have, BTW it looks like I drove the OP away  :-)

No worries...I'm enjoying the dialogue. I had taken a few days off CN for fishing. What I would love to do is pay one of our experienced members to find me a kit. Filters and a reasonable tube/setup. But I think sending an email to some of the mentioned vendors with some of the specs discussed would probably bear fruit. 

 

Now I need to start selling scopes and build up a bit of cash. In some ways I should start selling off my video game collection (I have a museum amount of video game systems/handhelds/classic computers). But it would take me way too much energy to do that. I'm sure my wife would help ship stuff. I do enjoy playing them and am just starting to get them setup in my new house. But maybe I could sell some of the rare ones that are not very fun to play. They are more collectables rather than useful.


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#57 Vondragonnoggin

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Posted 11 June 2019 - 09:20 AM

No worries...I'm enjoying the dialogue. I had taken a few days off CN for fishing. What I would love to do is pay one of our experienced members to find me a kit. Filters and a reasonable tube/setup. But I think sending an email to some of the mentioned vendors with some of the specs discussed would probably bear fruit. 

 

Now I need to start selling scopes and build up a bit of cash. In some ways I should start selling off my video game collection (I have a museum amount of video game systems/handhelds/classic computers). But it would take me way too much energy to do that. I'm sure my wife would help ship stuff. I do enjoy playing them and am just starting to get them setup in my new house. But maybe I could sell some of the rare ones that are not very fun to play. They are more collectables rather than useful.

 

gaah.gif

 

If you can keep the video gaming at all possible......

 

wink.gif  No pressure.

 

Big video gaming enthusiast here. Atari, GameCube, N64, Super Nintendo, original DS, DS Lite, Switch, Xbox, Xbox One, Xbox 360, Xbox One X, PlayStation 2, PlayStation 3, PlayStation 4, Wii, Old PC’s with XP and Unreal 2004 with gigs of mods and maps, Diablo w/Hellfire expansion, Diablo II with Expansions, Quake III Arena with gigs of maps. VR headsets, a bunch of VR games.

 

Synthesizer with AY3 chip (Intellivision), 2 SID chip synthesizers (80’s Apple games). - Also a big music gear fan.

 

Again - No pressure. Do what you will with your collection......

 

There are other options like a pvs-7 or used older monocular.

 

I picked up a used Gen 3 Monocular with built in c-mount, 25mm, 50mm, and 75mm c-mount lenses, all in a pelican 1150 case for $700 a few years back. Older tube but still powerful enough to do narrowband Ha.

 

Others here on the forum using older devices as well. Recommend renting or finding someone local that also has a Monocular that you can at least hold up to an eyepiece for an afocal peek at what they can do before getting rid of collectibles.



#58 GOLGO13

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Posted 11 June 2019 - 09:53 AM

Hah...nice! I have most systems, only missing a few like Neo Geo, bally astrocade, Channel F...But I haven't collected for video game things in a long time. As I'm getting the systems setup, I am getting more the idea I don't want to sell them. Atari is my favorite, but I grew up on it. One thing I can't understand is why I continue to buy new systems and games. I hardly play new systems anymore. But, I'm a sucker for new tech like that. I'll need to be disciplined when anything else comes out.

 

I think I will just sell the C8 and C6 (which I really didn't need, just kinda wanted to try them out). My 103mm Vixen since I have the 81s and the 130mm SS. The 103mm is a great scope, but just not really needed now. And the AT60mm which I actually really like. But I have an HA setup for my TV60mm and a nice case...so the AT60 is a bit not necessary. However, I actually prefer the AT60 in general. It's a great value of a scope. But of course 60mm scopes are fairly limited. I figure I can get around 2K for the scopes which would cover a good amount of the NV setup.


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#59 GOLGO13

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Posted 11 June 2019 - 10:41 AM

Well...It's on like Donkey Kong. I am getting a MOD-3 C-Mount Night Vision Monocular with Gain Control - Filmless White Phosphor.

 

It's coming with a 1.25" Astrodon H-alpha filter 5nm.

 

I have multiple filters but not sure if they are useful for NV. I have h beta (lumicon), narrowband UHC Lumicon, OIII lumicon. And I believe I have some sort of IR cut filter I use for my HA solar setup. I think it's a baader.

 

Now I have to break it to the wife somehow before that bill comes in the mail ;)


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#60 Vondragonnoggin

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Posted 11 June 2019 - 10:54 AM

Regular visual filters in green and blue not useful for Night Vision. OIII, UHC, Hb 

 

5nm Ha will be great.

 

Start here for filter info that works with Night Vision 

 

https://www.cloudyni...s-used-with-nv/



#61 GOLGO13

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Posted 11 June 2019 - 11:34 AM

I have this filter also: https://www.baader-p...--l-filter.html

 

Not sure if that would be useful or not. I use it with my HA setup....and at this point I'm not sure why as I can't remember.



#62 Vondragonnoggin

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Posted 11 June 2019 - 11:59 AM

I have this filter also: https://www.baader-p...--l-filter.html

 

Not sure if that would be useful or not. I use it with my HA setup....and at this point I'm not sure why as I can't remember.

Not useful either. Intensifier response goes up to about 950nm for those L3 tubes. You don’t want to cut the response. In fact dielectric diagonals aren’t recommended because they also drop response above 700nm. If you are just doing narrowband Ha then a dielectric doesn’t matter, but galaxy hunting you’ll want that extended response.



#63 GOLGO13

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Posted 11 June 2019 - 12:15 PM

Ahh. I have both prism and dielectric diagonals. Hoping my 10 inch dob is good as is.

#64 Vondragonnoggin

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Posted 11 June 2019 - 12:20 PM

Ahh. I have both prism and dielectric diagonals. Hoping my 10 inch dob is good as is.

Read here about 10” dob

https://www.cloudyni...-needed-please/



#65 GOLGO13

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Posted 11 June 2019 - 03:02 PM

So in a orange light polluted sky, using a 640 longpass filter would be a good idea?



#66 bdg

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Posted 11 June 2019 - 03:11 PM

Comparing tube SNR after converting to dB is the way to do it. There very much is an asymptotic effect to increasing tube SNR and looking at it in terms of dB tells the full story. I think your ranking of tube performance is spot on. I come from an RF world and thinking about image tubes from the standpoint of an RF amplifier that's positioned first in a system is very helpful., 

 

I'm glad everyone is worried about EBI and how it can increase on a summer night. Without checking my notes, I seem to recall that EBI doubles for every 4C increase in temp. Even my highish EBI tubes work wonderfully in winter. I like the idea mentioned of making a cold finger for an image tube. Probably fairly doable and the temperature drop does not need to be considerable. There's a long history of cooling PMTs to reduce dark current. Same exact phenomenon with the same cure. 

how is the signal strength represented for NV tubes, I assume its in mV correct?



#67 Starman81

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Posted 11 June 2019 - 03:28 PM

So in a orange light polluted sky, using a 640 longpass filter would be a good idea?

 

Yes, should be good. I use the Astronomik UHC in a red zone often, which is a 640nm longpass but also allows OIII and H-Beta lines. 

 

685nm longpass would be my pick if there a bright moon in the same red zone. 610nm in slightly darker skies and no longpass in dark skies. Longpass filters are relatively cheaper than h-alpha so it's easier to have a few of 'em, depending on your skies/conditions. 


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#68 Vondragonnoggin

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Posted 11 June 2019 - 03:56 PM

Yes, should be good. I use the Astronomik UHC in a red zone often, which is a 640nm longpass but also allows OIII and H-Beta lines. 

 

685nm longpass would be my pick if there a bright moon in the same red zone. 610nm in slightly darker skies and no longpass in dark skies. Longpass filters are relatively cheaper than h-alpha so it's easier to have a few of 'em, depending on your skies/conditions. 

Whoa - did not know that about the Astronomik UHC - awesome info there. I’m using the Lumicon Night Sky H-Alpha which is also a 640nm. I think you suggested it to me years ago actually. Can’t remember exactly who gave the suggestion, but it’s a favorite. Even better to double a filter purpose for visual and NV though.


Edited by Vondragonnoggin, 11 June 2019 - 03:59 PM.


#69 11769

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Posted 11 June 2019 - 04:20 PM

how is the signal strength represented for NV tubes, I assume its in mV correct?

NV tubes have their own set of metrics that define performance without touching on signal strength in any obvious way. An equivalent figure can be worked out though. Unfortunately I can't provide a direct answer without some rambling. 

 

The SNR listed in a spec sheet is measured at 108 microlux, approximately equivalent to a moonless overcast night. That sounds very dark (and it is) but that's the illuminance falling on a scene, in this case straight into an image tube. In order to form a usable image on that overcast moonless night, the image tube is looking at a scene that is illuminated at ~100 microlux and the amount of light entering the tube itself is much lower. Consider how much light is reflected by most objects (well under 50% typically), losses in the optics that focus the scene onto the tube's photocathode, indirect illumination in that already very dark scene, possible shadows, you name it. A ballpark assertion that the tube sees ~10 microlux at most in that scenario is probably a generously safe guess. An emission nebula would be substantially dimmer than that. Does anyone know what a decent back of the envelope number would be?

 

The absolute lower limit to what an image tube can see is EBI, dark current. The photocathode is continuously boiling off thermionic electrons even in absolute darkness and that dark current produces a constant background glow. Any input light below that level is mixed into the mush and cannot be discerned. No tube performance metric, be it SNR or whatever, can correct for it. It's the absolute lower limit. EBI is measured in phot which is equivalent to 1e4 lux. Units in photometry are never the same and it always gets confusing. 

 

A good tube might have an EBI of "1", that's 1e-11 phot or 1e-7 lux. The background glow is 0.1 microlux while the scene being imaged is ~10 microlux in the example above, 100:1 ratio. Great, it's greater than the SNR of the tube which is say 30. SNR is setting the performance here. Now consider if the scene being imaged is in a shadow, under tree canopy, or indoors. The 10 microlux input can drop further still. The maximum allowable EBI for L3 filmless tubes is also "5", 0.5 microlux. A tube with an EBI of "5" is presenting a background glow that is ~20 times dimmer than the ~10 microlux scene that's out in the open on an overcast moonless night. Now the ratio is 20:1 and that tube with an SNR of 30 is operating in an EBI limited regime. An Omni 4 tube with an SNR of 21 but an EBI of 1 from 20 years ago will outperform that high EBI L3 filmless tube. Only gets worse if used indoors or under tree canopy, to the point of the high EBI tube filmless tube with an arbitrarily high SNR being unable to form an image. Only a uniform milky glow will be visible. I realize I still haven't answered your question. I just like stressing the importance of EBI. 

 

The input signal to a tube is optical and is converted to an electrical signal by the photocathode. A good tube has a photocathode response in excess of 2000uA per lumen with a 2856K blackbody source. There's often a similar metric provided for NIR, typically at 830nm. Units are different, typically mA/W. At this point, the quickest answer is that tube sensitivity, in electrical terms, is measured in terms of current, not voltage. A slightly cleaner answer is that it's in terms of electrons and it's convenient to represent that electron emission in terms of actual current. Voltage is used to accelerate electrons inside a tube but it's meaningless to think of the signals going thru an image tube in terms of voltage. 

 

Getting a photocathode to emit 2000uA would be suicidal for the tube. Since the input aperture of a tube is known (~18mm diameter), the 2000uA/lumen figure could be represented in terms of lux too, about 2000uA/3930lux (daytime) or about 0.5uA per lux. With the earlier 10 microlux illuminance level, the photocathode current that's the converted optical signal is only about 5e-12A. The actual dark current for an EBI of "1" is about 2.5e-13A or about a million and a half individual electrons (per second). 

 

That's the entire rambling answer. Input optical signal going into a tube is represented by three different photometric units. An equivalent photoelectric current can be calculated. At that point, all the magic in a tube is in terms of truly tiny currents. The MCP multiplies that tiny current through secondary emission and projects the amplified electron image onto the phosphor screen. Gets even more complicated beyond that. Without any numbers, I want to say that the MCP gain is much lower than the ~60-70k gain of the tube itself. There's additional "gain" that comes with the electrons striking the MCP being able to produce more than a few secondary electrons (200eV electrons striking the MCP and the work function of the MCP is much lower, few eV probably) and the amplified electrons on the output side of the MCP being accelerated to ~4000-5000eV before striking the phosphor screen. 


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#70 Starman81

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Posted 11 June 2019 - 04:39 PM

Whoa - did not know that about the Astronomik UHC - awesome info there. I’m using the Lumicon Night Sky H-Alpha which is also a 640nm. I think you suggested it to me years ago actually. Can’t remember exactly who gave the suggestion, but it’s a favorite. Even better to double a filter purpose for visual and NV though.

 

Yep, I'm running the the Lumicon Night Sky H-Alpha still in 2"--great filter. I remember getting the suggestion from you in the NV 2015 3 Perspectives article, actually. 

 

The Astronomik UHC I have only in 1.25", so really don't have a quick way to compare the two... I haven't had a chance yet to try it for visual myself yet, too busy on the NV side and plus that would require actual dark skies!


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#71 Vondragonnoggin

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Posted 11 June 2019 - 05:16 PM

Yep, I'm running the the Lumicon Night Sky H-Alpha still in 2"--great filter. I remember getting the suggestion from you in the NV 2015 3 Perspectives article, actually. 

 

The Astronomik UHC I have only in 1.25", so really don't have a quick way to compare the two... I haven't had a chance yet to try it for visual myself yet, too busy on the NV side and plus that would require actual dark skies!

I had to look it up. It was StarStuff1 that suggested the Lumicon Night Sky H-Alpha back in March 2014. I didn’t even have my 120ST yet. Was using Omni IV Tube in Litton M942, my thick film pvs-7, and a gen 3 pvs-4 in my mak 150 (and still totally loving NV views). I got my 120ST the next month in April specifically to do NV astronomy with.

 

But yeah - Astronomik UHC is the same with addition of OIII and Hb. I have a Lumicon UHC and Thousand Oaks lp2 and they aren’t like the Astronomik. I had to check those. The Astronomik is perfect for 640nm and up transmission.

 

Makes sense now remembering back why I liked the 610nm so much. I was using it in my F/12 mak primarily. Didn’t even have the 120ST yet, but think I already had my AT72ED.


Edited by Vondragonnoggin, 11 June 2019 - 05:51 PM.


#72 GOLGO13

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Posted 11 June 2019 - 05:47 PM

I notice Don Pensak www.eyepiecesetc.com has the astronomik in stock. Might just try it out.

Should I consider focal reducers for my scopes. Unfortunately the one for my 5 inch refractor didn't come with one. And that would be a tough one to find. But the 81s should be easy to find.

#73 Vondragonnoggin

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Posted 11 June 2019 - 06:05 PM

I notice Don Pensak www.eyepiecesetc.com has the astronomik in stock. Might just try it out.

Should I consider focal reducers for my scopes. Unfortunately the one for my 5 inch refractor didn't come with one. And that would be a tough one to find. But the 81s should be easy to find.

I wouldn’t worry about getting focal reducers specific to your scope - that’s for AP with a camera and not using a diagonal. You’ll be using focal reducers on the nosepiece of your mod 3. It won’t be the full reduction stated on the reducer. I don’t think anyone has got a regular reducer to work where they are meant to go - straight after focuser.

 

I use 2” .5x reducers and the way they work out is directly on the nosepiece I actually get .7x and with my 150 ST and the shorter back it has with low profile adapter and linear bearing focuser, I can put a 35mm extension before and after the reducer and have the whole thing screw on my nosepiece to get .67x

 

Others use .7x, .75x, .8x, etc

 

 My configurations to get actual .7x and .67x reduction:

 

Most applications:  NVD - nosepiece - .5x reducer - 2” filter - diagonal - telescope focuser (I use the short 2” ScopeStuff nosepiece so I can use a 1.25” filter instead of a 2” if I want) (.7x)

 

My 150ST with shorter back is:  NVD - nosepiece - 35mm extension - .5x reducer - 35mm extension - 2” filter - diagonal - telescope focuser (.67x)

 

Of course if used afocally much more reduction can be had by using longer focal length eyepieces than the Mod 3 eyepiece. Double the focal length eyepiece (55mm plossl) of the Mod 3 ocular (27mm)  and you reduce by .5x - when using 1x objective lens on the NVD

 

afocally also - half the focal length eyepiece (13.5mm) of the Mod 3 ocular (27mm) and you effectively give 2x magnification/focal ratio - when using 1x objective lens on the NVD


Edited by Vondragonnoggin, 11 June 2019 - 06:11 PM.


#74 GOLGO13

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Posted 11 June 2019 - 06:21 PM

Are 1.25 inch filters OK to use?



#75 Vondragonnoggin

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Posted 11 June 2019 - 06:27 PM

Are 1.25 inch filters OK to use?

Yes, but I have never found a 1.25” reducer that doesn’t vignette. I use 2” reducers. The Short ScopeStuff 2” nosepiece has an inset with 1.25” filter threads and 2” filter threads on the outside. You can use a 1.25” filter on the inset threads and a 2” reducer on the outside threads.

 

A little fumbly to start the 1.25” filter threading on the inset threads for my stubby fingers but ok once the first thread catches to screw on the rest of the way safely.

 

This is the c-mount 2” nosepiece with dual 1.25” and 2” threads

 

http://www.scopestuff.com/ss_c2bf.htm


Edited by Vondragonnoggin, 11 June 2019 - 06:29 PM.

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