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NV results under horrible sky conditions

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#1 mdaulton33

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Posted 23 August 2021 - 12:41 PM

So...this past Saturday I wanted to do a little experiment. How well will NV perform under suboptimal sky conditions?

The moon was one day short of full, seeing and transparency were bad, and humidity was nothing short of the Amazon....

Set up the 12" dob with 55mm TV Plossle, TNVC monocular, and Antlia 3.5nm H-alpha filter....

Objects - the Crescent Nebula - nebulosity is seen all the around the central star

               the Lagoon, Trifid, and Swan - all easily seen

               North American and  Pelican - seen hand held

 

I was truly amazed with the objects I could see under horrible sky conditions - I had to use SkySafari with my Nexus for location because there were so few naked- eye stars to see.

NV is a wonderful creation .....beware - it will ruin using just a regular eyepiece!!!

 

Marshall

 

 


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#2 bobhen

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Posted 24 August 2021 - 06:37 AM

So...this past Saturday I wanted to do a little experiment. How well will NV perform under suboptimal sky conditions?

The moon was one day short of full, seeing and transparency were bad, and humidity was nothing short of the Amazon....

Set up the 12" dob with 55mm TV Plossle, TNVC monocular, and Antlia 3.5nm H-alpha filter....

Objects - the Crescent Nebula - nebulosity is seen all the around the central star

               the Lagoon, Trifid, and Swan - all easily seen

               North American and  Pelican - seen hand held

 

I was truly amazed with the objects I could see under horrible sky conditions - I had to use SkySafari with my Nexus for location because there were so few naked- eye stars to see.

NV is a wonderful creation .....beware - it will ruin using just a regular eyepiece!!!

 

Marshall

Yeah. I live with a Bortle 9 sky and horrible light pollution and NV has continued to amaze me these past 5 years. Truly amazing views. 

 

Of course NV can't do much with the horrible cloudy, rainy, stormy, hazy, smoggy sky we have had this summer here outside Philadelphia, PA.  

 

Bob



#3 GOLGO13

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Posted 24 August 2021 - 07:03 AM

Usually when conditions are poor I don't get great results. I usually switch to glass and check out the planets, moon, and all other good light pollution objects.

I can still see night vision objects, but I know they can be a lot better under transparent skies.

#4 chemisted

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Posted 24 August 2021 - 08:25 AM

Usually when conditions are poor I don't get great results. I usually switch to glass and check out the planets, moon, and all other good light pollution objects.

I can still see night vision objects, but I know they can be a lot better under transparent skies.

I feel just the opposite. I was out at exactly the same time as the OP with similar sky conditions although the humidity was probably lower. I chose my NVD Micro with the Fujinon 50mm f/1.4 lens to which I attached my relatively new Optolong 2" 7nm filter. The Sadr region and NA/Pelican were very, very nice in the same FOV. Even the Eastern Veil was well shown as was IC1396. NV is truly a stunning tool and these results on a night when normal glass viewing would be out of the question says it all in my mind.

Edited by chemisted, 24 August 2021 - 10:35 AM.

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#5 GOLGO13

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Posted 24 August 2021 - 10:42 AM

I feel just the opposite. I was out at exactly the same time as the OP with similar sky conditions although the humidity was probably lower. I chose my NVD Micro with the Fujinon 50mm f/1.4 lens to which I attached my relatively new Optolong 2" 7nm filter. The Sadr region and NA/Pelican were very, very nice in the same FOV. Even the Eastern Veil was well shown as was IC1396. NV is truly a stunning tool and these results on a night when normal glass viewing would be out of the question says it all in my mind.

When I switch to glass it's not for DSOs, it's for bright objects not affected by transparency.

I don't know, I see big differences night to night with NV. Maybe my area is unique. The sky conditions here in WV are pretty strange. If I can't see many stars because of poor transparency, it directly seems to affect my night vision results.

Edited by GOLGO13, 24 August 2021 - 10:42 AM.


#6 GOLGO13

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Posted 24 August 2021 - 10:46 AM

The object I notice the biggest difference night to night is the Horsehead Nebula and the surrounding Nebula. The Flame is usually pretty good any time, but the Horsehead is a bit fainter and more subtle.

At least through my device.

#7 GOLGO13

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Posted 24 August 2021 - 05:14 PM

What are your gain and PC sensitivity specs? 

 

Mine is 61093 for gain and 2194 for PC sensitivity. But my EBI is .2 and SNR 33.7. I think mine is a decent tube but probably not a rockstar tube.



#8 chemisted

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Posted 24 August 2021 - 06:06 PM

What are your gain and PC sensitivity specs? 

 

Mine is 61093 for gain and 2194 for PC sensitivity. But my EBI is .2 and SNR 33.7. I think mine is a decent tube but probably not a rockstar tube.

Your tube is fine.  In fact, it is a real advantage to have that low EBI during warm summer nights.  In order to discuss viewing results I think it is best to be very specific about equipment.  I specified a 50mm f/1.4 lens with the 2" filter attached to the front of the lens for nebulae in Cygnus.  Have you done the same?  If not, give it a try - I think you will be pleased.  If you want to see my tube specs they are in the following thread:

 

https://www.cloudyni...specifications/



#9 GOLGO13

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Posted 24 August 2021 - 06:30 PM

I have some similar lenses. I plan on testing them out tonight. It's looking at least clear here tonight so far. Sky looks average.

I have a 135mm F2.8 and 35mm F1.8. And the Envis lens which is fast also.

I have just received today a 52mm to 48mm adapter and a 6.5nm F2 (F1.8-F3.3 optimized) 2 inch filter to test. I also have a 7nm regular one.

So I will be doing a lot of testing tonight.

Edited by GOLGO13, 24 August 2021 - 06:55 PM.

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#10 GOLGO13

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Posted 24 August 2021 - 06:33 PM

Looks like you have good gain characteristics. I've only looked through my unit, so it's always hard to know what others are like. I've only been able to go off of other people's experiences.

 

Based on the photos I've seen I feel like mine is probably fine. 

 

But I do find conditions can impact the view. So one night the view is dyno mite, and other nights it's just average or OK. 



#11 GeezerGazer

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Posted 02 September 2021 - 01:49 PM

Hey Go, it's been a week, did you test 'em?

 

I'll go out on a limb and predict that any differences between the 6.5 and 7nm filters are going to be subtle at best.  So I'm looking forward to your visual test results.  The Astronomik MaxFR (I am told) is marginally better than the standard 6nm H-a filter in terms of producing slightly less band shift.  But overall contrast on-axis is about equal.  And when used at f:2.8, no significant difference is seen.  But results differ, depending on whether the filter is mounted in front of the lens or behind it.  

 

I mount my filters behind objective lenses whenever possible because in that position, band shift vignetting is usually eliminated for my photos.  This produces a bit less contrast but produces a bigger fully-filtered FoV.  And when the focal ratio is f:2.8 or slower, band shift vignetting is virtually non-existent.  Mounting the filter in front of the objective lens concentrates the effect of band shift vignetting, so this is where you should see the value of a filter modified for focal ratios faster than f:2.  

 

Let us know what your testing revealed.  This is important regarding NV visual observations, even under horrible sky conditions.  

Ray


Edited by GeezerGazer, 02 September 2021 - 01:53 PM.


#12 GOLGO13

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Posted 02 September 2021 - 02:16 PM

Check the posts on the other thread related to the 6.5nm.

Basically the two filters are very similar. The 6.5nm has more issues with stray light from neighbors and such.

The only benefit I really found was with the Envis lens the 6.5nm does seem to not cut off as fast. That seems to be the only benefit I've seen so far. Very close to each other otherwise.

#13 GOLGO13

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Posted 02 September 2021 - 09:38 PM

Hey Go, it's been a week, did you test 'em?

 

I'll go out on a limb and predict that any differences between the 6.5 and 7nm filters are going to be subtle at best.  So I'm looking forward to your visual test results.  The Astronomik MaxFR (I am told) is marginally better than the standard 6nm H-a filter in terms of producing slightly less band shift.  But overall contrast on-axis is about equal.  And when used at f:2.8, no significant difference is seen.  But results differ, depending on whether the filter is mounted in front of the lens or behind it.  

 

I mount my filters behind objective lenses whenever possible because in that position, band shift vignetting is usually eliminated for my photos.  This produces a bit less contrast but produces a bigger fully-filtered FoV.  And when the focal ratio is f:2.8 or slower, band shift vignetting is virtually non-existent.  Mounting the filter in front of the objective lens concentrates the effect of band shift vignetting, so this is where you should see the value of a filter modified for focal ratios faster than f:2.  

 

Let us know what your testing revealed.  This is important regarding NV visual observations, even under horrible sky conditions.  

Ray

At 1x the 6.5nm gives a good amount more view before it cuts off compared to the regular 7nm. I'd imagine the benefit would be very good with the 3.5 version of this F2 optimized.

 

The other thing I don't like with it is the threading doesn't seem to be as nice. Not a big deal, but just an observation.

 

I'll try it again with the 135mm F2.8 lens. Last time I didn't see much difference between the two with this lens. But for the 1x it was a good benefit.

 

Now, today is the best sky I've had here in quite a long time. And it makes a HUGE difference in the views. I don't understand how my experiences can be so different on this particular subject.



#14 GOLGO13

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Posted 02 September 2021 - 11:23 PM

According to the clear sky charts we had above average transparency today. I saw a huge difference in my night vision performance tonight. This has been consistent for me so far with NV. Objects are brighter and more defined on these types of nights. These are the nights where the Horse Head nebula would be at it's best. And at 1x the Milky Way would be pretty good.

 

Also, it was helping my glass targets tonight (as expected). 

 

I just realized I'm probably more bortle 5 than 6. My reading tonight was the best I've had and it was 19.50 which is Bortle 5.6 I guess. 

 

Anyways. This is what I notice with NV. Transparency is very important. Not that you can't do NV in bad conditions, but there is a big difference when transparency is great.



#15 GOLGO13

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Posted 03 September 2021 - 12:50 AM

I should also point out that the hurricane remnants swept through the area. It reminds me of the big storms we'd get in St. Louis. After those storms came through we'd have great observing and transparent skies.

 

Eddgie posted this in one of my threads on Transparency:

 

"I am not sure about your location, but I know that the Smokey Mountains, not that far south of you, are thought to have gotten their name from the fact that the vegetation exhales volatile organic compounds that have a high vapor pressure.  In normal pressure and temps, these will form a smoky haze.

I have driven the Skyliine Drive and have noted that along the mountain chain, there appears to be a similar haze.

 

When the temps are cooler and there is a scrubbing wind, this haze can be swept off. I remember being on the Skyline drive on such a night about four years ago and I had my night vision gear.  The view from the Skyline drive was dramatic under those conditions.

 

And to your point, yes, this kind of atmospheric effect is pretty damaging.

 

I suspect though that this is possibly an atmospheric condition that you might be living under"

 

____________________

 

So it could be more than just transparency in my area. It could be that we don't often get good scrubbing winds here in the mountains. It actually is pretty rare that strong storms come through. In St. Louis strong storms were pretty normal. This is kind of a bummer for NV observing. But I usually can still get good observing in. Seems like the colder months have better skies. Of course I dislike observing in the cold. Just can be too much effort to get all those clothes on in addition to setting up scopes. 



#16 GeezerGazer

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Posted 03 September 2021 - 02:02 AM

Go,

Thanks for for the in depth report.  waytogo.gif  I didn't know you posted results elsewhere, duh!  

 

I live in the Central Valley of CA, and know the value of transparent skies.  Winters here typically have fog, and for the past 5 years, summers are filled with smoke from forest fires.  But even without smoke, summers can be tough on observing because of humidity mixed with high levels of particulates, mainly from agriculture.  I often see very little of the sky, even with NV from home.  So I empathize with you.  

 

My experience with a variety of H-a filters (3.5, 5, 6, 7, 8, & 12nm) showed how filter placement effected band shift.  The shorter the band pass, the more band shift caused vignetting (EoF darkening) with front mounted filters.  But as focal ratios increase (become slower), band shift becomes less intrusive.  Even a 3nm filter shows little or no band shift at f:5.  A 12nm shows none at f:2.  My 7nm, shows no band shift at f:2.8.  But most of my experience is with filters mounted behind the objective and in prime focus.  

 

Your findings concerning the H-a filters that are maximized for faster optical systems are not at all surprising to me.  The real value for the 6.5nm filter is found when they are used with extremely fast optics, f:1.8 or faster.  When used at f:2 or slower, the regular filter is pretty much a performance match for contrast.  When used front-mounted on objective lenses, the in-band FoV will be larger than the regular filter of equal pass band.  That is their real advantage.  When used rear-mounted in an f:1.8 or faster system, the result will include a bit more contrast.  But in my experience, these differences remain pretty subtle.  

 

Thanks for your report.  

Ray


Edited by GeezerGazer, 03 September 2021 - 02:08 AM.

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#17 Gustoresto

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Posted 15 September 2021 - 02:34 PM

U have been testing filters a lot and I'd like help nailing down a choice I can afford. First off some of the Ha filters are N of $300 which I don't want.   Lumicon makes a 2" Ha for $76 !   But I didn't see any 1.25. May have missed it.    2)  there are some people saying a UHC filter can approach the desired level of performance on dim emission nebulae like the Veil rosette, barnard's loop, etc.  I have them in both 1.25 and 2". First Q is for handheld use then.    3) In afocal use all the posts seem to say put the filter in front of the NVM.  Why can't it be in the EP nose like we normally would just using glass??   4) I can't seem to find a direct comparison between say looking up to zenith at the Veil w or w/o  the Ha or? filters except maybe one that more or less said don't bother w/o the Ha. (??)    My scope rig will be an AP friendly SN 8" F/4 OR an F/5 10" newtonian w a superb Swayze mirror.   Bortle 6 skies in SE PA  N of Philly where I can almost tease out visual the "teapot spout"  in Sag  in the So soupy skies toward Philly metro. (I'm 35 mi N of the city)    I also intend to couple a camera lens to the gen 3 wpt pvs 14 AW3 I intend to buy for handheld use, so 5)   Posts are saying use a F1.8 lens but what size ??   55mm 134mm or what  for handheld stargazing.  U can buy 55mm lenses on ebay for under $40!  Thx to all of U for helping.   This will B to wow people and me in my outreach sessions.   I'm maybe terminally infected w pursuing NV after scanning the milky way at the Cherry springs dark sky site w a TV $4K handheld unit w the w phosphor.   Never saw anything comparable except one miracle moonless night in the ID desert at Snake R birds of prey area Nampa ID.   Any little handheld device that comes even close to doing that near where I live is in the miracle tech dept yes?   Thx Gus



#18 a__l

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Posted 15 September 2021 - 06:54 PM

1. Will have to buy for $ 300
2. UHC for NV will not help you much. Low sensitivity Gen3 in this range, some PVS-14 lenses cut off this spectrum.
3. 55 TV? What is EP nose in your interpretation? You will have to find an appropriate adapter that is not found in nature. If the other end of the eyepiece, you normally screw a 2" filter onto the barrel of the eyepiece.
4. NV and H-alfa work most contrastingly on nebulae containing a maximum of hydrogen.


Edited by a__l, 15 September 2021 - 06:59 PM.


#19 GOLGO13

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Posted 15 September 2021 - 07:13 PM

The Astronomik UHC is somewhat unique and works like a 642nm long pass filter. It does let in some HA, but it's not very good for nebulas compared to a narrowband HA filter of 12nm or lower (I'd say a 6nm would be a good in-between). With any filters it's best to look at the spectrogram (think that's the right term). https://www.astronom...uhc-filter.html

 

But in general a UHC isn't going to work for serious nebula observing. Need a 12nm or less HA filter.

 

For my light polluted skies I prefer a 685nm long pass filter and a 6nm-8nm HA filter. A 3.5nm or 3nm may work for some folks depending on the situation. I have a 3.5nm and it seems good. But for me personally, anything from 3.5nm to 8nm is very close in capability and I sometimes have a hard time telling which is better. going from 12nm to 3.5 I can see an increase in detail in the 3.5nm. Still, the 12nm is pretty good also, and for some objects I prefer the 12nm.

 

For a camera lens, I suggest something lightweight. I have a 135mm F2.8 and I like it, but it's a bit heavy for me handholding over a long period of time. Unless I'm laying down it's not too bad. It's an older lens so that maybe why it's heavy.

 

For number 3 I never thought of trying the filter at the eyepiece. I can hand hold it to see if that works. 

 

If you have the money, I'd probably go 2 inch on everything and get the Televue 67mm setup. But also have the other options for a more zoomed in view.

 

Which device are you getting? That may decide what kind of adapters and filters you will need/want.



#20 Gustoresto

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Posted 16 September 2021 - 07:26 AM

It looks like I need to emphasize my tight cost constraints.   Aside from the bigbux getting the pvs14 3AW2, I want to start on the bottom end of basic gear for accessories which eliminates TV stuff.  You CN guys have been doing fine guiding me but I don't have the budget a lot of U seem to have.  Found on this forum:   To anchor the NVM over an EP the Baader microstage 2 adapter does that for under $50 and should clamp on my 2"  30mm APM 80* EP or maybe the 21mm Hyperion or? in my collection.     Then there seems to b a consensus U need an Ha or longpass filter and I'm trying to find a cheaper alternative to the $300+ ouch ones.      Can any of U comment on the Lumicon 1.25Ha for $55?(oddly Lumicon gives no nm spec) Maybe just try it and see?     And I'll just screw that into the EP like normal non NV use.    Re camera lenses for handheld scanning I've learned enough now thx except where to put the filters.  I'm confused w the adapters whether it's what I'm reading as a C mount or what and does the filter go in front of the camera lens or in front of the NVM?    And an adapter between a camera lens and the pvs14?    Thx Gus



#21 a__l

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Posted 16 September 2021 - 07:48 AM

It doesn't make sense for you to use an 80 degree eyepiece for NV. Enough 40 degrees. Hence a plossl EP with a focal length over 60mm will give twice the field.
Once again, if you didn't understand my previous post. Don't buy this Lumicon, it's a waste of money for NV.

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Edited by a__l, 16 September 2021 - 07:57 AM.


#22 GOLGO13

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Posted 16 September 2021 - 07:53 AM

For the PVS14 I believe it's afocal only. You could probably still be on a budget and get good enough stuff. Let's check some Ali Express options for filters.

Eyepieces and Adapters will be more interesting but quite possible I think.

#23 Gustoresto

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Posted 16 September 2021 - 09:12 AM

Got it; The Lumicon Ha is NG.   Lowest $ alternate found is yes ali express' optalong Hs 7nm 1.25" for $125.      Yes the pvs14 is afocal only so how to attach a filter between it and the EP?    1.25 or 2"?   (for afocal use w a scope)     I thought I may have read the pvs14 can use a c mt adapter but not sure.    I've been reading NV posts and ads till I'm Xeyed and am making notes to try to keep the info straight.  Also I read several posts explaining that the UWA EPs are not productive and will give edge of field darkening but I don't care about that. (The TV website says U can even use a 31mm 82* Nagler but it "won't give any advantage" over a narrow FOV plossl)     I simply wanted to avoid the expense of yet another high $ EP and use an ep I already own that the baader adapter will clamp on.   Maybe that 21mm hyperion would do.     I didn't mean to hijack a thread taking it from LP problems to equipment which is connected. Should I be using a PM??   Thx Gus


Edited by Gustoresto, 16 September 2021 - 10:23 AM.


#24 GOLGO13

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Posted 16 September 2021 - 10:37 AM

You could get the TeleVue 40mm Plossl and the 1.25 inch filters. And the TNVC adapter. That would be the easiest option I think. Maybe check for a used TeleVue 40mm.

#25 Gustoresto

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Posted 16 September 2021 - 11:00 AM

A used TV plossl is $100 + a TV adapter for the NVM for $50 +shipping.     The baader microstage 2 adapter is only$50 to position the NVM above the EP I already have.    A $100 savings.      Where/how do U attach yr filters on yr 135mm handheld setup and what adapter between yr NVM and the camera lens?   Later:   from Mike lockwood's testing:    So, for afocal viewing, the best place to put a narrowband filter is not in front of the NV unit, it is on the bottom of the eyepiece, the bottom of the Paracorr, or on a filter slide that sits below the Paracorr or eyepiece.  The cone of light from the primary mirror or objective lens covers less angle than the cone entering the nightvision unit.  BUT he says it doesn't matter in a fast scope [as much] and I have an F/4 SN8.    That's from Mike lockwood custom optics website  "adventures in night vision"  I found to be a BIG help esp in how to connect pieces.   


Edited by Gustoresto, 16 September 2021 - 12:09 PM.



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