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Narrowband Ha NV Astronomy - 50 Shades of Grey (observation skills)

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#1 Vondragonnoggin

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Posted 12 October 2015 - 07:05 AM

I was out viewing last night and hopping between brighter nebulae - Pac Man, North American, Pelican, Dumbbell, Crescent, Gamma Cygni, Eastern Veil, Western Veil, Iris, Heart and Soul, Cocoon, Elephant Trunk, plus some I couldn't readily identify by NGC number. I was noticing the subtle changes in Ha regions and have definitely picked up some skills in noticing more subtle variations from Ha regions of Milky Way to the brighter (a misleading term to those that actually have to travel to dark skies and use big scopes and aggressive visual filters to see them) nebulae.

 

I think observing with Image Intensifiers is much like observation with conventional eyepieces in that it takes time using them to really start recognizing where you might be in a patch of very faint Hydrogen vs skyglow. I now readily recognize the subtle background changes passing over faint dust and gases vs regions scarce in dust. Picking out the brighter areas, I usually know when I am in a catalogued nebula vs HII regions without one of the more popular listed catelogued record. This has helped me immensely in recognition on threshold objects in my small scopes. 

 

Using averted vision skills to grab more detail also is building skills in knowing where eyeplacement can get me the most detail of an object, or if I need to keep changing eye position or even quick movements of the scope to bring out peripheral movement detail.

 

Has anyone else noticed improvement over time in picking out new nebulae you once didnt notice, but just passed over in search of brighter, more well defined nebulae? It's very exciting to me. I think of what I may see after another year of observation in Ha filtering. Also look forward to an upgraded device next year to go to another level in fainter objects.

 

It is very much part of the appeal in using NV eyepieces and my manual mounts without goto. I am still challenged in observations, although now the challenges are real visual challenges in much larger scopes with conventional eyepieces. I am getting enough of the fainter nebulae to really appreciate what intensifiers do in light polluted skies while keeping to grab n go size equipment.

 

Any others have an object they couldn't detect awhile ago, but now readily detect with the same equipment and sky conditions and nothing but time behind the eyepiece as the changing factor?

 

For those relatively new to image intensified astronomy, have you noticed any skills starting to build already in recognition?



#2 The Ardent

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Posted 14 October 2015 - 12:01 PM

Today I was reading the October Sky and Telescope. On page 78 is a nice image of the Gamma Cygni clouds in H-a. I recognized those clouds!

It's a whole new world of observing.

#3 Vondragonnoggin

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Posted 26 October 2015 - 07:32 AM

I have started testing an NVD Micro with good MX10160 tube in it. Not quite an Ultra tube but very close.

 

Tube specs:

Photocathode Sensitivity >/= 2200µA/lm
Resolution >/= 64lp/mm
SNR >/= 28
EBI </= 2.5 x 10^-11 @ 23ºC +0º/-2º
Halo </=0.7mm

 

Doing A/B comparisons to older MX10160 tube in my Litton M942 monocular and my PVS-7 with older MX10130 tube.

 

Tube specs in Litton M942 that I know of:

Omni IV era

S/N >/= 22

Resolution >/= 64lp/mm

Halo </= 2.0

EBI </= 2.5

 

Tube specs that I know of in PVS-7:

Omni III + (enhanced)

S/N >/= 21

Resolution >/= 64lp/mm

Halo </= 3.0

EBI </= 2.5

 

Tube specs provided at time of purchase for PVS-7 tube and complete M942 Monocular with accessories from dealer. Bought used on ebay from Ed Wilcox. Older tubes silent. No autogating. Not thin filmed either.

 

NVD Micro on loan from a friend for extended testing.

 

Just brief testing last night, so will not post any kind of in-depth results yet, but will say I found the results interesting and consistent with getting high end astronomy gear.

 

Full moon last night. White Zone LP testing under skies where I could see maybe 30 stars total with my glasses on and even less without. Some serious Light Pollution Soup!

 

objects in 4.7" achromat - Iris, Crescent, Eastern Veil, Gamma Cygni, Pelican, North American

 

Just briefly - using 7nm Ha, all nebulae visible in High Performance Micro also visible in older devices. I will elaborate more after honeymoon period is over with it.

 

Another hint - there are differences there also obvious but might surprise you with exactly what they are and amount of differences too. Some filtering surprised me on which showed more differences. More pronounced with 610nm than Ha.

 

  ;)

 

PS - Just another hint for the new PVS-7 buyers not getting complete specs with their device - No need for hand wringing! Stop the wondering on if you miss out on something. You don't in the way you might think. Stay tuned. I need a few weeks to get over the honeymoon phase and also to get some variety of targets viewed. I will start a brand new thread when ready to post full reviews. It has a lot to do so far with the original premise of this thread.

 


Edited by Vondragonnoggin, 26 October 2015 - 07:35 AM.


#4 outofsight

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Posted 26 October 2015 - 02:43 PM

Please allow me to disagree (should have kept my old one until I had the new one in hand). I have it on good authority that you should not have kept your old one, but will be glad to hear about your new one. I had a Litton once, they make really good microwaves, but will still be glad to hear about your new one.

 

On to the important questions, VDN, when you say "good MX10160 tube", how does one know this and is there any relatively simple way for us to test and find lp/mm or signal to noise (S/N), for example? Also, isn't the MX10160 a tube that can be used in a PVS-7, so are tubes that can be used in the NVD Micro and PVS-7 interchangeable?

 

Another question, does glass matter in terms of connecting to a telescope? In other words, does chromatic aberration matter to night vision devices? I get the idea from reading about filters that it may matter, but am not sure. If I'm asking questions that should be started in a separate thread, please let me know. I'm still fairly unfamiliar with how these posts work and don't want to mess it up too much.

 

Eddgie, what information on the Litton PVS-7 convinced you that it was a good time buy? Really want to hear how it compares to NVD Micro, hope it's everything you want it to be and more.

 

Was out for over half an hour last night, when it finally cleared up, until 0411. Out in a t-shirt, don't even feel the cold, that's how powerful NV is.

 

And, last but not least, where do I sign for one of those NVD Micro loans?



#5 Vondragonnoggin

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Posted 26 October 2015 - 05:02 PM

When you filter out every thing but narrowband or near IR red, you cannot have blur caused by unfocused colors (wavelengths) stars are pinpoint sharp. I have several achromats. There is no blue, green coming through. Just red.



#6 Vondragonnoggin

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Posted 26 October 2015 - 05:03 PM

Have an achromat discussion elsewhere please. Start a new topic if you want, but I filter my views 100% of the time. I disagree greatly about CA when filtering longpass red or narrowband Ha.

 

This thread about observation techniques please.

 

:D

 

(I realize my smiley face does not take away the jerkiness of my post, but man, I get tired of hearing about CA and achromats, when I am focusing only red)

 

PS - I saw the same nebulae so far in older devices as higher spec device, but more noise and this is where observing skills can be used like averted vision, etc

 

Apologize for coming off rude, but will honestly start a new topic when I get more time in on new monocular and more A/B comparisons. I will relate how observing skills will come into play on the devices soon after too.


Edited by Vondragonnoggin, 26 October 2015 - 05:22 PM.


#7 outofsight

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Posted 26 October 2015 - 05:41 PM

Sorry for any digression, but thanks for your answer just the same, it is quite explanative, seems to make perfect sense. Not a lot of chroma to "aberrate" with a narrowed spectrum.

 

Your initial statement on observation skills, and The Ardent's statement "I recognized those clouds!" I found to be interesting and encouraging. Hope to increase my own observation skills, tonight's the first night I've had a c-mount to 1.25" adapter and a 0.5x focal reducer. But rain clouds are supposed to roll in.

 

Once again, sorry for anything off topic and look forward to anything you have to say about observation skills and updates in regard to posting #3.



#8 Vondragonnoggin

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Posted 26 October 2015 - 06:51 PM

For sure I will update when I have more comparative notes.



#9 mclewis1

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Posted 27 October 2015 - 08:17 PM

For further conversations about CA and narrow band filtering just reference one of the many fine high end Lunt solar scopes that are actually singlets. Solar viewing is probably the ultimate example of using narrow band filters.



#10 Vondragonnoggin

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Posted 01 November 2015 - 02:56 PM

New estimate for averted vision as it relates to I^2 astronomy.

 

Conventional eyepiece use and dark skies tell us from the reports of experienced observers that averted vision will give an increase of 1/2 to 2 magnitudes depending on observer, experience with technique, etc.

 

Averted vision with night vision devices in narrowband Ha viewing is having me see S/N gains of 4-6 so far in testing.

 

How I determined gains. Using A/B testing between tube in specs of 28 for S/N compared to 22 for S/N, the 22 S/N gains clarity in definition when using averted vision to be approx the same as the direct vision 28 S/N tube. Since I do not have a tube higher in S/N than that, I can only judge increase in 28 S/N tube by comparing aperture. The tube with 28 S/N using averted vision in my 120mm scope with focal reducer to F/2.5 to F/3 approximately, yields detail of using 152mm scope at F/3 to F/4 aporoximately with 22 S/N device. I have yet to try HP tube in my 6" directly, but suspect it will follow the same linear increase as long as focal ratio is the same.

 

Visual representation with 28 S/N tube - Horsehead in 120 ST direct vision looks like dark shadow over line of rising brighter gases (IC 434). Flame nebula standing out brighter than surrounding horsehead gases (IC 434).

 

Averted vision shows line of dark bank with brighter rising gases (IC 434) and dark shadow now with brighter glow around it, increasing definition and contrast with actual horsehead shape much clearer. Flame nebula showing more defined in contrast dark lanes throughout it.

 

These were observations under more than 1/2 moon out and only some 25 degrees away from nebula. Will re-evaluate when a moonless condition is available. I suspect the difference will be more prominent.

 

I will add more results as I continue testing with different apertures and the two monoculars.

 

Does anyone else have some results of averted vision compared to direct vision with NV gear?


Edited by Vondragonnoggin, 01 November 2015 - 02:59 PM.


#11 Vondragonnoggin

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Posted 02 November 2015 - 12:50 AM

Just realized this thread now looks weird because its missing big chunks of conversation. Didn't mean anyone had to delete posts, just didn't want the thread to digress.

 

Anyway - to answer a question on how one would know tube specs. There are two ways really. One is an accurate way with real numbers and one not as accurate but could bevery reliable. 

 

Accurate way - get soneone to test it with proper testing equipment. 

Not as accurate way, but could be fairly reliable - have someone that has been dealing in tubes for a long time as their prifession and get an estimate. A lot of the long time experienced NV dealers can look through a tube and tell you contract era, close estimate of EBI, Halo, Resolution, and S/N. I guess when you have looked through thousands of tubes, it gets pretty familiar with characteristics.



#12 Vondragonnoggin

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Posted 22 November 2015 - 12:05 PM

Ok, so skip the last method mentioned there for getting tube specs. My source I trust for the real deal answers (cnoct) mentioned in another thread no one can look at a tube and tell you specs just by looking. They can tell you very good tube or ok tube or low performance tube, or possibly even awesome high performance tube, but they cannot roll you out S/N, EBI, halo, PCR, lp/mm, or FOM.

 

Get a sheeted tube, papered tube, whatever you want to call it to get actial tube specs or go with some dealers description of very good tube.

 

I have now had many times out with the high performance Micro. It gets appreciated more and more everytime I use it.

 

My other appreciation goes to my other older tubes not as high performance. These are perfectly acceptable tubes yielding good results. If I did not have the experience of using this type of gear for a little while now, I would not appreciate differences as much. They are noticably better but still in a subtle way. Cleaner backgrounds, lower halo, some increase in threshold objects.

 

I have a new mx10130 tube in my pvs-7 and it is the same as differences described in micro with better mx10160 tube.

 

I had planned on selling older pvs-7 tube, but the fact is, it is a good performer and worth keeping to me as a spare or to build another device.

 

A lot more confirmations lately in viewing, that observation skills are beneficial for any type of eyepiece, standard or I^2.

 

The skills are slightly different, but same techniques employed. Picking out subtle differences with noise interference, EBI interference, recognition of faintest nebulae, etc. All very useful to hone skills while observing. Stop and smell the roses as you view objects. Repeated viewing allows more detail to be seen, as does spending more time on an object.



#13 Eddgie

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Posted 22 November 2015 - 12:16 PM

I had planned on selling older pvs-7 tube, but the fact is, it is a good performer and worth keeping to me as a spare or to build another device.

I picked up a broken PVS-7 with a Litton MX10130D tube, and I totally agree.

 

I have no idea what the specs on the tube are, but it is not the D+ that I see was a model after it, and I have to say that it is surprisingly close to the ULT tube.  

 

Only when the signal gets very weak does the difference assert itself, but as you said, it is subtle.

 

I can see almost all of the stars visible in the ULT Micro, and for bright nebula, it is very hard to see the difference.

 

With the ULT though, as the Nebula get fainter, it starts to pull ahead, but again, the difference is subtle.

 

To, me, the Litton 10130D is much closer to the ULT than it is to the 10130 C/UV.  The C/UV could not render stars as sharply and this was the most immediate difference in the MX-10130D.  Stars were much sharper.

 

I know all tubes are different, and maybe I just got lucky and got one on the high side performance wise, but I think the reality is pretty much exactly what you said.   You can see the difference in A/B comparisons, but it is more subtle than the specs would suggest until you are pushing to the limit of detection, where it starts to become a bit more apparent.  

 

And like you, I may keep this PVS-7.   After the repairs, it is like new, and people are so enjoying night vision (I took two devices to a dinner party last night, and well, people loved it) so having it as a third one day seems like a good plan.

 

I don't want to be a night vision hoarder though.  I just got finished selling a bunch of telescope stuff that I should have sold off a long time ago.

 

I totally want at lest two devices, but the logical part of me is saying "Ed, it is a slippery slope!"



#14 Vondragonnoggin

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Posted 22 November 2015 - 12:24 PM

"don't want to be a night vision hoarder though.  I just got finished selling a bunch of telescope stuff that I should have sold off a long time ago.

I totally want at lest two devices, but the logical part of me is saying 'Ed, it is a slippery slope!'"

 

Haha. What are you trying to say here? You know I have several.......

 

:roflmao:



#15 PEterW

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Posted 22 November 2015 - 01:21 PM

I believe you can test tubes with a tester... Which are probably as rare outside the US as tube spec sheets! Good to hear that the slightly less than "perfect" tubes are still good... So mine can't be too disappointing. Got nothing to compare to, stay in happy ignorance! D tubes... Is that A for excellent or D for latest gen... I got neither ;-(

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#16 Rickster

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Posted 23 November 2015 - 06:19 PM

Does anyone else have some results of averted vision compared to direct vision with NV gear?

 

I have been testing my PVS-7 at up to f25.  I find that at about f8, the green color starts to fade, and by f16 it is completely gone, leaving only black and white.  I am assuming the color fade is due to the cones in my eyes giving up, leaving only the rods to carry on. Resolution improves up to about f15, using averted vision on fainter targets.  Best compromise between resolution and ease of viewing appears to be about f8. 




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