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Night Vision Astronomy 2015: Three PerspectivesEAA
Discuss this article in our forums
Astronomy 2015: Three perspectives.
Night Vision at Unity
I2 (Image Intensified) Astronomy in Heavy
Light Pollution and the Smaller Scope
Night Vision with Large Aperture
Night Vision technology is a powerful tool to enhance observing. Like any observing method, it had its advantages and drawbacks. Three Cloudy Nights members offer their experience.
Night Vision at Unity
The Oxford Dictionaries defines Unity as, 1: the state of being united or joined as a whole and, 2: the number one.
One of the most common concerns about using telescopes is the limit of the telescope to show a wide field. We buy ever wider field eyepieces or very small telescopes in an effort to be able to see larger and larger areas of the sky. Along the way to ever wider fields, what we encounter is larger and larger objects and no matter how big the field of our telescope is, we quickly realize that there is always something that our telescope is not quite large enough to frame. My chapter of the article on night vision is focused on using night vision for very low power (1x, which we refer to as "Unity" and fields generally larger than possible even with binoculars.
I live 3.5 miles from the center of Austin Texas, which is now the 11th largest city in the US. My observing conditions are far from great, and often during the summer, a thin haze makes even 3rd magnitude stars difficult to the unaided eye.
For extremely low power viewing, I use two different devices, a Night Vision Depot Micro monocular, and a PVS-7 "Goggle". The goggle is something like a binoviewer. It has one lens and one tube, and the light is split by an internal optical device called a collimator, which brings the image to the rear and splits the light path to two eyepeices. The monocular is as the name suggests, a device that uses one objective and one eyepiece.
The lens and eyepiece focal lengths are about the same, so the result is that when viewing, you are viewing at Unity (1x). I also use clip-on afocal telescopes in 3x and 5x. These are called "Magnifiers" and simply clip over the front of the lens on the night vision device so it makes it very easy to change power. Other chapters will cover the different uses of these extremely versatile and powerful devices, and this chapter focuses on the very low power end of the night vision for astronomy spectrum.
One of the most compelling benefits of unity or low power viewing is the utter simplicity. You can walk out of your front door, with a device, a clip on lens, and a couple of filters, turn on my device, and be observing in a few seconds. There is no tripod, no setup, no need to dark adapt, and no need to stay in one spot. This last point is important because from my back yard, my sky is obstructed by trees in all directions except the south, so with a traditional telescope I have a very narrow strip of sky in which I can observe targets. The night vision devices make it possible to move up and down the street in front of my house and this allows me to clear almost any obstruction in any direction so that I get views around much of the sky. If I want to peer deep into the heart of Sagittarius, or catch M45 when it just gets about the rooftops, I can simply reposition myself by walking a few houses over.
The next great advantage of night vision is that with a simple 610nm pass filter (passes 610nm and near infra-red but blocks medium red and the rest of the visible spectrum) light pollution can be greatly attenuated. Generation 3 night-vision tubes were designed to show near infra-red so that IR illuminators could be used in very low or no light environments to provide sufficient light to view the environment, but not give a position away. This same characteristic makes it possible to use H-alpha filters to observe emission nebula in a way that would be difficult with the unaided eye unless you were in very black and transparent skies. With night vision and an H-alpha filter, very large nebula are available for viewing even from locations with light polluted skies.
Finally there is the low power itself. These devices have a true field of about 40 degrees and an apparent field of 40 degrees, so this means that when you use the standard lens, you are viewing at unity, or one power. With the light intensification, this 40-degree field becomes an almost magical view of a sky so filled with large scale structure that it almost defies description. On nights with good transparency, the southern Milky Way resolves into a fantastic complex of dense star fields, dark nebula, and a stunning array of deep sky objects. While the power I use for this is very low, many of these targets are quite large, and the entire Sagittarius region becomes a glittering showcase of small, bright DSOs. With a 12nm H-alpha filter, the Milky Way comes alive with nebula. Even at 1x, the Lagoon nebula is quite large and striking, but at 1x what is more remarkable is that it can be viewed in the same true field as the Trifid, the Swan, and Eagle nebulas, along with the great Sagittarius star cloud, M7, M22, M11, and many more! And this is all in a single low power field of view! Nebula like the North American are amazingly detailed, and when viewed with the very delicate and complex of the Gamma Cygni, and once again, these two big, beautiful nebula are captured in the same true field. The 5x magnifier provides enough magnification to make these targets quite detailed and interesting.
Off the Milky Way, the 40-degree true field reveals many very large aggregates of stars that can't really be viewed in a standard telescope. The wider the field, the more these very large aggregates seem to spring forward. Traditional large clusters like the Hyades and M45 can be seen in the same low power field, and the context of the sky really changes when you see how magnificent and rich these very large scale objects are. In a traditional telescope, you often trade off light gathering for true field. You can see fainter stars in a target at the cost of losing the framing of the target, or you can frame a target using smaller scope, but this comes at the expense of losing the fainter stars. With night vision, you can frame entire constellations and the reach is quite amazing A typical field will be filled with many more stars than can be easily counted. Entire constellations combine together to make fascinating new structures that in the absence of night vision, can only really be seen by the naked eye when skies are very dark.
Evan at very low powers from my light polluted skies, Orion, Horsehead (though not enough power to see the horse itself) and Flame are easy targets, and at 5x with the H-a filter, Orion is fantastic. The extent of the nebula is greater than I have ever seen using traditional scopes even under dark skies. Seeing it at very low power you get the true sense of scale on this fantastic nebula that is hard to appreciate when using traditional scopes that limit your view to a (relatively) small slice of sky.
This brings me back to my opening where I used the definition of unity: the state of being united or joined as a whole. When I use night vision at very low powers, I feel far more connected to the whole of the Milky Way and the night sky than I ever have before. The large scale structure of the great river of stars that connects our horizons becomes something that is almost alive with a population of stellar creatures great and small, and seeing it at 1x using an image intensified eyepieces I now have a sense of Unity that I have never really experienced using traditional equipment. I don't feel like I am looking at the Milky Way anymore. I feel like I am a part of it and I see the fascinating complexity of its structure in a way that I never thought possible.
For observers with easy access to high elevation dark skies, night vision might seem like a toy. For many of us though, the cost, time, and expense associated with getting a big telescope to dark skies, or even using a small good quality telescope under so-so light polluted skies, night vision offers a compelling alternative or compliment to existing equipment. I know that people perceive the cost to be high, but it does not take a lot of money to move into a decent night vision device. In my opinion, it is worth selling off a two or three telescopes that sit unused, along with a half dozen eyepieces that are gathering dust to enter into a world where portability, simplicity, and low powers make night vision observing easier and more fun than most people ever realized.
It is different, and it is not for everyone. I even used to think that. Having entered into it, I now find myself using low power night vision more than any telescope I have ever owned before and that is the biggest compliment I can pay it.
I2 (Image Intensified) Astronomy in
Heavy Light Pollution and the Smaller Scope
I would like to start off with a brief
background of my experience in Amateur Astronomy. In November of 2009, my then
8-year old son had been actively watching space programs and drawing pictures
of galaxies and star fields. I had an old pair of Vanguard ruby coated 12x50
binoculars with bk7 prisms I had bought a decade earlier for $40. Never got
much use until we both started to look up with them in 2009. My son desperately
wanted a telescope to see more. I did too. His mother, remarried and living in
another house let me know "I bought him a telescope for Christmas so don't
buy him one". Being the avid researcher that I am, I looked at
alternatives to keep peace and make my son a happy camper. Her pick - an
EduScience 100mm reflector from Toys r Us complete with plastic tripod. My
choice to not go against wishes of not buying him a telescope - Zhumell Tachyon
25x100mm giant astronomy binoculars on a heavy duty photo tripod.
We tried to get the scope working, but a shaky mess it was. Meanwhile the binoculars were a giant hit. We both wanted more. After joining Cloudy Nights in February of 2010, having been a silent lurker reading as much as I could, I bought an 8" Skywatcher collapsible dob. My son was perfect height standing to see zenith views. I took the scope out frequently with him. So much so, that I knew I was hooked on Astronomy and started an eyepiece collection.
After a year and a half, and many eyepiece purchases later, my son was tired of visual astronomy and I was not. He still is actively into astronomy, but more on the software side and using programs like Sandbox Universe to test gravitational theory and loves realistic space games that use real physics models. He is 14 at the time of this writing. We had taken the dob to dark skies and viewed nebulae, planets, galaxies, but my backyard location was a light polluted mess and galaxies or faint nebulae were not in reach. I also had three previous injuries to my back that were not liking the dob too much. I sold the dob and bought a Twilight II alt-az mount and an Explore Scientific AR127mm achromat. I began studying about filters. Filters for light pollution, filters for nebulae, filters for control of chromatic aberration in achromats. I loved that scope. It was very capable and to me the views were more pleasing than my dob. It had very steady views being absent of tube currents and quick to equalize.
I decided I wanted to see more. I looked into Astrophotography gear. I also read briefly on Astro Video and a brief report on the Collins I3 intensifier eyepiece. Also a report on the Binocular Photon Machine, a Gen 3 device with panoramic binocular eyepiece.
I decided AP was the way to go and promptly bought an EQ5P GEM, Modified Canon T3i, all the adapters, software, a netbook, etc.
I made attempts. I captured some bad moon shots, I tried focus tricks. I had a rough go of it. I missed my simple alt-az setup and silent viewing with no motors, wires, laptop, and polar alignments. I did not like GEM's!
I sold the scope, mount, camera, adapters, and all related gear to a friend who was very interested and needed good working equipment. The equipment was all good. I was the problem. It was too tedious to me just to see more in my light polluted location. I think I am the world's laziest astronomer!
I bought an iOptron 150mm mak-cass next and went back to visual observations.
I still used binoculars a lot and enjoyed two eyed views, having picked up several other pairs and a couple binocular telescopes in 70mm and 100mm sizes. I missed my refractor though. Saw a deal on an AT72ED refractor used and bought it. Great green color too. I bought better photo tripods with geared center columns and better fluid heads.
I began to research image intensifiers. I asked forum members about the BIPH Binocular Photon Machine. I asked a million questions and found the commercial astro offerings in intensified eyepieces were no longer available. I found out they cost quite a bit too, so I began taking advice on what to look for and started searching Ebay. In the meantime, I was pretty sure I was going to purchase a night vision device soon, so ordered a Skywatcher 120ST and a good dual speed focuser to hold heavy loads. Markus at APM of Germany set me up good. Installed my new focuser and shipped me my 120ST. I also ran across an Ebay deal from Ed Wilcox at Wilcox Engineering and Research for a Litton M942 Monocular with a Gen 3 tube in it, plus a whole bunch of extras like relay lenses for attaching to camera, adapters for SLR lenses, a 3x and 6x objective replacement lens and all for much less than a new Collins I3. I bought the package deal and put the c- mount adapter on after taking 1x objective lens off.
I then did as everyone on my forum suggested. Put on a 1.25" nosepiece and put it in my scope. I bought a few filters at recommendation of others. I bought a 7nm H-Alpha narrowband filter and also bought a 610nm longpass after seeing someone else buy a 695nm longpass. I thought the 610nm longpass would still allow me some hydrogen gas views while cutting light pollution to a reasonable level. I was right! It was brilliant to bring out contrast on clusters, edge on galaxies, globs, Milky Way sweeping.
Meanwhile my views of nebulae were nothing short of awe inspiring. With narrowband 7nm Ha filter, chromatic aberration was a non-issue in the achromat, as I suspected. I did not need to buy a color corrected Apochromatic refractor if only a narrow red notch at 656nm was coming through. Both AT72ED and 120ST were showing me views of Orion like I had never seen. I began to experiment with focal reducers too and found the Antares 2" .5x reducer eliminated vignetting in my device. I bought a used PVS-7 binocular, a military device much like a binoviewer. It was an older A/C housing that had a badly blemished tube ($800). I contacted Ed Wilcox again and asked if he had a Gen 3 MX10130/UV tube used he could sell me. He had one. I bought the tube ($1300) and replaced the blemished tube. From advice on my forum, I contacted Nightline Inc about a c-mount adapter for the PVS-7 so I could put a nosepiece on it. They had one left. I bought it and started using my PVS-7 as a binoviewer eyepiece in my scopes. I had been able to see in both devices, the horsehead and flame, but the Horsehead still required averted vision to see more than a dark shadow in my AT72ED. Much better definition in my 120ST, but still wanted more.
I bought a big Astro Telescopes AR152 F/5.9 achromatic refractor. Having the great results from filtering in my 120ST, I knew the big 6" refractor would give me the brighter view to see the Horsehead with some detail and no averted vision. I was right. I was using all three refractors on faint nebulae now.
Bought a Lumicon Night Sky H-Alpha filter also after looking at filter curves and getting the suggestion from another forum member. This one is a longpass 640nm filter and a little darker than the 610nm. I actually prefer it in the two larger scopes and prefer the 610nm in the smaller. More light on smaller scopes giving a smoother appearance in the intensifier. I found a 3nm Ha on Ebay new for $134 from a seller working for Omega filters. Normally they are very expensive at upwards of $900, but this one was worth the gamble. It is a frequently used filter in worst moonlight scenario. Not the toughest coatings like the $900 plus offering, but if careful with it, works great.
By this time, I am beginning to see a long list of faint nebulae having passed into Summer and beginning of Autumn. After reading a lot more and seeing some of the other forum members? devices, I decided to get a Gen 3 25mm device. A PVS-4 starlight scope. I found a T2 adapter on ebay. The objective catadioptric lens was replaced by the T2 adapter. This one gave me the wider views in my scope but was very large and heavy at nearly 3lbs. View was 65° vs 40° of the smaller 18mm devices I had. Variable gain too, but really only useful in biggest two scopes. The mak150 and AR152.
I tried many filters too. All visual filters for standard eyepieces (UHC, OIII, etc.) were disappointing besides the Baader Neodymium Moon and Skyglow filter. That one was decent for cutting light pollution, which gets amplified in the intensifier much like everything else and makes it a brighter green background and less contrast on astronomical objects, but not as effective as 610nm or 640nm longpass filtering.
I bought 35nm Ha and 685nm IR pass filters. Occasionally I use those as the 35nm Ha filter has a broad enough notch to allow more stars seen while cutting CA to pinpoint stars again. The 685nm is good for galaxy hunting but does not allow Ha to get through. Both get used, but infrequently. I bought an Astronomik 12nm Ha filter as well. By far, the most used Ha narrowband is my Baader 7nm filter, followed by 3nm anytime the moon is out. My 640nm and 610nm longpass filters get about equal time.
I later added a 4" wide single lens binocular eyepiece to my PVS-4 for some two-eyed wide views at low power. All scopes but MCT really operating at low power, but see a ton.
Oh yeah, onto what I have seen from heavily light polluted city backyard viewing!
Small list as example:
Lagoon, Triffid, Omega, Eagle, Cat's Paw, Gamma Ori Area Sharpless, summer globulars in stunning detail, too many Open Clusters to count, over 30 different galaxies, Rosette, California, North American, Pelican, Pac Man, Horsehead, Flame, Flaming Star, Lower's, Iris, Heart and Soul, Crescent, Eastern and Western Veil, NGC6974, NGC6979, Ced214, Cocoon, Cone, Elephant Trunk, Gamma Cygni, Butterfly, Dumbbell, Little Dumbbell, NGC7822, Seagull, Thor's Helmet, IC417, IC410, NGC7762, IC353, NGC2024, Barnard's Loop, NGC1975, numerous meteors, satellites frequently, and the list can go on.
I have seen more in the nearly two years of using Image Intensifiers than the previous 4 years without it. All very easy. All on easy to use Alt-Az mounts with no tracking. I continue to refine equipment, viewing techniques, filtering techniques, and keep asking a lot of questions. I am viewing 98% with I2 eyepieces. I have not lost any interest and it instead continues to grow in both seeing more, using better techniques, and learning about the technology.
I have been given immense help by members of the Cloudy Nights EAA forum the entire time. I try to give back what I can in advice and knowledge, as well as experiment and post results.
I usually start off without an observing plan, but have my smartphone running astronomy apps so I can identify what I find. It is such powerful technology even in small scopes, that the "stumble upon an object" way of acquiring targets for observation seems to work fine for me. I can identify on the smartphone and quickly look for other objects in the near vicinity and see if the intensifier picks it up. I continue to study the same objects a lot too, in order to pick up new details and better my observational skills. It does not do all the work for me! Sometimes the objects are still so faint as to need employment of special techniques like averted vision, scope tapping, peripheral movement detection, etc., to pick up the details. Sometimes, of course, they are just in your face like a photo too.
It has been the best decision in equipment to help really see more without needing to have a mess of wires or go-to tracking mount. I am a DSO fanatic and a Nebula nut. My favorite objects to look at. Planets and Lunar still get a chance with my MCT and standard eyepieces, but it is infrequently that I want to view them. So much to see!
My most used scope is the 120ST on photo tripod w/geared center column and a Stellarvue M2 mount. I use an adjustable observing chair with it.
I have found some great vendors in the business also. The following recommended:
Ed Wilcox - Wilcox Engineering and Research (tested tubes with sheeted specs) -
Ken at NAIT - PVS-4 best T2 adapter I have tried, PVS-4's, PVS-7's, c-mount for PVS-7 B/D body. -
Mo at AE Optics - PVS-4 parts. -
Night Vision Depot - one of the best companies to deal with for tubes, goggles, and the best monocular I have tried for astronomy - The NVD Micro Monocular which has a built-in c-mount and is adapted easily. -
Glynn at OwnNight - devices, tubes, repairs -
Bruce at Night Vision Universe - devices, tubes, parts, great pricing.
Nightline Inc - devices, parts, had my PVS-7 A/C c-mount adapter, great guys.
RafCamera - ENVIS adapter for 1.25" filters
Agena Astro - adapters, threaded extensions, filters, etc -
Scopestuff - adapters, nosepieces, reducers, threaded extensions, etc -
Many more on ebay and many of
these I listed had ebay storefronts.
Image Intensified Astronomy may not be to everyone's taste. There are naysayers apprehensive about green views, there are photon purists, there are those that simply want traditional methods, but it certainly fits for me.
Night Vision with Large Aperture
By The Ardent
This year I read some very interesting reports of night vision astronomy on Cloudy Nights. I decided to try it for myself. I?m a longtime visual observer and gear head. My city backyard prevents observation of most galaxies, nebulas, and dim planetaries. I can't see the Milky Way. While I make good use of what I have, it's frustrating to log yet another "not seen" target.
I purchased the PVS-7 night-vision goggle. It features a lightweight, waterproof, shockproof housing. 2 "AA" batteries provide weeks of use. Focuses like an eyepiece, no OCS or Barlow needed to reach focus. Two-eyed viewing with excellent collimation and no merging issues. C-mount adapter accepts numerous lenses and accessories. Works right out the box with supplied lens. Used with a dob, the goggles give a correct view image. This matches the view in my right-angle correct-image finder. It matches my star charts, my binoculars, and my naked eye view.
It does have some drawbacks: cost, green color, scintillation, narrow 40-degree field, 26mm eyepieces provide low magnification, not suitable for every telescope or target. Hexagonal "honeycomb" background pattern visible in bright environments.
The first night I used the PVS-7 with the supplied 1x lens and a Hydrogen-alpha filter. I saw the Gamma Cygni nebulosity, IC 1396, NGC 281, and best of all, the California nebula! I was hooked!
My main telescope is a Teeter 18" f/3.5 dobsonian. I couldn't wait to try the PVS-7 with the large aperture. Some accessories are required. The components of my night vision system:
PVS-7 NV goggle from NAIT with C-mount adapter.
C-mount to 1.25" adapter/ or 2" adapter. The 2" has threads for both 2" and 1.25" filters.
Or C-mount to 1.25" adapter/ 0.63x focal reducer combo
The focal reducer almost doubles the field of view, but coma becomes noticeable with the focal reducer.
Astronomik 12nm Hydrogen Alpha filter, 1.25 or 2". This is critical for viewing nebulae, but strongly attenuates stars.
Baader 35nm Hydrogen Alpha filter. Weaker nebulae response, but more stars visible. The Lumicon Night Sky h-alpha filter did not provide enhanced nebula viewing.
Baader 610 nm Longpass red filter. For removing sky glow and light pollution for viewing galaxies, clusters, and other non h-alpha targets.
Just like in astronomical imaging and solar observing, Hydrogen alpha filters play an integral role with night vision. Normally invisible or impossible targets like Sharpless nebulae and PK planetaries are visible, depending on their H-alpha emission. Oxygen III won't help here, night vision responds poorly at this wavelength.
Viewing nebulae with the 18" scope:
M8, M20, M17, M16. These famous prominent nebulae are just magnificent with night vision. Add an H-alpha filter, and the view is comparable to a long exposure image. "Simply glorious" seems a lacking description.
Gamma Cygni Nebula (IC 1318): With 12nm H-a, extensive detailed nebulosity. Lots of dark lanes and dust blobs strongly silhouetted against the bright nebula. Spans several degrees. Very similar to long exposure images.
Crescent Nebula (NGC 6888) Unfiltered: Only brightest part corresponding to visual observations seen. With 12nm H-a: complete loop seen. Mottling visible, especially on eastern loop, like "leopard spots"
North American Nebula (NGC 7000) Only vague outline faintly visible unfiltered. With 12nm H-a, sharp detail of wisps and concentrations of nebulosity mixed with dark lanes. "Mexico" region like a long exposure image, contrasting with dark "Gulf" Lovely prominent double star Espin 1451 visible along brightest part.
Sharpless 2-88: bright and obvious with 12nm H-a. Separate bright nodule seen.
Sharpless 2-90: like a fat lopsided crescent moon. 12nm H-a
The Elephant Trunk (IC 1396) Large extensive nebulosity with dust lanes. The "trunk" directly visible directly with 12nm H-a
The Pac Man (NGC 281) Only tiny brightest part visible unfiltered. With 12nm H-a, bright with distinct edges and scalloping. An imaging buddy found the live view similar to his H-alpha channel.
The Bubble Nebula (NGC 7635) This was observed from home in the city, full moon, and thin cirrus overcast. Visual versus night vision compared.
13mm eyepiece and Paracorr : no nebulosity, just stars seen
13mm eyepiece, Paracorr, and Oxygen III filter: some nebulosity seen with averted vision, very faint.
PVS-7 unfiltered: small rectangular nebula touching bright star. Honeycomb background of image tube interferes.
PVS-7 with 35nm H-a: nebula clearly seen with structure. Bubble evident. No artificial background.
PVS-7 with 12nm H-a: Bright knots in rectangular nebula. Bubble clearly defined. Dark lane to north, then more nebulosity, a division similar to the Lagoon Nebula
Cone Nebula (NGC 2264) Immediately obvious with 12nm H-a! Last year we observed this under dark skies with a 30" dob. Only visible faintly, with a H-beta filter.
Hubble's Variable Nebula (NGC 2261) Bright and detailed with unfiltered view. Dim and attenuated with 12nm H-a.
Horsehead (Barnard 33 and IC 434) Easy and obvious with 12nm H-a.
Gamma Cassiopieae Nebula (IC 59 and IC 63) Not seen unfiltered. Only IC 63 seen with 12nm H-a. Large with irregular shape.
NGC 6842: Invisible unfiltered, faint ghostly disk with H-a.
The Ring (M57): Transparent disk unfiltered. Opaque ring structure with 12nm H-a.
Dumbbell (M27) Like the Ring, this bright planetary isn't really a candidate for night vision. It does show interesting structure however. Unfiltered just the dumbbell shape is present. This corresponds to the pink-red "apple-core" area seen in images. Many faint stars seen in the nebulosity, but the blue central star is difficult. With 12nm H-a, the "apple-core" overlays the round body of the opaque nebula. No embedded stars visible.
NGC 7048: Not seen unfiltered. Easily seen round disk with 12nm H-a.
NGC 7027: Bright oval nebula with hint of dark lanes unfiltered. Definite dark lanes separate the nebula into three unequal lobes with 12nm H-a.
NGC 7026: Tiny, two bright flat ovals separated by dark lane unfiltered. Nebula larger with 12nm H-a. Looks like images on Internet.
NGC 7662: Nice detail with spherical outline unfiltered. Bright figure-8 inside elliptical envelope with 12nm H-a.
Sharpless 2-188: invisible unfiltered. With 12nm H-a, obvious, nice fat crescent like a coarse brushstroke. Barely visible under dark skies with a 30" dob and normal eyepiece + OIII filter.
P 84.9+4.4 (Abell 71) Not seen unfiltered. Large ghostly round disk with 12nm H-a.
P 103.2+0.6 (Minkowski 2-51) observed during full moon and cirrus overcast skies, in the city. 13mm eyepiece with OIII filter: not seen (was previously seen, barely, under dark skies) PVS-7 with 35nm H-a: faintly seen with central star.
With 12nm H-a: Disk clearly seen but central star attenuated by filter.
P103.7+0.4 (Minkowski 2-52) observed during full moon and cirrus overcast skies, in the city. Same results as above, but much smaller disk with no central star.
Only about 1 in 5 PNG/PK planetaries observed with night vision were visible.
Viewing galaxies was an unexpected bonus. Just a red filter in the city, or no filter under dark skies. A 2x Barlow helps with resolution. Like with normal visual observing, galaxies are much improved under dark skies. Surface brightness correlates with visibility.
NGC 7331: looks like a small M31. Four satellite galaxies visible in FOV.
Stephan's Quintet: all five visible from my light polluted backyard!!! I was sooo happy!
NGC 185 and 147: Satellites of M31 located about 5 degrees away in Cassiopeia. Not terribly bright, and 147 is difficult visually. Both are easy with night vision.
NGC 1275 (Perseus A) Easy with night vision, and about 15 other small galaxies seen in FOV, part of galaxy cluster Abell 426)
The fainter galaxies are challenging.
NGC 253 (Sculptor Galaxy) This bright target is stunning visually, even more so with night vision. Tiny, thin dust lanes visible around the core.
Not every galaxy works with night vision. Low surface brightness Barnard's Galaxy in Sagittarius and M33 aren't improved over visual.
In closing, the night vision experiment was far more successful than I expected. The view is upright and correct. No computer or cables required. Otherwise invisible nebulae and galaxies are visible, even from the city.
- Jeff Morgan, Relativist, GeezerGazer and 20 others like this