multi-bandpass narrowband filters for color  cameras are a definite hit in the amateur  

astrophotography community many people are using  them to photograph emission nebulae from light  

polluted cities with color cameras including  DSLRs but also dedicated astronomy cameras  

today i'm going to be reviewing three  options two of them are pretty well  

established as good budget options in the  two inch format the optolong L-eNhance  

is 229 optolong L-eXtreme is 309 and the last  one is new on the market it's the antlia ALP-T  

and it will retail for 380 so we have sort  of a good range here 229 to 309 to 380  

and they're all basically designed to do the same  thing which is to isolate the light from emission  

nebulae specifically the o3 emission line and  the h alpha emission line and the way that they  

work is that they pass the light at those specific  parts of the visible spectrum and how much of the  

light they pass around the emission line is called  the band pass and anything that is not included in  

those specific band passes is reflected away and  blocked from reaching the camera's sensor so in  

addition to being great filters for capturing a  mission nebulae they also work excellently for  

blocking light pollution which is why i'm testing  them here just outside of boston in a border sky  

with plenty of bright lights all around me from  houses and schools and street lamps and businesses  

now i want to make clear up front what these  filters are not good for which is photographing  

basically anything other than emission nebulae so  they aren't good at capturing natural star color  

they're not designed for capturing reflection  nebulae or other galaxies now galaxies are sort of  

a special case because if it's a galaxy that has a  lot of emission nebulae like m33 or the magellanic  

clouds then you might be able to get a cool photo  using these kinds of filters but it wouldn't be  

your typical galaxy photo like this which is  taken with broadband filters not narrowband so  

again their main use case is really for emission  nebulae nebulae that emit their own light from  

ionized atoms associated with the different gases  in the gas clouds like hydrogen oxygen and sulfur  

and importantly these clouds of gas emit  at very specific wavelengths of light  

that the filters can be designed to pass while  blocking all the other light so what i'm going  

to do with this video is complete reviews of these  three imaging filters including shootout results  

which i'm taking right now but before i jump in  let me just go through a couple quick disclosures  

i was not paid for these reviews i'm also not  given any talking points or anything like that  

anything in this video is coming from me and  me alone however i didn't pay for these filters  

optolong sent me the L-eXtreme for the purpose  of this review and Agena Astro which is a great  

online store worked with Antlia and they loaned  me the Antlia alp-t filter a few weeks before it's  

available for sale here in the states from Agena  and optolong L-eNhance i bought a long time ago  

but with proceeds from my patreon which is the  main financial support for this youtube channel  

so a big thank you to optolong and antlia  and agena astro and my patreon members your  

support really means the world to me and  it allows videos like this to happen so  

let's jump in now and i'm going to start with the  spectral response of these filters i measured each  

filter at home i'd put together a spectrometer and  a suitable lamp the last time i did filter reviews  

and these are the actual measured spectra with  my home setup and you can see from this that  

all three filters are pretty well centered on  the emission lines like they are supposed to be  

but the more expensive filters have the tighter  band passes as advertised the antlia have the  

five nanometer band passes the l extreme has  the seven nanometer and the l enhance has a  

24 on the o3 line and a 10 nanometer pass on  the ha line now something sort of interesting  

is taking these spectra and plotting them to  get transmission curves now my setup is not  

super high resolution but i still think i get  a pretty good idea of how the filters i have  

stack up against the plots that the manufacturers  publish so i can compare my particular samples to  

the suggested transmission curve for the filter  in general so starting with the l enhance i found  

the full width half maximum meaning the width  of the pass bands was accurate and they were  

also well centered in terms of transmission at the  emission lines my filter looks pretty close maybe  

just a few percent lower than the advertised peak  transmission but still in the high 80s so i think  

pretty good with the l extreme the 03 was well  centered the ha pass may be just a tad off but  

like i said it's hard to say at my resolution  of my spectrometer and the peak transmission  

was in the mid 80s for both lines so i think just  a little bit lower than the published uh low 90s  

or 90 percent that uh opted along uh suggests  the antlia tested pretty well the passes were  

well centered on the emission lines and they  were of the right width of five nanometers  

the peak transmission for the h alpha line looked  to be above 90 percent which was quite impressive  

but the transmission on the o3 line was maybe  just a tad under the advertised 85 percent i  

think it was closer to 80 percent for my sample  turning briefly to physical characteristics the  

l enhance gets points for being available in two  inch one and a quarter inch and a canon clip in  

it's the only one of these three filters that  has the clip in format available it comes the  

two-inch version comes in a semi-clear plastic box  with nice foam insert to hold it the filter cell  

has minimal knurling on the top and is smooth on  the sides it measured 6.93 millimeters thick when  

you include the threads and 4.97 millimeters above  the filter threads taking it apart with a spanner  

wrench the glass filter itself measured 45.93  millimeters wide moving on to the l eXtreme the  

only difference is that it's not available as a  clip-in filter but in every other way it's really  

just like the l enhanced so i won't bore you with  the details there and finally the antlia alp-t  

alp stands for anti-light pollution but they also  call it the golden filter because the coating  

on one side makes it appear gold it comes in a  sturdy plastic box with a magnetic cover and a  

waxed sleeve closed with a security sticker  and that's on the inside of the plastic box  

it measures 7.2 millimeters thick with threads  and 5.02 millimeters above the threads the glass  

filter itself if you take the filter cell apart  measures 46.46 millimeters wide so now on to  

the real world tests these were all taken on the  same night from my bortle 8ish yard in somerville  

massachusetts just outside of downtown boston  there was a waxing gibbous moon out and so the  

conditions you can imagine this is a very light  polluted sky and these are all going to be shot  

at f 5.4 with a focal length of 464 millimeters  and the target is the flaming star and tadpoles  

nebulae in auriga to start out as a baseline  here is a half hour integration with a stock  

canon t7 and here is a half hour with the optolong  l enhance added in the light path with that  

still that stock canon t7 and again here's a  half hour integration with the lx stream now  

and finally a half hour  integration with the antlia alpt

okay now let's turn to a full spectrum modified  canon 60d so you know this is a modded dslr but  

it could also stand in for a dedicated astronomy  camera which which come already full spectrum  

and here's the baseline there with no filter  and again a bortle 8 sky with moonlight and  

now with the L enhance added you can see a big  difference and now a half hour with the lx stream

and finally the antlia alpt

okay so now that we have an idea of the shots full  size let's take a look at some side by side crops  

starting with the canon t7 and zooming in on the  flaming star nebula and you can see with a stock  

camera that the reflection nebula does come out  a bit even from a bortle 8 sky with moonlight so  

that's pretty interesting you can you can also  see it i think a little bit with the wide band  

pass of 24 millimeters on the L enhance the  03 line but reflection nebulae aren't really  

going to come through with the tighter narrow  band filters like the lx stream or the antlia  

and now let's look at the same crop  but with the canon 60d full spectrum  

on this one you can really see the lx  stream and the antlia alpt are pretty  

neck and neck in terms of contrast and light  pollution reduction and they also have the  

tighter stars from the tighter band passes so if  you're after that you can see a difference there

the tadpoles are a bit more interesting  uh for this comparison because there  

actually is o3 signal in there and i think all  three filters did really well um both with the  

stock dslr that you're seeing here and with  the full spectrum canon 60d you're seeing now

all right last side by side we can look at the  noise from the light pollution and at the bright  

stars in the field this is from the middle of the  picture in terms of noise since the l enhanced  

lets in more light pollution you do get a noisier  image even with identical integration time because  

after you subtract out that light pollution  you're still left with some photon noise from  

the light pollution the lx stream and the antlia  alpt do look well matched in in the regard of  

you know the lower noise and the higher contrast  on the sky there's only one halo that i see in in  

all the pictures and it's on the bright star with  the lx stream filter with the brightest star in  

the field there is a little faint halo there i  can zoom in on it so you can see it a bit better  

but i don't see it on that star with no filter  or the l enhance or the antlia alpt so i think  

i can conclude L-eXtreme did cause the halo there  everything that i've gone over in this video plus  

more is available in my reviews on my website  astrofilters.com all the all three reviews are up  

now and you can also examine the full size images  and use this fun slider feature i just added to  

compare with and without filter i will try to  make these living reviews so if i come across any  

mistakes or things that need updating i'll update  them on the website so i hope you can check that  

out if you're interested in any of these great  filters and i'd appreciate if you use my affiliate  

link now seeing all of my current members here  on my patreon campaign and if you want to see  

your name in the credits of future long nebula  photos videos you can sign up over on patreon.com  

nebula photos and we now have over 500 members so  it's a big cool community and there are a bunch  

of benefits outside of just your name in the  credits of long videos some of those benefits  

include i now i did one exclusive video and i'm  working on a second exclusive video just for  

patreon uh there are monthly zoom chats where  you can ask questions of me and other people  

on the chat there is a discord community which is  really cool very vibrant lots of stuff going on  

there including monthly imaging challenges with  prizes a quarterly group imaging project where  

we're all working on the same deep sky object  together and patreon also has lots of different  

communication methods you can direct message me  straight through patreon.com you can also do it  

on discord and so there's a lot of cool ways to  connect and really get involved and so if you want  

to accelerate your learning further after watching  some of my videos consider joining over on patreon 

it starts at just one dollar a month and  again the link is patreon.com nebula photos  

until next time this has been Nico  Carver at Nebula Photos. Clear skies!