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!