cweinhei
sage
Reged: 01/14/06
Posts: 254
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I see there are two kinds of H-alpha filters: narrowband (~7nm) and broadbande (~13nm). I'm planning on buying one to use with my DSLR. Which one should I buy or do I really need both?
Which brand do you guys like?
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Orion Atlas EQ-G w/ EQMOD
8" F/4 LXD75 Schmit-Newt (Flocked)
JMI NGF-55D Focusor
Hutech Canon Rebel 350 XT (Clear filter)
DSI Pro (for guiding)
Shoestring USB Shutter Control
Shoestring Focusor Control
HNSky,PHD,DSLRFocus,WCS,Iris
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Tonk
Post Laureate
Reged: 08/19/04
Posts: 4346
Loc: Leeds, UK, 54N
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I would like to know this too ...
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Televue 85, GM-8/Gemini, Canon 40D (unmodded), Canon 450D (modded w/Astronomiks clip-ins - UV/IR, OWB)
Coronado SM60/BF10, Baader Herschel Wedge
Leeds Sky Clock Ripon Sky Clock
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Rankinstudio
sage
Reged: 04/05/08
Posts: 409
Loc: Salt Lake City, UT, Lake Powel...
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I third that, would be neat to see some examples...
Cheers
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Freddy WILLEMS
Carpal Tunnel
Reged: 11/13/05
Posts: 2538
Loc: Hawaii, Honolulu
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I had the 7nm with my unmodded D10 and was not happy with it, I sold it !
Now I have a modified D40 and want an H Alpha filter again.
The 7 nm took long exposure times before getting any results. I would try a 12nm or 13 nm again before buying a 7nm.
I'm not an expert in the H alpha field !, but I did see a lots of great results taken with DSLR's and 13 nm H Alpha filters.
Just my two pennies here.
I'll try to dig out some webpages. I saved a bunch of websites about DSLR and H Alpha, but my computer crashed and all the information was gone. I think if you google DSLR and H Alpha you're getting close.
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Freddy
Meade 14" LX200 GPS UHTC GPS on permanent pier
Celestron C 14" Peltier cooled for planetary imaging.
Meade 10" LX200 & TITAN 50:1 mount Gemini 'go to'
Meade 127 mm f/9 APO & TITAN 50:1 mount Gemini 'go to'
W/O 102 mm f/7 APO doublet
Orion 80 mm f/7 ED
DFK 21AU04.AS
ToUcam 840 II pro
Canon 10D Unmoddified
Canon 40D Hutech moddified
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Igor
super member
Reged: 04/20/06
Posts: 125
Loc: Croatia
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In my opinion the narrower the better because H-alpha line has wavelength of exactly 656.28nm, everything else is LP. Recently I bought Astronomik 12nm Ha filter because its cheaper 
Some time ago there was discussion on this subject but I could't find it.
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GSO 250/f5 dob
Skywatcher Explorer 130p @ EQ3
Baader modified 350D and bunch of old M42 lenses
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gavinm
scholastic sledgehammer
Reged: 08/26/05
Posts: 804
Loc: Auckland New Zealand
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Theoretically, deep sky objects will exhibit enough spectral line broadening that a filter that is too narrow will miss a sizeable portion of signal, so wider might be better. Fortunately there's not too much light pollution around this wavelength.
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Gavin
Mt Albert Grammar School Observatory
Auckland, New Zealand
http://www.mags.school.nz/astronomy/index.html
12" LX200R F6.8 AP
SBIG ST7-XME + CFW10
Moonlite SCT focuser w/ temp
Skywatcher Equinox ED80 Pro (ADM dovetail)
+ other stuff
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Coliwabl
scholastic sledgehammer
Reged: 01/01/05
Posts: 834
Loc: Dallas, Oregon, USA
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I've been using the Astronomik 13nm Ha filter with my Canon 20Da and have gotten fair results. I've attached a photo of the filter as well as a shot of IC434 as an example using it. Good luck!
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SkyWatcher Pro EQ-6 w/Skyscan
SkyWatcher 180mm MAK
Meade LX200 8" GPS SMT
Meade 80mm 5000 ED APO
WO 66SD + Flat-2 Focal Reducer
Orion Starshoot Autoguider
Astronomik Ha,OIII,and SII Canon cmos clips
Canon 20Da
Registax 5.0
Photoshop CS4 Extended
Images Plus 2.8
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Coliwabl
scholastic sledgehammer
Reged: 01/01/05
Posts: 834
Loc: Dallas, Oregon, USA
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Here's a shot of IC434 I took using the filter.
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SkyWatcher Pro EQ-6 w/Skyscan
SkyWatcher 180mm MAK
Meade LX200 8" GPS SMT
Meade 80mm 5000 ED APO
WO 66SD + Flat-2 Focal Reducer
Orion Starshoot Autoguider
Astronomik Ha,OIII,and SII Canon cmos clips
Canon 20Da
Registax 5.0
Photoshop CS4 Extended
Images Plus 2.8
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justabob
Carpal Tunnel
Reged: 05/05/07
Posts: 1673
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I use the 13nm clip in. There are several examples in my gallery.
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http://www.pbase.com/rkn/astro&page=all
Vixen Sphinx SXW
Meade sn6
Canon EF 200mm f/2.8L II USM Lens
Hutech 1000d
Self modded 350d
ST8300c on order
DSI PRO II
Bob
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justabob
Carpal Tunnel
Reged: 05/05/07
Posts: 1673
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Ha and rgb
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http://www.pbase.com/rkn/astro&page=all
Vixen Sphinx SXW
Meade sn6
Canon EF 200mm f/2.8L II USM Lens
Hutech 1000d
Self modded 350d
ST8300c on order
DSI PRO II
Bob
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cweinhei
sage
Reged: 01/14/06
Posts: 254
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Wow. Love the Ha+RGB shot of the horse head nebula. Ha+RGB is my primary motivation for getting one.
Why did you guys choose the clip in version vs. the 2" screw on filter? Is the 2" filter easier to change? If I recall, I think the price is about the same isn't it?
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Orion Atlas EQ-G w/ EQMOD
8" F/4 LXD75 Schmit-Newt (Flocked)
JMI NGF-55D Focusor
Hutech Canon Rebel 350 XT (Clear filter)
DSI Pro (for guiding)
Shoestring USB Shutter Control
Shoestring Focusor Control
HNSky,PHD,DSLRFocus,WCS,Iris
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Nils_Lars
Post Laureate
Reged: 01/04/08
Posts: 3385
Loc: Santa Cruz Mountains , CA
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I also went with the 13nm clip in so I could use it with lenses or scope and it is another barrier to dust getting into the camera.
I have had good results using it to enhance my RGB shots with another layer and I love having to option to shoot something when the moon is out.
I am still not sure if using it to shoot objects heavy in Ha is better exclusivly with the filter or as a combination with RGB or RGB only and making a greyscale out of the red channel.
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Erik
Orion Atlas Self Hypertuned (EQMOD)
Orion ED 80
Williams Optics VII reducer
Celestron 8" SCT
Orion Starshoot Autoguider
PHD guide
Canon 400D Hap Griffin Mod w/Baader filter
Astronomik clip-in LP filter and 12nm Ha
Stilleto CVF and Bahtinov mask
Tamron 75-300mm&28-80mm lenses
NexImage webcam
http://www.flickr.com/photos/31986095@N05/
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KevinUK
Vendor (DSLR-AstroMod)
Reged: 08/22/07
Posts: 720
Loc: N 51'53 W 00'25
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Another thumbsup for Astronomik clip, either 6 or 12nm forall the reasons mentioned above.
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DSLR AstroMod
DSLR filter removal and replacement packages
http://www.dslrastromod.co.uk
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s58y
Postmaster
Reged: 12/12/04
Posts: 5492
Loc: Eastern NY
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I have the 13nm Astonomik and 7nm Baader H-alpha filters. At first I tried the 13nm, but ended up with fuzzy stars or haloes, for some reason (and apparently not because of no IR blocking). Also, on nights with a bright moon, the sky background was still noticeable.
Now, I use a 7nm Baader filter. The stars are better, but still slighty fuzzy, compared to shots with a Hutech IDAS or Astronomik UHC filter. Maybe this is normal with H-alpha filters? For some reason, the haloes always seem elongated in the horizontal direction of the DSLR.
The sky background is darker with the 7nm. On his website, I believe Samir Kharusi recommends 6 or 7nm filters, if you have really severe light pollution.
One problem with the Baader filter is that the mounting ring is too wide to fit inside my old Nikon 800mm telephoto lens (rear filter slot). The astronomik and IDAS filters fit OK.
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Hutech 30D, SBIG ST-402 autoguider
SV80S, TV102iis
Old camera lenses: 800mm f/5.6, 180mm f/3.4
AP900, Barndoor tracker
http://www.pbase.com/s58y
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cweinhei
sage
Reged: 01/14/06
Posts: 254
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Have you tried a 7nm or 13nm H-alpha filter in combination with a Hutch IDAS filter? Does that help get rid of the halos?
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Orion Atlas EQ-G w/ EQMOD
8" F/4 LXD75 Schmit-Newt (Flocked)
JMI NGF-55D Focusor
Hutech Canon Rebel 350 XT (Clear filter)
DSI Pro (for guiding)
Shoestring USB Shutter Control
Shoestring Focusor Control
HNSky,PHD,DSLRFocus,WCS,Iris
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s58y
Postmaster
Reged: 12/12/04
Posts: 5492
Loc: Eastern NY
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Quote:
Have you tried a 7nm or 13nm H-alpha filter in combination with a Hutch IDAS filter? Does that help get rid of the halos?
I never tried combining two filters to suppress haloes.
Let me show you examples of these "haloes" - maybe it's just "star bloat", and this is normally seen with H-alpha images?
Here are 3 test images, taken in 2006 at a place with light pollution readings of about 20.3 on the original SQM. They were taken with a Canon 30D at f/4.9 with a SV80S telescope + unmatched TRF2008 reducer. Mount was a G-11 and autoguiding was used. The target is NGC7000 -- North America Nebula.
These are full-frame, uncropped single subexposures of either 5 or 10 minutes. Usual dark+flat+bias calibration was done in Images Plus. Post processing with Photoshop involved extracting the red channel and replacing the blue + green channels with the red. A single gamma adjust from 1.00 to 2.20 was done using the Photoshop levels function. No other processing was done, except reduction to 750x500, conversion to 8-bits and then JPEG conversion with quality = 9.
1st shot has no filters. 5 minutes, ISO 400, new moon:
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Hutech 30D, SBIG ST-402 autoguider
SV80S, TV102iis
Old camera lenses: 800mm f/5.6, 180mm f/3.4
AP900, Barndoor tracker
http://www.pbase.com/s58y
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s58y
Postmaster
Reged: 12/12/04
Posts: 5492
Loc: Eastern NY
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Second shot is with the Astronomik 13nm filter, 10 minutes, ISO400, 27% moon.
Note that the stars are larger than on the first image, despite being dimmer. Note: It's hard to focus an H-alpha shot, since only the red pixels respond well in the small star image used for focusing. You see a checkerboard pattern with mainly red pixels.
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Hutech 30D, SBIG ST-402 autoguider
SV80S, TV102iis
Old camera lenses: 800mm f/5.6, 180mm f/3.4
AP900, Barndoor tracker
http://www.pbase.com/s58y
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s58y
Postmaster
Reged: 12/12/04
Posts: 5492
Loc: Eastern NY
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Third shot is with the 7nm Baader H-alpha filter. 10 minutes, ISO800, 59% moon. Note the background is actually brighter, because of the ISO800 + much brighter moon. The bloated stars are smaller than the 2nd image, but still larger than the first.
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Hutech 30D, SBIG ST-402 autoguider
SV80S, TV102iis
Old camera lenses: 800mm f/5.6, 180mm f/3.4
AP900, Barndoor tracker
http://www.pbase.com/s58y
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s58y
Postmaster
Reged: 12/12/04
Posts: 5492
Loc: Eastern NY
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BTW, here's what a finished narrowband shot with the 7nm Baader looks like:
(note: This was taken from a darker site in 2008).
finished shot
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Hutech 30D, SBIG ST-402 autoguider
SV80S, TV102iis
Old camera lenses: 800mm f/5.6, 180mm f/3.4
AP900, Barndoor tracker
http://www.pbase.com/s58y
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justabob
Carpal Tunnel
Reged: 05/05/07
Posts: 1673
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Interesting. What filter is on your Hutech 30d? Clear or astronomic ir cut? I ask because I noticed much more in the way of star halo effect with my self modded 350d "no filter replacement" than my new 1000dh with the mild ir cut, when using the ha filter. My 80ed also seemed to cause more bloat and halo than my meade sn6 reflector or a quality camera lens would.
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http://www.pbase.com/rkn/astro&page=all
Vixen Sphinx SXW
Meade sn6
Canon EF 200mm f/2.8L II USM Lens
Hutech 1000d
Self modded 350d
ST8300c on order
DSI PRO II
Bob
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Samir Kharusi
scholastic sledgehammer
Reged: 06/14/05
Posts: 977
Loc: Oman
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Quote:
I see there are two kinds of H-alpha filters: narrowband (~7nm) and broadbande (~13nm). I'm planning on buying one to use with my DSLR. Which one should I buy or do I really need both?
Which brand do you guys like?
The filter to get is the Astronomik 6nm Clip Filter (with certified 90+% transmission at Ha, available only by direct purchase from Astronomik in Germany). The uncertified filters available from US retailers are probably fine, but I did not want to take the risk. The full answer can get very, very long. But these comments may lead you in the right direction:
Doppler line broadening is very minute, fast focal ratio broadening is also minute. Both these are generally under a nm. They do matter if you are talking of filter bandwidths of a few Angstroms (NB 1 nm = 10 Angstroms). Unsharp stars are due to misfocus, not really the Bayer Array, since the Ha leaks onto the G pixels in Canon DSLRs so loss of resolution is trivial. I have a few pages addressing filter issues on my website. 13nm filters are, frankly, too wide if you have a lot of light pollution. Been there, done that. Pay up and get the best up front, as indicated above. If you are willing to use 2" filters then the Bayer 7nm Ha CCD is also great. I do own the Bayer 7nm, Astronomik 13nm and Astronomik 6nm, but I have not shot the same target with a couple of these for comparison. Some things just take too long for our short lifespans.
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Bored? Peruse my website:
http://www.samirkharusi.net/
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justabob
Carpal Tunnel
Reged: 05/05/07
Posts: 1673
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Samir, If you are willing to make a comparison of the 13 and 6nm filters I just picked up a Canon EF 200mm f/2.8L II USM Lens. I believe you also have this lens. Lets pick a target, iso number and length of subs ect. Perhaps not a perfect test but it might be fun.
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http://www.pbase.com/rkn/astro&page=all
Vixen Sphinx SXW
Meade sn6
Canon EF 200mm f/2.8L II USM Lens
Hutech 1000d
Self modded 350d
ST8300c on order
DSI PRO II
Bob
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s58y
Postmaster
Reged: 12/12/04
Posts: 5492
Loc: Eastern NY
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Quote:
Interesting. What filter is on your Hutech 30d? Clear or astronomic ir cut? I ask because I noticed much more in the way of star halo effect with my self modded 350d "no filter replacement" than my new 1000dh with the mild ir cut, when using the ha filter. My 80ed also seemed to cause more bloat and halo than my meade sn6 reflector or a quality camera lens would.
The 30D has the Hutech UV/IR blocking filter. For some reason, I never can find a sharp focus point when using either of the H-alpha filters, compared with an Astronomic UHC or IDAS LPS filter (or no filter). The problem was worst with the 13nm H-alpha filter. Maybe some other setup would get the worst bloating with the Baader 7nm filter?
Unfortunately, I can't use the Baader 7nm inside my ancient Nikon 800mm lens, so I may end up getting one of those Astronomik 6nm clip filters, an Astronomik 48mm threaded 6nm filter (rim is narrower than the Baader), or even a 50mm round Astrodon 5nm filter to fit inside the lens.
Murphy's law says if I get the 6nm clip filter, I'll soon move to either a full-frame DSLR or a real astrocam. If I get the 5nm Astrodon, I'll never move to a real astrocam. If I get the 6nm threaded filter, I'll end up with a camera requiring square 50mm filters.
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Hutech 30D, SBIG ST-402 autoguider
SV80S, TV102iis
Old camera lenses: 800mm f/5.6, 180mm f/3.4
AP900, Barndoor tracker
http://www.pbase.com/s58y
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cweinhei
sage
Reged: 01/14/06
Posts: 254
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It looks ro me like the halo is only a big problem for really bright stars. Is that the conventional thought? I didn't notice the halos in your shots above.
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Orion Atlas EQ-G w/ EQMOD
8" F/4 LXD75 Schmit-Newt (Flocked)
JMI NGF-55D Focusor
Hutech Canon Rebel 350 XT (Clear filter)
DSI Pro (for guiding)
Shoestring USB Shutter Control
Shoestring Focusor Control
HNSky,PHD,DSLRFocus,WCS,Iris
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Samir Kharusi
scholastic sledgehammer
Reged: 06/14/05
Posts: 977
Loc: Oman
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Quote:
Samir, If you are willing to make a comparison of the 13 and 6nm filters I just picked up a Canon EF 200mm f/2.8L II USM Lens. I believe you also have this lens. Lets pick a target, iso number and length of subs ect. Perhaps not a perfect test but it might be fun.
Hi, it's actually that specific lens (and others) that have steered me towards a pop-in, clip filter. As I said, it's a very looong story. Used to be that the only pop-in Ha filter available was a Hutech, but that had to be used with a UV/IR blocker (because it leaked some IR). My DSLR at the time had clear glass. When I acquired another modded DSLR (with UV/IR blocker) Hutech had stopped selling the filters. So I bought the Baader 7nm 2" Ha. An excellent filter, narrower than my 13nm Astronomik. At the time Astronomik had problems with manufacturing their 6nm Ha, even though they were still being advertised. I was in correspondence with the owner of Astronomik. When they finally sorted out the fabrication issues, they also offered a pop-in version. This was a godsend! Usable with the 200mm lens wide open (also with all my lenses from 14mm to 600mm). The difference between the 6nm and the 13nm is actually immediately obvious. The image through the viewfinder is much dimmer, and autofocus is rarely possible with the 6nm. Last time I autofocused on a street light about a mile away. I do have an image with the Astronomik 13nm and the 200mm lens here but not much use for comparison. Like most stuff in astrophotography, without a controlled, side-by-side comparison one can easily end up with the wrong conclusions. Stuff like light pollution and post processing are very critical. Of course, just being able to use your 200mm lens at f2.8 instead of f4.5 (2" filter attached at the front of the 200mm lens with step-down rings) is worth quite a bit. So far the only nagging issue I have experienced was that in a C14 Hyperstar the Astronomik clip filter showed more flare from bright stars than my 2" Baader, but I had not used both filtyers on the same star field; so was it the star field that had much brighter stars? or the filters? I doubt that the flare had anything to do with the filters, but if somebody reports something similar then it would be worth examining.
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Bored? Peruse my website:
http://www.samirkharusi.net/
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justabob
Carpal Tunnel
Reged: 05/05/07
Posts: 1673
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Ok Samir, and we are using different cameras as well. Too many variables indeed. I have yet to try the ha filter at my dark site so I am curious as to the improvement over my home suburban site. But I am pumped about this lens, seems like an ideal solution at 200mm.
--------------------
http://www.pbase.com/rkn/astro&page=all
Vixen Sphinx SXW
Meade sn6
Canon EF 200mm f/2.8L II USM Lens
Hutech 1000d
Self modded 350d
ST8300c on order
DSI PRO II
Bob
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s58y
Postmaster
Reged: 12/12/04
Posts: 5492
Loc: Eastern NY
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Quote:
It looks ro me like the halo is only a big problem for really bright stars. Is that the conventional thought?
You can see off-center reflection haloes around the two bright stars in Orion's belt in this narrowband shot:
haloes
It's not clear that they're caused by the filter, of course.
--------------------
Hutech 30D, SBIG ST-402 autoguider
SV80S, TV102iis
Old camera lenses: 800mm f/5.6, 180mm f/3.4
AP900, Barndoor tracker
http://www.pbase.com/s58y
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Samir Kharusi
scholastic sledgehammer
Reged: 06/14/05
Posts: 977
Loc: Oman
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Quote:
Ok Samir, and we are using different cameras as well. Too many variables indeed. I have yet to try the ha filter at my dark site so I am curious as to the improvement over my home suburban site. But I am pumped about this lens, seems like an ideal solution at 200mm.
The narrowband filters do make a HUGE difference to the visibility of nebulae even at a very dark site. Here is a comparison (sort of, since integration times were not equal) using a not particularly narrowband filter (40nm passband at Ha). Worth a click, IMHO. Generally I found that you need subs about 3x as long as for white light, minimal length for white light at a dark site is one minute at f2.8, narrowband 3-minutes. Adjust subexposure length for focal ratio. Since the subs can get very long for slow OTAs one might wish to start with a very short lens. A Canon 50mm/1.8 or 50/1.4 are excellent at f2.8 in Ha, and almost any mount should be able to track that for 3 minutes unguided. Note: because there is NIL chromatic aberration when shooting narrowband, f2.8 works well with these 50mm lenses, but in white light one needs to close down to f4. I have also come to the conclusion that the bulk of the imaging time (say, 75+%) should be with the narrowband filter, the white light is really just to provide star colors.
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Bored? Peruse my website:
http://www.samirkharusi.net/
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justabob
Carpal Tunnel
Reged: 05/05/07
Posts: 1673
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Very nice Samir. I have a two week holiday this new moon and adding ha data to my 50mm Cygnus is on the list of targets. I will try it at f2.8 as you suggest. But I think I will go with 5 min subs, because I am building a collection of five min darks at various temps.
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http://www.pbase.com/rkn/astro&page=all
Vixen Sphinx SXW
Meade sn6
Canon EF 200mm f/2.8L II USM Lens
Hutech 1000d
Self modded 350d
ST8300c on order
DSI PRO II
Bob
|
KevinUK
Vendor (DSLR-AstroMod)
Reged: 08/22/07
Posts: 720
Loc: N 51'53 W 00'25
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Quote:
Quote:
It looks ro me like the halo is only a big problem for really bright stars. Is that the conventional thought?
You can see off-center reflection haloes around the two bright stars in Orion's belt in this narrowband shot:
haloes
It's not clear that they're caused by the filter, of course.
Hi I get exactly the same off-centre affect shooting with my modded 450D and Astronomik UHC clip in filter through my Meade 8" SN . I am still unsure what causes this.
The focus looks fairly sharp and only the bright stars with haloes have their centres skewed. If it was rotation or coma all objects would be similiarly effected and focus would be compromised and soft in final image which it isn't.
--------------------
DSLR AstroMod
DSLR filter removal and replacement packages
http://www.dslrastromod.co.uk
-------------------------------
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