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Old 27-04-2015, 04:42 AM
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iceman (Mike)
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Review: Astrodon Narrowband 3nm H-Alpha and 3nm OIII Filters

Slawomir Lipinski has been kind enough to write a review of the Astrodon Narrowband 3nm H-Alpha and 3nm OIII Filters astro imaging camera.

You can read the review on the IceInSpace Reviews page, or directly by clicking on the link below:

Review: Astrodon Narrowband 3nm H-Alpha and 3nm OIII Filters

Thanks very much to Slawomir for taking the time to write the review.

Last edited by iceman; 28-04-2015 at 04:38 AM.
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Old 28-04-2015, 04:38 AM
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Review posted.
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Old 28-04-2015, 06:22 AM
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Nice review, Slawomir. It has always been obvious to me that the assertion that narrow filter bandwidth requires longer integrations is false but nice to see someone demonstrate this empirically.

Cheers,
Rick.
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Old 28-04-2015, 04:57 PM
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Thank you Rick.

There are many myths in the field of astrophotography; I believe that an open dialog and shared experience can help everyone in learning to create better images.

Only recently I understood that quality filters are as important for astroimaging as are good spark plugs in a car.
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Old 28-04-2015, 07:15 PM
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Nice review, and my experience with my Astrodon NB filters mostly matches yours.

However I decided to go for a 5nm Ha instead of the 3nm for 2 reasons.

The first is that while you're correct that the narrower OIII and SII filters do get the same signal at the relevant wavelength, with much less noise, this isn't necessarily true for the 3nm Ha filter. As I understand it a Ha filter of about 5nm and above is also passing NII light whereas the 3nm is only Ha. This will mean that when imaging objects that are relatively bright in NII, such as planetary nebulae, you would require longer Ha exposures to get an equivalent amount of signal, or you would also need to image through an NII filter and combine that in your processing. Either way your imaging time is increased, but of course only on objects that are bright in NII.
I've got no idea how much this would impact "in the real world" when imaging a nebula like M16 as I've never seen an image of it through an NII filter.

The other reason is that I've always found that my stars are much tighter in Ha images relative to OIII and especially SII images so I figured the slightly larger stars through a 5nm Ha vs a 3nm Ha filter will help me balance my magenta stars in my NB images.
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Old 28-04-2015, 08:18 PM
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Thank you Hugh for your feedback and for sharing your experience.

I had to go for 3nm filters due to extreme light pollution in my area, and because these filters work better with the Moon up.

I guess the perfect solution would be to have both 3nm Ha and 5nm Ha, depending on the target. Oops, did I just suggest spending more money on astro gear?...
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Old 28-04-2015, 09:36 PM
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Haha oh no! I had considered that!

My light pollution is extreme, I image from a balcony just next to the Sydney CBD, it's ridiculous but it's what I've got...
The Astrodons have made it much more tolerable though.

If you're interested I did a quick comparison between my 5nm and 7nm Ha a while ago:
http://www.iceinspace.com.au/forum/s...d.php?t=126305

And also between my 3nm and 8.5nm OIII:
http://www.iceinspace.com.au/forum/s...d.php?t=125922

I couldn't believe the difference when I first saw the difference - it must be an even bigger improvement for you coming from 12nm to 3nm
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Old 29-04-2015, 10:28 AM
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I asked Don from Astrodon whether 3nm Ha is the way to go with my new AP Riccardi Honders scope.

He said I would be better off staying with the 5nm as 3nm blocks N11 and the 5nm does not unless I was imaging in a light polluted area in which case the 3nm was the way to go.

As far as was 3nm OK with F3.8 he said yes it was.

I remember Berts Honders 3nm Ha images that had a lot of grainy grit background black clipped look and I was not sure if that was his processing error or from the filters. It looked badly black clipped. Still not sure but the 5nm Ha from Astrodon I have been using (just replaced it with a new one because of a chip) is sensational at a dark site with smooth backgrounds fairly quickly and terrific detail.

3nm may be good for things like planetary.

Greg.

Last edited by gregbradley; 01-05-2015 at 04:21 PM.
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Old 29-04-2015, 04:02 PM
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Quote:
Originally Posted by gregbradley View Post
3nm may be good for things like planetary.
Or when photographing from a site with very heavy light pollution, as the article indicated

Last edited by Slawomir; 29-04-2015 at 05:11 PM.
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Old 29-04-2015, 07:01 PM
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Quote:
Originally Posted by pluto View Post
I couldn't believe the difference when I first saw the difference - it must be an even bigger improvement for you coming from 12nm to 3nm
So true, with 3nm filters I can enjoy once again photographing nebulae - 12nm filters were just not good enough. But again, I also live very close to the city, maybe less than 2km from the central point of Brisbane's CBD.
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