HA Filter for imaging.

leon · #1 09-10-2008, 08:26 PM

Hi Guys, if I was considering purchasing a HA Narrow band filter for imaging, what would be the better, moderately priced one that I should be looking at, or should I just stick with my 72mm Hutech LRP, which is presently attached to the rear of the Tak.

Suggestions would be much appreciated.

Thanks, Leon

Bassnut (Fred) · #2 09-10-2008, 09:05 PM

OH yeah, Ha is the go, even for traditional LRGB. Many gurus have lately substituted Red or Ha, and trashing Lum. It offers far more detail and pollution filtering over Lum. Counter intuatively, useing Ha doesnt reduce other filter contribution to an image, due to the huge prevalence of Ha in most objects over all. Galaxys often are an exeption tho, it works best on emmission nebula. Exposure times are longer tho, much longer over Lum. Stars are tighter, background is lower and detail jumps out. For a DSLR, id say a 15nm Ha filter would be the go, but up to 3nm is available (albiet with obscene exposure times, I use it on a Hi QE cooled CCD, its awesome).

Pratically, its an essential tool for nebula, I wouldnt do without it, get one if you can. For Galaxies, not so much.

leon · #3 09-10-2008, 09:37 PM

Many thanks Fred I will look into it a bit more, are you saying that I could/should use one of these filters in combination with the already attached Hutech Filter, or have I read this wrong.

Leon

AlexN · #4 09-10-2008, 10:04 PM

I've bought a Ha filter simply for imaging with the moon and my horrible light pollution problem...So if I can collect 2hrs worth of Ha data on 4 objects a month, then when I go to a dark site for new moon weekend, I'll collect 2hrs of color data, then use the Ha data as a Lum channel... (mind you, thats all in theory for me at the moment as I've still got to get normal imaging under control

)

I would say that from what I've seen, a 13nm Ha filter is an essential item for deep sky imagers.

leon · #5 09-10-2008, 10:15 PM

Thanks Alex, I was actually looking at the 13nm one, however having said that, there not cheap, are they.

Leon

Bassnut (Fred) · #6 09-10-2008, 10:33 PM

Leon, the Hutec filter passes Ha, infact passing Ha is the main reason for changing the stock filter.

AlexN · #7 09-10-2008, 10:40 PM

Nope... I got the Baader one, cost me I think $445 at Bintel... The problem is now I want SII and OIII as well...

Tandum (Robin) · #8 10-10-2008, 01:52 AM

Leon, Ha Hb So OIII are bandwidths of light which are beyond visible light and below infrared light. A modified camera can detect this light and records it in the red pixels on it's sensor. Using filters to capture these various light frequencies allows you to map these channels to different colours in post processing, resulting in some of the amazing images we see today.

You'd really want a mono camera to do it justice as your modified canon can only see them in it's red channel which is only 25% of the sensor. This means exposure time needs to stepped up by 4x when using a colour camera.

leon · #9 10-10-2008, 12:55 PM

Thanks Robin I see what you mean, I might just leave this for the moment.

Leon

seeker372011 (Narayan) · #10 10-10-2008, 06:15 PM

Quote:

Originally Posted by Tandum

Leon, Ha Hb So OIII are bandwidths of light which are beyond visible light and below infrared light. A modified camera can detect this light and records it in the red pixels on it's sensor. Using filters to capture these various light frequencies allows you to map these channels to different colours in post processing, resulting in some of the amazing images we see today.

You'd really want a mono camera to do it justice as your modified canon can only see them in it's red channel which is only 25% of the sensor. This means exposure time needs to stepped up by 4x when using a colour camera.

True but not impossible

I have had some small degree of success with a DSLR and an ED80

eg

http://www.flickr.com/photos/9178472...71841/sizes/l/

and a single shot colour camera (QHY8 ) and ED80
eg

http://www.flickr.com/photos/9178472...89812/sizes/l/

would you be happy with similar results?
sure a dedicated mono would be better but the single shot comes in handy when you want to shoot a colour image..if you dont have a permanent observatory it may be a challange to colect data through filters over many nights to construct aRGB or LRGB image

I think it was Alen Chen from memory at one of the Advanced AstroImaging confrences maybe a year or so ago? who put together a presentation showing the fine results he has got in narrowband with a single shot colour camera, so I am certainly not alone .

dont rule it out is all I am saying

gbeal · #11 10-10-2008, 07:10 PM

While I won't argue that a OSC camera and Ha is an uphill battle, for goodness sake don't discount it on the advice of one or two.
I have a OSC camera, and use the Baader 7Nm Ha. It is great, really great, and while the moon is about it opens up new possibilities, so I urge you to try one Leon. If it isn't what you expect or want then on-sell it, but I am all but certain you will love it.
PM if you want a few sample shots, but the shot from Narayan is indicative of what you will get.
Gary

leon · #12 11-10-2008, 09:27 AM

Narayan, I quite like the look of those images, nice captures indeed, and Gary, many thanks for you added advice, much appreciated.

Leon

dugnsuz (Doug) · #13 13-10-2008, 01:52 PM

Hi leon,
Is this what you mean?
http://www.sciencecenter.net/hutech/haimage.htm

I'm interested too as we seem to fit all the criteria...we both have spectrum-enhanced(modded) DSLRs and IDAS LPS filters.
From the article seems all you might need is the Kenko R1(R60) filter and they're pretty cheap!

What do you think?
Doug

leon · #14 13-10-2008, 04:45 PM

You Know what Doug, that shouls just about do it I reckon, and they are a hell of a lot cheaper.

Now that I recall, I have seen these filters on the Hutech filter site, but have not taken much notice of their capabilities.

I wonder If one can get one of these in OZ.

Many thanks.

Leon