Imaging in Ha - Faint Galaxies

Ric · #1 01-10-2007, 10:25 PM

Hi all, I have been trying to image some faint induvidual galaxies and galaxy clusters in Ha but have been having mixed success.

They dont seem to come up as well as in Lum if at all, could this be as a result of the wavelength I am imaging on and the type of light being emitted.

Would I need to extend my exposure times for Ha as well, generally around 20 second images x 100 subs in alt/az is usually sufficient.

All thoughts greatly appreciated

Cheers

ballaratdragons (Ken) · #2 02-10-2007, 12:17 AM

Ric,

I am not familiar with exposures using Ha, but 20 seconds isn't going to capture many faint fuzzy clusters (sounds like a disease).

Maybe some of the brighter ones like the Leo Trio, or Virgo Cluster, but faint clusters will need a lot more than 20 second lights.

jase (Jason) · #3 02-10-2007, 08:58 AM

Ric,
Galaxies emit over a broad wavelength range and do not generally contain much information within the 656.3nm that is Ha. Therefore it is best to take exposures using a luminance filter (or unfiltered) to boost your S/N ratio for galactic targets. This is certainly important if you are imaging very faint galaxies.

Having stated this, there is an emergence in the astro imaging community (predominately in the US) around Ha imaging of galaxies. It is possible to achieve and does emphasise the HII regions, but best performed on much brighter subjects such as those in our Local Group.

Ric · #4 02-10-2007, 10:56 PM

Hi Ken and Jase, thankyou for your thoughts and input it was greatly appreciated.

Ken, I have found that in Lum with a series of 20 second exposures, around 100 t0 150 images I can quite happily image galaxies down to almost mag 17. But in Ha I will have to stick with mag 8 to 9 galaxies as Jase suggests.

Cheers