Atik 460 ex with baader narrowband filters - exposure?

[michaelmorris]

I'm just starting on the long road of learning narrowband imaging with my new Atik460 ex mono camera. I have the standard set of Baader narrowband filters.

With the Atik460 being a relatively commonly used CCD camera and the Baader narrowband filter set being very popular, I presume there quite a few people out there with this combination.

What relative exposures do people tend to use when using the Baader Ha, OIII and SII filters?

Thanks

[sloz1664]

Hi Michael

I usually image around the 15 - 20min exposures. I'm imaging at f4.9 with 6nm filters. Again it also depends on what target you are imaging so as not to overexpose any cores or bright stars.

Steve 

[michaelmorris]

28 minutes ago, sloz1664 said:

Hi Michael

I usually image around the 15 - 20min exposures. I'm imaging at f4.9 with 6nm filters. Again it also depends on what target you are imaging so as not to overexpose any cores or bright stars.

Steve 

Do you use the same exposure for all three filters?

[sloz1664]

Usually, again it depends on what subject I'm imaging. narrowband is not as strict as RGB which are usually weighted to give a balanced image. Narrowband is more subjective. I usually start by doing a few test shots to see what signal I'm getting and evaluate from there. I also look at fellow Astronomers images and gather as much info as I can as a benchmark.

Steve

[ollypenrice]

In NB the cores of stars are going to be white anyway. Why worry about over exposing them? The stars may end up a bit big but you can deal with that in processing in several ways. The key thing is to get the faint stuff! 20 minutes sounds OK to me. Don't throw out aircraft or satellite trailed images. Use a cosmetic repair on the individual subs and/or a sigma clip stacking routine, though in 20 min subs reaching the 10 or so per filter to make it work optimally may take a while.

Olly

[MattJenko]

Go as long as it takes to get decent signal. I use a 414ex and the Baader NB filters and range from 15 mins to 25 mins. As mentioned above, there is no colour balance to worry about, you just want signal and you can always do quick RGB versions if you wanted to get normal coloured small stars back into the image if you feel they are bloated as Olly points out.

[kirkster501]

I do 10 mins for NB and 5 for LRGB.  I know I need to do longer but 20 mins sub is a lot to lose under the flightpath I am on.  I am (or will) be experimenting with longer subs if the cloud ever clears.

[ollypenrice]

5 minutes ago, kirkster501 said:

I do 10 mins for NB and 5 for LRGB.  I know I need to do longer but 20 mins sub is a lot to lose under the flightpath I am on.  I am (or will) be experimenting with longer subs if the cloud ever clears.

I'd sort out the cosmetic fix on the individual NB subs and go for longer.

Olly

[graemlourens]

I've got the same setup as you, with an ED80 reduced, at F6.3 at a relatively dark location, and i've found 20 minutes to be a great exposure time for my setup (for all filters). Some people do expose OIII longer to compensate for the (mostly) weaker signal, but it really depends on the target, your sky and your mount.

In Post processing you'll have to compensate for the strong HA in any case, even if you expose OIII & SII longer. Also maybe have a look at 'Tone mapping' approach of J-P Metsavainio that will allow you to handle the weak OIII & SII signals of most larger nebulae.

A warning to save you lots of pain: Not every target has enough OIII & SII (or even HA!) so do your research before you setup for a whole night of imaging OIII, just to find out the next morning that you have pretty much nothing (happened to me!). A helpful website to determine if there is even any signal that makes sense to capture is Bill Snyders website (http://billsnyderastrophotography.com/?page_id=2973) where he shows you the individual masters of many beautiful targets out there.

Another tip: Do not even try to capture OIII in Moonlit nights or generally in dusk or dawn, you will just be wasting your time, and OIII is already hard enough to catch on certain targets in a perfectly dark night, let alone during summer nights or with moonlight (even if its just 30% illuminated). HA on the other hand is pretty resilient as long as you're not aiming too close to the moon.

Hope to have saved you a few headaches i had in the past 2 years!

Kind regards, Graem