3nm vs 5nm Ha Filter...? Let’s compare images...

[PhotoGav]

Apologies, I am not the first person to ask this question as there is much discussion on here about which filter is ‘better’ a 3nm or a 5nm Ha narrowband filter? I would like to know what people’s current opinions are and ideally see some images posted that compare Ha subs of the same target through 3nm & 5nm Ha filters. Ideally the comparison would be with Astrodon filters as that is what I am aiming for, but I am aware Chroma now provide an alternative realistic option.

So, a plea to you good folk using Astrodon narrowband Ha filters, please post your opinions and images and help me make the right choice. 

Thanks in advance...!

[Davey-T]

Hi Gav, I have both 3nm and 5nm HA Astrodon filters mounted in the same filter wheel ready to do a comparison just need some decent skies to compare them.

Dave

[Rob63]

1 hour ago, Davey-T said:

Hi Gav, I have both 3nm and 5nm HA Astrodon filters mounted in the same filter wheel ready to do a comparison just need some decent skies to compare them.

Dave

Would a difference (5nm - 3nm) between those two give you a pseudo NII filter? could be an interesting one to try.

[PhotoGav]

4 hours ago, Davey-T said:

Hi Gav, I have both 3nm and 5nm HA Astrodon filters mounted in the same filter wheel ready to do a comparison just need some decent skies to compare them.

Dave

You are a potential total superstar. The forecast is good for this weekend, so it would be superb if you could fire off a sub of each on a range of targets? I might even have to give you a can of cider at SGL SP2019 if you did that!

[Jonk]

Gav, I had the same question for the man himself - here was his reply:

Hi, Jon,

 

In most cases, the 5 nm is a better choice,, unless you have alot of light pollution.  Then, go 3 nm.  Also, higher-res objects like planetary nebula, Wolf-Rayet bubbles, etc. could potentially be targets for separating the NII from the H-a, but then, these generally require longer focal length scopes.  Lastly, astrophotographers generally want all the photons they can get and they don't care whether there's NII in with the H-a in their H-a filter.  Some emission nebula have some NII and by going to 3 nm, you may see a decrease in signal.  So, for these reasons, the 5 nm is a more general filter if you only want one.  Of course, I have access to a lot of filters, so I have a 3 and a 5 nm H-a filter in my 10-position filter wheel. 

 

Best Regards,

 

Don

 

Don Goldman, Ph.D.

-----------------------

 

Hi Don,
 

Thanks very much for the quick response.

 

I'm in the suburbs of a city so my LP isn't the worst, but still not very dark. This is why I can't decide on the Ha filter to go for - probably leaning towards the 3nm?
 

Here's a screenshot of my first NB effort in progress, using the HST pallet, unfinished, but I've gathered some 1800s subs using the Baader 7nm / 8.5nm set.

----------------------

Hi, Jon,

 

As long as you can accept some loss of signal for some objects, but incredible detail for faint nebulosity, then you can't go wrong with the 3 nm.

 

Best Regards,

 

Don

 

Don Goldman, Ph.D.

[steppenwolf]

16 minutes ago, Jonk said:

As long as you can accept some loss of signal for some objects, but incredible detail for faint nebulosity, then you can't go wrong with the 3 nm.

That's why I bought the 3nm BUT that's not what you are looking for and I'm sorry, I can't give you a comparison between the 3nm and 5nm. The arguments for getting either one are all valid - it just comes down to personal choice neither is 'better' than the other and at the end of the day, much is dependent on the specific object you are imaging as to whether the NII is a significant consideration or not!

[PhotoGav]

@Jonk - that’s interesting, though in reply one he says that 5nm filters are definitely the way to go and then in reply two he says that 3nm are exactly what you want... I’m confused!

@steppenwolf - that’s the real issue, there is no ‘right’ answer, either would do the job excellently. I suppose I’m trying to work out whether it is ok to save a bit of money by going for 5nm, or is actually a good idea to go for 5nm or results will generally be better from a 3nm (except for the occasional NII rich target - are there many of them anyway? examples please!) or perhaps I wouldn’t even notice the difference between the two, in which case why not save the money??!!

[Jonk]

I thought the same but after reading it more than once, the answer is like any when choosing imaging equipment - choose what suits your conditions, target, focal length etc.

If money were no object, you might choose a 3nm ha and an NII and combine these different wavelengths and assigning the combined images to whatever colour channel you like, again depending on the target.

For me, as I certainly have LP to contend with, I will choose the 3nm as and when I feel confident enough to buy one! 

[Adam J]

I got the 5nm, I live in a orange zone and I would say the 3nm is not required. I think it would need to be a red zone or very close to the moon to see a big difference. Stars will be a little smaller with the 3nm though. 

[Laurin Dave]

Hi Gav

Some planetary nebula e.g. M27 are nitrogen rich, I think that the Astrodon site has examples of it through 5 and 3nm Ha filters, or at least it did when I looked in August. If it's any help Ian King advised me to get 5nm Ha and 3nm Oiii...  I got 5nm in both because he had them in stock.  3nm more moon proof I believe.. although I'm more than happy with my 5nm.

Dave

[PhotoGav]

Thank you for the continuing interesting comments.

@Jonk - that's just a crazy idea! All that money, all that time, all that processing.... would be interesting though!

@Adam J - thanks, the 5nm is sounding good.

@Laurin Dave - that's really useful, I had a read through the FAQs on the Astrodon website and it is very informative. Great to hear that you are a happy imager with both 5nms. Can you point me to some examples of your pics please?

I think that I am edging towards a 5nm Ha and 3nm OIII... now, for the cash?

[Laurin Dave]

5 minutes ago, PhotoGav said:

@Laurin Dave - that's really useful, I had a read through the FAQs on the Astrodon website and it is very informative. Great to hear that you are a happy imager with both 5nms. Can you point me to some examples of your pics please?

Hi Gav

I posted a 'quick' Bubble nebula earlier tonight, an M33 with Ha on 1 November and I have an album on this site that has a couple of versions of M27 and a Crescent Nebula, all with input from the Astrodons.

Dave

[Jonk]

46 minutes ago, PhotoGav said:

All that money, all that time, all that processing....

Pahaha that applies regardless doesn't it?!

[PhotoGav]

1 hour ago, Laurin Dave said:

Hi Gav

I posted a 'quick' Bubble nebula earlier tonight, an M33 with Ha on 1 November and I have an album on this site that has a couple of versions of M27 and a Crescent Nebula, all with input from the Astrodons.

Dave

Dave, perfect, thank you. You are selling the 5nms very well with those images. I have enjoyed looking through your recent posts, both NB and not. The Esprit 150 is a corker too. I’m really happy with my Esprit 100 and that 150 is very tempting!

[Laurin Dave]

16 hours ago, PhotoGav said:

Dave, perfect, thank you. You are selling the 5nms very well with those images. I have enjoyed looking through your recent posts, both NB and not. The Esprit 150 is a corker too. I’m really happy with my Esprit 100 and that 150 is very tempting!

Thanks Gav,  snap!  I'm thinking about getting an Esprit 100

Dave