A little advice about H-Alpha filter. Should I buy one?

[Snoani]

After several years to taking astrophotos with limiting equipment, earlier this year I finally purchased my first guided rig, which I am rapidly adding too.  I think that I have fallen down the rabbit hole. 

My latest acquisitions are a ZWO ASI 1600MM, filter wheel with 5 spaces and LRGB filters.  However, with the weather and the Moon as it is, I would like an option for this camera when LRGB is not really an option.  I have considered narrowband but while I have an aesthetic appreciation for narrowband images, and the necessity if you live in an area where this is the only practical option, I am more of a fan of broadband imaging and the colours that this will produce.  

I live in a Bortle 3-4 area and so have this luxury, particularly to the south which has basically no light pollution, and so I was about to order a H-Alpha filter with the belief that I could use this as luminance for emission nebulas.  However, before I ordered I decided to a little more research and I am now doubting whether this filter is a good option or not.  

Essentially, from the research that I have done I now think that I understand that adding H-Alpha as luminance will give a washed out pink nebula but that it is still possible to blend H-Alpha images into an LRBG image (to each separate colour channel in different proportions but particularly red) to produce a more striking image.  My editing software is an old version of Photoshop (CR2) and Affinity Photo and I use both to edit images for the advantages that each give. 

What I would like to know is whether the community here would recommend an H-Alpha filter or not?  I have an increasing wish list and I wouldn't want to buy a filter if it wouldn't be of significant benefit when there are other things that would.  If it is not an option that would be particularly beneficial, I think I would rather put the money towards a cooled OSC camera for the summer months, which at some point I will buy anyway, but I obviously don't what to waste if I can help it.  

Your advice would very much be welcome.

Jem

 

 

[Space Oddities]

I think an Ha filter is a must have, especially when the Moon is up. I like those broadband looks as well, but the HaRGB images are also very pleasing to show some details or colors you cannot see otherwise.

I often see narrowband filters as a way to re-balance the colors in your picture. The sensor is flooded with photons from other wavelengths, so the Ha's voice cannot be heard... a narrowband filter is a way to give the mic to this wavelength

Also since you have a mono camera, you can create your own looks, by combining Ha with LRGB with your own parameters. You can find online some free HaLRGB data and see what you can get out of it, compare wIth LRGB only, see what works best for you.

This being said, Ha filters are really cheap nowadays, especially on the used market. You have some entry level brands like ZWO, or more expensive ones from Baader, Astronomik or Chroma, with different bandpasses to fit your needs. I think you can't go wrong with any of them, even if it's only as a way to image during foul Moon!

PS: I think DeepSkyWest has free and very clean HaLRGB data to play with, you just need to give up an email:  https://www.deepskywest.com/free-downloads-v2

Best way to make up your mind, IMO, is to try it yourself!  

Edited December 27, 2020 by Space Oddities

[Snoani]

Thank you very much for your advice.  I will definitely take a look at the link have a play with the data available.  

[rickwayne]

Second the "buy it!" advice. Probably the best hardware bang for the buck in all of astrophotography.  I don't understand why using Ha as luminance on an emission target would wash out the other colors -- by definition, luminance should not affect the color balance at all, though of course as image brightness goes up, the available range of saturation necessarily decreases. Getting that right in Photoshop is going to be more of a challenge, I admit.

I suppose if you're aesthetically unmoved by false-color narrowband images, monochrome Ha will seem like the rankest heresy to you 🙂. But IMO you can do some really lovely stuff that way too.

 

[kirkster501]

On emission nebulae I never use a traditional luminance and always use Ha as the "detail" channel.

I am also dubious of the need to do a luminance on other objects such as galaxies if you bin the RGB at 1x1.  Indeed, this is my strategic direction.  I add up all the RGB to make a synthL and then sharpen and work on the detail on that before blending back into the RGB. 

OSC has no lum channel....

[rickwayne]

The advantage to luminance on RGB targets is that you're collecting photons (roughly, for argument's sake) three times as fast as with any one of the color filters. And since human vision relies much more on luminance data than on color to discriminate detail, you can rapidly build up sharply-defined images whose color can be much fuzzier (and thus take less dark-sky time to acquire). Even binned x1, you can shortchange the color data and blur out the noise, and no one will  be the wiser b/c their eyes are oohing and  ah-ing over the detail  that your luminance channel  provides.