Ha tests

cometcatcher (Kevin) · #1 09-07-2014, 03:03 AM

How am I supposed to do deep sky with a big bright moon out there? Well I could do Ha I suppose. Just some tests to see what would happen. The Ha filter is a medium bandwidth 30nm, camera was a full spectrum modified Nikon D70s, SW120mm refractor at F4 with Orion 0.8x reducer, HEQ5 Pro unguided with just one 5 minute sub at ISO 400 for each of M16, M17 and M8 / M20. Focus is a bit off.

jsmoraes (Jorge) · #2 09-07-2014, 03:59 AM

Good images. Better than mine. I need try these objects to decide if I will mantain the filter wheel or not. In other words: finish with my tests.

With the full Moon perhaps Halfa plus few lights can do some good results. Why don't try an experience with a bi-color: Halfa as red, blue as blue and the green as luminance

cometcatcher (Kevin) · #3 09-07-2014, 09:32 AM

I would need a deeper blue or violet filter. I've been intending to get one but haven't got around to it yet.

jsmoraes (Jorge) · #4 09-07-2014, 12:53 PM

Try something more easy: use the green channel of a RGB as luminance. the blue channel of a RGB as blue and use Halfa as red channel. And process as bi-color, similar to Hubble palette

See the tutorial from Ken Crawford
Clipping Masks and Color Mapping for Narrowband Processing
in http://www.imagingdeepsky.com/Presentations.html

Why not ?

I tried, without great success, with M 8. I used a RGB photo and I played with it:
http://astronomia-e-astrofotos.10697..._rabble_k5.jpg

The original post with all them: http://astronomia-e-astrofotos.10697...013-td993.html

cometcatcher (Kevin) · #5 09-07-2014, 01:08 PM

Thanks. There's a lot to learn about it. One drawback I've seen from my cameras when working with channels is that the individual channels are quite noisy. And usually one channel is noisier than another. I'll see if I can post some examples later.

jsmoraes (Jorge) · #6 09-07-2014, 09:48 PM

That's normal for DSLR cameras.

My Canons, 350D and 1100D have more noise in red channel, followed for blue channel and less noise in green channel. Because this I apply noise filter with different values for each channel. Noise filter in full RGB is only in the final of the process to smooth the background.

note: some noise aren't noise. They are faint capture of that color. Althought they act alike. My Halfa has many of them: nomal, my Canons aren't modified.

cometcatcher (Kevin) · #7 09-07-2014, 10:18 PM

Ah okay. Yeah my Pentax isn't modified. The Nikon is and they respond very differently when trying to get the colour right, whatever that is lol.