NGC 4236 LRGB

[STEVE333]

This is my first narrowband LRGB image. It is definitely a lot more work than my old DSLR images.

All the new equipment and new processing techniques is a bit overwhelming. I even dreamed about it last night!

This is a pretty dim target, at least it is for me (magnitude 10.5). Barely detectable in the Raw images. I used much shorter exposures this time in an effort to prevent saturating so many stars. Still learning what exposure lengths make sense for my filters and LP conditions. Most APers seem to take longer Lum exposures than they do R/G/B exposures. My Lum filter captures so much more signal that I ended up using a shorter exposure for the Lum than for the RGB filters (afraid of saturating all the stars). That may be all wrong, but, just sharing what I did. So much to learn.

Good news is that all the equipment worked very well, and, my "anchor" on the USB extension cable prevented any disconnect problems. The only problem I'm still having is getting the APT Auto-Focus Aid to work reliably. I'm really looking forward to the next version of this tool. It caused my Blue data to be a bit out of focus. Not a disaster, but, not as good as it should have been. Other than that I'm very happy with APT.

Such a dim target needs more time, but, only one clear night was available and I did the best I could. I didn't get to bet till 1:30 AM which is late for me. I'm still recovering from that one!!

IMAGE DETAILS:
WO Star 71 (ii) telescope, ZWO LRGB filters, Moonlight Stepper-Motor, ZWO Filter Wheel, ASI1600MM Pro camera, MMAG autoguider, CEM40 EC mount
L 60 x 60 sec, R/G/B 15 x 120 sec each (Total Exposure - 2 hr 30 min)
iPolar, APT, PHD2, Pixinsight
North is left in the image.

FULL FOV



CROPPED VERSION


Thanks for looking.

Steve

[Larry 1969]

Nice capture Steve! Only 2.5 hours on target? That's great!

[Baskevo]

This looks great Steve! I would be very interested in your process after stacking--are you still doing a lot of the same processes that you used on the DSLR? Or are you finding yourself using any new ones?

[STEVE333]

This looks great Steve! I would be very interested in your process after stacking--are you still doing a lot of the same processes that you used on the DSLR? Or are you finding yourself using any new ones?

Since I'm new to this NB processing I would take everything I say with a grain of salt. Here's what I did:

1) Stacked L, R, G, and B images separately.
2) Registered the stacked R, G, and B images.
3) Temporarily combined the images into a single RGB image.
4) Determined maximum image size that would not include any vignetting of the R, G, or B image and cropped.
5) Separated the cropped image back into the R, G and B channels.
6) Defined DBE sample points for R image. Applied same DBE to all three (RGB) images.
7) Performed MLT noise reduction on R, G and B images.
8) Used LinearFit to match the three images.
9) Combined the three images using PixelMath into a single RGB image.

After step (9) I followed my normal DSLR processing to optimize the RGB image including Non-Linear processing.

10) Stacked and optimized the L image including Non-Linear processing.
11) Registered the L image and the RGB image using StarAlignment.
12) Separated RGB image back into R, G and B images.
13) Used LRGBCombination process to combine L with R, G and B.

This may be all wrong, but, that's what I did to produce this image.

Cheers,
Steve

[Baskevo]

That is pretty close to what I do I did not try cropping a combined image though that's clever... Everything else is essentially the same
So you combine the images before stretching? With narrowband, I stretch the frames before color combination usually, but I have heard you are supposed to do it the other way with LRGB frames. I'm sure there are reasons, not that I know lol

[Graeme1858]

This is my first narrowband LRGB image. It is definitely a lot more work than my old DSLR images.

All the new equipment and new processing techniques is a bit overwhelming. I even dreamed about it last night!

You're dreaming about astrophography! Brilliant!

Narrow band imaging does seem like a lot of work (to a DSLR geezer!) but it was definitely worth it. It must be nice when it all comes together. Nice NGC 4236 Steve.

Regards

Graeme

[Juno16]

Steve,

Very nice image of a very tough target!

I have not noticed this galaxy before or seen it imaged. Good work taking on a tough project!

I really cannot imagine your learning curve!

I know that as a beginner (only a year and a half into AP) when I learn new things, I am really amazed at my new find. I had been doing things a lot harder, (or not at all), then I learn a much easier and much better way! It is really neat and feels good to find ways to do things and do them better.

You are an experienced AP'er and know what you need to do, just figuring it all out with different equipment and techniques must be very challenging!

Jumping from a master dslr imager to dedicated mono astro is a huge challenge and you eagerly took it on. You are doing wonderfully! Keep moving up the steep curve and sharing your excellent work with us!

[Mac]

Great work Steve...

Keep the mind engaged in learning new things.

[MariusD69]

Awesome! Well done, Steve!

[TheButcher]

Very Nice Steve!