Quickie M42

[LightningNZ]

8x 3 minute subs of M42. AT65EDQ scope with Nikon D5100, IDAS LPF.

Stacked with bias and flats in DSS and processed in Photoshop. This was quick and lazy. :lol:

[cometcatcher]

Nice quickie! How do you find the IDAS LP filter with blue reflection nebula?

[PeterEde]

Nice

[LightningNZ]

That's why I got this filter - reflection nebs are no problem at all. OTOH I still get mild to annoying gradients in my images from light pollution, and I have yet to do actual side-by-side comparison without the filter, so I can't be such how much of anything it's removing. :shrug:

[raymo]

Nice and sharp and colourful, great job for a quickie.
raymo

[cometcatcher]

Be cool to see a comparison Cam. I've been eyeing this filter for some time but it's not a cheap one.

As for gradients, I have them also. Many of mine appear to be on the CMOS sensor itself. It has a green / magenta cast to it right through the middle of the frame. Flats, darks and bias do nothing to remove them. I have to software flat field every image I take.

[LightningNZ]

I've imaged everything now that I have easy access to at this time of the year so if I get another decent night I'll take one without the IDAS. I got mine 2nd hand so only paid about $100 for it.

The gradient is NOT on your sensor - if it was then the flats would fix it. Flats, darks and bias won't affect anything that's in the sky, just in the optical train.

I get the green/magenta thing too, and where it occurs on my images and how far across them depends on where I'm imaging in the sky and how much movement/rotation there is relative to the light pollution. Dealing with gradients is sadly a core skill for the astrophotograhper these days. My new technique is to duplicate my image twice. Blur one very strongly (150+ pixels), darken it and subtract it from one of the the others. Now use your original as a colour layer on your corrected image - adjusting opacity to suit. The bright colours will stay, the dark background will be too dark for you see the colour difference. You've effectively neutralised the luminance and recoloured, but it's a bit more gradual.

[cometcatcher]

I use the "apply image" method in photoshop. It works great unless the nebula is big.

This is an example of the gradient I get. Perhaps I described it incorrectly saying it's "on the sensor". I believe it is some kind of amp glow. Doesn't matter where I point it in the sky, it's in the same relative position with the same colours. My Nikon D70s has it bad but my Pentax K-x only has it at the extreme edges. If it wasn't for extreme stretching it wouldn't be noticeable.

[LightningNZ]

How low in the sky was that image Kevin? Do you get the same if you image the zenith?

If it were amp glow then darks would remove it. I never bother with darks cause 1) I don't seem to need them since I moved to the D5100, though for the 300D they were inescapable, 2) they take too much time.

[Camelopardalis]

Nice one Cam! Love the way the colours are coming through :thumbsup:

[cometcatcher]

That particular image was very low, but even with high elevation it's still there. Not sure what is going on. My camera has the same sensor as the D5100.

[multiweb]

Very nice. Sharp and tidy picture. :thumbsup:

[LightningNZ]

Cheers Marc - I'm surprised to see some of the real experts posting kind messages in this forums of late. :lol:

The thing that really cracks me up is that I think this is a really rubbish picture - technically it's got nothing on the Lagoon pic that I also posted recently, but that one's only had 2 replies... I'll reshoot this target properly sometime next month.

Cheers for all the nice comments everyone. :)

[cometcatcher]

Not in the context of a "quickie". It's fine for what it is as a quick gratification pic.

Do you do requests? I would like to see more nebula pics with the IDAS filter to get an idea of what it's like. Stuff with blue reflection nebula would be a bonus too.