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Rosette Nebula HA Moonlight test


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Shot of the rosette taken last night in strong Moonlight. I'm now getting used to what the hydrogen alpha filter can do and how far I can push the processing.

This is 54 minutes worth of data through the 200mm L lens on modded 550D mounted on the astrotrac, individual exposures were 140 sec,

still getting a little banding but on the whole I'm quite pleased with it.

Mel

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Very good image Mel! Can I ask what filter you use? Clip in? And did you use the lens wide open? Thanks

Spencer

Thank you Spencer, yes I did use an Astronomik 12nm HA Eos clip filter behind the 200mm lens, regarding the aperture used I've just started using stepping rings instead of the diaphram.

If you look at the cropped shot of the Pleiades below this was taken with the same lens stopped down to F4, 8 point diffraction spikes that would look great on a Christmas card but not to my taste.

The Rosette was shot with a 72mm - 52mm step down ring (£2.59 ebay) giving an effective aperture of F3.8 and no diffraction spikes, I think this will be my standard set-up from now on.

Mel

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Everybody has already said this is a great image, but if I may add a comment, I think it could be slightly improved.

In my opinion the background is too black and the star edges are too hard (surely an artifact of star masking)?

Whether you choose to correct or not these things (which are only my personal opinion and a matter of taste), this is still an excellent image :)

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Very nice Mel...

You can easily get 4-5 mins with an astro track but need to balance the camera like any mount, unfortunately the astrotrac usually gets set up with a ball head and camera plonked on top... it suffers the same as any mount in this case.. My best results were when I mounted the camera and ball head on one end of a flat bar and made a counterweight for the other.. find the balance mid point and mount that to the astrotrac.. It ticks away without even noticing a camera and lens/telescopes on it..:)

Ignore my rabblings if you have the astrotrac full arrangements :(

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Brilliant result from highly portable kit. It really is as sharp as you like. Like Siovene I think you could probably get even more out of the faint background sky. It may be just a tad clipped?

You can stop down that lens easily without creating diffraction spikes. Just make a simple front aperture mask. I shot the Pleiades to try it and it worked perfectly. Different sized holes produce different F ratios, of course.

Olly

APERTURE-MASK-XL.jpg

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Brilliant result from highly portable kit. It really is as sharp as you like. Like Siovene I think you could probably get even more out of the faint background sky. It may be just a tad clipped?

You can stop down that lens easily without creating diffraction spikes. Just make a simple front aperture mask. I shot the Pleiades to try it and it worked perfectly. Different sized holes produce different F ratios, of course.

Olly

Olly

Does that change the f ratio exatly as you would expect? i.e masking down to 50mm gives you an f4 ratio? And what would be the effect if it not accurately centred?

old_eyes

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Shot of the rosette taken last night in strong Moonlight. I'm now getting used to what the hydrogen alpha filter can do and how far I can push the processing...

Mel - that's a really impressive image of a great subject.

I really must do some more narrowband imaging. It seems like the only clear skies I get are when there is a strong moon.

old_eyes

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