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M16 quickie

Tim

By Tim
in Imaging - Deep Sky

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Tim

Tim

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I am posting this just to keep my hand in, it's been a while since I have posted anything, I have been playing around with different combinations and stuff, and am waiting on a new 10" tube any day now.

I was thinking of selling my underused C9.25, so decided to give it one last run, with QHY8 camera and new Astronomik 6nm Ha filter, focally reduced to run at around f4.7. After seeing the results of the pics I am now in two minds about letting it go :)

This is just a quick grab of 7 x 20 mins on M16, and a 5 min process in PS. Doing some more of it as I type, but binned this time.

Cheers

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Tim

Tim

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Actually, a little info would be good, I am using a Ha filter on a OSC camera, what is the best method for DSS stacking etc considering that the image needs to become grayscale? Do I need to alter from the usual AHD interpolation?

Thanks

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ollypenrice

ollypenrice

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Exceptionally good, Tim. The Eagle is an excellent test because of the pair of doubles NE of the claw (a big and a small star in each pair.) You have them cleanly split even though, I assume, using the OSC in NB costs you a little resolution. Can't help on using NB over a matrix though, I have never tried it. I look forward to hearing more on this. SteveL, perhaps would be the man to tell all.

Given how low this is for you, your guiding is tickety-boo! A few of us have been chuntering our discontent over guiding low in the south recently but you have perfect stars.

And now the million dollar question; how did you f reduce to below f5?

Olly

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Tim

Tim

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With a loooong extension tube Olly, took it to within 2 turns of the max adjustment on the focusser.

I did this at F10 the other week, and was suprised to see that the pair of doubles you mention were not only cleanly split, but one of them has a very close smaller neighbour, and that was readily defined too. In fact I had to check a proper pic of it just to make sure it wasn't an artifact.

Did manage 1 x 3600 sec sub last night on this, and thankfully woke up just as the OTA dipped into viewing the obsy, so was able to cover the lens for the final few minutes to save the frame. Will have a look at that later.

Cheers

Tim

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SteveL

SteveL

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Actually, a little info would be good, I am using a Ha filter on a OSC camera, what is the best method for DSS stacking etc considering that the image needs to become grayscale? Do I need to alter from the usual AHD interpolation?

Thanks

Having done this quite a lot :) I think I can answer this.

You will have to stack in superpixel mode, so each pixel is really made up from the r/g/g/b data, rather than ever pixel being made up of its own pixel colour (red for example) and the other two colours for that pixel being interpolated from its neighbours (if you see what I mean). Super pixel mode will create and image half width half height, but thats really all you have grabbed anyway if you only want the red pixels. Load the very red final image into photoshop and extract the red channel, and you are no using data that was created ONLY by the Ha data.

If your data can stand it, you could 2x drizzle when stacking to get a full size image again.

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ollypenrice

ollypenrice

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Having done this quite a lot :) I think I can answer this.

You will have to stack in superpixel mode, so each pixel is really made up from the r/g/g/b data, rather than ever pixel being made up of its own pixel colour (red for example) and the other two colours for that pixel being interpolated from its neighbours (if you see what I mean). Super pixel mode will create and image half width half height, but thats really all you have grabbed anyway if you only want the red pixels. Load the very red final image into photoshop and extract the red channel, and you are no using data that was created ONLY by the Ha data.

If your data can stand it, you could 2x drizzle when stacking to get a full size image again.

Top post. Thanks Steve.

Olly

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SteveL

SteveL

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It took me a while to work that out in my head. A 3000x2000 One Shot Colour camera that produces a 3000x2000 colour image is making up 3/4 of the data :) It should, to be strictly accurate, only produce a 1500x1000 image if you want colour data that is created only from original data, and not made up to fill in the gaps.

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Tim

Tim

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Hang onto that OTA! What reducer were you using Tim, did you get much vignetting and what about field flatness, looks good as far as I can tell.

Celestron 0.63 Martin. 2" fittings all the way through to OAG which comes down to m42. I forget the spacing atm, but a lot longer than usual, can look tonight. The stars at the edges are stretched a little, but not as bad as I expected, especially using the qhy8.

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