Hi all
After surviving yesterdays massive hail storm, I got up in the wee hours just after moonset to get M42 with Berts 300mm f2.8 flourite lens.
I took 4x10 mins ISO 200, IDAS uv/ir and Baader UHCS filters, modded 350D, masked with a 2x 1 min ISO 200 image for the bright parts, dynamic and colour stretching in IRIS used, masked in Photoshop, noiseware used to finish off. I was after the faint Ha regions around M42 itself.
Larger version here http://www.iceinspace.com.au/uploads...ilteredmed.jpg
Scott
Thanks everyone
It might be the filters causing the abberations in the bright stars as normally the UHCS is in scopes F4 or slower, not F2.8 so I might try stopping down to F4 next time.
Scott
Heres a version processed without colour stretching just dynamic stretching in Iris , and masking in photoshop
Larger version here http://www.iceinspace.com.au/uploads...ilteredmed.jpg
This shows the background faint cloud better.
Scott
PS, Octanes method of doing flats works well too, I emulated that here, after finishing imaging I took the lens with camera still on to my PC with paintshop pro showing just white on the monitor , pointed lens at that for a flat field
This shows the background faint cloud better.
Scott
PS, Octanes method of doing flats works well too, I emulated that here, after finishing imaging I took the lens with camera still on to my PC with paintshop pro showing just white on the monitor , pointed lens at that for a flat field
Great work Scott.
Just wondering if it would be better to use a grey screen on the PC instead of pure white for flats, or won't that make any difference?
I am intrigued by the star aberation in the star images, they do not seem to appear in some of your previous images with the same lens. For example the NGC253 image. Do you know what is different as I have same star problem with the Sigma lens I just purchased. I am wondering if it is tied up with the filter inside the camera (mines a Baader UV/IR) and am considering removing it totally.
I love the extended nebulosity you've picked up here.
And yes, the method I use for flat frames appears to work quite well. You just have to make sure you've got no aberrations on your LCD screen first and that it is evenly-illuminated. I've seen non-even illumination on some cheap notebooks.
Thanks all.
Andrew, I set the exposure to "auto" when taking the flats, that way correct exposure will happen, and I guess the brighter the screen the faster the shutter speed for the flats, as long as screen is evenly illuminated it should be okay. The actual flats look greenish, thats because of the UHCS filter.
Terry, I have two 2 inch filters, an IDAS uv/ir filter, and a Baader UHCS filter
screwed together. They sit inside the canon mount that in turn screws onto the back of the lens. There is a slight amount of play, I can hear the filters rattle slightly when I pick up the lens, Im thinking that this may cause them to not be completely flat, causing the abberations around the bright stars. If I use no filters at all I get star bloat in bright stars but nice even round ones, as my 350D has no internal filter at all, just clear AR coated glass, because I wanted to experiment with IR photography.
The above is what I think is happening anyway.
Scott
I noticed the aberations are symetrical about the centre so I don't think it is because of tilt or looseness of the filters. The really are remarkeably like the aberations I get and I have a cut Baader filter in my camera (in addition to the sensor coverglass) so there are 2 optical windows between the imagiing surface and the lens.
I am half tempted to go back into the camera and completely remove the filter but am not sure if I would be able to reach infinity focus with the lenses I have (although most do focus a little past infinity).
The more modern lenses seem to be optimised to take into account the extra optical surfaces in a DSLR sensor.
Im tempted to try an image with my unmodded 350D and see what happens, or even put the uv/ir filter ahead of the uhcs rather then behind it, though I cant imaging changing the filter order would affect anything?
Scott