I finally got around to processing the 9 half decent frames I ended up with from Lostock. I was plagued with guiding errors all night and threw out many more than I kept. I think my PEC got lost on the worm, making my RA dance about every few minutes. It was impossible to control it manually. Anyway, although a little dissapointing, here is the result:
Meade LXD55 SN10, Canon 300D (Stock) UHC-S Filter, MPCC, 9x3min ISO800, manually guided exposures. And yes Striker, I used darks flats and bias!! Processing in ImagesPlus and Photoshop CS2.
VERY nice there. Its a deep image, the dark skies of Lostock and the UHCS filter make all the difference dont they? Did you reach the sky background ok with the original exposures?. At Newcastle I aim to get the Histogram peak about 1/3 the way across, which with the 10 inch F5.6 requires about 10 mins at ISO 1600 with the UHCS filter.
I tried ISO1600 initially at 3 min. That didn't lift the histogram much off the left. But still, the centre of eta carina looked overexposure on the camera's LCD. That worried me, so I dropped it to 800. So I guess that you can still go deep without skyglow at Lostock. At home, without the filter, 3 min reaches the skyglow easily, but I have not tried it with the filter.
Nice image Tony,
I'm wondering if you did a few shorter exposures with 1600 ISO and stack them in too, would that help?
Also do you recommend the use of UHC-S Filter in most imaging situations with the DSLR for astro?
Nice stuff Tony.....I admire your dedication to manual guiding....I personaly like to go have a chat while imaging...sorry for stirring you up at Lostock....hehehe
Glad to see you using Flats and darks in your processing...lol
Frustrating when those little things crop up Tony. Nice shot under trying conditions.
Yes Paul you are right. Imaging wise, Lostock was very frustrating for me with the dew and my mount problems. Not to mention my remote dying as well. Thanks for the rescue on that one. Without your help I would have achieved nothing.
Nice image Tony,
I'm wondering if you did a few shorter exposures with 1600 ISO and stack them in too, would that help?
Also do you recommend the use of UHC-S Filter in most imaging situations with the DSLR for astro?
Thanks Andrew.
Using shorter exposures can have its advantages. In my experience, guiding errors are reduced and so is the general star size, making for "crisper" images. The down side is that you need many more of them to make a good image and you also have to sacrifice some "depth".
I don't have a lot of experience with the UHC-S filter, but so far it seems to work well on emmision nebula and not so well on refelection nebula. I haven't tried it on a galaxy yet, but I am interested to find out.
Nice stuff Tony.....I admire your dedication to manual guiding....I personaly like to go have a chat while imaging...sorry for stirring you up at Lostock....hehehe
Glad to see you using Flats and darks in your processing...lol
Thanks Tony. You took the stirring as well as you dished it out, so all is well.
Wow Tony! Did the unprocessed image have that palette of colours? It is a very dramatic image. Well done.
Thanks Rod,
Here is an unprocessed jpeg of one of the subframes. I don't process my images that way, but it will give you a good idea of what the camera "sees". My unprocessed stacks are almost black, due to linear conversion.
I always thought less, but longer low ISO images would be better then more, shorter high ISO ones, but it seems not to be. I once did a single 1/2 hour ISO 200 shot of the Lagoon, it was nowhere near as good as stacking two 15 minute images at ISO 1600. It should have contained the same amount of "information" of the image but no matter how much fiddling I couldnt get anywhere near the detail as the 2 ISO 1600 shots stacked. I mentioned at Lostock that I deliberately move the scope slightly between each exposure (by moving the guidestar pick off prism in the off axis guider slightly). This means that when I stack the images, each one is moved slightly, this sees that the same actual pixels arent stacked on top of each other, as I think some of the noise ocurrs in the same pixels each time. Moving them smears out this noise,(at least it seems to work here), so I will always shoot deep sky stuff at ISO 1600 filtered, however unfiltered, ISO 400 (5 to 10 mines each) seems to give best results, as at ISO 1600 the stars "bloat" a bit without the filter to cut them back.
Scott
I mentioned at Lostock that I deliberately move the scope slightly between each exposure (by moving the guidestar pick off prism in the off axis guider slightly). This means that when I stack the images, each one is moved slightly, this sees that the same actual pixels arent stacked on top of each other, as I think some of the noise ocurrs in the same pixels each time. Moving them smears out this noise,(at least it seems to work here),Scott
Interesting Scott, that's also the same principal we use in planetary imaging when stacking avi's. This movement weeds out the noise and increases detail.
At home, without the filter, 3 min reaches the skyglow easily, but I have not tried it with the filter.
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