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Showing results for tags 'cats eye'.
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I found the object very difficult to process due to the extremely bright core. The problem is that with 600s sec exposures, it was not possible to see anything but white in the core region. On inspecting the corresponding FITS images I discovered that whilst the ADU values of my CCD where not at their maximum level they where in the non-linear region of the my camera, which starts at around 47000 ADU's. After trying various techniques, I eventually watched an Adam Block tutorial video on how to create a high dynamic range image using CCDstack. Here, the approach is to take much shorter exposures (I choose 60s) and then combine them with the 600s exposures. The combination is done on a per pixel level by instructing CCDstack to reject any pixel from the 600s image that is 40000 ADU's or above and to replace it with the corresponding pixel from the 60s image. The result is a high dynamic range image for the LRGB channels which I then processed via my conventionally PS and Pixinsight workflow. The image represents just over 8 hours integration.
Just a quick report on some observations to test out the Skywatcher Discovery AZ Goto mount I got off Dobbie on SGL a week ago. Although I've tested it briefly before for a few hours on a couple of nights, tonight as it was getting dark looked promising, even with a few high clouds still floating around. From around 8:30pm the sky was nice and clear, and pretty steady too, although there was a small breeze blowing. After first setting the mount up, leveling it, and doing a 2 star align I got down to some testing. For this I used initially a Celestron 4SE which I'd got from Chris on here on Monday just gone. After aligning with both Vega, and then Polaris, I settled on the first Messier that was well placed up in Lyra to view, M57. The mount slewed to it and placed it in approximately in the 7 o'clock position near the edge of the view with a 32mm Celestron plossl EP. It was very easy to pick out still, even though not centred. Using the PAE option on the mount to centre M57 to fine tune the positioning, I then went across to M13. This got close again, but used the PAE again to centre it to fine tune it. As the sky was darkening well, and the seeing was pretty good M13 was a beautiful sight even at the low magnification with the 32mm EP. I then used my 14mm Baader Morpheus EP to get a closer look. After soaking up M13 for a few more minutes, I then slewed across back to M57 to look at that in the 14mm EP. I didn't use any filter at all on M57, and could quite easily see the ring structure pretty well. I then wanted to test the double double not far away in Lyra in the Celestron 4SE, so skewed across to that. Using the magnification with 10mm, 6mm & 5mm EPs with the 4SE I couldn't get a good enough focus with the scope, although this could have been down to the scope still cooling down perhaps. I then decided to try my new Altair Astro Starwave 102mm f11 frac on the stand, which was probably close to the max 5kg weigh on the mount, but was curious as to how it might do none the less. After carefully fixing it in position, I once again zoomed in on epsilon Lyrae. This fared better with the higher mags, but with the breeze blowing on the longer tube of the f11 frac this caused the view in the EP to wobble a little during gusts. Going back to M13 to see if the positioning was still OK, M13 honed into view very nicely. As the sky was looking the best it has been for a few weeks, I then decided to try for M81 & M82 in Ursa Major. These stood out extremely well in the 14mm Morpheus on the Starwave , and could just keep both galaxies within the same field of view with the Morpheus. I then went across to look at M27 in Vulpecula, which once again showed extremely nicely in the 14mm Morpheus EP. During this time a next door neighbour was having a party, as there were quite a few young teens walking around in the street behind my garden, so I decided to start calling it a night before too much alcohol was drunk, and nosey kids started noticing the large scope pointing up at the dark sky, but before I went in I decided to look for the Cats eye nebula in Draco (NGC6543) which I'd looked for before, but never found, so was hoping with the Goto it should be quite easy to find. After keying in to the keypad the NGC number, it slewed off and settled in what seemed like the correct area of Draco according to SkySafari. Looking through the Morpheus 14mm EP I could see straight away the Cats eye glowing away just off centre. Popping in the 10mm EP to make sure it wasn't just my imagination, it became obvious even more. I now know why it's called the cats eye nebula as it really does glow well for just over an 8th magnitude brightness. As the party was cranking up even more outside, I packed away all my gear, but even though I could have stayed out for another few hours at least, I was extremely happy to have notched up a new object to see in the Cats eye nebula. With clear skies, and the darker nights approaching even more, I'm hoping to notch up some more Astro candy for my eyes to feast on. Hoping that tomorrow night if the skies are clear I can get out once again if the skies are clear, with no boom box beating away in the background! The Goto mount is working very well, and seems to able to handle all my scopes, right up to the Starwave, although this does suffer with a little wobble if breezy. All in all a very nice night, if much shorter than I would have liked due to the party going on next door!
My first attempt at imaging a rather unusual looking deep sky object, the Cat's Eye Nebula. Since the core is about x1000 brigher than the surrounding nebula, to avoid a burnt out core, I decided to create a LRGB high dynamic range image by combining 600s and 60s exposures. Since my camera's (Trius 814) non-linear range starts at about 47000 ADU, I used CCDstack to replace any pixels above 40000 ADU's from the 600s exposures with the corresponding ADU value from the 60s exposures. I then processed the object using my normal workflow via PS and Pixinsight. Comments and criticism are welcome. Alan LIGHTS: L: 13; R:8:G:10; B:9 x 600s. L:30; R:21;G:20;B:25 x 60s. Esprit 150 and Trius 814. DARKS: 30. BIAS:100. FLATS:40 all at -20C