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Saturn RGB


Freddie
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Nice one Freddie, nice bit of red there, yet again another Saturn with the Vortes Storm area clearly visible.

I think if i want to to Saturn i will have to take my scope out or hope it 'moves' more in my favour in the next couple of months.

Well worth doing the RGB Freddie it produced a nice detailed finish for you well done mate.

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Thanks guys. I was pleased with how it came out but have had a bit of a reprocess and calmed it down a bit.

gallery_7987_2065_8378.jpg

These are the RGB files (after processing) that I captured. It is the blue as expected that let things down a bit.

Red

post-7987-0-04258900-1361448785_thumb.jp

Green

post-7987-0-14207400-1361448810_thumb.jp

Blue

post-7987-0-36705900-1361448836_thumb.jp

Lets hope for some more good imaging conditions as Saturn moves closer.

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Very good images Freddie. Very sharp - I presume you used the Celestron for this? if so, do you have a special focuser, or is this the standard celestron focuser? I would also like to know how you aligned the separate RGB images prior to merging them. I do it manually in PS, but I wondered if there was a better way?

chris

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Great Images Freddie - Excellent result on the capture and processing, and lots of detail emerging on the rings and disk. Looking forward to opposition and hopefully some more clear weather to add to the excellent images currently being produced. Nice to see this level of detail from the C925, rather than the bigger C11/C14s - starting to hope I might get somewhere near this with some luck and practice.

Jake

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Wow Freddie, that is something. looks like i was wrong about doing 15fps on red and green.your seeing must have been good, blue is so much better, it looks like you had better trans and seeing than i first had. My blue sucked compared to this. i only went to 15fps on blue, and it didnt help. it was still awful and dim. Im very interested in the processing are you saying you stacked 1000 frames per channel ? that seems rather small. Also do you know what f ratio or focal length you was at ? what gain settings ect ?

Excellent job well done

Edited by neil phillips
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Thanks for the comments guys.

Chris, that's with the stock focuser. At these high focal ratios, there is a reasonable range of critical focus position. I only use the CPC for planetary work so don't have a problem with the stock focuser. At lower focal ratios, the range in critical focus position is much smaller so an improved focuser may be required, but I never use low FR so no problems.

What is critical is collimation. The CPC holds it well, but when I check I use metaGuide and spend time to get it as best as I can using my full imaging set-up. The other thing that is important on an SCT is to approach focus from the same direction each time. For me, anticlockwise on the focus. This is because there will be slight movement on the mirror as it moves to achieve focus so you need to move in the same direction when focusing for collimation and again the same direction when focusing on the planet.

I use WinJupos to combine the RGB files. Takes a bit of getting used to but very good tool after a bit of practice.

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Hi Neil, sorry didn't see your post until after I had put that last reply up.

I use a 4x powermate so this is F40, ~9.2m FL. I know this FR flies in the face of conventional thought but with a perfect set-up with good quality powermate and Baader filters I apear to get away with it. I use the same on my Jup images.

I actually captured 2811 frames for R and G and 2182 for B. The gain was 840 for R, 850 for G and 920 for B. The exposure was 1/13 for R and G and 1/9 for B. The trans wasn't great as there was a touch of mist, which probably helped with the seeing. I then stacked the best 40% in AS!2 so 1124 R and G and 873B. The histogram on capture was maybe 40% for R and G and even less for B. Gamma 100 (it's a USB cam) though I have experimented with a touch of gamma previously.

After stacking I actually stretch (just moving the white point) the image a little in PS before going into R6. I have found that if you put a low histo image into R6 it will automatically stretch it even if you tell it not to!! I also think it over does the stretch, so I do it myself and ensure R6 doesn't.

Then a bit of noise reduction, levels for black point and cropping before going into WinJupos.

As I said in the previous post, I do try and keep my collimation spot on which I think helps a lot.

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Hi Neil, sorry didn't see your post until after I had put that last reply up.

I use a 4x powermate so this is F40, ~9.2m FL. I know this FR flies in the face of conventional thought but with a perfect set-up with good quality powermate and Baader filters I apear to get away with it. I use the same on my Jup images.

I actually captured 2811 frames for R and G and 2182 for B. The gain was 840 for R, 850 for G and 920 for B. The exposure was 1/13 for R and G and 1/9 for B. The trans wasn't great as there was a touch of mist, which probably helped with the seeing. I then stacked the best 40% in AS!2 so 1124 R and G and 873B. The histogram on capture was maybe 40% for R and G and even less for B. Gamma 100 (it's a USB cam) though I have experimented with a touch of gamma previously.

After stacking I actually stretch (just moving the white point) the image a little in PS before going into R6. I have found that if you put a low histo image into R6 it will automatically stretch it even if you tell it not to!! I also think it over does the stretch, so I do it myself and ensure R6 doesn't.

Then a bit of noise reduction, levels for black point and cropping before going into WinJupos.

As I said in the previous post, I do try and keep my collimation spot on which I think helps a lot.

Hi Again Freddie. im very surprised you can beat seeing at 1/13th secs exposure. But beat it you have. your conditions must have been a lot better than what i first had. Especially at F40. your location seems to deliver very well indeed. I will experiment with slower exposures after seeing this. but unless seeing is good i dont think it will be anywhere near as tight. what capture software do you use, with ic capture, 1/13th secs will give a frame rate lower than 13fps. though i belive fire capture can be tailored to the exposure. To say im surprised by your settings and result is a understatement. Yes collimation is important. but even with good collimation comditions have to play ball. As you know its all important. it seems you had the lot. Just amazed Freddie. such a great job. Excellent. Cheers for sharing the info. it tells me a lot

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I don't think f/40 is too extreme in some circumstances, especially with a DMK/DFK. I was getting up to around f/35 with the SPC900 last Spring when I was imaging Mars. Certainly for the pixel size of those cameras the maths doesn't make it look unreasonable.

As the pixel size comes down of course smaller f-ratios can achieve just as much.

In theory, anyhow :)

James

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Thanks for your comments Jam1e1 and Theo.

Neil, Stuart, When I got my 4x I did think F40 was going to be for very special nights only, but I actually use it most of the time. All my RGB Jupiter shots are also F40. I try and keep the exposure as short as I can by using highish gain but the one thing I don't worry too much about is having 35-40% histo. which most people would say is a really bad idea. This allows a shorter exposure and higher frame rate obviously and I find that for any given conditions it is more important to get the short exposure than aim for 60-70% histo. Obviously conditions were good on the 19th but I apply that logic all the time. As I said earlier, I then do a stretch after stacking (having selected all alignment points manually as I think it gives better results than the auto option) as R6 will do an autostretch on low histo stacks even if you tell it not to and it over does it. Have you ever noticed that? I was surprised when I noticed it. I would never normally stack less than 1,000 frames, but lacked enough good B ones and I would rather stack fewer good ones than add bad ones to the stack.

A bit of careful processing in R6/WinJupos and PS and you can usually overcome the effects of high gain and low histo. Obviously good seeing (which I clearly had on the 19th) is important but you may want to experiment with some lower histo captures.

I use ICcapture and doing the math was capturing at ~9fps R&G and ~7fps for B. The whole process took about 17 mins to capture but doesn't look like that has caused too many issues though there is a funny line on the left side of the planet if you look.

Anyway, lots of processes that go against convention but I think have worked ok on my Jupiter shots as well as this Saturn.

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Hi James, just seen your post after sending mine. I totally agree with you, though most would say F25-30 is where you should be.

As I say, I use F40 most of the time. I was kind of forced down that route as I wanted to use the same filter set as for DSO (which is all set for a 2" focuser) as easily as possible when changing over. So wanting a top quality 2" barlow/powermate ended up with the 4x powermate. Very rarely now would I find a need to go down to 2x and therefore have to use my DBK. You do however have to ensure your scope is operated and setup/adjusted as best as it can be, as F40 is not very forgiving.

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