After complaining about the difficulty of imaging with a Dob (link), I went and got myself an EQ6, better barlow and decided to give Jupiter a more serious attempt before it's gone for good.
The images from 3 days at the end of October are below, along with a grayscale animation of Io + shadow + GRS. The blue channels were absolutely rubbish so I decided to create some RG false-colours along-side them to compare. Which do you guys prefer? The detail seems identical to me, looks like the blue channel doesn't have anything useful in it.
Also although the seeing on 31/10/2008 was absolutely fantastic (I've never seen it that good!) and incredibly better than the other days, the final image quality doesn't seem to be that much better. Have I reached the limits of my 200mm Newt?
They're pretty good - I agree the 31/10 doesn't look quite as sharp.
Maybe it's as simple as the seeing wasn't as good?
Maybe the processing is letting you down?
Also don't forget that Jupiter is a long way past opposition now and it's getting very difficult to get a good image of it since it's only visible right after sunset for a short while.
What camera and filters are you using? How long are you capturing for?
What's your processing routine?
I'm not a fan of the RG composites.. I'd only use that technique if you weren't able to capture a B channel at all due to clouds or something.
The colour will always be off if you don't use a real B channel. and when the seeing is good, B has a wealth of high contrast data in there, especially when the GRS is visible.
Sorry for the novel I wrote below but I just want to illustrate I've put a lot of effort into each capture/processing stage
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Originally Posted by iceman
What camera and filters are you using? How long are you capturing for? What's your processing routine?
I'm using an SPC900NC with Baader UV/IR filter, capturing for 60-90 seconds. Images first split into R/G/B, then ppmcentred followed by processing in Registax (Gradient Align @ 95%) separately and recombined+offset in GIMP and further touchup in AstraImage.
In terms of webcam settings, Brightness: 50%, Gamma: 0% and:
The gain was carefully picked in each configuration (barlow extension, shutter speed) so as not to saturate the red channel nor be so dark that I got no detail.
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Maybe the processing is letting you down?
I've spent many, many hours on the same data. There doesn't seem to be much difference between whether I chose 60 or 90 seconds of data, 100 or 300 frame stacks, nor if I let AstraImage do all the wavelet processing instead of Registax prior to combining channels. I've also tried many combinations of wavelet processing and deconvolution, sharpening, etc .. still can't improve on this.
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They're pretty good - I agree the 31/10 doesn't look quite as sharp.
Maybe it's as simple as the seeing wasn't as good?
Well in the actual final image for 31/10, you can see much more detail in the bottom of the planet that's not visible in the other two images. I even slowed the shutter speed and lowered the gain as the seeing seemed great. I've included animations below to give an idea of the seeing on the 3 days (left to right with Oct31 being the third GIF - it's so still!).
In terms of my B channel, I started a thread about it last week but got no response so I assumed no one had my B channel problem. I've also included a snapshot of my channels below - B is just junk regardless of seeing! Also what's interesting is that my best shots have been with gain (or WB-Red) that was higher than what was appropriate - high enough to saturate the red channel such that it no longer had much detail but contributed to brightening up the image, with the G channel providing most of the detail (the image with the GRS is an example).
I took many movies at different settings each night so I might try processing the 1/33 shutter Oct31 movie. Perhaps the 1/25 shutter blurs things too much even with decent seeing?
Thanks,
Ash
Last edited by deadsimple; 05-11-2008 at 12:01 PM.
It sounds like you're on the right track, Ash. Judging from those gif's, the seeing has just been really bad. Especially the first 2.
It doesn't look as wobbly in the third, but the detail is still smeared - there are different types of seeing and the first two may be induced by tube currents AND jetstream, whereas the third one looks like the type of jetstream where fine detail is smeared away.
How's your collimation? Do you know it's good/right?
Keep practising! You can turn your skills to saturn, soon!
It doesn't look as wobbly in the third, but the detail is still smeared - there are different types of seeing and the first two may be induced by tube currents AND jetstream,
Yeah perhaps I don't know what 'good' seeing is - I've only owned my telescope for about 7 weeks now, but the first wobbly GIF is typical of what I've been seeing on 80% of nights. Though Jupiter being at 40 degrees when I'm imaging probably isn't helping,.
I usually fan-cool the telescope horizontally for 2 hours, with 15 mins fan-off settling time before each imaging session. I've never stayed up to image anything at 2am, so perhaps the temperatures will be more stable around then, good when Saturn comes around.
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How's your collimation? Do you know it's good/right?
I check every session or so but haven't touched it in a while as it holds collimation well when I'm careful handling it. I was out of focus on Venus the other day and managed to grab a shot of some of the collimation (shown below, but inner reflection not visible).
I suppose there's room for improvement, but at least it's not severely off.
Ash, the images and the animation are quite good, especially considering how new you are to the game!
The collimation image you've attached shows that its is clearly out by a bit.. getting it spot on is very important for planetary imaging, the slightest bit out can make a massive difference to the image quality..
I would try to get it as accurate as you can, or if someone close to you can do it, then it might be a good idea to ask for a hand/quick rundown on how to get it spot on..
Cooling in an 8" isn't usually necessary, as the small mirror will generally equalize with ambient rather quickly on its own.. 2 hours of fan time is HEAPS! You might want to try cooling it on a 45° angle, or even just mounted on the EQ6 at ~27° this way, the warm air has an easier time escaping from the telescope, as hot air rises, it will naturally flow out of the OTA. This might make 3/10ths of a ants toe difference, however, any improvement at all is worth going for..
You're going well mate, keep it up!
We'll have to meet up some time when saturn is back in the sky and have us a planetary imaging night !
I've just started imaging with my C8 (which needs a clean) and SPC900 NC as well and my pics are not as good as that.
I'm using a C8 and 2X TV Barlow on an old old EQ5 driven with a Gotostar system. The Gotostar system is ok it's...just my old !+?0D% mount that is causing heartache. Also the C8 focuser is causing heartache..I need a cheap SCT crayford....any ideas on this?
Anyway I'm using K3CCD capture and Registax. I've just toyed with Astraimage today ...very nice.
Anyway if I could obtain images like yours I'd be pretty content...for awhile at least.
Attached are some of my efforts in the last week.
Oh... one last thing...blue light is of such a wavelength that it suffers from "Rayleigh Scattering" in the atmosphere..but you already knew that.
I wanted to ask how you archived RGB imaging with the software? Did you just shut down the other channels? Excuse my nobishish.
Wasyoungonce : a good cheap SCT crayford is the GSO unit, it costs $139 from memory, and has 10:1 dual speed reduction for accurate and precise focusing.
Understand, the longer the focal length is, the harder it will be to focus, your C8 with a 2x barlow has a focal length of 4m, it will infact be a bit longer or shorter than this due to the distance between the barlow lens and the CCD, Ash's 8" newtonian with a 3x barlow is ~3.6m focal length, again, give or take a bit due to distance from the lens to CCD.
Your images are a very good start also, you must never be discouraged with early results.. Look at their upsides, and where you can improve, rather than comparing them to other peoples images.. Thats my advice..
I suspect my imaging achievements could only get better than my starting point, 28 Oct 2008...web cam commission date.
In fact just getting Jupiter in the FOV of my C8 and web cam at prime on a 2X barlow .... with my mirror "image shift" was an achievement in itself. Damn I need a mirror lock!
I have been looking around for an SCT focuser and have narrowed it between the William Optics SCT 10:1 or the GSO focuser.....due to price.
I like the William Optics Linear SCT focuser but it costs too much in Aust!
I don't want to to take wind from Ash's post...his images are very good and his post has inspired me
Ash, the images and the animation are quite good, especially considering how new you are to the game!
Thanks for the kind words. I hope I haven't asked too many face-palming questions since I started a couple of months ago
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I would try to get it as accurate as you can, or if someone close to you can do it, then it might be a good idea to ask for a hand/quick rundown on how to get it spot on..
Well I'm not that thrilled with the cheshire/sight-tube as it's not super accurate and still comes down to what I perceive as being "close enough". From the beginning I was planning to use the SPC900NC to assist in collimation but overlooked the fact that I wouldn't have a lens on it anymore!
I'm not too keen on playing with the adapter/lens too much, as I want to avoid getting dust on the CCD. I do have a spare crappy webcam handy though, now to get a door stop and some tape . Would a laser collimation approach be recommended instead?
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You might want to try cooling it on a 45° angle
Yeah I usually start it off at about 20 degrees for the rising hot air, and if it's windy I later place it horizontal so it gets more cross-sectional area to let the wind work its way through. I'm not so worried about dust, etc anymore as I'll probably upgrade the scope by the time it gets dirty enough
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We'll have to meet up some time when saturn is back in the sky and have us a planetary imaging night !
Yeah definitely. I've missed a couple of events due to house-sitting but now that that's over I'm keen on experiencing some dark skies and seeing other people's setups and imaging routines.
Anyway I'm using K3CCD capture and Registax. I've just toyed with Astraimage today ...very nice.
Yeah I started with K3CCD but switched to WxAstroCapture for the higher-framerate preview and because I found K3CCD interfered a bit with WcCtrl.
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Oh... one last thing...blue light is of such a wavelength that it suffers from "Rayleigh Scattering" in the atmosphere..but you already knew that.
Yeah I understand that, but still don't understand why the channel looks so incredibly bad. There is obviously detail there but there's so much grain, pixelation and blockiness that makes me think it's a hardware or imaging problem. See this for example.
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I wanted to ask how you archived RGB imaging with the software? Did you just shut down the other channels? Excuse my nobishish.
I'm not sure what you mean. The images that are captured to AVI have all three (R/G/B) channels. I separate them with RGBSplit, centre each and process each.
Then I get the final processed image from each channel, "Colorify" each channel in The GIMP (i.e. red channel goes from grayscale to being actually red, etc). Then copy and paste the colorified R and B on top of G, setting the "Layer Mode" to "Screen" so the channels are combined properly. Then just offset each layer, perform more per-channel or mixed-channel processing, etc.
If I want RG, I "Colorify" the green channel to aqua and stack the red channel on top. I'm sure AstraImage and other software might be able to do it more easily but I find I have a huge amount of control over each step when I do it the long way
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I don't want to to take wind from Ash's post...his images are very good and his post has inspired me
If I inspired anyone, then that's one goal met . Keep up your effort, your results will only get better!
It was the dozens of threads (archived over several years) I read on this forum that made me decide to get into amateur astronomy, when I realised what results can be achieved in the average backyard without spending too much upfront.
I was afraid to be sucked into aperture fever. I almost was but for some reason wide-field + long exposure is starting to pull me in ... not that I have any equipment that can achieve that, but those milky way shots I see lately look so good
Laser collimation is a good way to get it pretty spot on, however, you have to make sure your laser is correctly collimated, otherwise it will send you in the wrong direction.. there are a few that come collimated (do a search on the forums...) they are really quite good.. I had a baader collimator for my 8" skywatcher newtonian, and it was fantastic...
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. Damn I need a mirror lock!
