Where do I go from here?

[Demonperformer]

I need advice ... Every photo I take of Saturn ends up looking like the attached image. OK, they' re nice enough to look at, but when you compare them with the images produced by others on the forum (e.g. http://stargazerslounge.com/imaging-planetary/170334-saturn-january-08-2012-rgb-full-set.html) they leave an awful lot to be desired.

And I desire it!

But no matter what I try altering in the way I take the pictures, nothing seems to get me where I want to be, or even to the same postcode as where I want to be.

So come on, what am I doing wrong? How can I improve? Feel free to be brutal about my technique if you need to - the end will justify the means

Thanks.

[jgs001]

Not sure from that... but I'd suggest listing the kit in use also... Bit of detail about the barlows etc... it looks good on the 8se at 400x...

[Space Cowboy]

What camera are you using? If its a webcam then you need more frames to reduce the noise (6 min avi) and higher gain (at least 70%) but gamma set low. Bottom left image is in the right area.

[Demonperformer]

Thanks for your replies.

John: 8SE with neximager. The 2x barlow does not say what it is (always a bad sign), but if I remember correctly, it came with a skywatcher telescope. 3x barlow is a TAL.

Stuart: The 1200x image was taken with a 5 min avi. 5fps, 1/5s, brightness set to maximum. I have been doing gain and gamma the wrong way round (high gamma, low gain) so will try that. I was told some time ago that 'brightness' is on the input side (more signal) and 'gain' is on the output side (amplification of the same signal), but I've never really been sure what 'gamma' does, except it seems to work like a fine-tuner for overall image-brightness.

[themos]

The comparison link you posted was from someone who lists Hawaii as their location. You are not in Hawaii, are you? Saturn is very difficult at the moment over here because it's so low and you know why they build big telescopes in Hawaii and not in the UK...

added: Saturn reaches 60 degrees altitude in Hawaii, 30 deg in England.

[Demonperformer]

So, I should move to Hawaii

Like it, but not sure how practical it would be

[themos]

No, just use Jupiter!

[jgs001]

The neximager is I believe basically the same as the spc900, so in other words a slow colour webcam. I'd start there, look for a high speed usb2/firewire mono camera. Mono cameras are far more sensitive than colour, it's to do with the way the Bauer matrix works. my qhy5v is far better than my spc900 as a lunar/planetary camera, the only time I use the spc900 now is to add colour to the mono image of the qhy5v, I've not sussed multi filter imaging yet.

I know, more costs

Of course moving to Hawaii will certainly help, but that will cost a heap load more

[themos]

Yes, John, but first you hit the limit of what one camera can do and then you upgrade.

[Space Cowboy]

Yep, thats been your problem gamma and gain. My best Saturns last year were taken using 0 gamma and 80-90% gain. You don't need a mono/high speed camera to dramatically improve these images.

[Jupiterholic]

Yeah, I really wouldn't beat yourself up comparing your stuff to Freddy's. As mentioned previously, the guy is in Hawaii, very experienced and uses a C14. C14's were practically invented for planetary imaging. The best planetary imagers in the world use C-14's and with good reason.

I'd say gain and gamma are definitely what you need to work on. Plus try a barlow but not too powerful. Try a 2x to start off with. The more powerful the barlow, the dimmer the image will be, the higher you'll need to push gain and the more noise will be in your final shot.

Plus if you're anywhere in Gt Britain there's one tried and tested way to get a cracking image. I guarantee you it'll work... Go out and photograph the planet every single time its clear. Because the more you do it the more chance you have of hitting one of our extremely rare 'good seeing' nights. And to do well on Saturn in the UK, you need good seeing!

[themos]

Go out and photograph the planet every single time its clear.

this

[LukeSkywatcher]

Simply put:

The difference is Hawaii and a C14 scope.

DP how does Saturn look visually in the scope? I only ask cuz i am dying to see it in my 8SE.

Jupiter visually last week was FANTASTIC...............even without using a barlow. It was the size of pea held at arms length and banding clearly visible. I think i was using an 8-10mm EP.

You will LOVE it.

[neil phillips]

You can get good saturn images in the uk with a 8 to 10 scope. Saturn is dim hence bigger scopes often do better, as Stuart says its the gain thats the problem here.At first i thought it was exposure that was way too low. But having read you mention 1/5th secs, than thats quite slow. So clearly your gain must be low. when pushed ive imaged saturn at 100% Gain but that was for 6mins at 30 FPS so many thousands of frames controlled the noise somewhat. Its always better as Stuart said to drop gain down just a touch to say 90% but with a smallish scope ( 8" ) That might not give the best push. If you can get lots of frames high gain can be controlled. but at 1/5th your not getting lots are you. So just experiment with gain at 90 to 100%. Set your exposure as fast as you can but only with the image looking considerably brighter on the live avi than these. what i dont know is how low your gain was so i cant tell how much you can speed up exposure. But if you can put gain up to high and increase the exposure speed. ( even 1/15th is quite slow ) compared to my 1/61 secs ive been using on jupiter. using a 245mm scope ( my Orion ) i was able at oppossition ( its not bright enough yet granted ) to shoot at 1/30 secs exposure full gain and just a slight increase on gamma. Gamma i find seems to work better on saturn than jupiter why i never found out. But i had less onion skin than using gamma on jupiter. Try using gamma set to default. and experiment with a slight raise of it, and compare the results. Gamma increases brightness but at the expense of contrast. contrast is lowered by raising the gamma. and will produce a slightly more washed out appearance. When i shoot Saturn i will try and shoot at 1/30 secs 30 fps for 6 mins. going slower as need be with higher powers its all in the juggling of exposure and gain that is the key to good planetary images.

think of it like this gain will be set to high 90 to 100% once set juggle the exposure to a setting where the image looks at least reasonably brighter than you had here. whatever that turns out to be, is all you can get with a 8" scope and saturn being so dim. But if for example you could stretch to 1/15secs exposure and the image is slightly dim ( and i mean only slightly ) often that would be better than slowing down the exposure more and having a brighter image on screen. Why ? well because the faster exposure setting beats poor seeing more. and more frames can be aquired. But this is the juggling i mention. If the histogram is too low and saturn is still too dim even with a 100% gain and a slight raise of gamma. then no, exposure must be slowed down more. or you will be back with impossibly dim saturns again. The fastest exposure while avoiding the dim problem, you will have to find out in the feild good luck hope this helps

[Demonperformer]

Yesterday morning, I went out and tried to capture Saturn using 30fps 1/30s exposures, zero gamma and quite a lot of gain, taking 6 min avi. I did a series of avi's [a variation of the old film camera idea of bracketing exposures] and this was the result.

Clearly, I have misunderstood the advice I have been given somewhere ...

[themos]

30fps on that camera is complete overkill, the camera will compress the frames to hell and back in order to fit the data rate to the USB1.1 bandwidth. I shoot 5 or 10 fps.

[Demonperformer]

Mmm ... that throws another element into the mix. My laptop uses USB2.0 rather than USB1.1 (if that makes any difference).

So, should I keep the high-gain-low-gamma scenario and just reduce the frame rate to reduce the compression, giving me fewer frames to stack (~3600 @ 10fps cf 10800 @ 30fps for a 360s avi)?

But doesn't that mean that I'm going to be limited in the amount of gain I should use (because fewer frames won't get rid of the noise that creates)?

:icon_scratch:

Thanks.

[themos]

. My laptop uses USB2.0 rather than USB1.1 (if that makes any difference).

Not important. The camera can't go any faster than it was designed. The laptop's USB ports can go slower so they have no problem with USB1.1 devices.

I shoot at zero gamma and middle gain and maximum exposure at 10fps. The gain is determined by the requirement not to overexpose. If you were to use SharpCap, you would be able to get a live histogram display (or a red highlights display) which lets you know if you are overexposing, in which case you turn the gain down. The maximum value that can be recorded on a pixel for these cameras is 255. I usually make sure that the maximum in each frame is about 220, the histogram display helps me check that.

Yes, at a lower frame rate you may end up with hundreds rather than thousands of frames (I get about 900). But if the seeing has good moments, even a few hundred frames can make a great picture. And remember, at 30fps, none of your frames have captured enough detail so stacking garbage produces garbage. At 10fps, you have some good frames in there so stacking (after quality filtering) can produce the desired effect.

[Olorin]

Hi DP, here is my technique, since I use the SPC900 and an 8" Newtonian I hope it will help you. First when I have the planet centered I raise the exposure and gain to the max. then I make sure my focus is right using a B mask (Spica is right there next to Saturn). I then return to the planet and reduce the exposure till I get the planet to be a bit too dim and then I do exposure +1. I then play with the gain to get a good image of the planet (not too bright and not too dim - you can use the histograms as well) make sure the gain is at 70-90%. the Gamma I usually put on zero or if I want some moons I raise it to ~1-2% (5 in sharpcap). For Saturn as it is very dim I take long AVIs (3-6 minutes) @ 10 fps. if the sky are very clear I use 5 fps. one last note - I noticed you get a yellowish Saturn - try to make sure that when you view the planet on screen it has that bluish color if it doesn't try to play with the color options till it looks better. I usually use a x5 barlow but you can also use the x2 and x3 stacked if you don't have a x5.

Hope all this helps

Dror

[michael.h.f.wilkinson]

I have a similar approach to Dror. I get my best shots when I adjust the controls (at max exposure time) until the background level is just above 0 and the maximum is just below 255 (I tend to aim for 245-ish) for each channel (RGB). Maximum exposure time gives maximum photons, the other settings ensure most of the analog-to-digital converter's range is being used, but without clipping. I find a 3x Barlow gives rather faint results, a 2x (at F/20) is better. I think 2.5x would be ideal.

I find I can do 15 fps or 10 fps (rarely 5 fps) for best results. Anything higher is wasted.

[neil phillips]

Sorry i misunderstood i thought you was using a imaging source camera the spc wont go above 10 frames asec without compression as mentioned the lines you see are caused also by maxing out the camera ( high gain ) and saturns low surface brightness

I dont want to be a kill joy but you might be seeing the limits of your equipment on saturn at the moment. even my 245mm scope and sensetive camera struggles on saturn. Ive had those lines your getting when i maxed out the spc 900 on a dim saturn apologies for misunderstanding. Not sure what Advice to give other than keeping powers lower to reduce the strain on the camera with a brighter image. from the smaller power being used. Uneless anyone else knows a way to get more from your setup

[Space Cowboy]

30fps at 1/30 is too much. 10fps at 1/10sec over 6 mins keeping the gain around 90% and stack at least 1000 frames. What capture software are you using btw?

[Demonperformer]

10fps at 1/10sec over 6 mins keeping the gain around 90% and stack at least 1000 frames.

Thanks to everyone for your continued advice, the concensus of which seems to be more or less summarised by Space Cowboy. However, with rain due for the next few days, it looks as if I may have to wait a while before being able to implement it.

I use either Amcap or Sharpcap (1.5.0.304) depending on how I am feeling. @Themos: have had a look in Sharpcap and have not been able to find the histogram command. Could you give me directions, please?

Thanks.

[themos]

To the left of the Reticule button, there is a drop menu that is initially set to No Transform. Set it to Histogram and you'll see a histogram below your image.

[michael.h.f.wilkinson]

My best results on Saturn were these:

using a 2x TeleXtender and

using a 3x TeleXtender on GP-C8. Before I got an IR-cut filter, the best I got with EP projection was

This is intermediate in magnification to the previous two, hence my desire for a 2.5x TV PowerMate