help needed imaging saturn

[Muddy Diver]

I am surprised that each time i try to image saturn I end up with stacked images which are so bright that any detail I may have captured is lost. I believe that I have some detail as when over processing I get patterns on the surface but it looks awful. The more still frames I stack in registax the brighter the image. So, is it best to image saturn with the image in my capture software set to very low brilliance so that I cant actually see the detail in the hope that the stacking and processing will bring the image out?
I'm using a neximage. ( and with my 4" Mak i'm not sure if i'm supposed to see detail or not anyway). I found that turning down the brilliance in registax did not help neiter did adjustment of contrast.

If anyone has a frame from an AVI which shows the brightness of the recorded AVI compared to the end result, this might help me gauge how dim I need to record.

[davidpretorius]

can you extract an image from your avi and post it?

early days i used to underexpose, but now am close to a finished product.

are you auto processing in registax or manual. also do you have histostretch or intensity checked at stack stage???

here is one of icemans saturn frames from an avi

do you have a screen shot of the neximage settings??

[[1ponders]]

Hi Muddy, what sort of fps, exposure, gain and brightness settings are you using? Do you leave the autowhite balance on when capturing. What program do you use to capture with and have you heard of WcCtrl for adjusting you settings?

[Dennis]

Hi Muddy

If your image capture software has a Histogram display that can show you how many photons and at what brightness level you are collecting, then I recommend you use that function.

My software, K3CCDTools, shows a Histogram bar starting at 0 and going to 255 (8 bit). If I see the number 255, I know that the image is too bright and that anything over 255 is “seen” as white and therefore "wasted".

I usually tweak the brightness, gamma or gain to keep the Histogram between 150 and 230 so the whites do not saturate.

2 to the power 8 is 256, hence the Histogram range from 0 (black) to 255 (white).

Hope that makes sense

Cheers

Dennis

[Muddy Diver]

Thanks for the response. I can see I'm entering a very technical area!
David, My version of Registax seems to differ from yours in that I have not yet been offered the choice to process manually i.e. no tick boxes for auto or manual etc. The version I am using is 2.1 as comes with the neximage camera. is this more advanced as i seem to have overwritten my previous version with this one?

I have not seen a histostretch or intensity option at the stacking phase but do get an option for histostretch and Gamma curve at the wavelet processing stage. I did manage a better image from last night by adjusting the camera settings and have a screen dump from this session along with a frame and final image. I have no screen dump from the evening of the 18th when the image was too bright but have a frame from then also. see attachments.

Paul, I dont remember the FPS setting but have since realised that this makes a huge difference, As mentioned above, I have n recollectoin of the settings from the previous evening (bright image) but have managed better since then. The auto white balance was on for last nights image but not sure for previous. Never heard of WcCtrl whats that?

Dennis, that all makes sense, i think! There apopears to be no option for histogram during the capturing process.

All in all, I feel that I accomplished much by trial and error in the short period of visibility I had early evening yesterday tonight will be better i'm sure.

[matt]

Muddy

I've also got the NexImage webcam, so I'm hopefully able to help.

You can update your version of registax to V3 via the toolbar at the top of the screen. Visit the Registax website and download for free.

I noticed in your screen capture image you have your auto exposure box checked. Uncheck it. That will give you control over shutter speed and gain, which will help you greatly when capturing those precious avis.

Good luck, and keep asking questions:)

[Robert_T]

It's all a bit daunting at first Muddy, but trial and error is a great teacher :)

do what Matt says below and get control over your gain and shutter speeds (download Registax 3 too it is better) With Saturn you'll want to be using the slowest shutter speed you can so you can reduce gain to well below halfway. You've got the camera set to 5 frames per second. This is fine, but a bit wasted unless seeing is excellent. For most conditions 10fps is best.

You'r probably best to err of the side of underexposing. What I did with each planet was to take a wide range of exposure settings and then took note of what worked - it's a little different for each planet too!

If you find your stacked images are too bright try repeating but with the Histostertch unchecked.

Anyway, good luck!

[davidpretorius]

hey those ones are looking good.

as the boys have said, manual exposure is the way to go!!

i would suggest

50% bright
50%contrast
0% gamma to start and maybe lift a tad later
100% saturation

at lower magnifications ie without barlows and powermates, you may have to go to 1/100 or 1/250 etc

as the magnification increases, you use 1/25 or 1/33 etc.

at the moment, try gain lower, but most guys now have lifted the gain to get more detail.

and definately download registax 3.0.1.24 from memory

[Muddy Diver]

:doh: I uploaded 4 images earlier to show you a frame,, although dont know how as I only selected three. Deleted the dupicate one, or so I thought to show a frame. Must have deleted the frame and left two end result shots!

So here is a frane David.

Thanks all for the comments on the exposures. I have been relying upon what I see in the screen preview not what is to be easily processed I think. I'll note down the settings next time or do a screen shot with every recordiong so I can learn whats best.

I played with exposure on Sat night shooting Jupiter but actually came up with a new set of problems which I wont go into here so I might need to list down all the suggested levels and try them methodically.

Registax version 3 downloaded.

[Muddy Diver]

Thanks Matt. Nice to hear from another neximage user. I was wondering that due to my small aperture, capturing detail is always going to be a challenge so would it be better to do a RAW update to the neximage. Is this possible?

As in a previous reply I foumd the improvement gained by switching off auto exposure. I still need to develop my settings for each planet though. At the moment, trying to keep the object centered while playing with the settings in the dark and focussing is challenge enough. Once adept I will add in the screen dump to record the settings once I'm happy and save it to the file with the AVI. Just wondering what else I can do in the spare time I have while imaging.

[Muddy Diver]

Thanks

[Muddy Diver]

Thanks Robert. Tried this with v3 and it makes a difference. I'll try with the bright file and post the result.

[Robert_T]

Muddy, you can do the RAW mod with the neximage same as the Toucam. I wouldn't recommend it though, least not yet. Any improvement it yields is VERY subtle and it's a hell of a lot more complex and difficult to use well so best to get used to standard mode first.

cheers,

[Muddy Diver]

Thank you sincerely to all the helpers in this thread. Further collimation, all the help here and good seeing allowed me to take the following two images of saturn. I am thrilled and cant thank you enough.
:bowdown:

For the first time I actually glimpsed cassini's division through the eyepiece and the larger of the two shots using a 2X barlow shows it in the image. I'm stoked!:thumbsup:

[davidpretorius]

well done muddy!!!

that single frame, i believe could be brighter, ie more gain or higher exposure. do not be worried about using higher gain. stacking will dramatically reduce the noise.

with raw mode, you want great seeing to make use of it. It is easy to implement ie get your camera into raw mode, but it only operates at 5fps. so you either image for longer to get 500 to 1000 odd frames, or with someting like jupiter which rotates so quickly, you are restricted to 90 seconds capture ie 450 frames. so theose 450 frames had better all be in focus! - hence great seeing.

raw is great for star work and dso's etc. I believe it brings out more detail in planets, but as rob says, you need everything else spot on.

I would say tracking would be essential otherwise you need twice as many passes to get a decent amount of avis!!

Let us know how jupiters goes, It has its opposition in May, so the more practise you do now the better. Also saturn is around at night when everything is still cooling ie 10 - 12pm. Jupiter is around from 4 - 6am. Everything is still and stop cooling, so a telescope will have everything the same temp ie no tube currents. It is worth leaving the scope out if the weather looks great and getting up. The seeing will be better

keep at it!!

[Muddy Diver]

Er, thanks DP. Actually this was my end result i.e stacked and processed (well, I am only a newbie) :)

But the advice on gain is sound. I have been reducing this to get better picture overall quality on the lap top while imaging but noted the loss of detail when doing so. Will increase next clear skies.

I'm interested about the cooling of my telescope. I knew this affected larger optics in dobs for example but was under the impression that the temperature had very little effect on Maks due to the heavier, thicker optics. Am i mistaken? if so I will leave it under the balcony to stabilise next opportunity.

Thanks again. even though my final image is not as good as your raw frames, I was delighted when I processed this one. What staggered me was that the detail just leapt out as soon as I played with the wavelet setting (no6 to 50 or thereabouts). Must be doing something right as the images are getting better.

[matt]

It's looking good Muddy.

Just the one thought re: gain. The less frames you plan on capturing, the less gain you shoud use to capture those frames. With fewer frames gain=grain and it's pretty much impossible to get rid of it with so few frames.