Seeing was pretty lousy last night here in Canberra and I've not got the collimation of my new SCT anywhere near under control, but wanted to post my first Saturn regardless.
This was taken around 2 this morning using the NexImage and 2x barlow in the 9.25.
Think we pushed the gain a little too hard to compensate for very ordinary transparency, so a little grainy and blue coloured.
Settings: from memory - 1/25 shutter speed, 15fps, 75% gain, gamma=0.
All up we hand-picked about 40 frames and aligned and stacked in Registax. Very little adjustment to wavelets.
Zero post processing.
Like I said, it's not much but we've got our first cuppla runs on the board.
this is my 70% gain saturn from a few nights ago with 1671 stacked, with no hand picking.
So yes, if you are going to go less frames, then less gain.
Bird and mike and co have been discussing higher gain and lotsa images ie 2000.
So find a good system to estimate seeing (ie can you see the cassinni division thru the eyepiece and is it stable) and if it is good, then high gain (70%) and lotsa images stacked otherwise, less and less
It seems that this little planet is very hard to get spot on!!
Hi Matt, great to see you picking up a nice saturn image with the new scope. Agree with the guys, less frames to stack then less gain. Also as Asi says don't run faster than 10fps - information is lost. That said, and I may get howled down here, I'm not a big fan of using as much gain. I prefer to run longer exposure time (as high as the fps - eg up to 1/10th sec exposure at 10fps) and keep the gain down below 20%. I find this gets the light you need without the grain. Give each method a try under differing conditions and see which you prefer is probably good advice.
Yeah, we tried fewer fps but found the image became so dark it was very hard to see on the screen.
I know that others have written about it being better to have a slightly darker image and I understand that stacking produces a brighter image from all those dark frames, but how do you get a focus etc when it's so dark on the screen?
We tried letting Registax do all the work for us with the original 3000 frames we'd captured, but the result wasn't as good. Which would have made the issue of gain a little less significant.
We suspect we're not setting our quality filter/s correctly and are not really sure where to place those green lines on the graph, just before you click align?
You need to set all those lines to the right of the curve Matt (hopefully you know what I'm dribblin' on about here)
As to focussing on dark images...get it so it's bright on the screen (it's beside the point how you do that...plenty of gain/brightness/gamma if warranted) then focus/lock the focuser....then set the settings as you would normally do & fire away! At least that's how I do it.
This may help you a bit Matt. Check out the links posted in this thread. It's not specifically anything to do with any of you saturn problems but makes for an interesting read none-the-less.
Don't forget Ken your image looks like you are not using a barlow. When you increase image scale you need higher gain or else the image will be under exposed. Higher gain means more grain and processing artifacts.
Matt, collimation is your next issue to deal with. You have a good start and with some good seeing and a thoroughly cooled scope you will make big steps each time. That said I have waited 2 years to get the Saturn image I recently posted. It is very dim and the larger I go the more frames I need. Which means I need lots of good seeing.
Congrats on joining the frustration club. Hope to see more images from you.
Happy to be a member of the frustration club, in something of a sick and twisted way
And you are spot-on about collimation. I've not tweaked it yet, although it looked good the other night on a star test at good mag (10mm EP) on a 2nd magnitude star.
I've already got Bob's Knobs and will install when I'm feeling up to it. Am also looking at buying an artifical (Pico) star.
Am looking to make SCT collimation something of an obsession
Would definitely like a night of 7-8/10 seeing and a Lymax cooler
Any other details Ken? fps, shutter speed? Did you do much with wavelets or any other processing?
That's a crisp little shot on my screen.
Matt, I had it set at 25 fps and 1/100th shutter speed.
In the wavelettes I set 4, 5, & 6 at around 3.7
I don't touch 1, 2 or 3 as they seem to ruin a good image.
Nothing done in PhotoShop on that particular image as it seemed reasonable left alone.
But Paul is correct in that my image is not Barlowed. It is just the Toucam at Prime Focus (whatever mag that is at f5 with 1500mm f/l). As I can't do higher mag stuff yet I may experience the same problem you are having when I give it a go.
Geez Ken! 25 FPS?? I don't usually touch 1, 2, 3 waveletts either....but I've found if you have HEAPS of frames (2000 or more) which I had once, I gave it 100% #2 waveletts & nothing else & it came out GREAT!! (I did'nt post it 'cos I had the onion ring effect in it)
My first Saturn!
