Tues Aug-9-2011 waxing 90% gibbous moon @ 560mm ; stacking?

[mtbdudex]

Image taken Tues Aug-9-2011 9:54pm, waxing 90% gibbous moon @ 560mm, below is crop and posted @ 1024pix wide.

Q: I have 10 of these just taken, how do you guys/gals stack the DSLR images from your Canon's?
I've seen others do it, so naturally being curious I'd like to try that to compare the improvement, see if its worth the extra time.

I shoot in RAW, they are full size 15.1MP, not webcam.
As I scanned thru the 10 images I can see individual portions have slight more detail here and there.

Specs:
EXIF data: T1i, 70-200mm f2.8 L, ISO 200, Exposure 1/250 sec, Aperture 5.6*, Focal Length 400mm*
(*note: actually the 2.0 and 1.4 TC were on, so 560mm & f 8.0 are the correct, the sensor does not do double stack TC's data...)



btw, as discussed in another thread I now take a 1.5-2 sec over exposed image to see if clouds are by the moon, for this shot appeared cloud free.
(that's internal lens reflection LH green ghost image)

[ohata0]

I've stacked moon images using photoshop (cs5). It is rather time consuming...especially if you're just using a tripod. The moon not only "moves" but it also rotates slightly, so you can't simply "line up" all of the images and call it a day.

In the end, I've only really used manual methods to stack my moon photos, because the software that I've used (IRIS and DSS) don't work w/ moon photos, and photoshop doesn't seem to have enough "data" to align the shots correctly.

Here's a link to my post in the Shooting the moon! thread: My Stacked Moon shot if you're interested. I stacked about 8 photos.

Mostly, I don't think you'll get any improvements regarding sharpness. If anything, it may end up making the image less sharp actually (any differences between the images, atmospheric distortion, or simply misalignment of the images, would end up blurring details). It would help remove noise though, and bring back details that are hidden from noise.

You normally don't have to worry about noise that much though, when you're working w/ moon shots.

I say give it a shot and if it's not for you, it's not for you. At least you tried, and now you know.

I'd imagine that if you were using some sort of EQ mount though (a barn door tracker, or similar device), then it wouldn't be as complicated (as long as you've set it up correctly) as the moon in each image should stay in the same spot, making alignment (the hard part) a lot easier/quicker.

Oh, a tip, if you plan on trying out the stacking...get a rough alignment and then do a generous rough crop. Not as tight as your 1st image, but a bit more than your 2nd. Cropping out the useless data will help speed up photoshop as it'll have less data in memory. Just don't crop too much...after fine tuning your alignment, you'll crop it again.

[martyn_bannister]

Have a look at Registrax. You can stack DSLR stills or AVI's from a webcam. I have never got on with Photoshop for stacking more than a couple of layers.

[andyman82]

An easy way to do it in CS5 is to open up the picture bridge, highlight all the pictures you want to align, then go to tools -> photoshop -> load files into photoshop layers.
Select all the layers (in photoshop), then go to Edit -> auto align layers and choose auto or whichever one suits your fancy. Then go back to Edit and choose auto blend layers, and use the stack option. That's one way to do it pretty quickly and it does work very well with moon shots, I use it all the time to make very large composites... it does all the stretching and aligning very very well even with 20+ pictures.

[jodelak]

pardon my ignorance on this one, but what benefit would stacking do?

[spit]

registax, i really cant see it being done in PS, the wavelengths will turn it into a masterpiece if you dont over do it

[Bernoulli]

This is an interesting topic for me and I've done quite a bit of experimenting over the past couple of years on stacking Moon pictures. Let me share with you what I've learned and I would love to hear from others out there about their experiences.

For Moon shots you stack for two reasons:
1. Decrease noise.
2. Decrease the smearing effects of atmospheric turbulence.

There is another reason for deep sky photography, bringing out dim objects. But that doesn't apply for the Moon because it's brightly-lit. Shooting the Moon is more like portrait or product photography than anything else.

Long story short, with fairly steady seeing, stacking will reduce sensor noise at all FL's. This noise is at the pixel scale and, unless you are at 100% crop, you probably won't see it anyway so there is no need to stack. If you are going to create images at 100% crop, I found some benefit from stacking up to about five images, no improvement above that. You should always shoot the Moon at the lowest ISO you can get on your camera, which is 200 for my T2i. At that ISO there is very little noise anyway. But I usually shoot five and stack them.

If you downsample your shots (go from 3000x3000 pixels to 1000x1000 for instance) this has exactly the same effect as stacking since you are averaging 9 pixels to get 1 and this will knock down noise just as well as stacking 9 images but you lose image scale.

At FL's above about 3000 mm and you might get some benefit of decreasing the effects of atmospheric turbulence. Turbulence on a decent night with the Moon high in the sky is on the arc-second scale and one arc-second on the moon is only 1.9 km (1.2 miles). So you will see this effect only at extreme magnification. To reduce this, you want to stack as many shots as possible, dozens if you can. Shots at these magnifications rarely appear on this forum but that's how the super-zoomed in images are made, usually using a webcam that essentially takes a movie to obtain lots of frames.

To stack DSLR images in Photoshop, first select only the very best shots. I usually take 8 to get 5. Throw out anything that is even the least bit suspect due to sudden severe turbulence or the sudden appearance of 60 lbs of excited Australian Shepherd on my deck (see my avatar).

Stacking is easy:
1. File --> Scripts --> Statistics
2. "Choose Stack Mode" to "Mean"
3. Check "Attempt to Automatically Align Source Images"
4. Browse to get your files, hit "OK" and it'll take a couple of minutes.
5. Once it's done, flatten the image with Layer --> Flatten Image

And that's it!

I usually use a 900 mm refractor with a Barlow that gives me an EFL of 2970 mm. I shoot the Moon in three segments since it won't all fit in one frame, using 8 shots per segment. I pick the best 5 or so of each and stack as above. Then I take the three stacked segments and merge them into one really big image (File --> Automate --> Photomerge). The resulting image scale is huge, with the Moon's disk being 5700 pixels across. The image below is at 100% crop scale.

Anyway, I hope this post wasn't too long or (yawn) boring.

[spit]

its been said from some advanced AP imagers, lunar stacking isnt always in the best interest if using a quality scope and DSLR, but i always had a better average stacking a 'few' frames-- IF i got a good stack, however this is where photoshop failed me, its true about a full crop, naturally your just not getting the image scale or resolution, but back to PS, have you tried registax?

[Bernoulli]

Originally Posted by spit

. . . but back to PS, have you tried registax?

I haven't tried it but I'm not sure Registax does DSLR frames. Seems like there was a thread to that effect on here sometime in the past but I might have remembered wrong.

[martyn_bannister]

Bernoulli: Long, but very informative, thanks for sharing.

On your scope, to get the quoted EFL, you have the DSLR mounted on a T-Mount on the end of the barlow in the focuser? i.e. magnified prime focus?

[Bernoulli]

Thanks Martyn.

Yes, I use scope - barlow - camera. I don't use a T-mount, I use the thingy shown below. Fits right where the eyepiece would.

You can use a diagonal between the scope and the barlow to make the camera easier to look through if the Moon is high, but if you try to put it between the barlow and the camera, thus lengthening the distance between barlow and camera, you get a ridiculous amount of magnification that you can't even use so that doesn't work.

Let me also comment that the "Attempt to Align" has never failed me. It seems to only stack those portions that appear in all of the frames so you might get a result that isn't exactly rectangular. Be sure to leave some space around whatever you are actually trying to image.

[spit]

if you wanna get power imaging like that- its best not to over sample/under sample, EFL around 4000for a DSLR would be about right,you need about .25-.33 arc/sec resolution, i still dont think photoshop stacking or photomerge work very well

[mtbdudex]

Rick;
Thx very much;

I will try this on my moon shots.

As a side note, just Friday early morning I got 6-7 in my Perseid meteor shower attempt.
Can I use this process to stack those individual images?

They were taken from tripod so star rotation happened.
I'm hoping "Attempt to Automatically Align Source Images" will rotate the frames then stack them, like DSS does.

[martyn_bannister]

Originally Posted by Bernoulli

Thanks Martyn.

Yes, I use scope - barlow - camera. I don't use a T-mount, I use the thingy shown below. Fits right where the eyepiece would.

Yes, that's what I call a T-mount or T-adapter. The "nose" which fits into the eyepiece tube has an M42x0.75 thread on it, which is the T-Mount onto which an adpater for your particular make of camera fits.