PDA

View Full Version : Moon shots 101 - help.



Fat Tone
22nd June 2005, 01:26
Last night the sky was fairly clear, the moon low and large just above the roof tops across my street so I thought I'd have a go a taking a pic using my binoculars.

I put my Kodak CX7540 on a small tripod on the window sill and held the 10x50 binoculars (focussed on infinity) leaning against two edges of the open window frame - far from ideal I know but I had no other way of supporting them.

With the camera on wide-angle and fully auto I got shot 1 below. Maximum zoom got shot 2.

I then swiched to centre-exposure and centre-focus, which produced shot 3 and I couldn't get it any better.

So, how do I improve this? I think it is an auto-focus problem but I wasn't able to capture focus and then put the bino's back as it is difficult to find the moon with that magnification.
I guess I could fix the bino's, and move the camera/tripod and use the timer? Or am I just aiming too high here (pardon the pun).

BTW, originals are ~4MP, shots below are small jpgs but I think show all the problems well.

az
22nd June 2005, 02:49
You will not really be able to get it much better. The optics of the binoc aren't made for this, atmosphere disturbance (especially in urban areas) etc. add their own problems. There is a reason good moon photos are relatively rare :)

If you really want to be masochistic, fixate the binoc and cam to something, use aperture priority mode so you can stop down a bit (lens is sharper then - on my Dimage 7i F5.6 is about the sweet spot), use the lowest ISO available and use the self timer. Then go see if the exposure was so long the moon moved too much during that time, creating blurriness. Open the aperture a bit and try again.

BTW, it is a common mistake that the moon is "nice and big tonight". It's an optical illusion. Your eyes can't measure the distance to the moon, and your brain uses the context of the image to guess the distance - and thus changes the size. This is why the moon in unaltered images is never as big as you sometimes see it with your own eyes. Try this: make a fist and open it slightly, so that you can look through the hole created by your thumb and index finger, then look at the moon through that - it'll look smaller because your brain has no context to put it in, assumes it cannot be farther away than the horizon (the farthest you can ever see on earth), and therefore must be quite small (because it creates only a small image on the retina and isn't far away) - so it creates only a small image of the moon for your conscience. When, however, the moon is directly above house roofs, near the horizon, etc., the brain assumes that it must be quite far away and therefore must be really big to still project an image of that size on the retina - so you are presented with a blown-up image of the moon - look at it through your fist or through a toilet paper tube or something, and it'll be small again.

AZ

VJ
22nd June 2005, 03:39
The last one looks pretty good from an exposure point of view. It seems only to have suffered some motion blur...

The sweet point of most lenses is with the aperture set 1/4 away from wide open (i.e. on my lens, the aperture ranges from 2.8 to 33; the sweet point is at around 7-8).

This is what az is referring to, aka "the Moon illusion":
http://www.space.com/scienceastronomy/solarsystem/bigmoon_000105.html
(google has many more links)


Jörg

Dr Mordrid
22nd June 2005, 07:50
And this is what you get with a Meade Deep Sky Imager Pro through a small spotting 'scope;

http://digitalvideo.8m.net/moon-meade.jpg

$399 with color filters for doing deep sky color shots with the big 'scope.

Dr. Mordrid

Fat Tone
22nd June 2005, 07:53
I should add that viewing the moon directly with the Binos is much better than the pic. Its the camera/bino interraction that I think is my main problem.

If I get that quality Doc, you'll hear me cheer from here :)

Jon P. Inghram
22nd June 2005, 11:37
I took this moon picture with a Nikon 4300 hand-held and an old Celestron Cometron CO-62 with a 25mm eyepiece. If I remember correctly I set the camera to manual focus and moved it out to infinity. I then focused the scope while holding the camera up to the eyepiece until the image looked crisp (the camera has a manual focus assist mode where areas of sharp focus are highlighted on the display.) Looking at the EXIF data it seems I had the camera set to automatic exposure control too.

Fat Tone
22nd June 2005, 11:45
Nice!

I shall be having another try tonight (weather looks fine, moon still pretty full) with the following improvements:

Binoc reasonably well clamped
Camera in Landscape mode - no auto focus :) Didn't realise that last night - Doh!
Use of EVF (well rear LCD) to check focus into Binoc
timer operation
practice on distant object in daylight
May also try B/W mode.


Still won't be anywhere near as good as Jon's, but should be fun.

Fat Tone
22nd June 2005, 16:05
Best attempt so far...a bit of an improvement but not outstanding.

Fat Tone
22nd June 2005, 16:51
My final attempt. No oil painting ;) but perhaps not bad for a £150 camera and some cheap binocs.

az
22nd June 2005, 18:53
Not bad :) Clearly, the optics are what's limiting you.

AZ

VJ
23rd June 2005, 01:08
I agree...
Given the set-up you use, I'd say that is a great picture! :up:


Jörg

Fat Tone
23rd June 2005, 01:15
Thanks Guys. It is frustrating that I cannot get it any better when I can see a much more detailed view of the moon by holding the binocs to my eye. Focussing them into the camera using the rear display is surprisingly tricky, and the moon is actually filling quite a small portion of the view so not that many pixels are being used. I considered taking my A2 home (bigger zoom, higher res etc etc) but I think that would present more physical problems with mounting and coupling.

Perhaps someone will buy me a telescope for my birthday and I can do a lot better then :)

Edit: The moon was very low in the sky and my line of sight was straight over the nearest large city. Hopefully it will be higher come September so the atmospheric path will be shorter and less turbulent too :)

Jon P. Inghram
23rd June 2005, 10:30
You can try using blind deconvolution to sharpen the picture, Unshake (http://www.hamangia.freeserve.co.uk/index.html) for example.

VJ
24th June 2005, 02:06
Not really a problem for the pictures posted here, but interesting for some:

The techniuqe of stacking images:
http://www.tawbaware.com/is_help/imgstack_help.htm

Usefull if
- camera has limited long exposure time
- camera exhibits lots of noise
- required exposure time is hard to predict (just stack and see what happens, you can omit one or two if necessary)


Jörg

Jon P. Inghram
25th June 2005, 08:30
Don't use B&W if you're using a achromat refractor, use color and pick the color channel or channels that are best focused. On my picture red and green were much better focused (you can see the yellow around the rim of the moon, the blue image was smaller.) After deconvoluting the full sized image it didn't do too bad.

Fat Tone
7th June 2006, 00:41
A good friend of mine has just got himself a 6" newtonian on a very sturday mount and a manual controller, with plans for a full GOTO system. He put his Toucam on the back and stacked a few images to produce these. Total spend so far £500.

az
7th June 2006, 01:56
Very nice!

Dr Mordrid
7th June 2006, 10:20
:up: :up:

Dr. Mordrid

KvHagedorn
7th June 2006, 12:20
What type of Binoculars are you using? I remember thinking my 10x50 Bushnells were all fine and ok, but then got some Celestron 9x63s, and WOW.. what a difference good optics make! That's why they cost so much more.. and people pay it.