Landscape Of Cheese

David Mitchell

David Mitchell

Well-Known Member
Hi all,

I have decided to get into astrophotography (just to be a bit different lol) you might have seen a thread up a bit back for me looking for a long lens for solarphotography, I plan to get a telescope soon and bolt the NEX onto it.

I don't have my telescope yet so I made do with the longest lens I have, my Tair 300mm, I then stacked two 2x teleconvertors onto it and bolted it to my NEX tonight, here is what I got:



Wonder what sort of cheese its made from :D
 
Brian Moore said:
What was the ultimate focal length...? Was it 1200?...Or what...?
Click to expand...

Erm, lets try and work this out lol although not ideal I didn't want to crop the frame too much and I found that at this magnification I got the most amount of moon on the sensor.

So its a 300mm lens, 2x tele makes it a 600mm, then another 2x tele makes it a 1200mm, then the 1.5x crop factor would make it a 1800mm equivalent - for once something useful with crop sensors!

The image is 'ok' and more than I would have actually hoped for on my first attempt, the moon does move rather fast through the frame at this focal length!

This was shot at quite a high ISO (6400) when I get my telescope I will be able to drop it quite a bit. Also the moon is a very very bright target as its in full sunlight, I actually shot the later images with a -2EV setting as I don't have a moon filter (basically an ND filter).
 
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It sounds like you are going round in circles a bit there ...

Cropping from less telecomverters will give you more resolution in the final image than your method. That is a fact!

Also, you don't want to be using an nd filter if you are having to use such high ISOs ...

Less 2x tele converters will also mean higher light gathering power which will allow the use of lower ISO... Which will increase your potential for resolution!

Do the experiments, you will see what I mean!
 
Good effort though Dave.

I have a x2 tele con for my Zuiko lenses, and they are as much use as mud flaps on a snail in terms of maintaining a decent level resolution. I use my tele cons less than I find the urge to take my mask off. However, thinking openly, it's certainly a matter of preference regardless.

By maxing the ISO like you have done will certainly decrease the quality further. Slightly confused why you've done that if it is the quality your trying to maintain.
If it's distance you are prioritising over res.... You've got it in one.

Out of curiosity, how long was the exposure time?

Looking forward to the results with the telescope.
 
I know that the image is a bit degraded, ISO 6400 isn't the highest the camera can go to - this image was kind of a test to see what I could do with a basic 30 year old tele lens, shutter speed was 1/250 I believe, I think this shot was taken using the burst stacking mode on the NEX which fires multiple frames and then stacks them (much like HDR but without changing the exposure). My tripod isn't really stable enough at this magnification though, the telescope I will be getting has a tripod that should do a better job (although not high end).

I will clean my lenses a bit more and try on another night to see what I can manage - I actually enjoyed just pointing the camera at a dark bit of sky and run an exposure of say 3 seconds, really interesting to see what faint stars you could see.
 
David Mitchell said:
shutter speed was 1/250 I believe, I think this shot was taken using the burst stacking mode on the NEX which fires multiple frames and then stacks them (much like HDR but without changing the exposure)
Click to expand...
Without changing the exposure?... You've completey open the top of my cranium, grabbed the contents, threw them in a blender for 3.26 hours.... And poured them back in...... :)

Is this not called bracketing?....... With the benefit of stacking what's been bracketed? :/
 
David can I suggest that I don't think it is necessary to treat the moon as a dark subject and up the ISO or use long exposures, as you say the moon does move rather quickly, treat it as a daylight shot, ISO 100/200 f5.6 I thnk you will get sharper results, I don't have any examples but have shot at these settings with a 300 and got reasonably good results after a crop of course....
 
Dan Cattermole said:
Without changing the exposure?... You've completey open the top of my cranium, grabbed the contents, threw them in a blender for 3.26 hours.... And poured them back in...... :)

Is this not called bracketing?....... With the benefit of stacking what's been bracketed? :/
Click to expand...

The camera takes identical images with the same exposure settings, its used on telephoto shots where you might get a bit of wobble - basically it stacks the images together to get a non wobbly image, example is if 1 of the frames is slightly blurred but has detail in 1 section it will use that part of that image and stitch it together with another part of another image.

@Kev - the issue with using the teleconvertors is that it dropped the f stop down quite a bit so would be shooting at somewhere like f18 even with the lens shot wide open, this is why the ISO is bumped up a fair bit, shooting it at just 300mm the moon is a very very small part of the frame. Its why I was looking at getting a longer lens - did have a look at some of those mirror lenses, however I will be going with a telescope shooting a focal length of 1000mm f5 so will be much better than maxxing out a shorter lens!
 
David Mitchell said:
The camera takes identical images with the same exposure settings, its used on telephoto shots where you might get a bit of wobble - basically it stacks the images together to get a non wobbly image, example is if 1 of the frames is slightly blurred but has detail in 1 section it will use that part of that image and stitch it together with another part of another image.
Click to expand...

David... I think your secretly from the moon. o_O
Now we are onto wobbly images?? You've completely lost me.

Is that what this 'burst mode' does then?
 
Dan Cattermole said:
David... I think your secretly from the moon. o_O
Now we are onto wobbly images?? You've completely lost me.

Is that what this 'burst mode' does then?
Click to expand...

At that level of magnification any tiny tweak would blur the image slightly, stacking images are used quite a bit in astrophotography, usually what happens is a video is taken instead, and then a stacking program is used to stack the frames from the video into a single composite image.
 
I thought image stacking in astrophotography was largely a noise reduction exercise?
Wobbly images can be avoided by using a good tripod and a cable release etc
 
Is this slightly better? 1000mm focal length F5, Sony NEX 3a, ISO 200:

 
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