Moon too bright to focus.

[4th]

I have taken a few astrophotos using a camera only. I recently bought a small, second hand refractor and tonight tried mounting a mirrorless camera with a T-mount.

I aimed for the moon as an easy target, but the live view image was a burned out , featureless white disc, making focus a matter of guesswork. (Metering was set to " spot", but all settings gave the same result.)

As the lens has been removed, there is no iris to stop down and DoF preview is also unavailable.

 

Is there an easy way to "stop down" an overbright moon using a T-mount?

[ecuador]

I've never used a mirrorless, but, surely, you can switch to manual exposure and liveview will follow your settings, right?

(and sorry for calling you Shirley)

[Starlight 1]

Cut a bit of paper to fit inside the lens front and then cut a hole out of the paper , so let say lens 4" bring this down to 2" hole see if that works.

[ecuador]

Oh, but focusing on the full moon is not very easy, so in any case you might want to do your focusing on a bright star instead. But you'll still need manual exposure.

[happy-kat]

Manual mode, Fast exposure and low iso. Try iso 100 and 1/250. 

[4th]

1 minute ago, happy-kat said:

Manual mode, Fast exposure and low iso. Try iso 100 and 1/250. 

Did all that. All manual. 100 ISO. Shutter speed has no effect on what's on live view. Depth of Field indicator would have- if there was a lens in place. I've been going through camera menus , but can't get it to darken without an f stop setting, as the (non existent) lens is effectively wide open.  Passing cloud worked, but not ideal...   Dimming the camera screen had no effect . The pinhole idea might work, but sounds very fiddly.  I was hoping for something really obvious that I had overlooked. 

[JemC]

What camera are you using,

[4th]

25 minutes ago, JemC said:

What camera are you using,

Olympus OMD EM1.  Reading the manual now...

In fact, the electronic viewfinder doesn't dim when the DoF preview button is pushed, because the electronics crank up to keep the brightness constant, but it does show the change in focus.

It's possible to get the Dof button to lock down so it will darken to the chosen f number with a lens on, but with no lens in place, it does nothing. Happy-Kat's thought that liveview brightness would follow manual settings is correct for DSLR's but doesn't seem to be true for mirrorless. Too clever by half.

 

I think I got it. Following up on Happy Kat's comment, I found that "Live view boost" was turned on. That's what keeps the screen brightness constant, I think. It is now darkening as expected when shutter speed goes up.  I'll go try outside if the snow hasn't started.

 

Thanks for all the replies. You smacked me upside the head and got me thinking.

 

 

[JemC]

i used to have Panasonic mirrorless, only tried it once with telescope, i was able to change the settings in manual when connected to scope,
not sure how the Olympus works, sorry i can't be of more help

I do know you have quite a good setting on that camera though, check this site out,

 http://www.creativeislandphoto.com/blog/olympus-live-composites-star-trails

[4th]

Yes. Turning that setting off worked. This probably isn't the greatest moonshot in history, but it is blowing a 40-50 mph wind outside, so a bit of shake is unavoidable.

[Starlight 1]

Well done looking good PS I stay inside lol

[johnfosteruk]

Cracking shot for a single frame. You've got some nice crater detail on the western limb and the exposure is just about right for me

 

[4th]

Thanks. I'm quite chuffed with my first telescope pics. Fixing that illumination problem made focussing possible. Too many menus on the EM1.

Quite nice to have the onscreen view though,  instead of bending over an eyepiece. I must try wifi via  a tablet .

This close to full moon is  not, I expect, the best time to expect much relief detail. We'll see how the rest of the month goes.

By "single frame" I assume you mean most moon photos are composites of some sort? I've tried stacking wide frame night sky shots (with not great results) - but is it also  worth doing with the moon?  I can't get higher magnification than this, on prime focus , so I had supposed single frame was the only possibility. I must do some reading.

 

[johnfosteruk]

18 minutes ago, 4th said:

By "single frame" I assume you mean most moon photos are composites of some sort? I've tried stacking wide frame night sky shots (with not great results) - but is it also  worth doing with the moon?  I can't get higher magnification than this, on prime focus , so I had supposed single frame was the only possibility. I must do some reading.

It's not so much about magnification as preserving detail through the 'seeing' 

You may have noticed the view wobbling, like heat haze on the road on a hot day. This is the same thing - atmospheric turbulence boiling your photons into soup!! Also in cameras you have noise, like grain in your old film cameras.

The abbreviated version is capture many frames of the same image, 'stack' them in software to average out the noise and piece together the good sharp detail. Have a look through the lunar imaging board for examples of what can be done (and to be fair the same principle applies to all astrophotography, not just lunar)

The longer (and well worth reading version) is here courtesy of SGL member JamesF

[4th]

Thanks for that.  The principal problem tonight was vibration due to wind. The telescope is a Starlight 80 (£60 from a charity shop) and pretty light, so it was bouncing about a bit. Earlier, I had some weird shimmer which turned out to be hot air from a neighbour's chimney. That's before we even think about sensor noise and Micro four thirds sensors!

I'll have a read of that link.

Thanks again to everyone. It's great to have willing help out there.

[mattd85]

Nice work