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Another - what causes this?


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I was out the other night even though the cloud was thick: Desperate to grab a few shots I turned to the moon. The image below is a single frame taken using a 460ex mono. No filter used. Exposure was 0.001 sec. No binning.

A simply auto stretch was applied in PixInsight, no other processing.

What has caused the strange lighting effect?

Is it IR reflection as I haven't used an IR filter?

post-15911-0-03886500-1450713878_thumb.p

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  • 3 weeks later...

It isn't glare, it's electronic. Your CCD has anti blooming gates which stop bright stars producing bleed lines running vertically downwards from them. 'Scientific' CCDs don't have these and give a more linear response but do give bleed lines from bright sources. The moon is so bright that the anti blooming is being defeated. I've always found this when I've tried to use a deep sky CCD camera on the moon. You could try an Ha filter. This would not only block a lot of the incident light but the surviving light would be of long wavelength and less distorted by the seeing. After that you could try an aperture mask. You simply have too much light for the camera which is, after all, optimized for capturing the almost lightless objects out there! I have to say that, while I've seen this quite a few times, I've never been minded to try very hard to overcome it and never have. I've always settled for a fast frame camera on my rare lunar excursions.

Olly

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That's interesting, Olly. I never knew that!

Most people use webcams or dedicated planetary cams for the Moon and planets as they're so bright. These cams take vids made up of short exposures which you then stack in, say, Registax. Or you can use a DSLR, especially if it has video mode, but stills can be very successful too.

Alexxx

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You could try turning down the ISO setting on your DSLR, so that you actually get an under exposure. Even when I shoot the moon through a normal lens I would chose a maximum of 400 ASA, preferably 100 ASA and at least 1/400th at f11. Through a scope I would be down at 1/4000th at 25 ASA. If I could. If not. Maximum shutter speed with the lowest ASA number and then use the +/- to take it at least to -2 under expose. If it's too dark try adjusting it back a bit.

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You could try turning down the ISO setting on your DSLR, so that you actually get an under exposure. Even when I shoot the moon through a normal lens I would chose a maximum of 400 ASA, preferably 100 ASA and at least 1/400th at f11. Through a scope I would be down at 1/4000th at 25 ASA. If I could. If not. Maximum shutter speed with the lowest ASA number and then use the +/- to take it at least to -2 under expose. If it's too dark try adjusting it back a bit.

The camera in use is not a DSLR ...

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It isn't glare, it's electronic. Your CCD has anti blooming gates which stop bright stars producing bleed lines running vertically downwards from them. 'Scientific' CCDs don't have these and give a more linear response but do give bleed lines from bright sources. The moon is so bright that the anti blooming is being defeated. I've always found this when I've tried to use a deep sky CCD camera on the moon. You could try an Ha filter. This would not only block a lot of the incident light but the surviving light would be of long wavelength and less distorted by the seeing. After that you could try an aperture mask. You simply have too much light for the camera which is, after all, optimized for capturing the almost lightless objects out there! I have to say that, while I've seen this quite a few times, I've never been minded to try very hard to overcome it and never have. I've always settled for a fast frame camera on my rare lunar excursions.

Olly

Phew! I thought I had a serious equipment failure on my hands. I was using my ED80 scope with the aperture reducer on the front (the cover with the 50mm smaller opening). With all these cloudy nights I just wanted to photograph something. The evening wasn't wasted though. 

I've now learned that a 460ex without filters is not good as a lunar camera  :icon_biggrin:

That's interesting, Olly. I never knew that!

Most people use webcams or dedicated planetary cams for the Moon and planets as they're so bright. These cams take vids made up of short exposures which you then stack in, say, Registax. Or you can use a DSLR, especially if it has video mode, but stills can be very successful too.

Alexxx

I do have guide camera which I could use. Just never quite got round to it yet. So many targets to choose and so few good, clear nights.

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