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venus

I took a picture of Venus through my telescope (Celestron Astromaster 130eq) using a 10mm lens with a Barlow lens.

The picture isn't really good since I took it with my phone and I still don't have a camera.

Also, it isn't a matter of focus since I fiddled a lot with it.

I don't know what to do to clear the image and reduce the brightness. Should I use a filter? and which one?

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  • $\begingroup$ You've pretty much discovered digiscoping . If you google that term, you may find advice on mounting techniques to optimize photographing with a phone camera. $\endgroup$ – Carl Witthoft Apr 11 '18 at 19:18
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    $\begingroup$ Download an app such as Camera FV5 or so. You can adjust ISO and exp. time. I was able to get Saturn (although what was in the eyepiece and in the pic were not even comparable. But I was just hovering the phone . I think with a mount one can get relatively nice results. $\endgroup$ – Alchimista Apr 12 '18 at 8:22
  • $\begingroup$ Wait for Venus to get closer. At greatest elongation, its angular size will be 2X what it is now. $\endgroup$ – Mike G Apr 13 '18 at 0:25
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Phone cameras just aren't designed to take good photographs of astronomical objects. The sensor is too small and the configuration options (like exposure time) are minimal.

For astronomical photography, a better option is to use (the body of) a DSLR (or the analog version); the lens is provided by your telescope. Another option is a specialized CCD camera.

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  • $\begingroup$ Meh, phone cameras aren't designed to take good photographs of anything. $\endgroup$ – John Duffield Apr 30 '18 at 21:24
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It is possible to get usable photos of astronomical objects using a camera phone, but as @Glorfindel and @Jee say, in this case you need to reduce the exposure time. There are apps that give more control over the camera than the standard app (well that's true for iphones, not sure about others), which are free, or not expensive.

Using a filter would probably not work because the standard camera app is probably averaging the brightness over an area centred on Venus, so will likely just lengthen the exposure to compensate, getting you back to where you started.

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Your mobile phone will not give you control over exposure and focus and the image will be most likely overexposed if you took it against a dark sky.

Overexposure causes saturation of the pixels on the sensor, i.e. pixels that get the same photon count (the maximum possible value) but from points of different light intensity. Detail (Venus has none anyway) is lost on your sensor and cannot be recovered by image manipulation tools. There is nothing you can do in that case.

Only if you can set the exposure (and focus) manually then you will be able to get a usable image. If that is not possible you could try shooting when the sky is still light to force a shorter exposure time.

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  • $\begingroup$ Or sneak a flashlight beam onto the phone to produce a more-or-less uniform background. Pretty much guaranteed to not work well. $\endgroup$ – Carl Witthoft Apr 11 '18 at 19:19

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