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I can't get my camera to expose properly.

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#1 tpaairman

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Posted 25 May 2019 - 10:14 PM

I have a Celestron 127EQ, which I know is not exactly the best telescope to get.  I found out many of it's shortcomings after the return period was past.  But, as an example of my problem, I can see Jupiter decently well looking through the eye piece.  It's small, but it's there and you can clearly see the 4 main moons.

 

The problem comes in when I try to use my camera.  I have a Nikon D3300, but have recently bought a Sony A6000.  With the telescope, the Nikon was heavy and would cause the telescope to move from it's weight a bit, so framing was fun.  And being a DSLR, the mirror movement didn't help. But even when all was steady, I could never seem to focus in looking though the view finder.

 

With the Sony, it's better at focusing, and it doesn't move the telescope, however I can't seem to get the exposure.  No matter where I adjust it, it's either too bright to where it's blown out, out it's way to dark to see much.  It seems has to be a matter of adjusting the shutter speed and ISO.  The aperture is fixed on the telescope.



#2 m1618

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Posted 25 May 2019 - 10:33 PM

Depends on light pollution too. I have mine set at ISO 800. 30 seconds. It will/can look blown out... before stacking processing etc.
Another thread for examples: https://www.cloudyni...00-first-light/



#3 sg6

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Posted 26 May 2019 - 01:15 AM

Post reads that you are trying to obtain a single image? Is this correct.

If so then it also reads that you are trying for a single exposure of Jupiter.

 

Planetary images (Jupiter) is generally done by getting a short, 30-60 second video. Basically lots of short exposure frames (1/30 sec).

This video is fed into something like Registax.

Then you identify what appears to be the best frame.

You then tell the software to stack the closest 200 frames that closest match the "best" frame. 200 is an example value only, but seems reasonable.

Then the software stacks what should be the best 200 frames, you do not stack all the video frames as that means stacking good and bad frames.

 

Single shot of a DSO object is sort of similar. Getting one image is difficult so you take say 30 exposures each of say 20-30 seconds. You then load these into Deep Sky Stacker, and stack them. This really needs an intervalometer and you set DSLR to "B" for exposure length. Then set the Intervalometer to a short Delay of 10 seconds (to put it somewhere after hitting the Go button). Set an exposure length of 20-30 seconds, set a Wait of 15-20 seconds and set a cycle of 30 exposure. ISO 400 or 800, center target, focus, press Go. Wait 30 minutes for it all to complete. Oh yes, buy a memory card for this, it makes life easier.

 

That is the 2 basic options. The post reads like "photography", where you take a shot - landscape, wedding, etc. AP is not that approach.

 

If you are doing wither of the above approach then I guess you need to supply greater detail.



#4 tpaairman

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Posted 26 May 2019 - 03:15 AM

I know that in order to get a good final image I would need to take quite a few and process them.   But that won't do any good if I end up with 100 picts of a blown out, overexposed white disk.

 

Tinkering with this further tonight, I think I'm getting there.  I got a few shots that looked quite dark on the screen when I took them, but when I looked at one of the shots and zoomed in, it's not far off.  But I'm still not sure how to get the best focus since I can't really see it when I take the shot.  Yes I need to process, but I also need to focus as best I can to begin with.  Little bits at a time I guess.



#5 t_image

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Posted 26 May 2019 - 05:22 AM

I have a Celestron 127EQ, which I know is not exactly the best telescope to get.  I found out many of it's shortcomings after the return period was past.  But, as an example of my problem, I can see Jupiter decently well looking through the eye piece.  It's small, but it's there and you can clearly see the 4 main moons.

 

The problem comes in when I try to use my camera.  I have a Nikon D3300, but have recently bought a Sony A6000.  With the telescope, the Nikon was heavy and would cause the telescope to move from it's weight a bit, so framing was fun.  And being a DSLR, the mirror movement didn't help. But even when all was steady, I could never seem to focus in looking though the view finder.

 

With the Sony, it's better at focusing, and it doesn't move the telescope, however I can't seem to get the exposure.  No matter where I adjust it, it's either too bright to where it's blown out, out it's way to dark to see much.  It seems has to be a matter of adjusting the shutter speed and ISO.  The aperture is fixed on the telescope.

 

I know that in order to get a good final image I would need to take quite a few and process them.   But that won't do any good if I end up with 100 picts of a blown out, overexposed white disk.

 

Tinkering with this further tonight, I think I'm getting there.  I got a few shots that looked quite dark on the screen when I took them, but when I looked at one of the shots and zoomed in, it's not far off.  But I'm still not sure how to get the best focus since I can't really see it when I take the shot.  Yes I need to process, but I also need to focus as best I can to begin with.  Little bits at a time I guess.

 

So you have the perfect storm of things going against you. Here's some things that will help:

 

focus:

reminder: using an eyepiece and then replacing a camera into prime focus won't be the same distance to achieve focus.

Do know: once focus is achieved on one object (depending on quality of focuser mechanism) you should be able to swing to any other stellar target and it should be in focus. Since you have a newt, you should consult that section of CN for tips (like collimation, etc)...

People complain about focusing on a difficult target all the time and I just ask why not focus on an easy target to achieve focus with the scope? Like a bright Moon or a clear set of stars? Then without molesting the scope so it falls out of focus, just point it to desired target.

Sure scopes with mirrors have focus change issues due to thermal drops, but you shouldn't be losing focus so quick you have to continually worry about focusing. Use the focus magnify feature to assist.

  • make sure scope in collimation
  • focus on easy target in sky, then point to desired target
  • use magnify assist in live view,
  • video mode with a high ISO is usually helpful to help focus (remember you can change settings for your target later)

 

Planetary imaging:

this section of CN isn't usually the right location. Solar system imaging is the better section that discusses how to image planets.

That's because (as explained above post) you need really fast exposures of planets to freeze seeing distortion.

DSO imaging with a DSLR/MILC is a completely different method where a longer exposure is helpful.

You are also misunderstanding the limitations of a camera. Jupiter is very bright. It's moons are very dim.

Your eye (and dilating pupil effect) can see about 22 stops(steps of bright to dark) changes of light. So you can see Jupiter and the planets in an eyepiece. The limits of the stops of light is called dynamic range.

The camera sensor can (with RAW file) and properly exposed can resolve at most 14 stops of light. Any display, especially the LCD on the camera, only gives you 7 stops of light. This means you aren't going to see in live view a properly exposed Jupiter with a properly exposed set of moons in your live view. Either Jupiter will look too exposed, or you won't see the planets.This is also because the display is rendering in a crushed 7 stops of light mode (sRGB,Rec.709).....

If you took a properly exposed RAW image (max 14 stops) and color corrected it well, you may be able to squeeze the bright but well exposed Jupiter and the dim but well exposed moons into the 7 stops of dynamic range limit your computer display has....(hence the fancy HDR tvs promise the hope of a few stops more of range).....

I have been able to project a properly exposed Jupiter with properly exposed planets onto a HDR TV in live view with the help of a computer, a capture card and software that live color corrects. But you cannot do this well with a camera display....

 

A DSLR/MILC isn't an ideal planetary camera. Better ones have small pixels (=planet is larger), they have fast framerates, and they record in raw AVI frames that preserve the larger dynamic range your sensor can do.

 

Exposure:

remember for Jupiter with moons, you have to split the difference so you will have a good exposure to edit---but it may not look well exposed in camera except for maybe histogram reading (if you are versed in how to use such)......

You can however make the best of your equipment:

1. Start by switching to VIDEO mode (manual) --filmstrip icon (M), starting with highest ISO [with proper camera settings---I forget the menu options at the moment but there are framerate compensation and display mode that make this difficult. ALSO use fully manual settings for VIDEO mode. With the Sony's display for focus and exposure works best using this mode to view, then you can switch to still mode to take images....

2. frame the blown-out planet and the small moons properly in display.

3. set the exposure for 1/30 sec. (with give you realtime reaction) also best compromise to freeze atmosphere but capture faint moons.

4. drop your ISO until Jupiter barely stops being blown out.

5. Switch over to Still image (manual) *full manual..

6. take a sample exposure.

7. Look at the exposure with focus magnifier feature on still image review. Look at Jupiter to see if it is just not blown out.....Look to see if you can barely make out the moons [that are usually visible with highest ISO and 1/4 sec shutter....]

8. enable the "view histogram"

9 take the RAW image into your computer and see if you can color correct it (brightness/contrast) in photoeditor like Adobe Camera RAW Photoshop so Jupiter and the moons are exposed properly. You may have to mask to adjust separately, etc.

The best exposure will give you the easiest to edit image.

10 you will have to experiment with what works with your setup, use the histogram for tips on how exposure is working... Try to keep your exposure in ranges of 1/120 (fastest is idea) with the lowest ISO you can manage.....1/30sec will work.If you need longer for moons, then so be it...

 

You can otherwise expose for moons and Jupiter separately in different images and then just mask/composite them together...

In planetary, a single properly exposed image should have all your subjects visible.

The stacking of quick, continuous still images improves sharpness and detail.

Using video to capture lots of video frames to stack isn't ideal (although proper usual method of planetary imaging)

with the a6000 due to resolution loss. Better would be a camera with 4K video, but even then you are trading off getting short frames fast to reduce atmospheric bubbling, while losing the advantage of the resolution gain that stills will give you, though stills are at the expense of not being able to take as many stills in the same short amount of time (remember features on Jupiter change over a matter of minutes (planet rotation) so you can't play around.......So take a bunch of stills quickly!!!!

 

For DSOs on the otherhand, a single image usually won't look properly exposed. Even with editing in software, for DSOs, stacking will bring out faint details with a completely different stacking software application....

 

Note this "DSLR" section of CN will have the best advice for taking DSOs,

for more on how to do planetary the "Solar system Imaging and Processing" will have the best experts with the best advice to help...

 

Here's a guy that is using an a6500 and is getting some good exposure video of Jupiter and moons:

https://www.youtube....h?v=yau9JTL6SQU

(fast forward to see how he adjust settings live)

(remember you can't copy settings as he might have a different scope)...

Note he lives in FL which has a "seeing" advantage....

 

Cheers!


Edited by t_image, 26 May 2019 - 05:23 AM.



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