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Help! What did I do wrong?

 
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scitch



Joined: 29 May 2010
Posts: 461

PostPosted: Mon Jun 14, 2010 11:26 pm    Post subject: Help! What did I do wrong? Reply with quote

So, I was really looking forward to this stack, because this is a very strange spider (to me) and looks great under the microscope. But, the DOF through the camera is much smaller than the scope. I ended up doing a stack of about 135 images and it came out terrible. Usually, my stacks look pretty much like what I see through the microscope. This one does not. I'd love some suggestions. It's not so much the stacking software that was the problem, but the images themselves didn't look great.

Here are a few of the problems. With each change of focus, the subject moved slightly. Eventually, it reached a point where I had to re-center it. Is that the correct thing to do or was I trying a subject that was too deep?

Second, it looks like there's a meteor shower going on. What's with that? I've had some dark dust effects before, but there are dark, light, and everything in between streaking through this picture.

Third, what are those giant globes that it looks like this spider is holding?

Fourth, I couldn't identify any compound eyes. Are those clear sacs just above the globes its eyes?

This picture is a stack of 8 photos taken through a trinocular scope at around 10X (http://www.bhphotovideo.com/c/product/573469-REG/Konus_5426.html). The Sony a200 camera was set at F1, ISO 400, 3.2 second exposures lit with a halogen bulb from above. This one turned out better than the big stack, but not very close up. There's an unacceptable amount of dust streaks, but they are all dark. Is it possible to tell by the pattern whether they're on the eyepiece or the sensor?




This picture is from a monocular microscope at 40X with the same camera settings as above. The microscope is a couple generations older than this one: http://sciencekit.com/boreal-cmos-digital-microscope/p/IG0029981/ but I did not use the built in < 1 MP camera. I cropped it a little and auto-leveled it in Photoshop CS. It was lit with the halogen light from the other scope through a tissue paper tent with a reflector on the other side.



I tried to go in closer on the eye structure and I'm stacking that right now, but it doesn't look good.
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scitch



Joined: 29 May 2010
Posts: 461

PostPosted: Tue Jun 15, 2010 12:23 am    Post subject: Reply with quote

Here's the deeper image that I mentioned above. Clearly, there are lighting issues. But the rest isn't what I was hoping for either.



Thanks in advance,
Mike
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rjlittlefield
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Joined: 01 Aug 2006
Posts: 18866
Location: Richland, Washington State, USA

PostPosted: Tue Jun 15, 2010 12:33 am    Post subject: Reply with quote

Quote:
With each change of focus, the subject moved slightly. Eventually, it reached a point where I had to re-center it. Is that the correct thing to do or was I trying a subject that was too deep?

I'm not familiar with your type of scope. I'm under the impression that with most trinocular stereo scopes the field does not shift sideways as you change focus, but I gather that with this one it does. In that case there's not much recourse except to keep recentering the specimen. It would probably be better to do that more often. Otherwise you're going to lose a lot of frame space to streaky edges. Also those dust streaks get longer the farther you go between recenterings.

Quote:
Second, it looks like there's a meteor shower going on. What's with that? I've had some dark dust effects before, but there are dark, light, and everything in between streaking through this picture.

Any pixels that are consistently dark or bright in each frame will turn into streaks. Dark spots (streaks) are typically dust. Bright spots (streaks) are typically "hot pixels" that are due to electrical leakage on long exposures. The longer the exposure, the brighter the hot pixels, and the more of them will show up.

Quote:
Third, what are those giant globes that it looks like this spider is holding?

Those look like sperm packets. In spiders mating is a two-step process. First the male produces sperm from his abdomen and transfers it to his palps. Then he transfers it from the palps to the genital opening of the female.

Quote:
Fourth, I couldn't identify any compound eyes. Are those clear sacs just above the globes its eyes?

Spiders don't have compound eyes. Their eyes all have single lenses. The best of them (jumping spiders) have a fairly high resolution retina that sits behind a large lens to give good acuity. More typically they are low resolution. I'm not sure which "clear sacs" you're talking about, but I'll guess that the answer to your question is "yes".

Quote:
Is it possible to tell by the pattern whether they're on the eyepiece or the sensor?

Once the images have been shot, it's hard to tell. Before then, the easy method is to rotate the eyepiece and/or the camera. If the spots always stay in the same place, then they're on the sensor; otherwise they're someplace else.

--Rik
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