Astrophotography

[Shadowy Man]

I could be completely wrong but I thought that one of the points to stacking multiple images was that real objects like star will be consistent but noise totally random and so easy to filter out in processing.

Yes. That makes sense with digital imagery. But I am trying to understand why you’d take four separate exposures on one piece of film using 1/4th of the total needed exposure time, as Jimmy said, and expect that to be different than one exposure of the total time. I gave one possible option but I don’t know any others.

 

[Loren Pechtel]

I could be completely wrong but I thought that one of the points to stacking multiple images was that real objects like star will be consistent but noise totally random and so easy to filter out in processing.

Yes. That makes sense with digital imagery. But I am trying to understand why you’d take four separate exposures on one piece of film using 1/4th of the total needed exposure time, as Jimmy said, and expect that to be different than one exposure of the total time. I gave one possible option but I don’t know any others.

There would be no reason to.

Multiple exposures with film are done to combine different images, not for stacking.

 

[Jimmy Higgins]

Well, need to get extension tube for the telescope adapter. I'm just a bit short of out of focus. Battery also dead in camera, so I needed to charge it a little to test. Glad I did and didn't give up. I was able to get focus on the moon, but by holding the adapter outside the eyepiece area. I hate being stupid with the scope. Get the scope out, trying to polar align, it isn't there. It should occur to me that I haven't leveled the damn mount! But no, that'll take 5 to 10 minutes to remember.

I could be completely wrong but I thought that one of the points to stacking multiple images was that real objects like star will be consistent but noise totally random and so easy to filter out in processing.

Yes. That makes sense with digital imagery. But I am trying to understand why you’d take four separate exposures on one piece of film using 1/4th of the total needed exposure time, as Jimmy said, and expect that to be different than one exposure of the total time. I gave one possible option but I don’t know any others.

And for the record, I was throwing it out there and asking, not claiming it.

 

[Treedbear]

I could be completely wrong but I thought that one of the points to stacking multiple images was that real objects like star will be consistent but noise totally random and so easy to filter out in processing.

Yes. That makes sense with digital imagery. But I am trying to understand why you’d take four separate exposures on one piece of film using 1/4th of the total needed exposure time, as Jimmy said, and expect that to be different than one exposure of the total time. I gave one possible option but I don’t know any others.

There would be no reason to.

Multiple exposures with film are done to combine different images, not for stacking.

I'm totally guessing but maybe four separate exposures allows you to take full advantage of the film's or camera's dynamic range. Then the digitized data can be summed to obtain 4 times the sensitivity. Also, I'm not sure about film but with digital cameras I think random noise doesn't just contribute "background" noise but also contributes to the saturation of useful data points and therefore degrades the dynamic range over longer exposures. On the downside, for digital cameras readout noise will increase with increasing number of frames.

 

[Loren Pechtel]

There would be no reason to.

Multiple exposures with film are done to combine different images, not for stacking.

I'm totally guessing but maybe four separate exposures allows you to take full advantage of the film's or camera's dynamic range. Then the digitized data can be summed to obtain 4 times the sensitivity. Also, I'm not sure about film but with digital cameras I think random noise doesn't just contribute "background" noise but also contributes to the saturation of useful data points and therefore degrades the dynamic range over longer exposures. On the downside, for digital cameras readout noise will increase with increasing number of frames.

With a digital camera you take multiple shots without tracking the stars--each exposure will be in a slightly different position on the sensor. You align the images when stacking. The pixels representing the stars reinforce each other but the noise pixels do not.

 

[Jimmy Higgins]

Starting slow. I really need something to make the focus easier on the scope. Here is a picture of a large rock I saw orbiting the Earth. Also, officially I hate mosquitos.

 

[crazyfingers]

Speaking of the Moon, I took this photo with my camera last night. Canon Powershot SX50 camera.

 

[Jimmy Higgins]

Nice. I just found this article on low light ISO and sometimes where the noise comes from. I'm just programmed to use ISO 100, but with low light (or maybe longer exposure is more appropriate?) it is using too big a sieve.

 

[Shadowy Man]

Here's a daytime shot of the crescent Moon with Venus to the left of it. I had spotted Venus in the morning and noted its relative position to the Moon. That's how I was able to find it later in the day -- this photo was taken at about 12:45 my time. Tamrom AF 70-300mm lens at full zoom, ISO 100, F/7.1, and 1/500th second exposure.



I like how you can see how much greater the surface brightness of Venus is than the crescent Moon.

 

[barbos]

Speaking of the Moon, I took this photo with my camera last night. Canon Powershot SX50 camera.

View attachment 33780

I wonder if Saturn can be resolved by your camera,

 

[crazyfingers]

I don't know that I've ever tried Saturn with the camera. To try I'd have to look up where it is these days. For Jupiter I can tell that it's a disc and can see that there are moons. My guess is that Saturn might show that rings exist depending on the angle. Moons would look like stars. There would not likely be any colors.

It looks like Saturn can be seen in the early evening by the end of this year from where I am in the northern hemisphere. However it's on the other side of the sun at the moment so it would not appear as large as it would if it was on our side of the sun. Not sure what difference the distance would really make. But it will be another 15 years roughly before it's on our side of the sun. So worth a try come fall into winter this year.

I think that I looked at it back when I first got my Meade 6" reflector telescope. That was over 20 years ago. If I am recalling correctly it was a white oblong smudge.

 

[barbos]

I don't know that I've ever tried Saturn with the camera. To try I'd have to look up where it is these days. For Jupiter I can tell that it's a disc and can see that there are moons. My guess is that Saturn might show that rings exist depending on the angle. Moons would look like stars. There would not likely be any colors.

It looks like Saturn can be seen in the early evening by the end of this year from where I am in the northern hemisphere. However it's on the other side of the sun at the moment so it would not appear as large as it would if it was on our side of the sun. Not sure what difference the distance would really make. But it will be another 15 years roughly before it's on our side of the sun. So worth a try come fall into winter this year.

I think that I looked at it back when I first got my Meade 6" reflector telescope. That was over 20 years ago. If I am recalling correctly it was a white oblong smudge.

It's visible most of the time of the year and there is no need to wait for 15 years to get close to it. it happens every year and the difference is not that large,.

https://stellarium-web.org/

find it there and take the picture. It says closest approach will be around July 4 - 8.94 a.u.
And farthest 10.9 a.u. around February 4.

 

[Shadowy Man]

Saturn is about 10 AU from the Sun so it should vary from about 9-11 AU from Earth.

Wikipedia says the angular size of the disk will range from about 15-20 arcseconds, with the rings being almost double that across - actually wider than Jupiter’s disk.

 

[steve_bank]

What are all those dots? Camera noise?

Hard to imagine a 10 inch scope with a video camera is far better than astronomers had to work with.

I was never eally into it but I went to Stelaphane in Vt in the 80s and heard Dobson speak.

He made mirrors out of scrap Navy port hole glass and gave scopes away around SF.

 

[bilby]

Speaking of the Moon, I took this photo with my camera last night. Canon Powershot SX50 camera.

View attachment 33780

Why is it upside down?

 

[Treedbear]

Speaking of the Moon, I took this photo with my camera last night. Canon Powershot SX50 camera.

View attachment 33780

Why is it upside down?

You're upside down.

 

[barbos]

Saturn is about 10 AU from the Sun so it should vary from about 9-11 AU from Earth.

Wikipedia says the angular size of the disk will range from about 15-20 arcseconds, with the rings being almost double that across - actually wider than Jupiter’s disk.

Well, with 1" lens of typical long zoom camera I expect Saturn to be 2 pixels wide and rings twice of that. Just wonder if it can really be resolved as something other than a point object.

 

[crazyfingers]

Saturn is about 10 AU from the Sun so it should vary from about 9-11 AU from Earth.

Wikipedia says the angular size of the disk will range from about 15-20 arcseconds, with the rings being almost double that across - actually wider than Jupiter’s disk.

Well, with 1" lens of typical long zoom camera I expect Saturn to be 2 pixels wide and rings twice of that. Just wonder if it can really be resolved as something other than a point object.

This is a photo I took of Jupiter with the same camera I used for the moon above. Jupiter is definitely not a point object. If Saturn's rings are at an angle, I'm pretty sure that the camera would be able to show that the rings exist but as I mentioned, probably no colors. The camera is one of those superzooms. It has a small point and shoot sensor but a very long zoom. In the case of this photo, 204 mm. The camera can zoom farther. I expect that when I took this in 2012 that I backed off the zoom to get the moons in.

I don't recall how much care I took taking this or if the camera was in single shot mode or night shot which takes multiple shots and stacks them. The camera could probably do a bit better if I didn't take this hand held which I believe that I did.

 

[Jimmy Higgins]

I don't know that I've ever tried Saturn with the camera. To try I'd have to look up where it is these days. For Jupiter I can tell that it's a disc and can see that there are moons. My guess is that Saturn might show that rings exist depending on the angle. Moons would look like stars. There would not likely be any colors.

It looks like Saturn can be seen in the early evening by the end of this year from where I am in the northern hemisphere. However it's on the other side of the sun at the moment so it would not appear as large as it would if it was on our side of the sun. Not sure what difference the distance would really make. But it will be another 15 years roughly before it's on our side of the sun. So worth a try come fall into winter this year.

I think that I looked at it back when I first got my Meade 6" reflector telescope. That was over 20 years ago. If I am recalling correctly it was a white oblong smudge.

It's visible most of the time of the year and there is no need to wait for 15 years to get close to it. it happens every year and the difference is not that large,.

https://stellarium-web.org/

find it there and take the picture. It says closest approach will be around July 4 - 8.94 a.u.
And farthest 10.9 a.u. around February 4.

Looks like the minimum size if about 15 arc seconds and largest is 20 arc seconds for Saturn. Of course, Saturn is always worth looking at.

 

[Jimmy Higgins]

Saturn is about 10 AU from the Sun so it should vary from about 9-11 AU from Earth.

Wikipedia says the angular size of the disk will range from about 15-20 arcseconds, with the rings being almost double that across - actually wider than Jupiter’s disk.

Well, with 1" lens of typical long zoom camera I expect Saturn to be 2 pixels wide and rings twice of that. Just wonder if it can really be resolved as something other than a point object.

This is a photo I took of Jupiter with the same camera I used for the moon above. Jupiter is definitely not a point object. If Saturn's rings are at an angle, I'm pretty sure that the camera would be able to show that the rings exist but as I mentioned, probably no colors. The camera is one of those superzooms. It has a small point and shoot sensor but a very long zoom. In the case of this photo, 204 mm. The camera can zoom farther. I expect that when I took this in 2012 that I backed off the zoom to get the moons in.

I don't recall how much care I took taking this or if the camera was in single shot mode or night shot which takes multiple shots and stacks them. The camera could probably do a bit better if I didn't take this hand held which I believe that I did.

View attachment 33857

Saturn is definitely smaller than Jupiter. Controlling the shutter length would be critical to keep it from overexposing.