Schmidt–Cassegrain telescope UFO video. Bug?

[AmericanRoadwarrior]

Viewing this video I have become a bit obsessed in determining if this is just a crawling bug in the works.

http://www.youtube.com/watch?v=EC6MlZ8ib0s

The uploader is certain this cannot be a bug and that a bug cannot get into the sealed scope.

A few points in particular:

The motion is not in a straight line. It looks to me like the crawling motion of a small bug.

I believe the slight halo around it is an indication of something. It almost looks as if it's bending whatever it's crawling on.

I've also read that Schmidt–Cassegrain telescopes are not hermetically sealed so the pressure stays balanced and that a small bug could get in when changing eyepieces.

I'd be really interested in people's opinions. Thank you

[neufer]

I'm guessing a bird or a bat.

[geckzilla]

A bug should be very out of focus if it is on a lens or somewhere on or inside the telescope. He uses the ISS as an example of a satellite that passes in front of the moon, saying that it passes in under a second... sure, the ISS is one of our lowest orbiting satellites. One farther out should pass much more slowly.

[AmericanRoadwarrior]

A bug should be very out of focus if it is on a lens or somewhere on or inside the telescope. He uses the ISS as an example of a satellite that passes in front of the moon, saying that it passes in under a second... sure, the ISS is one of our lowest orbiting satellites. One farther out should pass much more slowly.

Are there not focal points within the camera/reflector telescope where a bug's shadow would be crisp?

If the telescope is focused on the moon, would something closer to earth be this sharp?

[AmericanRoadwarrior]

With my knowledge of how equipment focuses the crisp image looks to me like it's either in the equipment works (most likely) or close to the moon (it really doesn't give me that impression, something doesn't look quite right).

[AmericanRoadwarrior]

I'm guessing a bird or a bat.

Are you sure a bird or bat would focus at all? I would think it would be very blurry if it even showed up at all.

[Chris Peterson]

Viewing this video I have become a bit obsessed in determining if this is just a crawling bug in the works.

http://www.youtube.com/watch?v=EC6MlZ8ib0s

The uploader is certain this cannot be a bug and that a bug cannot get into the sealed scope.

It is almost certainly not a bug in the scope. But SCTs are not entirely sealed, and certainly get bugs in them.

This is something in the atmosphere above the scope. It could be a bird or some other living thing, but to me it looks like it's tumbling. I'd guess it's a piece of debris.

Just for scale, this is what a leaf blowing at 30 cm/s would look like if it were 1000 m above the scope. It's what a party balloon blowing at 1.5 m/s would look like at a distance of 5000 m. Both are perfectly reasonable scenarios. I've personally seen weather balloons that look similar. And an object 1000 m from the scope would certainly be very nearly in focus.

[AmericanRoadwarrior]

It is almost certainly not a bug in the scope. But SCTs are not entirely sealed, and certainly get bugs in them.

This is something in the atmosphere above the scope. It could be a bird or some other living thing, but to me it looks like it's tumbling. I'd guess it's a piece of debris.

Just for scale, this is what a leaf blowing at 30 cm/s would look like if it were 1000 m above the scope. It's what a party balloon blowing at 1.5 m/s would look like at a distance of 5000 m. Both are perfectly reasonable scenarios. I've personally seen weather balloons that look similar. And an object 1000 m from the scope would certainly be very nearly in focus.

I guess I really don't know how these scopes focus because I would think that it being focused on the distant moon closer objects would not be in focus.

Do these scopes auto focus? Are they built in such a way to focus on two objects at completely different distances at the same time?

Thank you

[AmericanRoadwarrior]

This is something in the atmosphere above the scope. It could be a bird or some other living thing, but to me it looks like it's tumbling. I'd guess it's a piece of debris.

I can understand a tumbling object changing sizes and shape, but not turning left and right.

[Chris Peterson]

This is something in the atmosphere above the scope. It could be a bird or some other living thing, but to me it looks like it's tumbling. I'd guess it's a piece of debris.

I can understand a tumbling object changing sizes and shape, but not turning left and right.

Why not? That's exactly what irregular shaped objects do when they're blowing.

[AmericanRoadwarrior]

This is something in the atmosphere above the scope. It could be a bird or some other living thing, but to me it looks like it's tumbling. I'd guess it's a piece of debris.

I can understand a tumbling object changing sizes and shape, but not turning left and right.

Why not? That's exactly what irregular shaped objects do when they're blowing.

Okay, you've got a good point there, and there is wind drag within our atmosphere.

But if the scope is focused on the distant moon would a near earth object also be this in focus?

[Chris Peterson]

Okay, you've got a good point there, and there is wind drag within our atmosphere.

But if the scope is focused on the distant moon would a near earth object also be this in focus?

Since the object is right at the resolution limit of the system (around 3 arcseconds per pixel) it's impossible to determine the quality of focus. It's not grossly out of focus, obviously, but more than that is difficult to say. Certainly, if you have the scope focused at infinity, an object 1000 meters away will be very close to focus- it would probably require something larger and with more obvious structure to really see that amount of focus error.

[AmericanRoadwarrior]

Since the object is right at the resolution limit of the system (around 3 arcseconds per pixel) it's impossible to determine the quality of focus. It's not grossly out of focus, obviously, but more than that is difficult to say. Certainly, if you have the scope focused at infinity, an object 1000 meters away will be very close to focus- it would probably require something larger and with more obvious structure to really see that amount of focus error.

This is where my limited knowledge fails me.

On the reflector telescope I've used in the past there was no infinity as far as I remember.

If a scope like this Schmidt–Cassegrain has an infinity setting and works like a camera this changes a lot for me and makes a big difference.
Now I would understand that it could focus on both objects at once if this is the case.

[AmericanRoadwarrior]

So if some of these scopes have an infinity setting would you be able to focus on Jupiter and then turn it to the moon and find it in focus?

[Chris Peterson]

Since the object is right at the resolution limit of the system (around 3 arcseconds per pixel) it's impossible to determine the quality of focus. It's not grossly out of focus, obviously, but more than that is difficult to say. Certainly, if you have the scope focused at infinity, an object 1000 meters away will be very close to focus- it would probably require something larger and with more obvious structure to really see that amount of focus error.

This is where my limited knowledge fails me.

On the reflector telescope I've used in the past there was no infinity as far as I remember.

If a scope like this Schmidt–Cassegrain has an infinity setting and works like a camera this changes a lot for me and makes a big difference.
Now I would understand that it could focus on both objects at once if this is the case.

A telescope is "focused at infinity" when parallel rays entering the system come to focus at the focal plane defined by the focal length of the instrument. Optically, a telescope of this size can be considered to be focused at infinity for any object outside the atmosphere. That is, there is no effective difference between focusing on the Moon and on a star (their respective focal planes are less than a wavelength of light apart). There is a meaningful difference in the position of the focal plane for an object at the distance of the Moon and an object 1000 meters away. But that distance is still small.

There are a number of APODs featuring airplanes flying between a telescope and the Sun or Moon. In some cases a small focus error is apparent, in others not, depending on the focal length of the scope and distance to the plane. In all cases, however, the focus is at least close.

Click to view full size image

[AmericanRoadwarrior]

There are a number of APODs featuring airplanes flying between a telescope and the Sun or Moon. In some cases a small focus error is apparent, in others not, depending on the focal length of the scope and distance to the plane. In all cases, however, the focus is at least close.

Click to view full size image

This is a great help. Thank you

[geckzilla]

For some reason I decided to try maths and figured out that something that takes 1 minute to cross the moon has to orbit the Earth every 11.35 hours or so at a distance of 19000km. So in order for this blip to show up in the telescope it would have to be maybe 200 meters wide... ok, not so feasible.

[Chris Peterson]

So if some of these scopes have an infinity setting would you be able to focus on Jupiter and then turn it to the moon and find it in focus?

You can use the basic thin lens law to evaluate that question, 1/S₁ - 1/S₂ = 1/f

Click to view full size image

For a typical amateur telescope with f = 2 meters, taking the distance to Jupiter as 7.5 x 10¹¹ meters and the distance to the Moon as 3.8 x 10⁸ meters, you get a difference in the position of the focal plane of 11 nm, or just 2% of the wavelength of visible light. So yes... focus on the most distant star your scope can see, and there will be no measurable focus error when you view the Moon.

Note that an object 1000 meters away will come to focus 4 mm from the plane where objects infinitely far away come to focus. That's a significant focus error- certainly one that you'd want to correct for. But that doesn't mean you could easily tell that a small, featureless silhouette at that distance was actually out of focus a bit.

[AmericanRoadwarrior]

Thanks guys.

Well, now I'm more perplexed than ever. I seem to be abandoning my initial belief that this was a crawling bug in the works.

There seems to be an amount of "how you view it" having effect on what you think it might be, at least speaking for myself.

The zig-zag motion was the main factor in thinking it was a bug crawling. Watching it in 1080p full screen I thought I could almost see legs.

If it is "up there", it does appear to be spinning or tumbling. The uploader mentions "it's a little more than just spinning making that motion".
I kind of doubt there is enough atmosphere/wind drag near the moon to cause a tumbling object to zig-zag like this.

Another observation against it being a bug is it's overall straight trajectory.

[geckzilla]

The object almost has sinusoidal motion. It's too regular for a bug crawling. Chris's explanation of an object, perhaps even Art's bird or bat, blowing and tumbling in the wind is a very satisfying one to me. Anything else is just grasping at straws.

[rstevenson]

...So yes... focus on the most distant star your scope can see, and there will be no measurable focus error when you view the Moon.

Are binoculars so different from telescopes? I ask because on those occasions when I switch from viewing stars or planets through my 7 x 40 Nikon binoculars to viewing the Moon, I always have to refocus a little. Something to do with binocular vision, I suppose?

Rob

[Chris Peterson]

...So yes... focus on the most distant star your scope can see, and there will be no measurable focus error when you view the Moon.

Are binoculars so different from telescopes? I ask because on those occasions when I switch from viewing stars or planets through my 7 x 40 Nikon binoculars to viewing the Moon, I always have to refocus a little. Something to do with binocular vision, I suppose?

Binoculars are no different. Yours focus the same on stars and the Moon. But the example under discussion involves a video camera at the focal plane. When you use a telescope visually, you add a variable lens into the system, that of your eye (and even if you are quite presbyopic, it still accommodates somewhat). How your eye focuses on a star compared with the Moon is probably affecting you. It's perceptual, not strictly optical.

[rstevenson]

After asking the question, I wondered if maybe my eyes are "stopping down" when I view the brighter Moon, and since my eyes are not in like-new condition, this is affecting their focus.

Rob

[Chris Peterson]

After asking the question, I wondered if maybe my eyes are "stopping down" when I view the brighter Moon, and since my eyes are not in like-new condition, this is affecting their focus.

Possibly. Also, the primary focusing surface of your eye is the cornea, not the lens. And the cornea isn't perfectly shaped (astigmatism is the most well known aberration). So the less of your cornea that has light passing through it, the fewer aberrations you typically have. Aberrations are often perceived as focus errors, and corrected (to a degree) by selective focusing.

[Nitpicker]

The object almost has sinusoidal motion. It's too regular for a bug crawling. Chris's explanation of an object, perhaps even Art's bird or bat, blowing and tumbling in the wind is a very satisfying one to me. Anything else is just grasping at straws.

Agreed. It appears to behave like a party balloon to me. Quite close to Regulus, too, so be on the lookout for balloons as well as asteroids on Thursday:
http://asterisk.apod.com/viewtopic.php? ... &start=675


Don't you just love this misinformation age?