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Help! Crazy morphing planets!


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The conditions were perfect last night. Still skies, no moon, no cloud, no shimmering. So I powered up the rig at 11-30pm and tried to get a quick video of Saturn. But all I got was a crazy unresolvable shifting image. I spent ages double and triple checking everything, but the Bahtinov mask showed the focus was spot on and there were no clouds or trees obscuring the view. At first I thought I thought it was caused by extreme turbulence from warm air in the OTA (8 inch dob), but after 30min or more of waiting and checking everything it didn't change one little bit. I moved the mount around to a bright star right near the zenith and got exactly the same type of image with that (so Saturn isn't about to supernova!). I checked down the tube as well to make sure there weren't any major obstructions.

I haven't got brilliant planetary images of saturn before, but they've at least been recognisable! And this was definitely Saturn (not that a star should be showing up like this anyway!). The whole thing is in an obsy as well so it hasn't been knocked or taken apart since the last time I got some images. Now I'm just worried that there's something wrong with the sensor. Has anyone else seen anything like this?

I've attached the movie file from the camera (Canon 600d). Hope someone can help, I'm at my wits end with this!

Edit: Forgot to say, this video was taken with a 3x barlow at 10x digital zoom.

MVI_0255.MOV

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I can clearly see diffraction fringes, which suggests this might well be a star. The fringes are not symmetric, which hints at a scope being out of collimation. Even if the sky looks steady, there may be thermals at certain points near the horizon (due to warm roofs, motorways with traffic, etc).

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  1. That doesn't look like Saturn to me.

Whatever it is, it looks like it's out of focus

Also looks out of collimation

It also looks like there's lots of thermals going on, which suggests that the mirror hasn't cooled sufficiently yet. Or there was some other heat source causing a thermal (houses, patch of concrete/road, wooded area?)

Sometimes there's just bad seeing, even when it looks OK to the naked eye. patience is a virtue in planetary imaging.

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Well, it could certainly be explained by any one of, or a mixture of, any of those suggestions, but I've checked everything pretty thoroughly. Firstly, it's definitely weird and it's definitely Saturn!

-I haven't checked the collimation, but the scope is permanently set up in an obsy and I haven't moved it from the mount since I bought it about a year ago and I've been imaging Saturn, Jupiter, Mars and the moon with it, so it would be very weird if the collimation is suddenly off whack. It also doesn't explain the image not being still.

-The seeing was the best I've seen in a very long time and the scope had been cooled for half an hour, which may not be enough for it to completely cool, but I've never seen anything like that before even straight after removing the lens cap after a hot day! I've never had any noticeable problems with thermals either. But obviously I can't rule out a freak set of circumstances.

-As for the focus, it was exactly where I left it from last time I imaged Saturn a couple of weeks ago and I checked it with a Bahtinov and shifted it up and down a bit and saw the "Bahtinov crosshairs" move in and out of alignment, so I can say with certainty that the focus was spot on.

What I will do next time I have the chance is check it with an eyepiece. That would at least eliminate a problem with the camera. Bizarre thermals or falling out of collimation I can live with, but as much as anything I'm hoping someone has seen something similar and can reassure me that the camera isn't broken! It is by far the most vexing thing that has happened to me in my many years of imaging.

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It certainly didn't seem logical for it to be a camera error to me either, but it's reassuring to hear someone else say it! If I'm not too tired from being up late last night trying to figure it out I'll have another shot at it tonight and investigate further.

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Well, I checked it again last night and the same result, so I plugged in an eyepiece and it was the same throught that.

Firstly it's good news in that it's not a camera problem. It's also very unlikely to be a scope problem as I can't think of anything that would cause such movement in the target. The diffusion pattern was also perfectly symmetrical when I adjusted the focus off, so the collimation is fine too.

For me that just leaves the seeing or thermals, which I find really odd because it's happened two days in a row and never before to anything like this extent in the last six or seven years of stargazing! The rig hasn't moved in all that time, there have been no major developments/changes in the local area that might cause increased thermals and anyway it's happening to targets in all directions.

Very strange. Hopefully it'll just correct itself. Thanks for all the ideas.

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Can you tell us a bit more about your obsy? Possible that warm air escaping out from it is messing you about? How recently was is it ok?

Sent from my iPhone using Tapatalk

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I would have to say that despite your insistence of this being Saturn that it is a star not a planet.

Even an out of focus , ill-collimated 'scope would still show a pretty recognisable disc with 'ears'.

In your OP you say that you got "exactly the same sort of image" looking at a bright star near the zenith , something that would not happen if the original target was the ringed planet.

I would hazard a guess that you had targeted Spica or possibly Antares originally.

I've taken the liberty of converting and stacking your MOV and the offset diffraction rings are very apparent , lending more weight to the answer.

post-21219-0-81379900-1404331838_thumb.p

post-21219-0-87568200-1404331985_thumb.p

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That's a normal amount of turbulence for low stellar objects in poor seeing. Your collimation looks way off though - even with the poor image stability you can see it's a fair way out.

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Can you tell us a bit more about your obsy? Possible that warm air escaping out from it is messing you about? How recently was is it ok?

Sent from my iPhone using Tapatalk

Completely agree Steve. In all my years of imaging I have never ever seen a planet look that. It is out of focus, with serious colour dispersion. I would also say that is clearly a star.

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