Star test images, first attempt - how did I do? (1 Viewer)

[4th_point]

Thank you, B. Your contributions on this site, along with those from Hermann, Henry, and Joachim have made me a more astute consumer. I still have much to learn but have paid attention to the posts and recommendations. I feel fortunate to have comments from you all in this thread.

Thanks,

Jason

 

[tenex]

Why are the rings showing so much color in these photos? They seem unlikely to be long time exposures due to turbulence, and the results (which I didn't photograph) were quite monochrome when I tested my own scope.

 

[4th_point]

Why are the rings showing so much color in these photos? They seem unlikely to be long time exposures due to turbulence, and the results (which I didn't photograph) were quite monochrome when I tested my own scope.

That's a good question. My guess is that it is either my camera, the LED torch, or both. The torch gets hot with extended sessions and I think that the colors get stronger then.

Either way, I have only been concerned with the patterns, and not the colors, so I have not investigated.

 

[kabsetz]

I think all three scopes look very good for spotting scopes. I have not been successful with my photo efforts, but it seems typical that photos exaggerate CA compared to what I see visually. To me, air turbulence does not seem to be much of a problem, if any, in your photos. If there is significant turbulence, you see it as a variable image when viewing visually, and if there is none or almost none you can see, it should not mess up the photos either.

 

[jring]

Hi,

I think air turbulence is the reason for the rings being so deformed from circles at times (and to varying degrees in different images of the first example). If it wasn't turbulent air, we would see the same deformation with two images of the same side of focus and also this would mean we have serious aberrations, which should be quite visible as a fuzzy image at 60x.

When doing a star test visually, the brain will integrate away spurious deformations due to air currents and the rings tend to look a lot better than with an image. One could probably use astro imaging techniques like lucky imaging in combination with stacking to emulate this behaviour.

Joachim

 

[4th_point]

I think all three scopes look very good for spotting scopes. I have not been successful with my photo efforts, but it seems typical that photos exaggerate CA compared to what I see visually. To me, air turbulence does not seem to be much of a problem, if any, in your photos. If there is significant turbulence, you see it as a variable image when viewing visually, and if there is none or almost none you can see, it should not mess up the photos either.

Thank you for the comments.

Jason

 

[4th_point]

One could probably use astro imaging techniques like lucky imaging in combination with stacking to emulate this behaviour.

Lucky imaging theory is interesting, Joachim. Thanks for mentioning it. I take about 20 photos to get a decent one, depending on conditions.

 

[4th_point]

I tried taking some photos of artificial stars outdoors today. I didn't get many good shots. Probably due to my photography skills and definitely with the heat haze.

This was outside of focus with my favorite scope, using sunlight and a green Christmas ornament. I think Henry had mentioned using a green ornament, so I have made sure to have one handy for this sort of activity.

Unfortunately, I didn't get any good photos inside of focus.

 

[jring]

Hi,

green is good as this is the color optics tends to be optimized for - unlike the red He-Ne laser often used for such stuff - and also only one color, so no problems with CA.

Was this one of the scopes we have seen before? This one looks a bit elliptic which would be a sign of astigmatism. That is, if it was not due to heat haze. If it is really astigmatic, the main axis of the ellipse should flip by 90 deg when on the other side of focus.

Joachim

 

[4th_point]

Thanks for the information, Joachim. This was a different scope and I think that the elliptical shape was due to heat haze. By the time I got my camera settings close enough to capture a decent image the haze got bad. I missed my window of time when the haze was minimal.

I didn't see the shape flip on the other side of focus either, but am planning to get better photos sometime in the future.

It's fun and a bit frustrating at the same time! I have some ideas for a better setup outdoors.

Jason