Starship Asterisk*

[quote="Amir"]yes, l should have said [b]Newtonian telescopes[/b] instead of [b]Reflector[/b].
but i guess your SCT is not considered a merely a reflector since it takes the advantage of both refraction & reflection. it's referred as Catadioptric.[/quote]
Yes, although a catadioptric is a subset of reflecting telescopes. However, I also have a Newtonian that uses a flat piece of glass to hold the secondary. It is a true Newtonian (parabolic primary, flat secondary diagonal), but has no spider arms to cause diffraction spikes. It couldn't be considered catadioptric.

[quote="Chris Peterson"]They occur in telescopes that have occluding structures supporting something (a secondary mirror or a camera) in the optical path. That includes many, but not all reflectors. My SCT, for instance, uses a glass plate to support the secondary mirror, and no diffraction spikes are produced.[/quote]
yes, l should have said [b]Newtonian telescopes[/b] instead of [b]Reflector[/b].
but i guess your SCT is not considered merely a reflector since it takes the advantage of both refraction & reflection. it's referred as Catadioptric.

[quote="Amir"]since you all mentioned, yes they are beautiful spikes. in reflectors they are inevitable, but if you wanted to have them in the images you take with your refractors, make a + with two piece of string in front of your telescope.[/quote]
They occur in telescopes that have occluding structures supporting something (a secondary mirror or a camera) in the optical path. That includes many, but not all reflectors. My SCT, for instance, uses a glass plate to support the secondary mirror, and no diffraction spikes are produced.

FWIW, this image was shot with a refractor. But the diffraction spikes don't look real to me. I would guess they were added by a Photoshop filter during post processing, and not by any sort of aperture mask during the exposures. That is, I don't think they are actual diffraction spikes.

[quote="wonderboy"]yeah you owls have got to stick together <snip> you two'll chew em up![/quote]
[i]Chew?![/i] Certainly not! :wink: I'd be happy to leave the pellets here if you'd like, though. :D

[quote="Amir"]oh, i just realized why your avatar is an owl, owlice!![/quote]
8-) (My son took the picture I use for my avatar [with a zoom lens, obviously]; I like it, so use it.)

neufer!
I had been so enjoying this morning's earworm, and now it's been replaced and Lucy and Ethel's rendition of that number is playing on the video screen in my head! I'll get you for this!

[quote="DavidLeodis"]I like the picture, which very effectively captures the scene.[/quote]
I do, too; it's a lovely shot.

I like the picture, which very effectively captures the scene. Watching the Moon going through its phases is always fascinating. :)

[quote="Amir"]looking at moon, there are two strange objects at 1 and 7 o'clock in the background, what are they?[/quote]My guess is that they are composition artifacts (copies of stars), as they happen to be about 16 pixels to the right of unusual dim Merope and HIP 17776. Either that or [i]space junk[/i]... :wink:
[img]http://img532.imageshack.us/img532/8039/whatarethese.png[/img]

[youtube]http://www.youtube.com/watch?v=8YhTKiFEMAg[/youtube]

oh, i just realized why your avatar is an owl, owlice!!
since you all mentioned, yes they are beautiful spikes. in reflectors they are inevitable, but if you wanted to have them in the images you take with your refractors, make a + with two piece of string in front of your telescope. (i read this in S&T or Astronomy, i don't remember which one.)

looking at moon, there are two strange objects at 1 and 7 o'clock in the background, what are they?

yeah you owls have got to stick together, god help anyone who comes on here with a name regarding a mouse or something, you two'll chew em up! The diffraction spikes in this picture are really pretty. You get better ones than them though.

Anything for an owl! :-)

Owlice, Thank you!

They are [url=http://en.wikipedia.org/wiki/Diffraction_spike]diffraction spikes[/url]. I find them very pretty in this picture!

Is there a name for the blue cross that appears on bright stars, as in this picture?

Love the terminator curve and the highlighting of the peaks and valleys! Does anyone know if there exists a 3D pic of a closeup of the terminator line of the moon? If so, could you post it here? Thanks.

[url=http://apod.nasa.gov/apod/ap100326.html][img]http://apod.nasa.gov/apod/calendar/S_100326.jpg[/img] [size=150]Young Moon and Sister Stars[/size][/url]

[b] Explanation: [/b] [url=http://apod.nasa.gov/apod/ap050513.html]A young[/url] crescent Moon shares the western sky with [url=http://www.naic.edu/~gibson/pleiades/pleiades_myth.html]sister stars[/url] of the Pleiades cluster in this pretty, [url=http://morrisastronomy.blogspot.com/]evening skyscape[/url] recorded on the [url=http://science.nasa.gov/headlines/y2010/19mar_equinox.htm]March equinox[/url] from San Antonio, Texas. In the processed digital image, multiple exposures of the [url=http://apod.nasa.gov/apod/ap010906.html]celestial scene[/url] were combined to show details of the bright lunar surface along with the Pleiades stars. Astronomical images of the [url=http://apod.nasa.gov/apod/ap060109.html]well-known Pleiades[/url] often show the cluster's alluring blue reflection nebulae, but they are washed-out here in the bright moonlight. Still, during this particular night, skygazers in South and Central America could even watch the 5 day old Moon occult or pass in front of some of the brighter [url=http://www.lunar-occultations.com/iota/pleiades/pleiades.htm]Pleiades stars[/url].

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