Starship Asterisk*

A Cosmic Zoo in Cepheus

Explanation: Sprawling emission nebulae IC 1396 and Sh2-129 mix glowing interstellar gas and dark dust clouds in this nearly 12 degree wide field of view toward the northern constellation Cepheus the King. Energized by its central star IC 1396 (left), is hundreds of light-years across and some 3,000 light-years distant. The nebula's intriguing dark shapes include a winding dark cloud popularly known as the Elephant's Trunk below and right of center. Tens of light-years long, it holds the raw material for star formation and is known to hide protostars within. Located a similar distance from planet Earth, the bright knots and swept back ridges of emission of Sh2-129 on the right suggest its popular name, the Flying Bat Nebula. Within the Flying Bat, the most recently recognized addition to this royal cosmic zoo is the faint bluish emission from Ou4, the Giant Squid Nebula. Near the lower right edge of the frame, the suggestive dark marking on the sky cataloged as Barnard 150 is also known as the dark Seahorse Nebula.

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Wow, get a load of the 18 diffraction spikes on bright foreground star Alpha Cephei in the upper right! So, why does this TAKAHASHI FSQ-106EDX4 REFRACTOR produce 18 diffraction spikes? (I'm sure Chris has addressed this question before somewhere...)

At first all my brain saw was a face that may be that of an ape of
sorts! I thought How can this be a zoo! Then i was shown the flying
bat! Lastly the elephant! Truly is a zoo!

orin stepanek wrote: ↑Thu Aug 17, 2023 3:51 pm ElephantTrunkBatSquidSeahorse1024.jpg
At first all my brain saw was a face that may be that of an ape of
sorts! I thought How can this be a zoo! Then i was shown the flying
bat!
PIA23126-CepheusC&Bregions-SpitzerST-20190530.jpg
Barnard-150_LRGB_HIGH-RES1024.jpg
Lastly the elephant! Truly is a zoo!

Thanks for posting this image of star formation in Cepheus, Orin! I love it!

Ann

johnnydeep wrote: ↑Thu Aug 17, 2023 12:37 pm Wow, get a load of the 18 diffraction spikes on bright foreground star Alpha Cephei in the upper right! So, why does this TAKAHASHI FSQ-106EDX4 REFRACTOR produce 18 diffraction spikes? (I'm sure Chris has addressed this question before somewhere...)

alpha cephei - alderamin.png

Because the primary optic used was a Sigma 135 mm f/1.8 lens, which has nine diaphragm blades. An odd number of blades produces two spikes per blade, an even number of blades produces one spike per blade, since pairs of spikes overlap.

The description at Astrobin further says, "The squid was highlighted with a 1h exposure with the fsq10," so the refractor only covered a small part of the frame.

Ann wrote: ↑Thu Aug 17, 2023 6:29 pm

orin stepanek wrote: ↑Thu Aug 17, 2023 3:51 pm ElephantTrunkBatSquidSeahorse1024.jpg
At first all my brain saw was a face that may be that of an ape of
sorts! I thought How can this be a zoo! Then i was shown the flying
bat!
PIA23126-CepheusC&Bregions-SpitzerST-20190530.jpg
Barnard-150_LRGB_HIGH-RES1024.jpg
Lastly the elephant! Truly is a zoo!

Star formation in Cepheus. Image credit: Spitzer Space Telescope/NASA / JPL-Caltech

---

Thanks for posting this image of star formation in Cepheus, Orin! I love it!

Ann

I'm wondering how Orin and you found that image. It was unattributed in Orin's post and didn't seem to be from any of the APOD text links. I gig a google image search on it and it shows up here and a few other places:

https://www.sci.news/astronomy/spitzer- ... 07248.html

Joe Stieber wrote: ↑Thu Aug 17, 2023 6:42 pm

johnnydeep wrote: ↑Thu Aug 17, 2023 12:37 pm Wow, get a load of the 18 diffraction spikes on bright foreground star Alpha Cephei in the upper right! So, why does this TAKAHASHI FSQ-106EDX4 REFRACTOR produce 18 diffraction spikes? (I'm sure Chris has addressed this question before somewhere...)

alpha cephei - alderamin.png

Because the primary optic used was a Sigma 135 mm f/1.8 lens, which has nine diaphragm blades. An odd number of blades produces two spikes per blade, an even number of blades produces one spike per blade, since pairs of spikes overlap.

The description at Astrobin further says, "The squid was highlighted with a 1h exposure with the fsq10," so the refractor only covered a small part of the frame.

Thanks. Dumb question: why would a lens have a diaphragm? Is that simply the exposure shutter? And how does the 1 hour exposure imply the refractor only covers a small part of the frame, and what does that even mean, and why does it matter as far as diffraction spikes are concerned? (Ok, maybe that's really 4 stupid questions...Yes it's still true that I know virtually nothing about astrophotography.)

johnnydeep wrote: ↑Thu Aug 17, 2023 6:46 pm

Ann wrote: ↑Thu Aug 17, 2023 6:29 pm

orin stepanek wrote: ↑Thu Aug 17, 2023 3:51 pm ElephantTrunkBatSquidSeahorse1024.jpg
At first all my brain saw was a face that may be that of an ape of
sorts! I thought How can this be a zoo! Then i was shown the flying
bat!
PIA23126-CepheusC&Bregions-SpitzerST-20190530.jpg
Barnard-150_LRGB_HIGH-RES1024.jpg
Lastly the elephant! Truly is a zoo!

Star formation in Cepheus. Image credit: Spitzer Space Telescope/NASA / JPL-Caltech

---

Thanks for posting this image of star formation in Cepheus, Orin! I love it!

Ann

I'm wondering how Orin and you found that image. It was unattributed in Orin's post and didn't seem to be from any of the APOD text links. I gig a google image search on it and it shows up here and a few other places:

https://www.sci.news/astronomy/spitzer- ... 07248.html

Check out Cepheus the King!

johnnydeep wrote: ↑Thu Aug 17, 2023 12:37 pm Wow, get a load of the 18 diffraction spikes on bright foreground star Alpha Cephei in the upper right! So, why does this TAKAHASHI FSQ-106EDX4 REFRACTOR produce 18 diffraction spikes? (I'm sure Chris has addressed this question before somewhere...)

If I can make a wild, unscientific guess, from Wiki, Alpha Cephei rotates at a super fast rate. It makes one complete rotation in 12 Earth hours. Compare to the Sun's speed at about 30 Earth days. Just like in the movies when a spinning bicycle wheel at a certain speed slows the rotation to a stop and can even look like it is spinning backward, maybe if we are seeing Alpha Cephei from the top, we might be seeing it throwing out illusionary spikes because of its speed?

orin stepanek wrote: ↑Thu Aug 17, 2023 7:04 pm

johnnydeep wrote: ↑Thu Aug 17, 2023 6:46 pm

Ann wrote: ↑Thu Aug 17, 2023 6:29 pm

Star formation in Cepheus. Image credit: Spitzer Space Telescope/NASA / JPL-Caltech

---

Thanks for posting this image of star formation in Cepheus, Orin! I love it!

Ann

I'm wondering how Orin and you found that image. It was unattributed in Orin's post and didn't seem to be from any of the APOD text links. I gig a google image search on it and it shows up here and a few other places:

https://www.sci.news/astronomy/spitzer- ... 07248.html

Check out Cepheus the King!

Ah, yes, 'tis there indeed, farther down than I scrolled before. Thanks.

De58te wrote: ↑Thu Aug 17, 2023 7:08 pm

johnnydeep wrote: ↑Thu Aug 17, 2023 12:37 pm Wow, get a load of the 18 diffraction spikes on bright foreground star Alpha Cephei in the upper right! So, why does this TAKAHASHI FSQ-106EDX4 REFRACTOR produce 18 diffraction spikes? (I'm sure Chris has addressed this question before somewhere...)

If I can make a wild, unscientific guess, from Wiki, Alpha Cephei rotates at a super fast rate. It makes one complete rotation in 12 Earth hours. Compare to the Sun's speed at about 30 Earth days. Just like in the movies when a spinning bicycle wheel at a certain speed slows the rotation to a stop and can even look like it is spinning backward, maybe if we are seeing Alpha Cephei from the top, we might be seeing it throwing out illusionary spikes because of its speed?

I can't tell if you joking with me or not, but I'm sure the rotational speed of a star has nothing to do with the optics generating spikes. Stars are point sources for all astrophotographic intents and purposes. And even if a star happens to measurably fluctuate in brightness so quickly that it's brightness might vary within the span of an hour long exposure (as this was), that would also have no bearing on the optics creating spikes.

As for what's really causing the spikes, see the answer by Joe Stieber above.

johnnydeep wrote: ↑Thu Aug 17, 2023 6:54 pm

Joe Stieber wrote: ↑Thu Aug 17, 2023 6:42 pm

johnnydeep wrote: ↑Thu Aug 17, 2023 12:37 pm Wow, get a load of the 18 diffraction spikes on bright foreground star Alpha Cephei in the upper right! So, why does this TAKAHASHI FSQ-106EDX4 REFRACTOR produce 18 diffraction spikes? (I'm sure Chris has addressed this question before somewhere...)

alpha cephei - alderamin.png

Because the primary optic used was a Sigma 135 mm f/1.8 lens, which has nine diaphragm blades. An odd number of blades produces two spikes per blade, an even number of blades produces one spike per blade, since pairs of spikes overlap.

The description at Astrobin further says, "The squid was highlighted with a 1h exposure with the fsq10," so the refractor only covered a small part of the frame.

Thanks. Dumb question: why would a lens have a diaphragm? Is that simply the exposure shutter? And how does the 1 hour exposure imply the refractor only covers a small part of the frame, and what does that even mean, and why does it matter as far as diffraction spikes are concerned? (Ok, maybe that's really 4 stupid questions...Yes it's still true that I know virtually nothing about astrophotography.)

This 135 mm lens is designed primarily for "conventional" photography where you would use the "exposure triangle," a combination of film/sensor speed, shutter speed and lens opening (the diaphragm) to produce the desired effect; change one and at least one of the other two needs adjustment to get the same exposure. I don't see any specific mention of the f/ratio used for this image with the 135 mm lens at Astrobin, but I suspect it might have been stopped down a little to improve sharpness. Unlike an astronomical scope designed for infinity focus, a conventional photography lens must cover a range of focus distance and is sometimes a little "soft" at the maximum opening, especially a fast lens.

Joe Stieber wrote: ↑Thu Aug 17, 2023 8:42 pm

johnnydeep wrote: ↑Thu Aug 17, 2023 6:54 pm

Joe Stieber wrote: ↑Thu Aug 17, 2023 6:42 pm
Because the primary optic used was a Sigma 135 mm f/1.8 lens, which has nine diaphragm blades. An odd number of blades produces two spikes per blade, an even number of blades produces one spike per blade, since pairs of spikes overlap.

The description at Astrobin further says, "The squid was highlighted with a 1h exposure with the fsq10," so the refractor only covered a small part of the frame.

Thanks. Dumb question: why would a lens have a diaphragm? Is that simply the exposure shutter? And how does the 1 hour exposure imply the refractor only covers a small part of the frame, and what does that even mean, and why does it matter as far as diffraction spikes are concerned? (Ok, maybe that's really 4 stupid questions...Yes it's still true that I know virtually nothing about astrophotography.)

This 135 mm lens is designed primarily for "conventional" photography where you would use the "exposure triangle," a combination of film/sensor speed, shutter speed and lens opening (the diaphragm) to produce the desired effect; change one and at least one of the other two needs adjustment to get the same exposure. I don't see any specific mention of the f/ratio used for this image with the 135 mm lens at Astrobin, but I suspect it might have been stopped down a little to improve sharpness. Unlike an astronomical scope designed for infinity focus, a conventional photography lens must cover a range of focus distance and is sometimes a little "soft" at the maximum opening, especially a fast lens.

Thanks, but, due no doubt to my lack of understanding of common photography terms and concepts, I don't see how that answers my questions. But that's ok. I'll have to read up on this stuff.

johnnydeep wrote: ↑Fri Aug 18, 2023 1:07 pm

Joe Stieber wrote: ↑Thu Aug 17, 2023 8:42 pm

johnnydeep wrote: ↑Thu Aug 17, 2023 6:54 pm

Thanks. Dumb question: why would a lens have a diaphragm? Is that simply the exposure shutter? And how does the 1 hour exposure imply the refractor only covers a small part of the frame, and what does that even mean, and why does it matter as far as diffraction spikes are concerned? (Ok, maybe that's really 4 stupid questions...Yes it's still true that I know virtually nothing about astrophotography.)

This 135 mm lens is designed primarily for "conventional" photography where you would use the "exposure triangle," a combination of film/sensor speed, shutter speed and lens opening (the diaphragm) to produce the desired effect; change one and at least one of the other two needs adjustment to get the same exposure. I don't see any specific mention of the f/ratio used for this image with the 135 mm lens at Astrobin, but I suspect it might have been stopped down a little to improve sharpness. Unlike an astronomical scope designed for infinity focus, a conventional photography lens must cover a range of focus distance and is sometimes a little "soft" at the maximum opening, especially a fast lens.

Thanks, but, due no doubt to my lack of understanding of common photography terms and concepts, I don't see how that answers my questions. But that's ok. I'll have to read up on this stuff.

I take it as the image was made through two telescopes (maybe two cameras, as well). One is wide angle... that telescope is the ordinary camera lens, which like all camera lenses has an iris inside that allows the amount of light it collects to be controlled (and is what makes the 18 spikes). The other is a longer focal length telescope that was used to make a long exposure, high resolution image of the central part. Then these were composited into a single image.

Chris Peterson wrote: ↑Fri Aug 18, 2023 1:19 pm

johnnydeep wrote: ↑Fri Aug 18, 2023 1:07 pm

Joe Stieber wrote: ↑Thu Aug 17, 2023 8:42 pm
This 135 mm lens is designed primarily for "conventional" photography where you would use the "exposure triangle," a combination of film/sensor speed, shutter speed and lens opening (the diaphragm) to produce the desired effect; change one and at least one of the other two needs adjustment to get the same exposure. I don't see any specific mention of the f/ratio used for this image with the 135 mm lens at Astrobin, but I suspect it might have been stopped down a little to improve sharpness. Unlike an astronomical scope designed for infinity focus, a conventional photography lens must cover a range of focus distance and is sometimes a little "soft" at the maximum opening, especially a fast lens.

Thanks, but, due no doubt to my lack of understanding of common photography terms and concepts, I don't see how that answers my questions. But that's ok. I'll have to read up on this stuff.

I take it as the image was made through two telescopes (maybe two cameras, as well). One is wide angle... that telescope is the ordinary camera lens, which like all camera lenses has an iris inside that allows the amount of light it collects to be controlled (and is what makes the 18 spikes). The other is a longer focal length telescope that was used to make a long exposure, high resolution image of the central part. Then these were composited into a single image.

Thanks. That clears it up a bit for me. And I did in fact miss the other details about the imaging equipment listed at astrobin:

https://www.astrobin.com/g6612z/ wrote:
Imaging Telescopes Or Lenses:
Sigma 135mm F1.8 DG HSM (Art) · Takahashi FSQ-106EDX4
Imaging Cameras:
ZWO ASI2600MC Pro

So, two telescopes/lenses, and one camera I guess. Though now I'm curious how those three things are used together.

I would love it if Yann Sainty collaborated more with Marcel Drechsler! Would love to see an image of StDr 124.