APOD: A Spectrum of Nova Delphini (2013 Aug 23)

[geckzilla]

I think I need a picture book for dummies on this.

[rstevenson]

What do you mean by flash photo? The "flash" part is confusing me. Surely you don't mean firing a flash.

Shirley rarely means what he says.

Rob

[neufer]

What do you mean by flash photo? The "flash" part is confusing me. Surely you don't mean firing a flash.

Shirley rarely means what he says.

<<The Travels of the Three English Brothers is an early Jacobean era stage play, an adventure drama written in 1607 by John Day, William Rowley, and George Wilkins. The drama was based on the true-life experiences of the three Shirley brothers, Sir Anthony Shirley, Sir Thomas Shirley, and Robert Shirley. Since George Wilkins is thought by some to have worked with Shakespeare on Pericles, Prince of Tyre around 1607, the question of his participation in this collaboration has drawn the attention of some Shakespeare scholars. The play was acted by Queen Anne's Men. Its 29 July Register entry states that the play was performed at the Curtain Theatre, though this information is likely inaccurate; The Queen's company is thought to have moved on to the Red Bull Theatre in 1604 or 1605. Francis Beaumont's The Knight of the Burning Pestle, also of 1607, refers to The Travels as a Red Bull play.

Beyond the sheer entertainment value of the Shirleys' story, the dramatists were eager to draw cultural contrasts between Christian England and Muslim Persia, the key locale of much of the Shirley saga. Their play stresses the violence and brutality of Persian society (especially the practice of beheading) as a blatant discriminator between Persia and England. The English display their valor and resourcefulness when assaulted by violence and treachery; when an unarmed Sir Thomas Shirley is attacked by four Turks, he defends himself with rocks. The splendid English move the Persian "Sophy" (the play's version of the Shah) to verbal raptures — and inspire him to grant Christians tolerance in his dominions.

In addition to other real-life figures in the cast of characters (including the Pope), the comic Will Kempe appears in one scene. Himself noted for his travels, Kempe is shown in Venice, where he has a bawdy exchange with a Signor Harlakin (that is, harlequin) and his wife. Kempe reportedly met Sir Anthony Shirley in Rome; but whether this Venetian scene with Kempe is based on anything more substantial that the playwrights' imaginations is uncertain.

The final scene in The Travels of the Three English Brothers contains a noteworthy feature: the three Shirley brothers and their father, widely separate geographically, see and speak with each other through a magical device called a "perspective glass." This device is part of the traditional lore of magic, and occurs in other contexts: Robert Greene includes it in his Friar Bacon and Friar Bungay. Though the perspective glass operates thaumaturgically rather than technologically, it nonetheless provides a striking anticipation of modern communications.>>

[alter-ego]

I think I need a picture book for dummies on this.

I just got back from vacation where I have the tools to create a simple diagram for you. Two views below show orthogonal cross-sections of a simple telescope incorporating a prism (glass wedge) and a cylindrical lens. The left view shows how converging rays are further focused in the spatial axis by the cylindrical lens, but the prismatic bending does not occur in this plane. At the telescope focal plane, these rays are defocused from their normal point images. A (green) star is now a line segment at the telescope focus. To reduce confusion, I've left out the red and blue rays in this view. The right view shows RGB rays focused to the usual star-point image. However in this view the prism is bending the different colors to different angles, and the cylindrical lens has no power in this axis so the rays are not defocused. The resulting spectra now have "defocused" spatial extent in one axis while maintaining the maximum spectral resolution in the other axis.

Two cross-section views showing the orientations of a prism wrt the cylindrical lens, and how they affect the dispersive and non-dispersive planes at a focal plane, e.g. CCD

Hope this helps.

[geckzilla]

Hey, you are a pretty good illustrator. I think I do understand that part well enough. I think what I'm really getting caught up on is that I never understood how a camera attaches to and works with a telescope. I'm feeling really silly because that is probably more basic than the optics involved prior to that. Sorry for being a pain and thanks for trying to educate me. You don't have to help anymore, I'll get it on my own eventually.

[neufer]

I think what I'm really getting caught up on is that I never understood how a camera attaches to and works with a telescope.

The simplest way is to remove the lens of the camera and position the film/plate/CCD to be at the focal plane.

[geckzilla]

I'm not sure I trust your advice anymore, Art.

[bystander]

That is essentially what you would have to do. You will probably need an adapter, but the telescope becomes your camera lens.

[Chris Peterson]

I think what I'm really getting caught up on is that I never understood how a camera attaches to and works with a telescope.

The simplest way is to remove the lens of the camera and position the film/plate/CCD to be at the focal plane.

A telescope doesn't have a focal plane. A telescope is an afocal instrument. When used with a camera, you normally remove the telescope eyepiece, leaving just the objective to focus light on its focal plane (where you locate the film or detector). Once you remove the eyepiece, you have a focal instrument, not something that is a telescope anymore in an optical sense. All that's left is "telescope" in an informal sense, referring to the optical tube assembly.

You can also do afocal imaging with a telescope, where you leave the eyepiece in place, and image using the camera with its lens in place as well. The camera then takes the essentially collimated beam from the eyepiece and focuses it onto the sensor. In this case, the camera is doing the same thing your eye does.