Cassegrain focus

E17448

optical configuration telescope focus configuration

Cassegrain focus is a telescope optical configuration in which light is reflected by a secondary mirror back through a hole in the primary mirror to form a compact, accessible focal point behind the primary.

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All labels observed (8)

Label	Occurrences
Cassegrain focus canonical	2
Cassegrain configuration	1
Cassegrain focus of Gemini North	1
Cassegrain focus of Gemini South	1
Cassegrain focus of Gemini South telescope	1
Cassegrain reflector	1
Cassegrain telescope	1
Gemini North Cassegrain focus	1

Statements (44)

Predicate	Object
instanceOf	optical configuration ⓘ telescope focus configuration ⓘ
advantage	accessible focal plane at back of telescope ⓘ compact telescope tube ⓘ convenient mounting of instruments at rear of telescope ⓘ long effective focal length in short physical tube ⓘ
benefitFor	photometric instruments at rear focus ⓘ spectrographs mounted at rear focus ⓘ
commonIn	catadioptric telescopes ⓘ reflecting telescopes ⓘ
componentOf	Dall–Kirkham telescope design ⓘ Maksutov–Cassegrain telescope design ⓘ Ritchey–Chrétien reflector ⓘ surface form: Ritchey–Chrétien telescope design Schmidt–Cassegrain telescope design ⓘ classical Cassegrain telescope design ⓘ
contrastWith	Coudé focus ⓘ Newtonian focus ⓘ prime focus ⓘ
enables	mounting of heavy cameras at rear cell ⓘ use of diagonal mirrors for comfortable viewing ⓘ
feature	folded optical path ⓘ secondary mirror located near primary focus ⓘ
formsFocalPoint	behind the primary mirror ⓘ
hasFocalPlane	behind primary mirror cell ⓘ
historicalPeriod	17th century origin ⓘ
lightPath	light reflects from primary mirror to secondary mirror ⓘ light reflects from secondary mirror back through a central hole in the primary mirror ⓘ
locatedAt	back end of the telescope tube ⓘ
namedAfter	Laurent Cassegrain ⓘ
opticalEffect	increases effective focal ratio compared to primary mirror alone ⓘ
requires	central perforation in primary mirror ⓘ
requiresAlignment	primary mirror ⓘ secondary mirror ⓘ
typicalUse	amateur compound telescopes ⓘ medium to large professional telescopes ⓘ
usedFor	astrophotography ⓘ instrument mounting in professional observatories ⓘ visual astronomy ⓘ
usedIn	Cassegrain focus self-linksurface differs ⓘ surface form: Cassegrain telescope
usedWith	Barlow lenses ⓘ field flatteners ⓘ focal reducers ⓘ
usesPrimaryMirror	concave primary mirror ⓘ
usesSecondaryMirror	convex secondary mirror ⓘ

How these facts were elicited

The pipeline generated the facts above by prompting gpt-5.1 with this entity's name + description and the instruction below.

Instruction

You are a knowledge base construction expert. Given a subject entity and a description of it, return factual statements that you know for the subject as a JSON list of dictionaries(triples), where keys must be "subject", "predicate" and "object". The number of facts may be very high, between 25 to 50 or more, for very popular subjects. For less popular subjects, the number of facts can be very low, like 5 or 10.

# Requirements
- If you don't know the subject at all, return an empty list.
- If the subject is not a named entity, return an empty list.
- Include at least one triple where predicate is "instanceOf".
- Do not get too wordy.
- Separate several objects into multiple triples with one object.

Input

Subject: Cassegrain focus
Description of subject: Cassegrain focus is a telescope optical configuration in which light is reflected by a secondary mirror back through a hole in the primary mirror to form a compact, accessible focal point behind the primary.

Referenced by (9)

Full triples — surface form annotated when it differs from this entity's canonical label.

Ritchey–Chrétien reflector → hasSecondaryMirrorPosition → Cassegrain focus ⓘ

Cassegrain focus → usedIn → Cassegrain focus self-linksurface differs ⓘ

this entity surface form: Cassegrain telescope

ESO 3.6 m Telescope → hasFocalStations → Cassegrain focus ⓘ

GeMS (Gemini Multi-conjugate adaptive optics System) → mountedOn → Cassegrain focus ⓘ

subject surface form: GeMS

this entity surface form: Cassegrain focus of Gemini South

GSAOI (Gemini South Adaptive Optics Imager) → mountedOn → Cassegrain focus ⓘ

subject surface form: GSAOI

this entity surface form: Cassegrain focus of Gemini South telescope

NASA Infrared Telescope Facility → telescopeType → Cassegrain focus ⓘ

this entity surface form: Cassegrain reflector

Schmidt–Cassegrain telescope design → opticalConfiguration → Cassegrain focus ⓘ

this entity surface form: Cassegrain configuration

GMOS-N (Gemini Multi-Object Spectrograph North) → mountedAt → Cassegrain focus ⓘ

subject surface form: GMOS-N

this entity surface form: Cassegrain focus of Gemini North

Altair adaptive optics system → mountedOn → Cassegrain focus ⓘ

this entity surface form: Gemini North Cassegrain focus