Fx2 Astrograph f4 and f8 upper cage assemblies (DWS 23)

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Fx2 Astrograph f4 and f8 upper cage assemblies

This picture shows the upper cage assemblies for the f4 and f8 systems. Note the difference in the secondary mirror sizes.

The Fx2 was designed and built by myself with the design goal of having a convertible astrograph that will work at either f4 (1240mm fl, wide field) or f8 (2540mm fl, higher resolution field for smaller objects) by simply swapping out the upper cage assembly onto the lower OTA. The optics were designed by Roger Ceragioli and the results speak for themselves. They achieve excellent resolution over a full-frame CCD chip, with minimal edge aberrations. The primary mirror is an f/4 paraboloid made by Carl Zambuto. Collimation is established in-shop and once set, there is no need for adjustment in the field -- for either system.

The upper cages are fully rotatable without affecting collimation, so that a comfortable and convenient observing position can always be found. To change over from f4 to f8 it simply involves swapping out lenses in the focuser for the appropriate upper cage and then mounting that cage onto the lower part of the OTA.

Since the f/4 and f/8 configurations use different-sized secondary mirrors, the observer is afforded optimization of the f8 system for high resolution work by use of a smaller secondary. Both upper cages also use 3 vein spiders made from extremely thin veins that greatly reduce diffraction effects. For imaging these optics achieve near perfect resolution out to a 20 mm radius without distortion, easily accommodating larger chips.

Not only does the Fx2 work extremely well for wide-field imaging and high-resolution work, it is also a joy to use visually.

Please note: The following tables are updated every 24 hours.

Distribution of astrophotographers

This table shows the number of distinct astrophotographers who have been assigned and IOTD/TP award compared to the total number of images awarded.
	Distinct awarded users	Total awarded images
Image of the day
Top picks
Top pick nominations

Distribution of subject types

This table shows the distribution of awards per subject type, compared to the popularity of images of that subject type.
	Image of the day	Top pick	Top pick nominations	Total submitted
Deep sky
Solar system
Extremely wide field
Star trails
Northern lights
Noctilucent clouds
Landscape

Distribution of data sources

This table shows the distribution of awards per data source, compared to the popularity of images acquired from that data source.
	Image of the day	Top pick	Top pick nominations	Total submitted
Backyard
Traveller
Own remote observatory
Amateur hosting facility
Public amaeteur data
Professional, scientific grade data
Mix of multiple sources
Other
Unknown

The “AstroBin Image of the Day and Top Picks”, or IOTD/TP, is a long-running system to promote beautiful, interesting, peculiar, or otherwise amazing astrophotographs, with a focus on technical excellence. Learn more.

Submitted The date and time when you submitted this image for IOTD/TP consideration.	...
Views by Submitters (available since September 19th, 2023) Every image is assigned to 50% of available Submitters. In the event that at least 80% of them don't view the image before its time in the IOTD/TP process expires, it's assigned to the other 50% of Submitters and the process begins anew.
Promotions by Submitters When 3 distinct Submitters promote the image, it moves on to the next stage of the process: evaluation for Top Pick status. This requirement, in addition to anonymization of images and distribution to only a subset of them, prevents biases and ensures that the best images are selected.
Promotions by Reviewers When 3 distinct Reviewers promote the image, it moves on to the next stage of the process: evaluation for IOTD status.
Early dismissal Staff members have a lot of images to inspect on a daily basis, and they can dismiss images if they believe they don't meet the requirements for IOTD/TP selection. If an image is dismissed 5 times, it's removed from the process. This streamlines the process and ensures that any bias present in promotions could be overruled by other staff members.

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Fx2 Astrograph f4 and f8 upper cage assemblies

Fx2 Astrograph f4 and f8 upper cage assemblies

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Fx2 Astrograph f4 and f8 upper cage assemblies

Fx2 Astrograph f4 and f8 upper cage assemblies

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