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Takahashi CCA-250 Performance - one customer's brief first light impression.

Posted by Gregory Santos   09/05/2013 12:00AM

Takahashi CCA-250 Performance - one customer's brief first light impression.
Takahashi CCA-250 Performance - one customer's first light impression.

The deep sky image shown is an example of the *least* the CCA-250 can do -- it's only 25 minutes total, not perfect collimation, insufficiently processed, and at half-resolution.

Still, it has more detail than I could have gotten with triple the time using the TOA-130 (that's just photographic speed and linear resolution, nothing against the TOA-130 :-). Take a look at the smallest of the four background galaxies above the head of NGC 7331; the barred spiral structure is completely evident, despite the faintness and tiny size of the target. Wowie!

(PLEASE NOTE: The above enchilada was heavily size-reduced to meet the article submission limits for images - Ed.)

I don't know if other of your customers have the same goals as I had, but IMHO, the real strength of the CCA-250 is in what it combines in a single package:

* Fast native photographic speed (f/5)
* True compactness and portability (one-person field setup)
* Outstanding optical and mechanical quality (Takahashi, what more can we say?)
* Very large flat-field image circle (no flatteners to buy)
* Outstanding built-in focusing (no add-ons required, 52nm steps!)
* More linear resolution than almost any amateur-sized refractor
* Active cooling included (nothing to add on)
* Temperature sensing for ambient, primary, and tube interior
* Manufacturer-supported reducers and extenders
* Mount-ready integrated hardware (no plates to buy and install)
* ASCOM driver control interface (supplied)

These are roughly in order of my own predilections, others
may have a different order. But it's pretty difficult, if not impossible in the current commercial marketplace, to find all of that in one device. It can *almost* be done with other devices, but not easily, and not without some add-ons and iffy extensions. Potential customers may want to do what I did: add up the *total* expense to get another OTA even close, *then* compare to the price of the CCA-250.

Additional Notes:

* Be prepared to spend some time collimating to the degree required for use with a camera.

* The spot sizes are tiny, even at the edge of the field; so this OTA favors sensors with smaller pixels, which help to take advantage of the extraordinarily small spot sizes.

* The scope works quite well visually, despite the large central obstruction; but to avoid secondary shadowing, it's best to use 1 1/4 eyepieces at about 75x or higher magnification.

* Other than the ASCOM driver, no software is included, so be prepared to use or invest in a popular package such as MaximDL.

SPECS (from the Distributor's web site):

Optical System: Corrected Cassegrain
Effective aperture: 250mm
Focal ratio: f/5
Metal back distance: 193.5mm
Tube diamete:r ø306mm
Tube length: 870mm [34.25”]
Tube weight: 22.8kg [50.16lbs]
Power source: 12vDC x 2A

With the CR 0.73x Small Reducer

Focal length: 910mm
Focal ratio: f/3.6
Image circle: ø38mm

With the CR 1.5x Extender

Focal length: 1880mm
Focal ratio: f/7.5
Image circle ø40mm

With the 645 0.72 x Large Reducer

Focal length: 890mm
Focal ratio: f/3.6
Image circle: ø60mm

Greg Santos
member San Diego Astronomy Association