Imaging Gear

My current imaging scopes are a Takahashi FSQ106EDX and a new PlaneWave CDK 12.5.

The Takahashi is a widefield refractor with 4 elements, a virtually flat imaging field, and no false color. Focal length is 530mm at f/5, and at prime focus it illuminates an 88mm circle.

The PlaneWave CDK 12.5" is a corrected Dall-Kirkham design. This long focal length scope is the final piece of my new imaging setup. After experiencing the flat imaging field of the Takahaski, I couldn't settle for anything less with a long focal length instrument.

My imaging camera is a QSI 583wsg, which uses the KAF8300 chip. Pixel size is 5.4 microns, which tranlates to 2.1 arc seconds with the Takahashi. The sensor is 3326 x 2504 pixels, with a field of view of 1.9 degrees by 1.4 degrees on the Tak.  I'm binning the camera 1x1 with the PlaneWave, which gives 0.44 arc second pixels - oversampled for my seeing conditions, but seems to work OK. The FOV on the CDK is approximately 24 x 18 arc minutes.

The QSI is characterized by very low thermal noise, and has little fixed pattern noise. I usually run it at -20 degrees C except on very hot summer nights, where I drop back to -10 degrees C.

The QSI has a built-in filter wheel with 5 positions. They are currently filled with 1.25" Astrodon Generation 2Tru-Balance LRGB filters, plus the Astrodon 3nm Ha filter. The Astrodon filters are well matched to the sensor in the QSI camera - colors seem well balanced in general. If and when I add additional narrowband filters, I'll have to either buy another filter wheel, or upgrade to the new QSI 700 series camera. I also recently purchased the Astrodon V filter for light curve work.

With the Planewave CDK 12.5, I found that I was having a hard time finding good guide stars, given the much smaller field of view. I recently bought a Lodestar guide camera, and that seems to work great with the QSI and CDK. Plus, the crummy Meade Drivers are no longer a problem!

Probably the most important part of the entire setup is the mount - a new Astro-Physics AP1100. I can't say enough positive things about this mount - it's solid, well machined, and has very low periodic error. I splurged and got the version with the RA and Dec encoders, which I am still learning to make the best use of. Once (if) Astro-Physics releases the APCC software, I can create an all-sky model which, combined with the encoders, should give excellent tracking over the entire sky.

Focusing is done using a RoboFocus automated focuser on the Takahashi, which is controlled by Focus Max during image acquisition. The RoboFocus works fine, but it's definitely not up to the standard of the mount and camera in terms of fit and finish. The control box is on the amateur side, and the first unit failed after 2 weeks. RoboFocus replaced it, but it doesn't inspire a lot of confidence. I may look for another focus solution in the future.

The PlaneWave comes with a very sturdy Hedrick focuser and controller. PlaneWave has just released a new PlaneWave Interface program, which enables focus calibration and auto focus using the Hedrick focuser. It required me to change change to Maxim DL for image acquisition, which I did early in 2012. I am currently using FocusMax for auto focus, as it works with Maxim and my ACP automation software. However, PlaneWave and DC3 Dreams have recently worked together to create beta versions that use the PWI software with ACP. I plan to install this and test it soon.