Hyperstar System Information
* Meade 8" scopes are not available for hyperstar systems nor are there plans, as of March '12.
* The QHY9 KAF 8300 chip is a full- chip and requires a mechanical shutter. SBIG has a shutter design which gives constant exposure across the chip, but QHY does not. That makes the QHY mechanical shutters a non-starter for precision CCD photometry. Unfortunately, the SBIG 8300 camera is just too big; 4x5inch just takes up too much of the incoming light path, and in a non-circular profile too. And it's 1.8 lb, which I think is likely too heavy. Need an electronic shutter camera!
* ATIK 383L has mechanical shutter, recommends exposures over 0.2 sec
Cameras Compatible with 8" and Larger HyperStar Lenses
Using this Starizona online pixel calculator, I get...
QHY9 CCD with Hyperstar C8 f/2.1 (f2.1 is the only one on their list), 2.62"/px, and 159.4' x 121.3' or 5.37 sqDeg FOV
Using my program c:\qhy\stars.for I calculate ...
Also note that a calculator for counts on a CCD chip is here. Using 20cm diameter, 12cm secondary=hyperstar, 1 mirror, 1 lens, radius of photometry aperture=1.4" (ie 1 pixel is 2.62"),
| 8" = 50.26sqIn | Chip | Readout Noise | Full Well Capacity | Cooling, Wt. | FOV | Scale | Field Area | #Stars [mag 6.5-7.5] | #Stars [mag 6.5-9] | #Stars [mag 7-10] | U+B+V+R+I counts/px/sec m=7, 3"FWHM seeing disk | U+B+V+R+I counts/px/sec m=7, 5"FWHM seeing disk | U+B+V+R+I counts/px/sec m=9, 3"FWHM seeing disk | Verdict |
QHY9 Hyperstar C8 f/2.1 3.27in Diam = 17% obscuration |
KAF8300 | 9e- | 25,500e- | 510g -50C | 159.4' x 121.3' | 2.62"/px | 5.36 sqDeg | 2.2 | 14.8 | 42 | 77,000 m=7 | 36,000 m=7 | 12,451 m=9, 3" seeing disk | $2100 here and $2099 here |
ATIK 428EX Hyperstar C8 f/2.1 400g, min exp=1/1000s, 2.36in Diam |
71.2' x 53.4' | 2.30"/px | 1.06 sqDeg | |||||||||||
Atik 383L+ 4.41in x 4.41in =39% obscured |
KAF8300 | 700g -40C | 147' x 109' | 2.62"/px | ||||||||||
|
Notes:
*
KAF8300 shows great linearity from 1000 to 64000 making it great for photometry, described here.
* Atik recommends with their 383L+ camera (KAF8300) that you use a minimum of exposure of 0.2 sec. Is there shutter that much better than QHY's, where users are talking about 1-2 second minimum? This review liked QHY9 but settled on 4 sec flats.
* Why can't I just use an annulus mask to increase required exposure, for bright stars? Also, if you use just one comparison star, it would seem that as long as it stays at the same place on the chip, that you would only be getting a consistent magnitude offset, not important for detecting a transit, but important for a calibrated final magnitude. But then, the star itself if bright, will probably already have well-characterized calibrated photometry done in various bands, so only a depth of eclipse is required anyway.
* I think I should stay away from one-shot color cam's, as they're photometry even of eclipse depth will be very iffy.
* QHY11 large format is $5000 so forget it!
Desiccant QHY9 issue
* From 2009 QHYCCD forum
* maybe get tiny glass jar for holding desiccant strips; can regen in toaster. Pop them in the outer chamber regularly. They hold their own weight in water.