QHY9 camera?

Hi,
I'm wondering here if anyone has any thoughts on the QHY9 camera?
Seems good value for money considering the size of the chip.
www.qhyccd.com/QHY9.html
www.modernastronomy.com/camerasQHY.htm#qhy9

Michael.

Michael,

I agree really good value as compared to all the other makers

Do you know the physical size and pixel size of the sensor for the QHY16. They give no specs. I did go onto there forum and there is no mention of it.

I was also impressed with the QHY12, in particular the low price
and the small pixel size of 5 microns/pixel if you were applying short FL of around 400mm

Eamonn A

www.kingslandobservatory.com

In terms of the QHY16, it uses the KAF16803 chip.
www.ccd.com/pdf/ccd_16m.pdf
4096 x 4096 x 9um - Big chip

In terms of multi megapixel ccd cameras and resolution, I am wondering how useful they are and would like to know what others here think.
We normally try and match the pixel size of the ccd camera to the focal length to get an optimum resolution. The resolution which can be achieved on long exposures is usually limited to the seeing conditions of the atmosphere and a figure of 2-3 arcsec per pixel is normally used.
However, when using a multi megapixel ccd camera, the image may be quite big relative to the computer screen. To display the image on the screen, it may needed to be scaled down in size significantly. Also, processing several large images at one time can be quite demanding in both time and on the PC. If I understand it right, reducing the size of the image to make it easier to view on the web will reduce the resuloution of the image and reduce the benefit gained by using a camera with small pixels.
What do others here think?
Would we be better off sticking with ccd chips which have larger pixels?

Michael

michaeloconnell wrote:

If I understand it right, reducing the size of the image to make it easier to view on the web will reduce the resuloution of the image and reduce the benefit gained by using a camera with small pixels.

My thoughts as well. Such a large chip is beneficial if, say, you were planning to sell prints to publishers or as posters etc. For web viewing you're not really going to get the full benefit. At 4096 pixels squared that makes it almost 25% bigger than A0 (1189mm X 841mm) if printed at 300dpi. Major overkill for web-only viewing, which for any image will be compressed to 72dpi as a standard anyway (when exported from e.g. Photoshop).

Front a graphic designer's perspective, you can keep an image the same in physical dimensions while reducing the pixel count (A4 at both 72dpi for web and 300dpi for print), so you do have to think about what you want to use the camera for.

Would such a large chip be what you'd look for in relation to deep sky hunting of e.g. asteroids, variable star readings, etc due to the ability to zoom in when blown up at full size? I am no expert in this so if I am talking jibberish, forgive me!

Seanie.

Michael,

The QHY12 makes sense if you were using it with a tel lens of FL 400mm. You would obtain 2.25 arc sec/pix. However, using the QHY16 is 4 arc sec/pix. Irish conditions at best are around 2.5 arc sec. Of course there are exceptions I've recorded here of 1.6 arc sec. However, if you were to use it the cameras frequently then 3 to 3.5 arc sec may be typical. The QHY9 and 12 would be fine.

Using longer f ratios beyond these doesn't justify the the QHY9 or the QHY12. The well depth of the pixels is so small. 15 to 24 micron/pix would make more sense, and you have the advantage of more sensitivity (well depth). I use two cameras AP7 & AP8 at a FL of 4m, they have 2.2 and 1.4 arc sec/pix respectively. The stars are near pinpoint although they dance around a centre point because they are dealing with a sky resolution of 3 arc sec.

Eamonn A

www.kingslandobservatory.com

michaeloconnell wrote:

Would we be better off sticking with ccd chips which have larger pixels?

Michael

It depends - the pixel size of the CCD should be matched to your optics. With the C14, the optimum pixel size is about 24um. Also, bear in mind that larger pixel sizes may also give a better response.

On the image size question, downloading that amount of data would also be an issue to be reconciled. You don't want to waiting ages for images to reach the pc... As regards the graphics question, that would really be in the realms of "pretty pictures". But surely a bit of cropping would reduce the physical size of the image without degrading it at all. Of course, for science, you'd have a huge field of view - perfect for astrometry

FWIW

Dave