From: "mihalco" <mihalco@yahoo.com>

Date: January 21, 2010 11:40:51 PM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: New AstroIIDC user

Milton,

I agree. When comparing the sensitivity of individual pixels, the larger pixels of the ICX285 are certainly more sensitive than the smaller pixels in the ICX274. Sensitivity can be increased at the expense of resolution by binning.  I prefer to compare the QE of the sensors, which is independent of pixel size.  Unfortunately, Sony doesn't provide real QE curves for theirs (only normalized to the peak).  Third parties have measured both the IXC285 and ICX274 QE's peaking right around 60%, with the ICX285's peak a bit broader and centered more towards the red than the ICX274.

Regards,

Kurt

--- In Astro_IIDC@yahoogroups.com, "milton_aupperle" <milton@...> wrote:

Kurt;

Actually, you need to compare the Sony CCD chip specs not those percentage graphs which are "relative". They have a sensitivity measurements in absolute terms for each CCD.

The Sony ICX274AL Super HAD CCD in the Scorpion has a sensitivity (page 11 of the Sony Spec Sheet) typically of 420.

The  Sony ICX285AL EXView HAD  in the Grasshopper has a sensitivity (page 9) typically of 1300.

So you can see it's basically 3 times as sensitive.

And you can find them by searching for Sony ICX274AL or Sony ICX285AL with Google.

HTH..

Milton Aupperle

--- In Astro_IIDC@yahoogroups.com, "mihalco" <mihalco@> wrote:

Here is a good camparison of the relative spectral performance of the various Sony chips:

http://www.ptgrey.com/support/downloads\

/documents/TAN2008006_Sensor_Response_Curve_Comparison_for_ICX445.pdf

See figures 3 and 4.  The Grasshopper 14S5M uses a ICX285 with 6.45 micron^2 pixels (area = 41.6 sq microns), the Scorpion uses an ICX274 with 4.4 micron^2 pixels (area = 19.4 sq microns).  The ExView HAD on the ICX285 is a bit more sensitive than the HyperHAD on the ICX274, but also a bit more red/IR biased.  When binned, sensitivity should be adjusted accordingly to the binning factors (x*y).

HTH,

Kurt

--- In Astro_IIDC@yahoogroups.com, "milton_aupperle" <milton@> wrote:

Mark;

No. They put different CCD's in different Grasshopper models, just like the Scorpions, Fleas etc.. The one I have (GRAS-14S5M-C) is 6.45 microns and it's an EXHAD CCD not a HAD (use Google to find the difference). Basically it means the CCD is about 3 times as sensitive as your 4.4 micron Scorpion is.

As far as filters go, I don't have a preference, except that they should be parfocal. I got a good deal on the Astro Don E series as they were being cleared out and were basically the same price as a Baader.

HTH..

Milton Aupperle

--- In Astro_IIDC@yahoogroups.com, Mark Gaffney <markgaffney@> wrote:

Hi Milton,

I thought I read that your Grasshopper is 4.4 microns too, is this the  

case? I guess there maybe other versions? I told the guy from Adelaide  

I`d get back to him with respect to the Astrodon`s but not at his  

exhorbitant price! Kurt`s just written with qualified praise for the  

Baader`s for their price. Do you think they`d be better than your run- 

of the -mill types like perhaps the Astonomicks, or any good at all?

Mark.