From: "doodlebun" <gbleser@bellsouth.net>

Date: April 23, 2010 9:51:01 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Final question about the Flea3...

Milton:

  Thanks much! The fever pitch over the Flea3 camera is running so high that some anxious astros have modified their DMK's by modifing it with a chip replacement (ICX618ala).  

 I don't want to do that. But I would like to be the first human to announce compliance with Astro IIDC. One obvious difference is that the Flea3 is a Firewire 800 device. I don't know how important that is.  Perhaps a Firewire 400-to 800 adapter would get the camera recognized. 

 Early indications are that is is IIDC compliant. You have enough irons in the fire so I will pester PGR to see if I can provide you with the internal model number down the road.

Thanks again,

Dave

--- In Astro_IIDC@yahoogroups.com, Milton Aupperle <milton@...> wrote:

On 22-Apr-10, at 12:04 PM, doodlebun wrote:

In the past week a ground swell of excitement is building for the  

new PGR Flea3 camera.

Anthony Wesley (Bird) is singing the praises of this camera but he  

doesn't use Astro IIDC.  He brought up a gain issue that I would  

like to hear some expert commentary by Milton before I spend $500+  

for this camera. Straight from the horses mouth...

Ok, I've heard back from PGR about something I noticed on the Flea3,  

I didn't want to say too much before checking with them in case this  

interesting behaviour was going to somehow "go away" in future, but  

they seem happy enough with it.

The Flea3 officially supports gain values from -2db to 24db, *but*  

this can be easily bypassed and gain values up to 33.2db are  

possible. The image is amazingly bright at 33.2db and the background  

noise is still very low. This is a killer feature of the camera, but  

you need software that will know how to access this extra gain or  

else you'll see a limit of 24db.

Coriander under Linux supports the over-gain values as-is, and for  

Windows users I've emailed Torsten about adding support into  

Firecapture for it.

The way to access the exctra gain is very easy really - the camera  

control registers have two ways to set the gain, either a slider  

value from 0 to 762 that is mapped onto gain values between -2db and  

24db, or using the "absolute value" registers where you write the  

actual gain value requested as a floating point number.

We don't currently support Absolute Gain registers in Astro IIDC. And  

each model has a different gain ranges too (my Grasshopper has gains  

from 64 to 746, my Flea has gains from 200 to 1023).

Also, we do check the expected range of all absolute registers and  

stick to those min max limits, so if the official upper limit is 24  

db, then that's as far as it goes. I will not send out of spec values  

to camera registers.

In the second case, using the absolute value register for gain its  

possible to input values up to 33.2 and the camera responds  

accordingly :-)

I have a really hard time believing that having extra gain is a good  

thing. I'd also like to see how they "quantify" noise levels versus  

gain too. Is this some eyeballed guess or do they do multiple runs and  

correlate the results? Noise is the measure of randomness and all gain  

does is amplify that noise. So I don't see how increasing the gain  

above range limits is likely to be "magical".

I recently did a gain versus noise measurements on my Grasshopper  

(this takes the better part of a day to measure the curves and noise  

characteristics, I only measured noise up to mid point of gain range).  

Frankly the noise levels go up Astronomically once your above 350 gain  

(min gain is 64, Max gain is 746). At a gain value of 746 max, the  

brightness is amplified by 43.00 times over what the brightness is at  

64 gain, but the noise is terrible and you need hundreds of frames  

stacked to compensate for this.

For DSO imaging, I have my Grasshopper gains at 251 which results in a  

2.71 times increase i brightness and about a 2.5 times increase in  

noise level over what I get at 64. Going higher drastically increases  

the noise level unacceptably, so that I need to shoot more frames  

which increases the total exposure time and night time up here is  

rapidly decreasing (doesn't get dark here now until almost 10:30 pm).

Lastly, I don't know if Astro IIDC 4.05.04 or earlier will recognize a  

Flea 3 camera or not. It depends on what the internal model number is  

and PGR doesn't tell me anymore what those numbers are until after the  

camera is shipping and they finally get around to document them in  

their camera manuals. I have removed this checking in Astro IIDC 4.06.  

A1 so I don't have to wait for them to do it anymore. However I can't  

guarantee all their cameras work - some models are not IIDC Compliant  

- so that's on your head now.

HTH..

Milton Aupperle