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

Date: July 31, 2008 2:18:43 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: First Light with PGR GRAS14S5M Camera

Hey Milton,

It's a wonder you got anything at all!  I can see the effect of the wind.

So you now live at 52 deg. north latitude, having remembered the Arctic Circle is at 66 

deg. + some minutes.  Gee, that's above Winnipeg!!

Whereforeareyounow??

Perry

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

Hi folks;

It cleared off last night, so I decided to try a quick test of the

camera on Messier 3 Globular Cluster. It has an easy to find 6th Mag

guide star to the south for the Off Axis Guider camera, so I decide

that would be the first target for the Mono Grasshopper GRAS14S5M

EXHAD camera.

Unfortunately, guiding was horrific last night with average tracking

being +/- 3 arc seconds and "spikes" of up to 20 arc seconds for RA

and Dec. This was due to the Jet stream being right overtop of me

(Arcturus and Vegas twinkling like mad), gusty surface winds to 60

kmph blowing the scope around and me not checking the scope balance

with the new cameras in place before using it. So of the 20 frames I

took over 40 minutes, only 6 are "pseudo usable". Not an ideal night

for a test, but better than clouds and rain.

It was 12°C at 11:30 pm, so I only cooled the camera down to +6°C so

that I didn't get too much condensation or run the risk of icing up

the glass cover plate. Visual magnitude at this new location (I moved

end of June) was about Mag 3.0 last night and there was a light haze

in the sky. It doesn't get dark here until around 11:30 pm and it

never gets really dark because I'm only 14° south of the Arctic Circle.

I used the Celestron F6.3 focal reducer on the C8 scope (effective

focal length about 1100 mm) and an IDAS LPR filter to reduce the light

pollution noise. The IDAS will reduce around 50% of the light

received, however without it I likely could not do more than 60

seconds without having the lost all the details from the background.

I shot a five two minute sequence of dark frames and then had Astro

IIDC auto subtract them from each two minute frame after it was

captured. I kept the gains very low at + 5% (100 out of 756), as high

gains bring out hot pixels and increase noise. However there is very

little noise,  hot  / cold pixels and no amp glow at all for this camera.

I average stacked 6 of the 20 frames collected and posted the

unprocessed Raw stack at:

http://tech.groups.yahoo.com/group/Astro_IIDC/files/Other/M3%2020080730_Grass_Sta

ck.jpg

I then log stretched it "a lot" and used some "cutoffs" limits to

reduce the background light to produce this image here:

http://groups.yahoo.com/group/Astro_IIDC/files/Other/M3%2020080730_Grass_Stretche

d.jpg

Nothing great image wise, but it does show the potential of the

camera. Noise and image quality wise I'm very pleased with the cameras

performance so far. I had an issue where the first frame out after a

long exposure was black (I believe it was a buffering issue as the

camera has 32 megs of Ram for capturing frames rapidly), but upgrading

the camera firmware to 0.09.01.30 solved that problem.

We have high thin clouds now thickening after midnight, so I'm not

sure if I'll get another chance until after it starts raining again on

Sunday. The weather here has been well below normal temperatures and

above average amounts of rain (or snow in the foothills), definitely

not conducive to doing DSO imaging.

I have a 5 slot color filter wheel on order and will hopefully get to

use it when I head off on my vacation in the latter part of August to

that dark sky site (Mag 6 to 7 skies) I go to each summer.

Milton Aupperle