From: "Tim" <tjp314@pacbell.net>
Date: August 8, 2008 10:31:01 AM MDT
To: Astro_IIDC@yahoogroups.com
Subject: Re: First Light with PGR GRAS14S5M Camera-Filters????
Wow!
Those pix are gorgeous!
So, how do you cool the camera? Like with the Flea?
I've got a milling machine and a couple of lathes. I've cogitated
about making a cooled enclosure for the whole camera, though sealing
it around the firewire port might provide something of an interesting
challenge...
How does the Starlight Xpress camera that uses the Exview chip compare
pricewise to the Grasshopper? (though it likely can't do the frame
rates, it's cooled).
planetarily,
-Tim.
--- In Astro_IIDC@yahoogroups.com, Milton Aupperle <milton@...> wrote:
Hi Tim;
On 6-Aug-08, at 11:53 AM, Tim wrote:
Milton:
Cool! I've been dying to hear how the grasshopper cameras perform,
but have been afraid to be the guinea pig (well, my wallet has been
the fraidy cat, mostly). Can you disclose the price?
As I mentioned in the "first light" camera report, it was under $3K,
which includes the $100 Dev kit, shipping and 5% Canadian GST taxes too.
I followed your recommendation from a while ago and put an old Meade
2" Nebula filter on my SBIG camera on my Megrez 80, for hoots. I live
7 miles north of downtown Los Angeles (can see the 'scrapers from my
house), and I have no trouble imaging 13th magnitude galaxies with it
(though lately I've been having annoying jumps in guiding my Nexstar
that I haven't quite sorted out yet).
I'm using a 2" IDAS LPR filter and that makes a huge difference in
removing city Light pollution from the CCD. Form the light curves
I've seen, I'm throwing out about 50% of the total light I would
receive from a star with the filter. Depending on altitude, the
background last night was 17,000 out of 65,535 at 30 degrees or lower
and around 12,000 out of 65,535 at 60 degrees for a 4 minute
exposure. Without the filter, I'd have a nearly white background in 2
minutes or less.
I had a really good seeing last night, with no surface winds, close
to zero turbulence and other than thin haze (Mag 3 visually, best
nights are about Mag 4.5 here) with a sporadic cloud, it was nearly
as good as it ever gets here in Calgary. I started imaging at 11:00
pm (still dusk here) and stopped at 3:15 am when the sun rise started
to increase sky brightness. I managed to image M5, M13 and M27 with 4
minute exposures and the Cooled (about -6°C below ambient, which was
11°C at 3 am) Mono Grasshopper on the C8.
http://groups.yahoo.com/group/Astro_IIDC/files/DSO/
M5_20080805_230551_L_MJA.jpg
http://groups.yahoo.com/group/Astro_IIDC/files/DSO/
M13_20080806_004858_L_MJA.jpg
http://groups.yahoo.com/group/Astro_IIDC/files/DSO/
M27_20080806_022236_L_MJA.jpg
I guided using my old color Flea camera on the Celestron Off Axis
Guider. I screwed up the dark frame process because I cooled the
camera first, then turned it on the camera (the temp rises 5°C as it
warms up in about 20 minutes) and then took the dark frames. I really
should have been running the camera while it was cooling down so that
it reaches equilibrium before doing the darks. That's why there are
hot pixel fly specs on the images.
Also the Mono cameras are less for giving of any tracking issues, so
my stars are a bit elongated on the RA due to PEC, especially M27.
Since I rarely get skies stable enough to do PEC with the HEQ5 mount,
so I have ignored it. It rarely is an issue with the Color cameras
because your using a 3x3 or 5x5 array of nearest pixels for
generating the RGB stars, which means any elongation is lost in the
averaging or turbulence. When your star is captured for each pixel
and under good skies, there is less tolerance and my measured PEC
oscillates +/- 2 pixels at 1100 mm focal lengths. It's supposed to be
good seeing again tonight, so I hope to hook up the barlow and do PEC
training with the HEQ5 on Arcturus and try imaging again.
TTYL..
Milton J. Aupperle