Oct. 2010
This month I finally broke down and
purchased a wide field of view camera, an Orion StarShoot Pro V2 color
camera, for imaging those large objects. My Meade DSI color
camera still works fine but I got tired of building mosaics of big
objects like the Pleiades, Andromeda, Rosette nebula, and the like.
The smaller pixels and large format makes a big difference in the
quality of the images.
I did however run into one problem, that being vignetting. The
DSI, having such a small FOV didn't suffer from that problem.
I ended up with a hot spot in the center of the image and the
outer edges were darker. To eliminate the vignetting I had to
apply flats during the processing of the raw images. I had been
shooting my flats during the day after taking the images by placing two
layers of T-shirt material over the end of the OTA and shooting flats.
I had applied these flats to my images but got all kinds of odd
results form reverse vignetting , light edges and dark central region to
a gradient problem across the image. I beat my head against this
for a number of weeks and finally decides that there has to
be something wrong with the flats. Perhaps stray light leaking in or
something.
Jan 2011
The problem I had with my previous flats prompted me
to build a light box to use in shooting them. I had read
about them but didn't think I needed one.
I made my box out of 1/4" foam core board readily available at Staples
and othe4r office supply houses. The box is a 12" cube with one
end having a 10" hole cut in it which fits the dew shield of my
SN8 . The segments are held together with the ubiquitous Duct tape
. I used blue painters tape to fasten the outside back cover which
should allow me to easily remove it should I need to replace
a bulb.
I put one 12v 25mA mini lamp ( purchased at Radio Shack) in each
corner of the back that fits over the dew shield. I placed another
panel with a 10" hole over the back about 3/4" from the one
holding the bulbs. This provides a bit more stability to the box when
slid over the dew shield.
I power the lamps with a 9V source to keep the brightness down.
I have only made one set of flats with it so far but have
noticed that there is a marked improvement in the quality of the
final image. I still need to experiment with the flats to
insure I get the best ones.
Oct 2 2013:
My Orion Star Shoot
Pro color camera bit the dust. It won't talk to the computer. I'm
not sure it can be fixed , though I have some acquaintances that
might be able to take a look at it. I got about three good
years out of it. Time to upgrade!!
Upgrade I did. Purchased a almost
new (still under warranty) SBIG STF8300c one shot color camera. The
camera has relatively small pixels, 5.4 microns, which allow it to get
finer details than the SSP which had larger pixels. The camera also has
TEC (Thermo Electric Cooling) that is regulated to keep the CCD at
a preset temperature. This feature keeps the read out noise to a
minimum. The warmer the CCD gets the noisier the image will be.
I've
taken a couple of test shot with the camera and am very pleased
with it's performance.
The table below lists the specifications
for the STF-8300 camera. Specifications are typical and can vary from
camera to camera and are subject to change without notice.
STF-8300 Typical Specifications
CCD |
Kodak KAF-8300 (mono or color) |
Pixel Array |
3326 x 2504 |
CCD Size |
17.96 x 13.52 mm |
Total Pixels |
8.3 Million |
Full Well Capacity |
~25,500 e- |
Dark Current |
0.002e-/p/s @ -10C |
Antiblooming |
1000X |
Shutter |
Even-Illumination, Mechanical |
Exposure |
0.09 to 3600 seconds |
A/D Converter |
16 bit |
Gain |
0.37e-/ADU |
Read Noise |
~9.3e- |
Binning Modes |
1x1, 2x2, 3x3, etc. - 15x15 |
Digitization Rate |
10 Megapixels / Second |
Full Frame Download |
Less than 1 second |
Cooling |
-40C max. from ambient |
Temp. Regulation |
+/- 0.1 degree |
Power |
12VDC, 3 amps max |
Interface |
USB 2.0 |
Computer Compatibility |
All Windows O/S, 32-bit and 64-bit, Mac
OSX |
Camera Body Size |
2 x 4 x 5 in (50x100x127mm) |
Mounting |
T-thread, 2" Nosepiece |
Weight |
1.8 pounds (0.8 kg) |
Backfocus |
0.69 inches (17.5mm) |
March 2014
Time to spend some more money. I've been
using the SN8 for all of my imaging to date. I thought it would be
interesting to see what kind of images I can get with the SBIG and
the ED80. The problem is that I'm using the ED80 as a guide scope
so I needed a replacement. The choice I made was the Orion 8891 Mini
50mm Guide Scope
. The plan was to use the 50mm and the DSI pro camera for
guiding which would allow me to mount it on the 8" Newtonian or the
ED80. To my pleasant surprise, the combination of DSI and 50mm scope
worked perfectly. The 50mm has a wide field of view which makes it easy
to lock on a star for guiding. The DSI Pro is sensitive enough to pick
up a large number of stars in the FOV and the guiding is spot on.
My next trial will be to hang the SBIG on the ED80 and see what I can
image. I'll wait for a little while longer for he weather to warm up,
though.
(stay tuned for updates )