For those who might be interested, here are some of the problems I have encountered and what I have done to compensate: (in the beginning, I used the C-5 and an SBIG 237 camera)
First of all, on the first few nights of imaging, I became aware of the
difficulty of locating objects in the light polluted sky with my
equipment. Because the C-5 does not have any computerized 'go-to'
capability without special
accessories, I was forced to search for objects that
in many cases were not visible to the eye, even through the
telescope. I tried several different techniques, including
star-hopping and pollution filters, before finally settling
on the setting
circles method. I would then locate a bright star in the sky
vicinity of the object desired and carefully align the setting circles on the
telescope. From there I would move the scope to the right ascension and
declination of the object to be imaged, and do a computer search under focus
mode for the object desired. This worked very well and most objects
were found within a few seconds to a few minutes of looking.
I also realized immediately that the counter weights provided with the C-5
balancing system were woefully inadequate for the imaging system I was
using. I solved this problem by putting some lead shot into a sock
and
hanging it on the counter weight arm. Without this improvement,
the tracking drive is so overloaded that it simply does not work properly.
The next problem which cropped up was focusing. I am sure that anybody
who has used a CCD camera is familiar with the time-intensive need to
accurately
focus the image on the chip. While I had had some previous
experience with these cameras, I was still surprised at how sensitive
the CCD is
to things like temperature and filter changes. After taking some
disappointingly mediocre images, I now routinely re-focus the
camera for each
and every image to be captured. I was particularly surprised to find
that there is
a noticeable difference in the
focus between the red filter and the other pair, green and blue. Thus, when imaging for color, instead of using the
color grab feature of the system, I take separate images through each of the
filters, and re-focus between these captures. Of course, the reason
is that the different colors are
refracted to slightly different focal planes by
the optical system and while this is not a problem for ordinary photography, it
becomes more so for the CCD camera due
to its extreme sensitivity to focus. As far as focusing
methods are concerned, I have had the best results with the technique described
by SBIG in their manual: watching for
the highest electron counts in the
focus window but this has also been a bit trying, due to the turbulence in the
atmosphere above me. It causes the focus to change wildly second by
second and it becomes necessary to exercise great patience and determniation.
Another problem which cropped up early on was that due to the design of the
C-5 mounting, I could not image much farther north than the zenith.
When the telescope is pointed
toward the north, the camera bumps into the bottom
of the mount. I should explain that I was using an Optec flip-mirror
between the camera and the telescope which of course extends the 237
farther out
from the OTA. This problem was solved by using a 90 degree elbow and
installing the flip-mirror and camera upward on the elbow. This
worked quite well at F:10 but I
discovered to my dismay that when my F:6.3
focal reducer r was in place on the OTA the focus throw on the primary mirror was too
short to image on the 237 chip. Thus, Iwas unable to
photograph any
object in the northern sky with the OTA operating at F:6.3.
The next problem which appeared occured occasionally when using
the track and accumulate feature of CCDOPS. I have discovered that
when I attempt to capture more than a few images
for the software to merge, I
sometimes got a double image result. I believe that the
problem is due to the software losing its lock on the chosen integration star
when the tracking motor
experiences a periodic error. I knew about
the periodic error from previous experiences with the C-5; it occurs
about every 5 minutes on my system. I finally minimized the
problem
by careful selection of the guide star for the integration software to
use in re-alignment of successive images. But when taking more than
5 or 6 images in track and accumulate mode, this
problem still croped up once in
a while.
Things dramatically improved when I acquired the C-14 in June, 2001, and I began imaging with a much larger telescope. Unfortunately, a new problem manifested itself almost immediately. I
found that I had great difficulty reading the setting circles on the C-14 due to the size of the mount and their location. This was solved a few months later when I acquired a device that attached
to the mount and gave a digital readout on a display window of the sky location. I apologize for the fact that I have forgotten the name and/or brand of this device but it did work very well.
Throughout the remainder of of 2001, all of 2002, 2003, and the first part of 2004, I was able to secure a considerable number of reasonably good photographs despite being located
in the middle of Salt Lake City where the light pollution is horrible and a lot of my time was taken up just finding things in the sky to photograph. One thing that did help was an upgrade in
camera - I do not recall just when that occurred but I sold my 237 camera on Ebay and bought an SBIG 402 which added substantially to the pixel counts in my images.
In the summer of 2004, we moved to Price and I sold my C-14 tripod, bought a dome and a pier and began imaging with this new equipment which is an absolute delight. I enjoyed a period
of wonderful astrophotography for some years and was able acquire some relatively good images. The images improved again when I purchased an ST-8 camera from SBIG. Also, I
added a CGE mount for my telescope which I believed would add substantially to my tracking accuracy, and I was right. The CGE mount worked quite well until I goofed one night.
Things proceeded well until some time in 2009, when I made a horrible mistake that literally shut down my entire operation for almost 2 years. One night I forgot to turn off the tracking
motor on my telescope. Since I had attached the camera to the scope and had firmly screwed in the cables that connect the camera to the computer in the dome, the telescope
rotated through right ascencion only until the cables which wrapped around it became taught and then everything froze solid. When I discovered my error a day or so later, the motor
on the telescope was still on but not moving at all. And the cords were stretched to their maximum ability while stopping the telescope from rotating at all in RA. The wrapping was so
tight that it had warped the metal casing on the ST-8 camera. Now, I was forced to send in the camera to SBIG for repair and send in the telescope mount to Celestron.
Unfortunately, when the mount came back, about 4 months later, it was not repaired properly. While it seemed to work ok part of the time,
it did not work as well as it had before and sometimes would not work at all. In the spring of 2010, I was forced to send it back to Celestron for
a second time. This time, it was gone for 5 months and I lost virtually all of that summer season of imaging. When I got it back, the same situation
existed - the mount worked sort of ok part of the time. I struggled with it for another 6 months before finally writing a letter to Celestron asking if they would take it
back as a down payment on a new mount. At that time, in the spring of 2011, they called me on the telephone and offered to repair the mount for the third time. I was about to turn them down when they said they would
pay the shipping both ways. That was the clincher that convinced me to try once more time. This time, the repairs only took about 6 weeks, and to my surprise and amazement, the mount now seems to function the way it
really should and once did. As of this writing, February of 2012, the mount continues to work the way it was designed to and I have taken a dozen or more good pictures recently and hope to continue to do so for the
foreseeable future.
January, 2015: Unfortunately, the CGE mount once again began to malfunction, during 2013. For some reason which I was never able to discover, it began to periodically and unpredictibly fail to track at all. I struggled with
it for many months before finally realizing that the mount was simply unreliable enough and unrepairable enough to be no good. I finally made the decsion to sell it and buy a CGE Pro, which I believed would once and for all
solve all my tracking problems. So, by sacrificing the value of my most valueable coin in my coin collection, the 1893 S Morgan for $3800, I bought the new mount and sold the CGE to a guy in Salt Lake for $300. I think
he knew of a way to make it work and re-sold it for a profit but that is speculation. I was happy to get the new one. But immediatly, I found a problem: the mount was almost impossible to polar align. I found to my chagrin
that the declination screw on the mount was extremely tight, much too tight to turn by hand, and it was only with the help of a friend and a large wrench that we were able to get a reasonable polar alignment. However, to be
fair, the first few images I captured look pretty good and I did settle down to do more astrophotography with a semblace of satisfaction.
Now, the latest problem: I have no idea why, but the mount absolutely refuses to hold a two-star alignment. Each and every time I use the scope, I find that I must re-align it. And to make matters worse, the instruction book tells me that there is a simple selection choice in the hand control menu that allows me to pick a previous alignment instead of the otherwise requirement of having to select 'factory reset' and going through the entire process
of slewing to the switch position, selecting a two-star alignment, doing that, and then selecting a couple of calibration stars. But the scope absolutely refuses to allow me to select anything else. There are supposed to be several
alignment options such as 'quick align' and 'solar system align' that I cannot even find anywhere in the hand control. I wonder if I got the wrong one by mistake.
Unfortunately, almost all of 2014 was taken up by my sister's passing and my need to supervise the funeral and the probate of the estate as executor, as well as
attending to the welfare of her two kids. So I have had very little time to deal with these problems. As I write this (Jan, 2015) I am still having to re-
align the scope every time I want to use it.