ASTROPHOTOGRAPHY TECHNICAL TIPS Last updated: 25 March 2002

Subject:	Hybrid Astrophotography
Sent:	Saturday, March 23, 2002 15:34:10
From:	vancegrn@primenet.com (Vance Green)
First, Mike, I just gotta be the 1,000,001th person to compliment you on
your great site.Whatta lifesaver!

My wife got me a ETX-60 for Xmas (the COSTCO $128.00 deal). As a kid, I
spent hours up on the roof of my parents' house with a cheap imported
2.4" alt/az refractor laboriously tracking down objects with star charts
and a lotta luck.the ETX found in a half-hour via GO-TO's what it took a
ten-year-old many tens of nights the "old-fashioned" way, and tracked
them too! Pretty amazing what $130 can buy-and the image quality is
there as well.

As a techie from way back (1st computer was an Ohio Scientific C1P back
in ' 78 - anyone remember those?), I quickly became intrigued with the
digital astrophotography aspects of this scope-I already have a Nikon
990-and bought the Digitronix Digi-T adapter after several handheld
"experiments" of holding the 990 up to the eyepiece.

Took some pretty good shots via the use-the-self-timer-as-a
shutter-release method, but being somewhat annoyed by the need to make
several button pushes on the 990 each time I took a shot (no fun when
it's cold out), I started searching for a better way.

I knew about the various remote control programs for the 990 such as
PhotoPC (http://www.math.ualberta.ca/imaging/ ), and being no stranger
to the command-line, set about experimenting with it. (Prof. Bowman, the
owner of the site, went way beyond the call of duty when a particular
version of PhotoPC would not talk via USB to my camera-he knows his
stuff). More info available at: http://www.charliex.net/cpix/cpix.htm as
well.

The GUI's available for PhotoPC offer WAY too many options necessary to
use the 990 for astrophotography and just get in the way, so I wrote a
little VisualBasic 3.0 app that shells out to PhotoPC with a command
entered in a text box-not very elegant, but it gets the job done. (VB
users-read up on the SHELL command on how to do this)

Now, I was able to take shots with the 990 WITHOUT needing to fiddle
with the camera between each.

The next phase of the overall project dealt with focusing-the LCD on the
back of the 990 is just TOO small to allow for fine focusing of planets,
although it's fine for larger objects like the Moon, where there's
enough detail to see the results. There was always a small difference in
the 'scope focus between finding the object in the eyepiece and
attaching the same eyepiece to the 990 (set for infinity) and fitting it
to the ETX, making most planetary shots nothing more than fuzzy discs.

Technology to the rescue, again. An often overlooked fact of most
digicams is that they continuously output video through the VIDEO OUT
port whenever they're turned on. This signal should be able to be used
to focus with if displayed on a TV.

My initial try at this was with an el-cheapo Taiwanese B/W portable TV I
had laying around.this worked, but added more bulky electronic stuff to
the (already) pretty cluttered setup.

Next try was with one of the TV to USB converters available-I reasoned
that with a USB HUB, I should be able to keep a real-time video window
of the camera preview open on the laptop as well as operate the E990
remotely. They 're cheap-under $100-and would be worth it if this
worked.besides the "real" uses of the thing (watching TV on the laptop
when you're supposed to be working!).

This setup works EXTREMELY well. I settled on the ATI TV-WONDER (USB
edition-$84.95 on the 'Net) after trying the AverMedia unit and giving
up on it (unstable operation under W2K). The ATI will preview input
video at 640 x 480 on my laptop-allowing for MUCH better focusing of the
ETX with the Nikon attached before taking a shot. And the whole mess is
more or less "integrated" on the laptop screen-I suppose if I wanted to
I could even run the remote 'scope control software there as well-but I
have to buy the overpriced 506 cable first ;)

Attached is an image of the cabling setup, and a screenshot of the whole
works while operating. The target in the preview window is my neighbor's
HAM antenna as seen by the ETX. Also a few "quick and dirty" images of
Jupiter and Saturn (no post-processing except crop/resample to smaller
size) from the 990.




 



Photo PC has the ability to remotely download the shot you just took, so
you can see what you're doing wrong in just a few seconds on the laptop
screen (I use PaintShopPro for image viewing/manipulating), rather than
try to figure out what to do on the teeny-tiny 990 LCD.

Another bonus-you can capture the video from the camera with the ATI
(albeit in a smaller resolution) and/or take 640 x 480 single-frame
captures, but the image quality of the 990 is far superior to these.
Watching the video can be enlightening, though, and also works well for
terrestrial observations.

Some gotchas with this setup: You can't set the camera ISO remotely. If
you want to set the camera for the highest ISO (more light sensitivity),
you have to do it in Manual mode, then plug the camera's USB cable into
the hub. The ISO setting will "stick" while you use the other remote
functions.

You can't go digital zoom over 2.5X remotely. If you want to set digital
zoom higher, do it on the camera and then plug in the USB cable,
whatever it was set to will "stick".

You can't use a cheap "unpowered" USB hub. The ATI wants 450mA off the
USB interface to run and unpowered hubs can't do this. I'm using a
Belkin F5U101 personally.

You can't go over 8 sec. exposure duration using PhotoPC. Longer seems
to only be doable with the Nikon remote shutter release, the "B" setting
and your finger, or the self-timer (and only on the 995-or so I hear).

Occasional strange camera lockups WILL occur during remote operation.
This is discussed on the PhotoPC site and seems to be due to lack on
information from Nikon on the camera communication protocol. Just unplug
the USB cable to regain control-there seems to be no permanent camera
damage.

USB control of the 995 is apparently still being worked on according to
the PhotoPC site. Serial control is the only option right now (requires
expensive or homemade cable).

READ and UNDERSTAND the information on the PhotoPC site- specific issues
related to device driver problems are discussed there. Pay special
attention to the instructions on what order you turn on power, then plug
in the USB cable. Get everything else up and going, turn on your
digicam, wait until the display is settled and normal, and THEN (and
only then) plug the USB cable in.

The object you're trying to image is never in the field of view AFTER
you remove the eyepiece you used to find it, screw it to the camera, and
remount it-this is due to the added weight of the camera. I've been
toying with the idea of a counterweight for this problem, but am open to
other suggestions.finding the object again can be very time consuming
(and frustrating).

While the above setup SHOULD work with other cameras, I'm a Nikon type
of guy, and can't speak to that. PhotoPC apparently will work with a
number of digicams based on a specific chipset-see the site for details.

And, as always, remote operation of any digicam is probably "outside"
manufacturer's specs and may void your warranty- YMMV.

It helps to create a "astrophotography" user profile on the controlling
laptop that uses a black desktop background with as few icons or other
bright stuff on it so as to not kill off your night vision.

Hope others have as much fun with this rig as I have-it's a gadget
lover's dream!

Vance Green
Tempe, Arizona

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