Originally posted by opiedog I'm intrigued though how you were able to use an external monitor to do the focusing. jordan
Hi Jorden,
I had a old 13 CRT TV left over after the Digital TV conversion in the Spring. I made a tall stand to place the monitor at a comfortable position by my telescope in my observatory. The K110D video cable went from the camera "mini USB" connector to the yellow RCA jack on the front of the TV. As soon as it is plugged in the LCD display goes blank and everything appears on the CRT monitor.
Remember, everything in astrophotography is manually focused. Even an AF lens must be used manually since the camera can't focus on a single bright star. Mainly I use telescopes or manual lenses anyway. You can't adjust in "real time", rather you check, adjust, check, adjust, repeat.
The problem is the dot is way too small to focus on the small LCD screen or viewfinder. With wide angle lenses you can't even see the stars. You can get close by pressing a lot of buttons: Display, zoom, center, increase zoom, repeat for each of many adjustments. I've done that in the past, and before I found the istD video cable I did that last week. This must repeated until you get the focus perfect. In astro close isn't good enough. The video monitor image is big enough to adjust using the 1 second display after the shot without pressing any camera buttons.
I often use an aid called a Bahtinov Mask. This "filter" is a black disk with an odd pattern of slots. It makes it easy to see how far off focus you are. Unlike any other method I've seen it also indicates the direction to turn the focus! I can make focus adjustments much quicker then just trying to make a round dot as small as possible.