Re: what chronograph to buy?
To answer your question directly, yes. Any chronograph that uses a skyscreen and/or ambient light will have this issue. Oehler, for the <span style="text-decoration: underline">most part</span>, being the exception, as that is a three screen system, spaced wide apart, with larger "eyes".
Any lower end ambient light driven chrony will have several issues.
The first being the light itself. On a bright, sunny summer day, the sun is high in the sky, and the screen is able to gather the most light. This gives it the best chance to grab the bullet's shadow as it crosses the screen. As light conditions change, so does accuracy.
The second is the bullets location within the screen area. As this location changes, it affects the screens ability to see the shadow. Different locations give different readings, and this affects the consistancy of those readings.
Some can live without the accuarcy, but want the consistancy. As in, it doesn't really matter what the ultimate velocity reading is, as much as it matters what the SD and spread numbers are. Keeping the above two points in mind, with most of the chronographs on the market, you're really not getting either.
The third issue is garbage electronics, light screens, and processors. This is really the stuff that costs the money. You are asking this equipment to measure very small items, moving very quickly. Any measuremnt instrument is only as good as its tolerances. Keep in mind that any manufacturers claims on tolerance will be under ideal conditions. Phone any one of them and ask them what their tolerances are, and if they do tell you, have a calculator handy. The answer will be disapointing at best. Most claim on the accuracy, few claim on the consistancy, as the design will not let them.
This is really what sets the Magnetospeed and Kurzzeit systems apart. The Magnetospeed does not use light at all, while the Kurzzeit system uses an infared light source and screen combination that is not effected by outside ambient light. The Kurzeit system also has large vertical screens that are basically immune to bullet placement. With the Magnetospeed, the design itself dictates exact, repeatable bullet placement.
There are other systems that use LED's and other illumination, but they are still hampered by those damn "eyes" that gather ambient light. Even if you did shoot indoors, in the dark, you could, in theory, solve the accuracy issue, but not the consistancy issue. And even then, you're still hampered by garbage tolerances due to cheap electronics and slow processing speeds, so you are no further ahead.
R.