Re: [APML] Beep on ST4

[Matt BenDaniel <matt@starmatt.com>]

At 01:34 PM 6/20/2002, Gene Horr wrote:
>Matt BenDaniel wrote:
>
>> Restarting the ST-4 tracking during an exposure can create a problem if you don't do
>> it exactly right. The guide star may jump to another position on the ST-4 chip. That
>> can lead to oval stars.
>
>I mistated what I meant.  I meant to imply restarting the entire exposure.  But
>some good came out of this.  Otherwise I would not have learned about:
>
>> The way to do it is to hold the MODE button down when you restart tracking (which
>> AFAIK is an undocumented feature). This tells the ST-4 to replace the guide star
>> exactly back where it started. But you have to do just right. I think you release the
>> MODE button once you see the little red dot on the LED display. It's so tricky that
>> I'm reluctant to do it, even though I've done it successfully on several occasions.
>
>Wow!  Thanks for this tip.  I did had no idea that this function was available.

That tidbit and other useful stuff is covered in Jim J's article:
http://www.abmedia.com/astro/articles/st4.html

That article states that you should wait until you see the first tracking error displayed (e.g. A3) before letting go of the MODE button. I'll defer to that.

In principal, you can interrupt tracking, change the settings and restart, all during the middle of an exposure. Again, I try not to do that, because I worry about making a mistake during the procedure.

The other time you might want to use that technique is if you lose (or turn off) tracking between exposures intended for stacking. It will make registration slightly easier, but I wouldn't worry too much about it. I try to keep the tracking going when I advance the film, so I don't need to restart.

Matt


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