Steve - I just offered it as an example - not as a suggested object to observe.
But actually, IF such an object were a slow moving TNO, with a l-o-n-g duration event, then you could do exposures with your Astrid of 1 to several seconds and you might reach mag 15.5. (That's why I run my Occult4 searches to mag 16 Target Stars).
[With my 14.5-inch I can get to mag 16.4 with a 1 second exposure. My 12 will get mag 15.5 in 1 second - but of course you need multiple data points in the drop].
As it's been mentioned a few times now, let's plan on having a NEUS chat session on Occult4 somewhat soon. I'll look ahead and pick a nite that will be cloudy for all. A later topic might be doing mobile observations and picking sites.
?? -G
George Viscome