While trying to test assess max range of the Spark I realize that's its quite hard to keep it in visual line of sight because it's so small...
Largest dimension when flying away is about 15 cm which is about 1 minute of angle at 500 m away.
1 minute of angle is often considered to be the "standard maximum" angular resolution that one can achieve ( https://en.wikipedia.org/wiki/Visual_acuity )
Actually, I'm able to eye track the Spark to about 700-750 m if it's in front of a cloud where there is higher contrast (but not on blue sky where I loose it around 500 m)

Do you think about a safe, convenient and easy way to make the spark looks bigger (for testing purposes) ?

I was thinking about a slightly (weighted or not) ribbon (like on kites) that would hang underneath but I'm afraid that it would get in the propellers during transit at 50 km/h.
For landing, I could catch the ribbon as the Spark goes down.

Would you see it better at twilight with lights on.

Maybe (despite the fact that LEDs are not so strong and I guess it would rather requires night than twilight, which is forbidden here.

In addition, that's usually not a time when i'm available to fly...

If you fly with the prop guards it makes it a little bit bigger...

Mimus Posted at 2017-7-15 09:35
If you fly with the prop guards it makes it a little bit bigger...

That is what I will go for :

modify one or 2 propeller guards with a way hook a small balsawood stick to it/them.
I'll use a red white worksite ribbon shorter that the length from the end of the balsa stick to the propeller so they can't interfere.

I'll cut 2 propeller guards to keep only the lock mechanism to the spark arms.
I've weighed the parts and it should not unbalance the Spark.

I'll take picture when it's ready (next week end probably)