You are on the right track as far as how its used, but its not for astronomy.

I think it's safe to say that we need another hint

Agreed.
Help us out Blue!

Here is a photo from the internet of this measurement device in use. That should help a lot. Who can get the name of the device?

Oooh, I know! It's the invisible measuring thingy! 

You tease! lol

In use? Okay. Well, given your other hints and your confirmation of my previous guesses... forest canopy in the image? Does it map forest canopy coverage? Density, perhaps?

I see the photo now..wow that's huge. lol
I'm guessing it's for laying out greenhouse supports or similar?

Nah, not that big. Ota fitting in that person's palm.

The suspense is killing me.

Spherical Crown Densiometers

*Ding Ding Ding* We have a winner!
Now I see what it's for. You measure the crown of a single tree, I think.
Hopefully Blue will confirm and tell us how it's used.

That's amazing. I never would've guessed that name. I totally got the method of use correct. 

Yup, with a very concise answer, axexandru has it!

Iarn had the use correct. It is for mapping canopy density in forests.

Hold instrument level, 12" - 18" in front of body and at elbow height, so that operator's head is just outside of grid area.
Assume four equi-spaced dots in each square of the grid and systematically count dots equivalent to quarter-square canopy openings.
Multiply the total count by 1.04 to obtain percent of overhead area not occupied by canopy. The difference between this and 100 is an estimate of overstory density in percent. (Assuming each dot to represent one percent is often accurate enough.)
Make four readings per location — facing North, East, South and West — record and average.

What do you have next for us, axexandru?

Very cool!
Ok Axe, back to you....

Hy,

I am busy at work right now, don't have time for a picture. Iarn, since you got the method of use correct and without it I would have never find the name of the device, I thing you should take this one, if Bluesmudge is ok with that.

I really don't have the time now, sorry.

Alex

Canopy density device? .... I have one of them! .... it's made by husqvarna! .. 18" bar.... awesome for bringing the canopy down closer for inspection!

Sure, I got your back Axe.

Coin for scale:

Thread puller for sewing?? I KNOW I've seen one before...

Yeah, it's a seam ripper. Nice one Menno. Post your pic!

I should stop playing this game before bed  Alright, Let's see what you've got for this thing: