Measuring What You See

[mikemarotta]

I received a Baader Micro Guide Reticle on loan from a friend whom I met on another discussion board. It took me a few nights and different instruments to get a handle on it. I still need more practice. My instruments are all manual control. So, the ten-inch (254 mm) focal length 2500 mm Meade "advanced" (i.e. fake) Ritchey-Cretien was a challenge because everything zoomed by pretty quickly. I settle on a National Geographic 70 mm f/10. I bought it used (and abused) about four years ago and it is held together with rubber bands, but I got some measurements. Unfortunately, it does not have enough aperture to split Polaris or the Double-Double in Lyra. (I have tried.) Be all that as it may...

I viewed the Trapezium in M42 and measured it as 1 division. It was pretty easy to align the Baader and let the stars drift across the scale. I did that several times. I calculated the size of Trapezium as 29 arc-seconds by 29 arc-seconds. Burnham's gives 12x13, but I am pretty happy with the first try. 

I also viewed Eta Cassiopeiae. They are close together, so I let them drift across the scale and measured them against the center between the two rows of divisions, which Baader says is 35 micrometers wide. From that, I calculated a separation of 10.3 arc seconds. I found online from a report at the Havering Astro club UK 13.4 arc-seconds. Again, I was satisified with the first attempt will try again another night.

Edited February 6, 2021 by mikemarotta
added image of reticle plate

[Paz]

These are great, but hard work without tracking - especially around the celestial equator where everything is moving at high speed! I've had lots of fun with one of these - measuring sun spots, moon craters, working out the distance to the moon by measuring it's total diameter and so on. A fun idea is finding a high speed (proper motion) star and a fast changing double, measure them now and make a note to measure them X years in the future - you will be able to notice actual changes much sooner with this than just by judgement/eye.

[Richard N]

Just reviving this thread but I too have one of those eyepieces. They are good fun to use to measure things. Well worth watching out for on eBay etc as they are no longer available. I suppose nowadays the easy way to measure is using photographs but these are nice for the visual astronomer.

 

Anyone else have one? If so, what are you using it for?

[Franklin]

The Meade Astrometric eyepiece is still available and quite similar to the micro-guide. 

[Paz]

I still have mine, most recently I've been using it to measure the size of sun spots.

[lunator]

I still have mine. I have used it for measuring doubles. Definitely a useful eyepiece 

Cheers

Ian