Last night was clear and cool, but most importantly, seeing had improved since the last observing session.
Circumstances allowed another brief test of the Megrez 110ED with a Celestron 1.25" prism diagonal.
Since Epsilon Bootes (Izar) was ideally placed, it was target #1.
At 76x, the first thing noticed was how crisp the star looked. The second thing noticed was Izar's companion snuggled up close to the primary. Woah! That was a surprise... I didn't expect it to pop into view at so low a power. Upping the mag. to 147x made the double even more obvious and began revealing the diffraction image.
It was easy to see that, a) the amount of spurious red had been largely eliminated, b) the image was cleaner and contrastier than I'd ever seen before and c) the bluish color of the fainter companion was now easy to spot.
Seeing was good enough to boost the power some more, but would the optics hold up? 187x looked as sharp. Just more image scale and better separation. The color contrast of the stars was enhanced further. 229x and Izar was still glorious. Finally, 306x was all the power I could throw at the star... and it didn't suffer at all. The limit this night was the seeing.
In my 33 years of fumbling around under the night sky, I can't recall an accessory (the prism diagonal) making such a profound change in a telescope's optical performance.
The Megrez was very good when used with it's mirror diagonal. But switching to a prism has lifted it to a whole new level. Spurious color has been cut in half. Overall image correction is markedly improved. I previously suggested that the prism seems to have upgraded the FPL51 objective to the level of an FPL52 lens. Well, how about an FPL53 doublet?? It's gotta be almost there.
Now the Megrez 110ED is running much closer to the Sky-Watcher ED120.
The brief session was capped off with a peek at Epsilon Lyrae (the Double-Double, Canada's favorite star ).
At 229x, just a perfect image. Four hard, sharp Airy disks, each circled by a faintly visible diffraction ring.
The stars looked "whiter" than before. None of the slight greenish tint previously observed when using the mirror.
Again, I suspect this is due to the improved color correction when using the prism.
In conclusion, I can't say that a prism diagonal will improve the performance of every fast, inexpensive ED doublet on the market, let alone other Megrez 110ED's.
But, it wouldn't surprise me if it'll help more than a few.
For the price of a good quality prism diagonal (even cheaper if ya find a nice used one), you could add $500 worth of performance to your scope.
That could be the deal of a lifetime!
P.s.,
I also hope the manufacturers and vendors of today's inexpensive ED doublets will explore the possible performance advantages of a prism diagonal when used in their scopes. If it can routinely boost image quality so dramatically, perhaps prism diagonals should come as standard equipment?
--------------------
A few telescopes of dubious value.
Understanding wife, two curious cats and one sadly departed.
Previous
Index
Next
Flat
Megrez 110ED + Prism Diagonal = WOW!! (Again)
Edit
Reply
Quote
That was a surprise... I didn't expect it to pop into view at so low a power. Upping the mag. to 147x made the double even more obvious and began revealing the diffraction image.
).
