Posts Made By: Ed Zarenski

Orion's belt stars are only 2.75 to 2.8° across, not 3.3

David Knisely wrote an excellent review of the 2.5x Powermate published on Cloudy Nights Reviews. the Powermate won hands down up against a meade 140 and david explains all the reasons why.

edz

Both the 18mm and 25mm University Optics orthos are outstanding eyepieces. Filed is just a little narrower than a plossl, not much. the edge correction is so good you could view objects right up to the edge with no difference in image quality.

edz

The 9mm UO measures 8mm e.r and the 7mm UO measures 6 e.r, but both eyepieces have the lens recessed nearly 2mm from the top of the conical barrel surface, so usable eyerelief is more like 6mm and 5mm respectively.

The Celestron 7.5mm Ultima measures 6.5mm e.r, but because of the recessed shaped of the top of the barrel, the lens surface is recessed nearly 3mm. So the usable e.r. on a 7.5 Ultima is only 3.5 to 4mm.

edz

Give me the one I can change the eyepieces in.

edz

You will find the answer in this post

http://www.cloudynights.com/ubbthreads/showthreaded.php?Cat=&Number=64769&page=1&view=collapsed&sb=5&o=&vc=1

Typically, moon shadow transits can be detected at 1/3 to 1/2 your normal scope resolution.

It would be much more difficult to see the moon preceeding the shadow across the face of the planet disk. It would be even far more difficult to see the moons as disks. Read here for that info.

http://www.cloudynights.com/ubbthreads/showthreaded.php?Cat=&Number=65250&page=1&view=collapsed&sb=5&o=&vc=1

Your 4.5" scope will easily show you the larger shadow transits even at fairly moderate magnifications and will show the smaller moons at higher power and is more than enough to resolve the larger moons to a true disk.

Ganymede's and Callisto's shadows might be seen with magnifications as low as 125x, even with an 80mm scope.
You might expect magnifications to be
160x-180x to see Io's shadow and
175x-200x to see Europa's shadow

edz

Tom,

#3 allows for tilt in altitude

#4 swivel left and right, is accomplished as a part of the Unimount head bracket. the attachment the L bracket screws into is similar to a lazy susan, not in shape but in function. This permits sweeping.

#5 is where the screw from the L adapter screws into the binocular. Even once tightened securely against the binocular, it still allows you to swivel the binocular, like an airplane tilting its wings.

This last may seem like an inconsequential movement, but without it in conjuntion with #4, you cannot use the binoculars from a seated position.

edz

There's one big difference in what we intepret as % illumination based on what you described above.

I consider this. If the enlarged full exit pupil I am watching is 30mm round, it's easy to understand it is 100% illuminated.

I believe it is true to say every point in the fully illuminated exit pupil receives light from every point on the objective.

By definition then, I take it as only entering light that produces a fully round exit pupil is contributing to 100% illumination. Any entering light that produces less than 100% round exit pupil is not contributing to 100% illumination.

If entering light causes that exit pupil to vignette, the shape seen is that of a sharply defined pointed ellipse or cats eye. If the size of that cats eye is now 15mm wide by 30mm, it is observed to be one half the width of the original exit pupil. This to me indicates no point in the exit pupil is now fully illuminated.

If light entering is producing an exit pupil 30mm x 15mm cats eye, then light from that portion of the objective is not providing 100% illumination to any point in the exit pupil. In fact if the exit pupil is half normal width, isn't it true no point in the exit pupil is fully illuminated, because no point in the exit pupil can be receiving light from every point on the objective?

Is it incorrect to say that for any point on the objective to provide 100% illumination, it must contribute to a full exit pupil?

edz

"Touring the Universe Through Binoculars" also has no constellation charts or finder charts, and no photos or drawings of objects. You must get a set of charts to use with it.

Crossen's book on the other hand has a whole sky set of charts in the back of the book and has detailed larger scale finder charts sprinkled throughtout the book. In addition he has included some of the best wide- field photographs showing areas of the sky for cruising with binoculars. Harrington's book dryly details more objects, but Crossen's book "Binocular Astronomy" is a far better choice, not only for binocular observers but also for small scopes.

edz

The Bogen 3047 has no fluid motions. It is either locked or unlocked to move.

The Unistar deluxe is rated to carry 30 pounds. it is similar to an alt-azimuth type mount.

How big and heavy are these Kowas?

How about the Bogen 501 head? Or a Unimount?

edz