I'm home recovering from a knee operation, ACL replacement, and thought I'd try my new-to-me Burgess Binoviewer in the daytime.
I set up my Stellarvue Blackawk 80mm, f/6, on a Unistar Heavy mount and tried the binos with a pair of Meade 25 MA EP's.
First off, the binoviewer would not focus without the OCA (no surprise) but focused easily with it and with a TV barlow. The views are very good, no issues with collimation. I was quite impressed with them in daylight.
I was wondering what sort of magnification/FOV I was getting with them and set out to compare binoviewer's field of view with my other EP's.
I set up a vertical tape measure across my yard, 76 feet away, and ran each EP alone and through the TV 1.25 2X Barlow. I aligned the top of my field of view with the zero on the tape and read the field in inches at the bottom of the view. A little trig and I have the actual field of view in degrees.
The results:
4mm UO Ortho .322 degrees/.145 w/ TV 2X (38.6)
5mm UO HD Ortho .459/.204 (44.1)
6mm UO HD Ortho .495/.224 (39.6)
7mm UO HD Ortho .558/.259 (38.3)
12.5mm UO Plossl 1.539/.726 (59.1)
19mm Panoptic 2.464/1.209 (62.2)
32mm UO Konig 2" 3.889 (58.3)
40mm Pentax XL 5.036 (60.4)
Binoviewer w/ OCA 1.099
Binoviewer w/ TV2X .628
Binoviewer w/ both .416
I screwed up and didn't measure the 25 MA's FOV without the binoviewer. But seems that the FOV of the binoviewer is right between the Plossl and the 7mm Ortho, perhaps equivalent to a 10mm EP. I think I need a pair of 40mm's!
In all of this I was wondering how to deal with these numbers. First I figured that getting high magnification and high FOV in the same EP was a good thing so I multiplied the mag X FOV and got the numbers in parentheses above. (Something strange with the 5mm HD Ortho???) That number also puts the Plossl high on the list.
Dividing the focal length of the EP by the FOV gave a similar picture of the EP's only in reverse (lower = better).
The 5mm's numbers seem to be way too high. FOV should have been on the order of .410 or so. Anyone else ever do anything like this with these EP"S??
I don't know if this interests anyone or not, but it does show the 19mm Panoptic with the best FOV, followed closely by the Pentax then the Konig. The surprise in my book was the Plossl.
On the flip side, the Orthos were all nearly perfect edge to edge in this test. I could see no degradation from edge to edge. Each of the other EP's showed some very minor softening towards the outer edge. My Blackhawk has a 2-speed focuser and when I really dialed in the center the edge was soft, but I could still easily read the tape measure to 1/16. In the 19 Pan, of the 39.25" I could see on the tape, only the outside 4 inches or so was soft. The others were proportionally about the same.
Is there a way to actually measure magnification? I haven't done any research, all I know is FL(scope)/FL(ep).
I also just realized that I didn't test my 14 UWA. It wasn't in my case...I wonder where it is?
I set up my Stellarvue Blackawk 80mm, f/6, on a Unistar Heavy mount and tried the binos with a pair of Meade 25 MA EP's.
First off, the binoviewer would not focus without the OCA (no surprise) but focused easily with it and with a TV barlow. The views are very good, no issues with collimation. I was quite impressed with them in daylight.
I was wondering what sort of magnification/FOV I was getting with them and set out to compare binoviewer's field of view with my other EP's.
I set up a vertical tape measure across my yard, 76 feet away, and ran each EP alone and through the TV 1.25 2X Barlow. I aligned the top of my field of view with the zero on the tape and read the field in inches at the bottom of the view. A little trig and I have the actual field of view in degrees.
The results:
4mm UO Ortho .322 degrees/.145 w/ TV 2X (38.6)
5mm UO HD Ortho .459/.204 (44.1)
6mm UO HD Ortho .495/.224 (39.6)
7mm UO HD Ortho .558/.259 (38.3)
12.5mm UO Plossl 1.539/.726 (59.1)
19mm Panoptic 2.464/1.209 (62.2)
32mm UO Konig 2" 3.889 (58.3)
40mm Pentax XL 5.036 (60.4)
Binoviewer w/ OCA 1.099
Binoviewer w/ TV2X .628
Binoviewer w/ both .416
I screwed up and didn't measure the 25 MA's FOV without the binoviewer. But seems that the FOV of the binoviewer is right between the Plossl and the 7mm Ortho, perhaps equivalent to a 10mm EP. I think I need a pair of 40mm's!
In all of this I was wondering how to deal with these numbers. First I figured that getting high magnification and high FOV in the same EP was a good thing so I multiplied the mag X FOV and got the numbers in parentheses above. (Something strange with the 5mm HD Ortho???) That number also puts the Plossl high on the list.
Dividing the focal length of the EP by the FOV gave a similar picture of the EP's only in reverse (lower = better).
The 5mm's numbers seem to be way too high. FOV should have been on the order of .410 or so. Anyone else ever do anything like this with these EP"S??
I don't know if this interests anyone or not, but it does show the 19mm Panoptic with the best FOV, followed closely by the Pentax then the Konig. The surprise in my book was the Plossl.
On the flip side, the Orthos were all nearly perfect edge to edge in this test. I could see no degradation from edge to edge. Each of the other EP's showed some very minor softening towards the outer edge. My Blackhawk has a 2-speed focuser and when I really dialed in the center the edge was soft, but I could still easily read the tape measure to 1/16. In the 19 Pan, of the 39.25" I could see on the tape, only the outside 4 inches or so was soft. The others were proportionally about the same.
Is there a way to actually measure magnification? I haven't done any research, all I know is FL(scope)/FL(ep).
I also just realized that I didn't test my 14 UWA. It wasn't in my case...I wonder where it is?
