image versus distance (1 Viewer)

hi iam new to this game and have never had look through a spotting scope
i am thinking on the zeiss 85 with 20 to 60 zoom and dont know what to expect i.e would a goldfinch fill the lens at say 300 yards or could i see a golden eagle at a mile.can someone give me some examples of what would be visible at certain distances at difirent magnifications.

regards.

cressi.

cressi said:

hi iam new to this game and have never had look through a spotting scope
i am thinking on the zeiss 85 with 20 to 60 zoom and dont know what to expect i.e would a goldfinch fill the lens at say 300 yards or could i see a golden eagle at a mile.can someone give me some examples of what would be visible at certain distances at difirent magnifications.

regards.

cressi.

Click to expand...

You would certainly see both species mentioned at the ranges you have quoted, but I'm afraid neither would fill the frame.


Clive

thanks for the reply,at what distance would i have to be to get a good image
on say 6x4 or 8x10 photo.

Rough indications: 10 to 20 yards for the goldfinch, depending on what you call a good image.
70 to 150 yards for the golden eagle, but not always, because atmospheric circumstances can be tricky above 50 yards.

For viewing 20x means 20x closer. So the goldfinch at 300 yards will appear to be at 5 to 15 yards with a 20-60 zoom eyepiece. The 60x image will ofcourse be darker and less good, so, also considering atmospheric circumstances, better count on 40x max for this type of calculations.

cressi said:

thanks for the reply,at what distance would i have to be to get a good image
on say 6x4 or 8x10 photo.

Click to expand...

You could use my digiscoping calculator to help determine this. At the bottom, it has a tool for estimating subject to camera distance by measuring the pixel dimension of the subject and then using the known digiscoping info. It can be used to tell us how close we would be to get an image of a particular size on the CCD.

I'll assume that we want the bird to fill the frame pretty well, so I'll assume a pixel dimension on the CCD of one half the CCD diagonal (1720mm) That would be a pretty tightly framed subject. Now I'll assume we are using a Swarovski ATS80HD and a CP4500 at a 2325mm equivalence (20x eyepiece and 24mm on the camera) and we can calculate the following.

For a 7.5 cm bird - 6.76 meters
For a 15 cm bird - 13.5 meters
For a 20 cm bird - 18.02 meters
For a 30 cm bird - 27.03 meters
For a 40 cm bird - 36.04 meters
For a 50 cm bird - 45.05 meters
for a 1 m bird - 90.1 meters