Binoculars shows a tail on Jupiter......?

[Rogering1]

Hi guys,

I've recently had my old Hoya 10 x 50 binoculars out for a test after being serviced, terrestrially & looking at DSO's all looks good, until I looked at Jupiter, it appeared to have a tail or teardrop effect.

Would you consider this is a collimation issue or.........

[jimmyjamjoejoe]

Does it happen on both eyepieces? I find my old greenkats give a slight tail if one ep is slightly out of focus. Focusing the left eye, then adjusting the right dioptre gets rid of it.

[NGC 1502]

One possibility is astigmatism in your eye, this would make a very bright object like Jupiter appear to have 'spikes'.

When using bins, I've only had a clean sharp view of Jupiter through some Fujinon bins, all the others I've used gave a blobbly/spiky image.

You can do a basic check for collimation by focusing on a straight horizontal line during the day ( a roof ridge against the sky is good ) then gradually draw the bins away from your eyes but keeping the centre of the field of view visible. The two images of the roof ridge should stay in line.

Or, put the bins on a tripod, put a distant object at the edge of the field of view using one barrel of the bins, then see where it is when looking through the other side. You can check collimation vertically and horizontally by putting objects at the top/bottom of the field of view as well as either side.

You must use a distant object for this, to avoid the parallax due to the two barrels looking from a slightly different position.

Regards. Ed.

[Rogering1]

Ah thank you,

that's a good tip, I'll try it!

[michael.h.f.wilkinson]

Glare can also be a problem in bright objects like Jupiter (my old Omegon 15x70 showed quite a bit of it, the Helios Apollo is much better in that respect). You could check whether the same effect occurs in stellar objects of different magnitudes.