Light streaks when observing Saturn with Mak 127

[Olli]

Hi all ,

so far I have only had a couple of outings with the Mak and all sessions have been on Saturn. Apart from the focusing which I still can’t get use to I seem to have issues when viewing Saturn. I’m not sure if this is normal or not basically when viewing the planet I seem to get I guess diffraction spikes going through the planet with a 14mm eyepiece. When looking at standard stars I don’t seem to get this affect but when viewing Saturn I can only describe it as  4 light streaks going through the planet which makes it sometimes to focus as well as trying to see the detail. When I do change the focus the spikes do get smaller but are still off putting.

 

any advice would be appreciated!

 

 

[DirkSteele]

A Mak wouldn't have diffraction spikes as it does not have spider vanes.  A little more information to help us diagnose the problem would be helpful.  Are the four "spikes" all orientated in the same direction?  Or are they perpendiuclar / random orientations?  Do the spikes run out into space off the planets surface / rings, and do they extend equally in both directions?

Couple of experiments for you to try to potentially eliminate culprits.  Do the spikes appear if using another eyepiece?  If they do, it may well indicate the issue is with the telescope.  If they do not, it may be the eyepiece.  Second, trying spinning the eyepiece in the eyepiece holder of the scope.  Do the spikes change orientation?  If yes, then the eyepiece may be at fault.  If not, the problem may be with the scope.  I note from your signature, you have a second scope.  The 14mm will be lower power in the ZS73 but do you see anything similar when looking at Saturn?

 

Saturn is quite a bright object which may well make the spikes easier to see.  Also try Jupiter.  Please also try to observe Vega. Do you see the spikes?  Assuming you keep Saturn roughly in the centre of the field, slowiy move Vega up and down the field in the centre to see if the spikes appear.  As Saturn has an apparent diameter, it may be that surface scraches in one of the optical elments are showing up. Vega won't have that diameter so you will need to move it to see if you pass over a scratch. 

 

While I won't advocate a full star test at this stage, if the seeing is good, use a high power eyepiece and defocus a star like Vega and expand the fresnel diffraction pattern so you expand 5-6 rings.  Does the outer ring look "hairy" especially outside of focus?  By hairy, I mean it looks like lots of little strands stand up off the outer ring.  I have seen this in a Mak before and is indication of surface roughness.

[mikeDnight]

You may have a telegraph wire crossing your light path somewhere in the distance, or perhaps the eye lens has oil on its surface from your eyelashes?  Or it could be there's something within the eyepiece, possibly on the field lens that needs cleaning off.

[Olli]

20 minutes ago, DirkSteele said:

A Mak wouldn't have diffraction spikes as it does not have spider vanes.  A little more information to help us diagnose the problem would be helpful.  Are the four "spikes" all orientated in the same direction?  Or are they perpendiuclar / random orientations?  Do the spikes run out into space off the planets surface / rings, and do they extend equally in both directions?

Couple of experiments for you to try to potentially eliminate culprits.  Do the spikes appear if using another eyepiece?  If they do, it may well indicate the issue is with the telescope.  If they do not, it may be the eyepiece.  Second, trying spinning the eyepiece in the eyepiece holder of the scope.  Do the spikes change orientation?  If yes, then the eyepiece may be at fault.  If not, the problem may be with the scope.  I note from your signature, you have a second scope.  The 14mm will be lower power in the ZS73 but do you see anything similar when looking at Saturn?

 

Saturn is quite a bright object which may well make the spikes easier to see.  Also try Jupiter.  Please also try to observe Vega. Do you see the spikes?  Assuming you keep Saturn roughly in the centre of the field, slowiy move Vega up and down the field in the centre to see if the spikes appear.  As Saturn has an apparent diameter, it may be that surface scraches in one of the optical elments are showing up. Vega won't have that diameter so you will need to move it to see if you pass over a scratch. 

 

While I won't advocate a full star test at this stage, if the seeing is good, use a high power eyepiece and defocus a star like Vega and expand the fresnel diffraction pattern so you expand 5-6 rings.  Does the outer ring look "hairy" especially outside of focus?  By hairy, I mean it looks like lots of little strands stand up off the outer ring.  I have seen this in a Mak before and is indication of surface roughness.

Hi Matthew 

thanks for the help. From my memory the spikes are pointing in different directions across the full view of the scope. I cant remember using a 24mm with the Mak so will have to test that. When using the 14mm previously with the 73 it was all okay as well as the 24mm. When I next have a clear night I’ll make sure to try vega. 

[Olli]

14 minutes ago, mikeDnight said:

You may have a telegraph wire crossing your light path somewhere in the distance, or perhaps the eye lens has oil on its surface from your eyelashes?  Or it could be there's something within the eyepiece, possibly on the field lens that needs cleaning off.

Unfortunately there aren’t any telegraph wires near where Saturn is as it was high above the trees, but that would make sense. I will have a check with the eyepiece , thanks for the help.

[mikeDnight]

6 hours ago, Olli said:

Unfortunately there aren’t any telegraph wires near where Saturn is as it was high above the trees, but that would make sense. I will have a check with the eyepiece , thanks for the help.

What kind of diagonal are you using? If its a 90° mirror or prism you should get perfect views, but if it's a 45° or 90° erecting prism you will get a fine difraction spike on brighter objects due to the joint between prisms.

[Olli]

19 hours ago, mikeDnight said:

What kind of diagonal are you using? If its a 90° mirror or prism you should get perfect views, but if it's a 45° or 90° erecting prism you will get a fine difraction spike on brighter objects due to the joint between prisms.

I was using the supplied diagonal I do have another  one somewhere so I’ll give that a go.

[Olli]

just a quick update in this , it appears it could be a eyepiece or diagonal problem ( which is good news) tried again tonight with a new eyepiece on a different diagonal and seemed to be fine and could see a lot more detail. Appreciate everyone’s help.