Planets - Disc doubling up

[Jaxxxxx]

Hey guys

Was out viewing Mars not long ago and seeing was not bad despite the dew getting very wet as the hours went on.

I seem to have an issue when viewing this planet and it is not as evident in other types of viewing such as stars, larger planets and the moon and nor in the deep space objects however is still there slightly.

The disc of Mars almost looks like it is appearing twice however it is following itself and merged together if you get me. Does this sound like some sort of collimation misalignment?

Please find attached my crude image to show you what I mean!

Cheers

[LukeSkywatcher]

Was the above image seen with a scope or bins?

This is one problem i have never encountered here before.

[Jaxxxxx]

Sorry the above image is a Microsoft paint example of what Mars was appearing like through my scope.

The same thing was happening at any magnification on all eyepieces so I am guessing it's some sort of misalignment.

[umadog]

In bad seeing you can get double images of Jupiter's moons but this comes and goes. Bad collimation will cause blurring. I can't see how it would cause a double image. If I were you, I'd learn how to do a star test (google it) and report back.

[jimmyjamjoejoe]

That's pretty strange... I could understand if it was through bins...

What scope you using? Very strange that it doesn't happen with any other object.

[LukeSkywatcher]

That's pretty strange... I could understand if it was through bins...

What scope you using? Very strange that it doesn't happen with any other object.

Exactly..............with mis-collimated bins this is an issue. With a scope...........i just cant fathom it out.

[Zachariah]

Not focused correctly?

[Peter Drew]

I have seen this effect during poor seeing or with a telescope that has not reached thermal equilibrium. With a lowish power Mars is small and quite intense which aggravates the situation.

[Carbon Brush]

Are you using a motor driven mount?

If so, it could be backlash in the RA drive.

When the scope is well balanced, the tube can rattle back/forth by the amount of free play in the drive. Just putting the scope a bit off balance will ensure the scope does not rattle.

I had a similar effect on Jupiter a year or two back. The simple check was to gently push the scope tube one way to take up the backlash.

It will be interesting to hear how you get on.

[haitch]

I got this in my dob last week.

Seeing wasn't too good but, as it seemed to be only noticeable off axis, I put it down to an internal reflection in the EP - teach me to use cheapo EPs (a 7mm Nagler type 1)

[Moonshane]

I think it's an inadequately cooled mirror too. I see this when aligning finders etc and waiting for the mirror to cool down.

[WayBig]

Check collimation, though I'd think it's probably lack of cooling period and thermals in the atmosphere if the planet is low down and it's early evening, especially if the double image 'shimmers'

[Ags]

I have seen this as well, on both Saturn and Jupiter - I have always put it down to insufficient cooling time or poor seeing.

[haitch]

Well two front surface mirrors with one right angles to the other should be unable to cause this effect however severely miscollimated.

Seeing or thermal equilibrium could possibly but I would think only briefly and not as a steady second image. You should notice them wobbling around.

Motor tick is possible but then again I would have thought you would actually see the tick too (I know I could when I stuck a Meade ar6 on my CG5 at high mag)

I would still go for some sort of internal reflection in the ep. Try placing Mars at various places in the fov and moving your eye around to see if you can get the images to move in relation to each other.

[Ludd]

I had exactly this sort of image of Mars last night while my C8 was cooling down. It was exacerbated by the scope being slightly out of collimation but, once it had cooled sufficiently, the doubling up disappeared. So I'd put it down to the scope not having cooled to ambient temps.

[knobby]

Off the wall answer coming

When feeling lazy, for a quick look at stuff I point my scope through the skylight in my extension (double glazed)

That is the exact effect I get ... just a thought!

[Tribal-Wolf]

Check the EP is screwed together tightly too and hasn't came loose. It sounds like it could even be eye positioning.

[Jaxxxxx]

Thanks for all the replys!

In answer to some questions the mount is not motorised and was left outside from early afternoon to late evening so over 6 hours so I doubt the double effect was a cooling issue. I have Televue Radians so double checked they where all screwed together and they seem fine.

I decided to fully re-collimate the Telescope earlier on today and have been out testing it however some major light pollution from the moon and early night rural lighting the conditions are simply not great at the moment. I will have another look at Mars later on tonight to see if the problem is still there and report back!

I decided to do a Star test as well at 180x to see if anything jumped out at me that might be an obvious fix. When checking against a Star Testing chart what I am seeing doesnt really look like any of the pictures and yet at the same time I am seeing similiar features on all.

To explain a little better if looking at the images from Astro Babys Star Testing guide my defocused star has the circular rings like the "Perfect Collimation" however not quite as smooth also the very outer ring is all jagged just like the picture showing "Atmospheric Turbulence" yet with hints of the image showing "Optical Surface Damage". I also get the very faint lines over the rings in the shape of the spider vains however they are sort of washed out over the circles.

Thanks

[jimmyjamjoejoe]

I have never seen perfectly round star tests, there is always an element of turbulence to it no matter how well cooled my mirror is. I always use polaris since i don't have tracking etc.

[Peter Drew]

I saw the same doubling effect with venus early this evening using a 6" refractor, the seeing was not good.