Egg shape stars on top of refractor image

[ollypenrice]

9 minutes ago, alacant said:

Why the tube couldn't be made a few cm longer, we've no idea. 

 

 

Agreed. At one times this mania for for short tubes was a William Optics speciality but the malady has spread...

Olly

[Adam J]

18 minutes ago, alacant said:

The laser enters via the lens. Have the lens about 50cm from a wall.

No. But anyway, the focuser should be OK as it is; we've yet to see a misligned ES focuser. The main issue with the ES's 80 is the backfocus; the camera needs to be held so far from the tube. Why the tube couldn't be made a few cm longer, we've no idea. 

You must first set the lens square to the tube. Only then can you assess tilt. 

Cheers

 

I think ES have a thing about allowing for Bino-viewers and protability. But in terms of imaging this is exactly the "feature" that put me off ES scopes. 

Adam

Edited February 17, 2022 by Adam J

[alacant]

18 minutes ago, ollypenrice said:

a William Optics speciality

Seasonal fashion perhaps? My gf thinks they look 'dead cute', especially as they come with a choice of colours. You can be sure they'll match any outfit perfectly. A far cry from our tatty reflectors which 'don't even look like telescopes'. 

Edited February 17, 2022 by alacant

[Uranium235]

Totally agree with @vlaivthat the compression ring is most likely to blame. I've long complained that there is no industry standard distance for safety undercuts and compression rings.... so most of the time they "pop" out at an angle when tightened up. 

If possible, do away with it and try to find a threaded solution.

Opening up your lens cell is a bad idea, it should only be performed by an expert, with an appropriate optical bench to test it on. I certainly wouldn't try it, unless you're willing to accept that you might break it.

[vlaiv]

26 minutes ago, Uranium235 said:

Totally agree with @vlaivthat the compression ring is most likely to blame. I've long complained that there is no industry standard distance for safety undercuts and compression rings.... so most of the time they "pop" out at an angle when tightened up. 

If possible, do away with it and try to find a threaded solution.

Opening up your lens cell is a bad idea, it should only be performed by an expert, with an appropriate optical bench to test it on. I certainly wouldn't try it, unless you're willing to accept that you might break it.

It seems that in this particular case - it was the lens that was tilted.

As far as I gathered from the discussion - lens was not opened but was properly aligned with optical axis - cell seems to be adjustable for tilt.

[ollypenrice]

Do you need a laser?  Some years ago I phoned TeleVue in the States because I had a scope of theirs which was giving shuttlecock stars inside and outside focus after it had been bumped. The scope had, like the OP's, a front lens cell but it wasn't held in alignment by three pairs of antagonistic screws along the optical axis but by three radial screws. I was advised to loosen the three screws, move the lens cell with my fingers and stop when I had concentric diffraction circles out of focus. This proved remarkably easy. At this point the advice was to tighten the three radial screws very gently, a little at a time, while ensuring that the concentric circles were not disturbed. This procedure worked and when I later imaged with the scope (which was intended only for visual) it gave round stars. I'd be inclined to try this using an illuminated ball bearing as the time-honoured artifical star, but using the antagoniostic screws to adjust the cell.

Olly

[alacant]

2 hours ago, Uranium235 said:

the compression ring is most likely to blame

Hi

We have already ascertained that this is not to blame. Or rather, the OP can only assess any issue with the compression ring after the objective lens has been aligned.

Cheers

[alacant]

1 hour ago, ollypenrice said:

Do you need a laser? 

No. Any method which aligns the lens is fine. The advantage of the laser is that it doesn't depend upon the focuser being correctly aligned. 

 

[ollypenrice]

11 minutes ago, alacant said:

No. Any method which aligns the lens is fine. The advantage of the laser is that it doesn't depend upon the focuser being correctly aligned. 

 

Yes, any tilt in the focuser needs eliminating before using a star test.  Actually I've had a refractor here for some time which needs the front cell adjusting and I've always assumed I'd get round to it using the method from TeleVue.

Olly