Help with Lunt 40 mm solar scope -is it defective?

[Felias]

Hi! I have just bought a Lunt 40 mm for my school, but I am having trouble setting it up. I have managed to focus with 20mm and 9mm Ploss eyepieces, but the tuning dial does not seem to work well, I can't see anything but a red disk. I have noticed that the whole filter cap is loose, and that I can rotate the whole thing around, not just the wheel. Is this normal? I don't want to tighten the screws myself, in case it's the wrong thing to do. Some pictures to show what I mean:

 

I can turn the front 360 degrees, I assume this is not right? Any help appreciated!

[Craney]

I will try to answer before somebody with greater learning steps in.

The knurled wheel in your pictures brings the components within the etalon 'on-band'  so you can see the solar features at Hydrogen Alpha wavelengths  (with a bandwidth of  1Angstrom ~ 0.7Angstrom  or whatever the scope is rated at.)

This is the so called 'tuning' of the scope.

All the focus is down at the other end.   Have you got a piccie of that end ?

You might need an extension tube etc to make all eyepiece designs come to focus.

Not sure about the rotation thing as I have never used a Lunt scope before.

Hopefully that might help you along a bit. These look nice scopes.   PST rival ??

 

Sean

[Craney]

If your scope looks like this ......   then the focus control is the numbered black component to the left of the diagonally shaped blocking filter.

If you undo the small sticky-out locking screw then you should be able to rotate the black flange with the numbers. This will focus the scope.

Those numbers are a nice touch as you can 'dial-in'  a value for a set eyepiece or if you are imaging.

 

 

[NGC 1502]

The knurled brass wheel does not affect focus, that’s the tilt tuner that can sometimes enhance the view. My 12 year old Lunt 35 is the same.  Most of the time the tilt tuner can be left in the home position (not tilted). In your first pic it looks like it’s on maximum tilt, the gap can be seen.

I think it’s very likely that you only see a red disc because you haven’t achieved focus using the focus wheel at the eyepiece end.

Not sure what you mean by the “filter cap” could you clarify?   Or do you mean the dust cap at the front end of the scope? Of course the dust cap must be removed for observing.

Ed.