Pentax XW 30mm and 40mm Return

[Ships and Stars]

24 minutes ago, John said:

What I wanted though, being still a "wide field junkie", was the neutral tone, sharpness and lack of light scatter of the XW's combined with a very large field of view. Unfortunately for my bank balance the Ethos range came along ......

Given the gradual & more recent TV price increases, you may end up money ahead John! My first view of the Veil last year with the 21E and OIII made me a convert. Up to that point, I hadn't really viewed much with the 21E that justified the price, but after that, I got it!

[Don Pensack]

Piero,

I did not check the Paracorr setting for the 30mm APM UFF eyepiece because you find its setting the same way you find the setting using the ES HRCC:

You use an eyepiece, any eyepiece, that you know the Paracorr setting for, insert the eyepiece, dial in the correct setting, focus the scope and lock the focuser

(figuratively, i.e. don't move it).  Insert the new eyepiece and focus using the tunable top.  The setting that results is the correct setting for that eyepiece.

So since I had been using a TeleVue eyepiece prior to using the 30mm APM, i simply inserted the eyepiece and focused with the tunable top.

I didn't even bother to look at what the setting was since coma correction was perfect and stars at the edge were tiny pinpoints.

 

Every time someone asks me what the Paracorr setting is for eyepiece X, I just ask if they have one eyepiece they know the correct setting for.

If they do, they know the setting for every eyepiece because the tunable top parfocalizes all eyepieces that focus within the range of the tunable tops adjustment (0.7").

Just focus using the tunable top.  Now, that won't give you extremely fine focus, which is why you still need to have a millimeter travel in the focuser.

Edited March 11, 2020 by Don Pensack

[Piero]

On 11/03/2020 at 04:15, Don Pensack said:

Piero,

I did not check the Paracorr setting for the 30mm APM UFF eyepiece because you find its setting the same way you find the setting using the ES HRCC:

You use an eyepiece, any eyepiece, that you know the Paracorr setting for, insert the eyepiece, dial in the correct setting, focus the scope and lock the focuser

(figuratively, i.e. don't move it).  Insert the new eyepiece and focus using the tunable top.  The setting that results is the correct setting for that eyepiece.

So since I had been using a TeleVue eyepiece prior to using the 30mm APM, i simply inserted the eyepiece and focused with the tunable top.

I didn't even bother to look at what the setting was since coma correction was perfect and stars at the edge were tiny pinpoints.

 

Every time someone asks me what the Paracorr setting is for eyepiece X, I just ask if they have one eyepiece they know the correct setting for.

If they do, they know the setting for every eyepiece because the tunable top parfocalizes all eyepieces that focus within the range of the tunable tops adjustment (0.7").

Just focus using the tunable top.  Now, that won't give you extremely fine focus, which is why you still need to have a millimeter travel in the focuser.

Thanks a lot for your very clear comment, Don. 

I don't find coma distracting in my F6 dobson, but it is certainly there. I might invest in a PC2 in the next 15% TV discount sales, as I love refractor-like views.