Skywatcher 10” Collapsible Dob first go

[ab1963]

I had my first session with my 10” Dob last night and was pretty impressed with the views I had,Used the Docter 12.5mm and Nikon Nav Hw 17mm and understand now what John B was saying about having a look through these eyepieces through a bigger aperture scope and was a very close and personal experience.
The Docter was sharp to the eof but the Nikon was 85% there which was unusual to me as in the refractors I have razor sharp to the eof is the norm and any advice to get the same eof sharpness would be appreciated....

[ab1963]

Alex was at my place this afternoon and has given me all the answers i needed so thank you Alex

[AG Hybrid]

Coma is a savage *******. Even the eyepiece experts Televue try to sell you a corrector.

[ab1963]

I think what I’ve learned from Alex is it’s a different type of viewing completely to refractors and eyepieces definitely behave differently in whatever type of scope you are using and after my chat with Alex just lets me know how good the 2 said eyepieces perform

[AG Hybrid]

I think those 2 eyepieces cost more then your scope. I think the Nikon alone costs more.

[mental4astro]

Andrew,

You have two very good eyepieces there, but they are created differently and have different applications as I mentioned to you on Saturday. The Nikon eyepiece is designed expressly to be use with refractors (convex focal plane, as have Maks and SCTs), so its performance in fracs is outstanding, as you know. But that Nikon is an optical mismatch with Newts (concave focal plane), and the outer edge aberrations you are seeing with your Newt are a symptom of this. Nothing wrong with the scope or eyepiece. Simply an optical mismatch.

That Docter EP is a VERY SPECIAL BEAST. It is rare to find an EP that can work pretty much equally well in a Newt as in a refractor.

As Adrian mentioned, coma in a Newt can be savage, but it is not responsible for the gross aberrations you are seeing with the Nikon EP. A coma corrector won't help with the Nikon EP as it won't correct anything else but coma, and not the field curvature, spherical aberration and astigmatism that the optical mismatch will be generating with the Nikon in your dob.

Also, remember the way we actually use our scopes - we don't do any serious observing at the edge of the field of view. Having a 100° AFOV is great, but when an object is at the edge of the FOV you will move the scope and not examine it closely at all if it is at the edge... This is something to keep in mind if there is a little distortion visible along the edge, and your Nikon will still be a very usable EP with your dob. May well mean that a coma corrector with your f/5 dob is not necessary either! :)

Alex.

[ab1963]

Yes Adrian they weren’t cheap but after using them in anything I have had Would only view through these 2 mainly so sold nearly all the eyepieces I had they are just that good and both barlow superbly

Again thanks Alex the dob is a totally different animal to what I am used to but when you explained it in layman’s terms I was ok with it , The Trapezium viewed with the Docter through this scope is pretty amazing