Getting a wider view?

[Roog]

Hi, I have a new Skywatcher 250p Dobsonian as my first telescope and in between the cloudier nights I have been having fun exploring the bright objects in the sky. I have been using a Baader 8 - 24mm zoom eyepiece which I find works well for a variety of viewing and apart from buying a 5mm eyepiece to see if I could pull the planets in a little, I have begun to wonder what there is to be achieved at the other end of the eyepiece spectrum, say a 30mm or 40mm eyepiece. 

Please forgive the dumb beginner question, but what do people use 30mm - 40mm EPs for and am I missing out by not having one?  

Many thanks Paul

Edited December 7, 2021 by Roog

[Nik271]

Some DSO are quite large and either look better or can only be seen whole  in a wider field. For example the Double Cluster, the Pleiades, the Andromeda Galaxy, the Triangulum galaxy, the Veil nebula, to name a few.

I guess your telescope is F5 and so has 1250mm focal length, You can get a 2 inch 32mm EP with 70 degree field of view and you will have almost 2 degree  of the sky visible in the EP. You actually need low magnifications for DSO, say about 50-60x. This is because some DSO are so dim and large that you need wider field and a big exit pupil, i.e. bright image to have a chance seeing them.

[Geoff Lister]

I have the flextube 250P, and I have a 2" 56mm super Plossl. It is a lot of glass, and, as it is my only 2" eyepiece, I have to swap adaptors to use it. Most of the time I use my 1.25" 32mm Plossl for the wider views.

[Roog]

Thank you both for your helpful explanations and experience,  it seems like it might be worth adding one to my growing list of astronomy bits! 

Edited December 7, 2021 by Roog

[Ricochet]

With an f5 dob you're not really missing out on having a 30-40mm eyepiece as the exit pupil (6-8mm) is too large unless you are at a really dark location. What you are missing out on though is a wider field of view. With your scope the eyepieces I would be looking at are the 21mm TV Ethos and the significantly cheaper option of the 20mm APM HDC, assuming that you don't need glasses to observe and can get your eye close enough to the lens. Another option would be an 82° eyepiece at around the 25mm mark. 

[Roog]

Thank you @Ricochet I can see that i need to read up on this. Thank you for your suggestions, as a glasses wearer I am finding viewing challenging at times.

[Zermelo]

You can explore the field of view to be had with a scope/eyepiece combination here.

A 32mm Plossl is a common choice for this purpose (red circle below).   A Stellalyra Superview 2" 30mm gives an even larger view (yellow), but these both give exit pupils over 6mm.

A 24mm 68° Explore Scientific is a popular choice (green) and will also give a wide view, with a 5mm exit pupil.

If that's a bit pricey, the BST Starguider 25mm is under £50.

 

 

 

[Roog]

Thank you @Zermelo that link is just what I needed, cheers