Wide view eyepiece for f5 reflector

[MartinT]

Hi, 

I have a skywatcher 130 and would like to look at getting a particularly wide angle, low power eyepiece. I have the 28mm 2" eyepiece it came with and I think that has a 56deg fov (though happy to be corrected here), but I see eyepieces listed with wider view and wondered about them. 

I've been told that the f5 of my scope is fast enough to cause problems for wider view eyepieces, especially at the cheaper end of the market. How problematic are these limitations? I've also been told that the advantage of using a 2" is the wider views possible. So does anyone have experience of a 2" wide-fov, low power eyepiece - particularly one that's good value (or one to save up for tbh!) 

Cheers, 

M

 

[John]

This current thread in the eyepieces section enquires about suitable eyepieces for a 200mm F/4.5 newtonian which is going to be a little more demanding on eyepieces than your 130mm F/5 but some of the information will be relevant:

https://stargazerslounge.com/topic/387007-eyepiece-recommendations-for-a-200900mm-newtonian-considering-the-baader-zoom-or-individual-eyepieces-around-the-same-price/#comment-4175578

From the recent post by Don Pensack in that thread it looks as if the APM Ultra Flat Field (UFF) 30mm, or one of it's clones, might be a reasonable option for you as well ?

 

 

 

 

Edited November 28, 2021 by John

[Zermelo]

Hello Martin,

you might find these threads useful:

https://stargazerslounge.com/topic/384223-wide-angle-eyepieces-question

https://stargazerslounge.com/topic/374844-caveats-with-wide-afov-eyepieces-in-fast-telescope

 

 

Edited November 28, 2021 by Zermelo

[MartinT]

Thanks both, really appreciate it 

[bomberbaz]

I believe these are along the lines of the Explore scientifics but a little reading has uncovered them to be a very decent eyepiece although that is from other peoples experiences, not mine

Opticstar XL 82° Ultra Wide Angle Eyepieces.

Personally in your focal length I think the 24mm is best giving a decent eye pupil of 4.8mm, magnification of 27 which is useful and a field of view of just over three degree. That said the 18mm still gives a 2.27 FOV but will have a darker background due to the higher mag x36 and smaller exit eye pupil at 3.6mm. 

It's all about personal preferences really. 

EDIT: The 18 mm is also quite a bit cheaper.

Edited November 28, 2021 by bomberbaz

[MartinT]

Thanks @bomberbaz I'll have a look 

[Zermelo]

Also, if you did want to try one of the "cheaper" 2" eyepieces you might look at the Stellalyra (GSO) Superviews.

In a 130mm F/5, they would behave as follows:

The 42mm and 50mm would have very large exit pupils, resulting in a light sky background and reduced contrast.

The 30mm has a 6mm pupil that may be OK, depending on local sky conditions. It has a 68° AFOV, not significantly greater than the stock EP you already have. The 3.1° TFOV given above compares with 2.4° ish for the stock 28mm.

Used at F/5 the edges of the field will suffer to an extent - you might want to read this thread if you were thinking of buying.

[MartinT]

Thanks @Zermelo that's really helpful - ta for the linked thread too. Very informative. 

[Gfamily]

There's a calculator available at the 'astronomy tools' website that will show you what the field of view will be for a variety of scopes and eyepieces, lined up against a variety of targets, such as the Moon and any of the Messier objects. 

Basically, it depends on the f/ratio of your OTA, the focal length of the eyepiece and the Apparent Field of View (which will depend on the design of the eyepiece). 

https://astronomy.tools/calculators/field_of_view/

There's a variety of tools that you may find useful - but don't get too stuck into them, just use them as guides rather than instruction manuals  

[Louis D]

Nice info, but I doubt the OP will ever see it since they last visited on May 14, 2022.

[Gfamily]

2 hours ago, Louis D said:

Nice info, but I doubt the OP will ever see it since they last visited on May 14, 2022.

Good point   - but it may be useful to someone else who's wondering the same.