2" EP

[redgiantjohn]

When I got my new dob it came with a 2" eyepiece adaptor I was just wondering what a 2" eyepiece would be used for? Would it give a bigger FOV? I'm in the market for an EP upgrade and would like to know if. 2" is worth thinking about cheers john:iamwithstupid:

[John]

2" eyepieces can give you a wider field of view than 1.25" ones. As an example, in the 1.25" size a 40mm focal length eyepiece can deliver a maximum effective field of view of 44 degrees wheras, in the 2" fitting, 70 degrees is possible which shows a lot more sky in the scope.

So for low power they are very useful.

[redgiantjohn]

2" eyepieces can give you a wider field of view than 1.25" ones. As an example, in the 1.25" size a 40mm focal length eyepiece can deliver a maximum effective field of view of 44 degrees wheras, in the 2" fitting, 70 degrees is possible which shows a lot more sky in the scope.

So for low power they are very useful.

Thanks for the info I've really got a dillema over which eyepiece to get as its probably the only one ill be able to afford this year,I've looked at a couple of the EP sets and they seem good value for money so I was tempted to look into getting a cheaper set just to get used to the different powers of the EP then when I know what sort of views I'm getting with the various sizes maybe upgrade to a better quality or.....

On the other hand do I jump straight in and get an EP between £50-100 that will be really good quality hmm descisions....

[DOBBY]

http://www.12dstring.me.uk/fov.htm have a play on that site...just enter your 'scope..& try out the views of objects with different lenses.

Nothing beats finding a local observing group tho... most people will be happy to let you try their eyepiece in your 'scope

[JamesM]

With the greatest respect to the suggested simulation - I don't find them that helpful to be honest. I do however agree with Dobby's suggestion about locating a local observing group or astro club (...that actually does some observing) as there is nothing quite like handling eyepiece for real, be it their size, the weight or ease of use. Recommendations are useful but there is a bit of subjectivity as to what feels comfortable to use and image tolerances such as sweet spots, sharpness to the edge of the field, pin cushioning etc. I would avoid buying any eyepiece kits as they will inevitably include one or two that you hardly use and you would do better spending the money on one good eyepiece at a time and build up your collection slowly.

You have enough posts to participate in the 'For Sale' section and there are always good eyepieces for sale that will set you off in the correct direction. In time you will no doubt replace these and as you bought them used, you are likely to get back the original money you original spent on them providing you keep them in good condition.

James

[umadog]

Let's be clear now, there is a difference between apparent field of view and true field of view. A 1.25" Nagler has an 82 degree apparent field of view. You don't need a 2" eyepiece to get a wide apparent field.

The apparent field of view is how large an angle the field appears to be at the eye. The true field is the angular extent of sky visible in the eyepiece. Roughly speaking, truefield is equal to the apparent field divided by the magnification. So what's the diameter of the eyepiece got to do with this? The apparent field of view is limited by the eyepiece's field stop. This is a circular ring which is projected onto your view and places the limit on what you can see. The edge of the field of view is limited by the field stop. The angular diameter of the circle created by the field stop defines the apparent field of view. IIRC, the absolute size of the field stop determines the true field of view. In other words, for a fixed apparent field of view to provide a larger true field of view you need an eyepiece design with a larger field stop. To get a wide true field and wide apparent field you want a 2" eyepiece. I'm sure all that is a simplification. Further details here:

Tele Vue Optics: Choosing Eyepieces

[TheThing]

A lot of complication here.

Simply put, a 2" EP shows you more. Try one on M45 come the winter and you'll see.

TheThing.

Sent from my iPhone using Tapatalk

[swamp thing]

Hi

TBH James advice about trying a few is spot on. 2" eyepieces are big, heavy and normally expensive.

The longer focal length 2" eyepieces often require you to re-balance your scope. This can become tedious so some sort of counter weight system is advisable.

You might find the longer focal length 1.25' eyepieces less hassle.

Good luck with your decision

Regards Steve

[redgiantjohn]

Well thanks everybody for the input I decided on my first EP and phoned through an order to telescopehouse I chose the meade 5000 series 5.5mm super plossl I was thinking it would give me some great detail on my favourite celestial object the moon,I also purchased a polarising lunar filter and they should be here friday I'm looking forward to the difference a decent EP will make I think next on the shopping list is an angle gauge

[spaceboy]

What scope do you have ?

[redgiantjohn]

What scope do you have ?

I have a skywatcher 150p dob