fov vs manification

[torr (James)]

Hi folks
Another easy question for someone

When using my F5 scope with an FL of 1000mm ...
Is an 5mmm TV nagler(82 Deg fov) going to have a similar similar amount of sky view in the the eypiece as a 7.5mm eyepiece with 50 Deg fov.?

The ratio between 82 deg an 50deg is 1.6 , can I use that as a multiplier to work out if eyepiece A at any focal length with a 82deg fov will give me the same view but magnified as eyepiece B with a 50deg fov and a focal length of eyepiece A * 1.6 ?

Did any of that make any sense

Looking at the Tele vue eyepiece calculator it apparently appears so too me , or have I had too much coffee today.

Im looking at a TV 7mm and maybe a 11mm nagler for general planetary and globular cluster viewing . This will give me roughly 142* / 284* mag and 90* / 180* mag with my 2* TV barlow .

Any recommendations will be appreciated thanks

Regards

Torr

[dannat (Daniel)]

I think if you divide the mag of the ep by the fov this gives a real fov thru the ep. so 5mm in 1000fl scope gives 200x, put 82 over 200 = .4 deg fov

7.5 in 1000 gives 133x, 52/133 = .39. So it appears the real view thru the ep's would give pretty much the same amount of sky to view

I don't think you'll go wrong with those magnifications

[Jeff]

I agree with Dannat's explanation, which also agrees with your coffee calcs.

Another option would be for you to go for:
Nagler 13mm: 77x for medium power cluster views (barlow to 144x for small objects)
Nagler 5mm: 200x for routine planetary/lunar, double star splitting (barlow if/when seeing allows)

Barlows are a great money saver (and handy for astrophotography), but some find them a hassle to be wielding them all the time for common/routine viewing.

Also, keep in mind that although Naglers are great, you need to "look around" in the eyepiece to see more than about 68 degrees at once. For this reason (and value), some Televue buyers tend to get Panoptics for lower power EPs.

Cheers,
Jeff

[torr (James)]

Thanks guys

I'm still not sure which way I'll go .

2 naglers , I can get a few quality plossyls for the money.

Unfortunately viewing before I buy isn't an easy option, I've been trying to get in contact with the local Bunbury amateur astronomy association (90kms from me), so far no luck.

[Starkler (Geoff)]

Originally Posted by torr

I'm still not sure which way I'll go .

2 naglers , I can get a few quality plossyls for the money.

Unfortunately viewing before I buy isn't an easy option, I've been trying to get in contact with the local Bunbury amateur astronomy association (90kms from me), so far no luck.

If you cant try before buying, I would definitely recommend doing a lot of research and buy 2nd hand. Buying 2nd hand if you dont like it you have the opportunity to on-sell at minimal loss. Imagine shelling out for a new 5mm nagler and being disappointed at shelling out so much if you cant handle the short eye relief.

When talking high end eyepieces, not all are equal and each have their own quirks and compromises to consider. For example not all naglers are equal and each is different in its own way. Theres only a few of those that I like and would own.

[tnbk00 (Daniel)]

My 13mm nagler is my most used ep in my collection.....

[rider]

Originally Posted by torr

Hi folks
Is an 5mmm TV nagler(82 Deg fov) going to have a similar similar amount of sky view in the the eypiece as a 7.5mm eyepiece with 50 Deg fov.?

The ratio between 82 deg an 50deg is 1.6 , can I use that as a multiplier to work out if eyepiece A at any focal length with a 82deg fov will give me the same view but magnified as eyepiece B with a 50deg fov and a focal length of eyepiece A * 1.6 ?

Torr

I had a similar thread some time back, the answers all boiled down to this:

Yes they will give the same FOV, but, in practice the difference can be likened to TV's - the 82 degree will be like looking at a wide screen 46 inch TV, and the 50 degree will be the same show on a 14 inch portable.

I bought the 82's and wouldnt go back.

Rider