Wide field eyepiece for a 1500 focal length

[04Stefan07 (Stefan)]

I have tried a 25mm and the moon just fits within view.

What would be a good wide field of view with this focal length?

32mm?

Thanks.

[Wavytone]

Assuming you're limited to a 1.25" barrel the choice is determined by the size of the field stop. At 1500 mm fl the diameter of the moons image will be about 13mm across.

This suggests your 25mm is one that has a field stop about 15mm, such as an old Kellner. The largest field of view is determined by the field stop (ie the inside diameter of the barrel) - not focal length.

For example the Televue Panoptic 24mm and Explore scientific 24mm 68 degree eyepieces has a 27mm field stop - pretty much the maximum possible - yet much the same fl as your current eyepiece.

A televue 32 mm plossl also has a 27mm field stop - same field of view, less magnification.

[04Stefan07 (Stefan)]

Woops sorry.

127mm aperture and focal ratio is 12.

[Amaranthus (Barry)]

Aperture makes no difference to FOV. At 1527mm FL, the 24 Pan will still give you the widest FOV of 1.07 degrees at 1.25" with 63x mag (i.e two full moons with room to spare).

If you go to 2", then and excellent choice is the 31 mm Nagler with 82 degrees AFOV and 1.7 degrees TFOV at 49x mag.

[Renato1 (Renato)]

On the 127mm Mak that I got a week ago, I've been happily using a 25mm Plossl and the wider 60 degree FOV Meade 25mm HD eyepiece - since they come closest among what I have of delivering the 2mm exit pupil that I want for DSOs.

The best eyepiece for it would obviously be the 24mm Panoptic, which gives exactly a 2mm exit pupil, but I could never bring myself to spend more on the eyepiece than I did on the telescope tube.

The good thing about long focal length telescopes is that otherwise average wide angle eyepieces still look reasonably good in them.
Regards,
Renato

[ausastronomer (John Bambury)]

Originally Posted by Amaranthus

Aperture makes no difference to FOV. At 1527mm FL, the 24 Pan will still give you the widest FOV of 1.07 degrees at 1.25" with 63x mag (i.e two full moons with room to spare).

If you go to 2", then and excellent choice is the 31 mm Nagler with 82 degrees AFOV and 1.7 degrees TFOV at 49x mag.

That eyepiece is probably worth almost as much as the 5" mak. Unlike fast F-ratio newtonians, with scopes like a 5"/f12 MCT it isnt necessary to buy the absolute cream of eyepieces to get decent performance. In a scope like that the Japanese made 30mm University Optiks MK-80 will do almost as well as the 31mm Nagler for less than 1/4 of the price and for about 40% of the cost of the 31mm Nagler the ES 30mm 82 deg will do very nicely in an F12 MCT.

Cheers
John B

[ausastronomer (John Bambury)]

Thinking about this a bit more, I would be very surprised if a 2" 30mm 80 degree eyepiece did not vignette in that scope, notwithstanding you could physically use it with a 2" diagonal.

You may be limited to something like a 24mm Panoptic, 24mm 68 deg Explore Scientific, or a 30mm to 35mm plossl, all with 1.25" barrels.

Cheers
John B

[04Stefan07 (Stefan)]

Thanks for the replies.

I am looking at a 1.25" eyepiece.

[Camelopardalis (Dunk)]

The baffle tube of the scope is only about 25mm so you shouldn't really notice any vignetting when maxing out the 1.25" barrel. If you want wider views, mount a short 80mm or so achro on top

[04Stefan07 (Stefan)]

What would offer decent views for something up to $100?

Either a 30 or 32 should provide nice wide shots of the Moon and DSO's.

[Regulus (Trevor)]

Stefan have a look at this Meade Super Plossl 56mm for $65. It should be a good wide field at about 27x mag and I think it is the 1.25" model, but a quick PM should clear that up

http://www.iceinspace.com.au/forum/s...d.php?t=118235

[ausastronomer (John Bambury)]

Originally Posted by Regulus

Stefan have a look at this Meade Super Plossl 56mm for $65. It should be a good wide field at about 27x mag and I think it is the 1.25" model, but a quick PM should clear that up

http://www.iceinspace.com.au/forum/s...d.php?t=118235

Hi Trevor,

Because those small Schmidt Cassegrains and Maksutovs have a narrow baffle tube, you are really limited to using 1.25" diameter barrel eyepieces in those scopes. Whilst you can physically use eyepieces having a 2" diameter barrel with a 2" diagonal, they will not work properly and will vignette the outer area of the FOV.

Cheers,
John B

[brian nordstrom (As avatar)]

Hi Stefan , I would look at either that 16mm T2 that will give 92x or the excellent 14mm UWA Meade giving 107x , both in the classifieds .
I have the 16T2 and its a very good eyepiece , I also have the 13mm T1 which Meade copied in the 14mm UWA and all reports say its the best eye piece Meade ever made .
My 5c .

Ps . all my Naglers perform excellently in all my scopes f5 , f8 and f10 .

Brian.

[04Stefan07 (Stefan)]

Thanks for the helpful advice.

Is there any point in upgrading the diagonal or nah?

[Merlin66 (Ken)]

No, the size of the baffle tube is the issue.
A good 32mm plossl would work well and have the potential for later use when you upgrade.

[Renato1 (Renato)]

I've just ordered the adapter that will enable me to attach an SCT 2" star diagonal to my 5" MAK, and it will be interesting to see what vignetting will occur with my 2" eyepieces, if any. My 5" older style Skywatcher MAK has the 45mm thread on the back, and a smaller exit hole than the newer ones.

If vignetting is non existant or minimal, the 2" diagonal and my 2" eyepieces may become permanent features on it.

This is because I was checking out 2" eyepieces in my 6" MAK on the weekend, and I was quite impressed with the images from my inexpensive 2" low power eyepieces in it. I thought the view in my cheap 26mm 2" GSO eyepiece was slightly better than that in my more expensive Meade 1.25" 25mm HD eyepiece. And I got other impressive sights using my Meade 56mm plossl with a SkyGlow filter on Eta Carina and the Lagoon nebulas. But probably the most impressive image was from an $80 30mm Ultra Wide Angle eyepiece I got from Bintel years ago.

Having a MAK's long focal ratio certainly irons out kinks in eyepieces. Anyhow, my fingers are crossed, hoping I haven't wasted US$34 on the new adapter.

If your MAK is the newer type with the bigger hole in the back - really, I'd think seriously about getting a 2" diagonal and the cheap GSO 2" eyepieces for it. Else, if it's like mine, wait for my results after I get my adapter.
Cheers,
Renato