Widefields for SCT

[Ziggy]

Hi Guys,

I'm obssessed with eyepieces, and have a couple of questions regarding 2" wide field eyepieces. Does anyone know what the maximum FOV for a 9.25" SCT is before the field starts to vignette. I couldn't find what I was looking for, but I'm sure there was a discussion on here a while back. I have a 2" diagonal obviously.

I'm looking for a wide field eyepiece, without going over board on price.
Here are a couple of options, with the approx mag & fov

Televue plossl 55mm 43x mag and 1.17 degree fov
41mm Pan 57x mag 1.19 fov (very expensive)
35 Pan 67x 1.01 fov
Vixen LVW 42mm 56x 1.29 fov
Meade SWA 40mm 59x 1.16 fov
Meade UWA 30mm 78x 1.05 fov
UO Konig MK 70/80 40mm 59x 1.19 fov

A few options there, and most of those are fairly similar. Any opinions on how any of these perform? Maybe there's something I've missed? I'm looking for the widest field of view possible, without the view becoming unusable I suppose. A kind of finder eye piece.

The Vixen has the widest FOV, but will it be wasted in my scope? The Pan 35mm is probably the safest bet, but how does the 41mm perform. I've read a few reviews of course, so just looking for some more opinions. The plossl is tempting cause of price obviously, even allowing for it's 50 degree fov.

Thanks for any help!

[AGarvin]

Another option is the Meade 56mm Super Plossl. With a 52 degree AFOV it's slightly wider than the Televue. In a C9.25 the figures would be 42X for 1.23 degrees TFOV. I've never used one personally, but here's a review on the sucker ....

http://www.astromart.com/articles/article.asp?article_id=356

[JohnG]

Hi

You have an interesting selection of eyepieces to choose from there, I am biased with my point of view as I have all TeleVue.

I asume that you are aware that the rear opening of any SCT below 10" is not a full 2" opening, therefore you do not get the full benefit of a 2" eyepiece, SCT's 10" and above have an extra threaded section that can be removed to allow the fitting of an EyeOpener or similar type of rear fitting.

I had a C-8 for quite a long period of time and found that my most used eyepieces were the 27mm and 35mm Panoptics with a preference towards the 27mm. In a 9.25 I would probably lean towards the 35mm Pan, slightly more magnification and because of that a darker background. In use, I doubt that you will ever hear a bad word about the 35mm Pan when used in an SCT, I will never sell mine. As far as the FOV is concerned, expect pinpoint stars to the edge.

Cannot comment on the "Holy Hand Grenade" the 41mm Pan, beyond my means.

Hope this helps a little, I am sure you will as many opinions as there is eyepieces, it all comes down to personal choice, if you know someone with a particular type of eyepiece, ask them to let you have a go with it in your scope, that is the only you will know.

Have fun selecting. lol

JohnG

[xstream]

If you can find one second hand I can highly recommend the Tele Vue 32mm Wide Field. They were the fore runner of the Pan Optics. Magic eyepiece in the SCT.

[[1ponders]]

If you check out the Peterson Eyeopener page there is a link to a chart that lists the usability of different focal length eyepieces with different objective sized scopes.

This is the 8" chart http://www.petersonengineering.com/spreadsheets/Eyepieces_for_8_inch_SCT.htm

And this is the 10" http://www.petersonengineering.com/spreadsheets/Eyepieces_for_10_inch_SCT.htm

The 9.25 is in the middle I guess :shrug:

[Robert_T]

Hi Ziggy, one you've missed in the 50mm 2 inch barrelled Takahashi LE eyepiece. This has a slightly larger FOV to a typical plossl. I have only used the shorter focal length LE's on the SCT, but am very impressed with them. Tak do recommend the 50mm for use in their Mewlon series of Dall Kirkham cassegrains so good for long focal length. Price is ~$600AU last time I looked.

[Ziggy]

Thanks for the replies. Thanks for those links to the Peterson site too. As mentioned by JohnG, I knew there was something about the rear not being a full 2" on the 9.25, thus resulting in vignetting if the fov is too wide. I think I'm on the right track there anyway. I did read somewhere that the maximum fov for an 8" is 1.07 degrees, so I imagine the 9.25 would be similar.

Anyway, with that many different choices, it might be a while before I make up my mind. The only question I have with the Meade Plossl is that there are both Chinese and Japanese versions of this particular eyepiece, with the Japanese being far superior apparently. I think this is the right series I'm refering too.

The Takahashi Plossl would be great I have no doubt, but I'd want to make sure it'd work ok before getting one at that price. I'll keep a look out for a second hand one though.

My main eyepiece at the moment is the 22mm Panoptic, so I'm looking for a wide field of view to use first, (hence maximum possible), then step up to the Pan with mag around 100x and 64 degree fov. That's my planning anyway.

Thanks for your help guys!

Zig

[ausastronomer]

These long focal length eyepieces you guys are mentioning 56mm meade 55mm TV, 50mm tak etc etc will not work in the C9.25 because of the small port, they will vignette. John G mentioned the 35mm panoptic and I know that works fine, I have my doubts about the 41mm panoptic working properly also. I would go with the 35mm Panoptic.

CS-John B

[Striker]

If you want some stats on what will and what wont work...check the peterson site out.

I dont know if they mention the 9.25" but they have the 8" on there. go down to how various eyepieces perform on SCT's

http://www.petersonengineering.com/sky/EO.htm