Wide field dreaming

[Camelopardalis]

Folks, tis the season and all, and what better way to idle away my commute than to think of something a bit different from my usual...a wide field scope :D

There'll be no such thing coming down the chimney this year, and this is all hypothetical for me as I'm not in a position to be buying anything right now, but I was entertained to think of the possibilities, and appreciate any suggestions... the goal being a scope with a nice wide field of view, decent image quality, sufficient light grasp to show plenty of detail in the globs and nebulae we're blessed with, but without costing the Earth...


100 / 110 / 120mm ED doublet... start getting a little costly and interesting to mount in the longer focal lengths (Orion's new f/6 110 Eon looks interesting, at a price :sadeyes:)

8" Dob... inexpensive but all the mainstream ones seem to be f/6 and I can get the reducer for my C8 and drop it down to around f/6.3, so not inspired by this option

8" newt... imaging newts are available in f/5 and even f/4 for a bit more than the Dob, but any disadvantages? I have a GEM that should carry one, but would prefer alt az


Anything else obvious I'm missing? Besides a bigger refractor or smaller newt/Dob :lol: just dreaming about options for a dedicated, limited use scope, for the really big objects and scooting along the Milky Way, not one scope to rule them all ;)

[skysurfer]

You want to capture the (small) constellation Camelopardalis in one field ? As it is rather close to the South Celestial Pole no tracking needed anyway and visible anytime, anywhere in AU... LOL !

But serious:

Well, Short Dobsons / Newtons (f/5 or shorter) have a disadvantage of collimation duty, but with 200mm this is done within a minute. There are enough f/4 or f/5 Newton for under $800.
Unlike the ED/APOs of 100-120mm which sell for at least the double.

BUT: a refractor has usually better images and requires virtually no maintenance. And an f/6 120mm has a larger true field than a f/6 200mm.
And modern cameras have no problems with using high ASA values such as 1600 or more so aperture is for AP less an issue than visual.

And, what about a 2nd hand telephoto lens ? I frequently a Canon 1.8/85mm for AP with very nice results ! I pictured the entire Southern Cross more times in one field and stars till mag +12.

[Camelopardalis]

Thanks skysurfer... the maintenance thing can't be underrated, but I can't reconcile the probable light grasp difference between even a 120 and an 8" newt/Dob.

I'm going to try my ol' faithful C8 with a reducer next time I get out, but the focal length/true field is still much less than I want ideally whereas a 120 f/6 could give a nice big field, about 4x greater off the top of my head. Hmm.

[Wavytone]

Dunk using a compressor on a C8 for visual use is a bit pointless... the central baffle and aperture in the back of the mirror cell restrict the maximum field of view to about 1.3 degrees. You might as well use a big eyepiece - an ultra-wide 40-50mm will show everything there is to be had in the vignetted field of view just as well as a tele compressor combined with a somewhat shorter eyepiece, and it will do it very well, whereas the compressor and a short eyepiece could easily end up being not so sharp.

To get MORE sky you need a shorter refractor like the ones you identified and it is for precisely the same reason I have a 102mm f/7 ED refractor, which fills a big 2" eyepiece giving a maximum field of view around 3.8 degrees which the C8 cannot come close to, no matter what you do to it.

I'll also add that with a similar setup (the refractor + my 180mm f/15 Maksutov) the refractor has become just a very big finderscope and to be honest i don't use it nearly as much as I expected; if there's a choice the Mak always goes on the mount but not always the refractor. FWIW you're welcome to try my refractor anytime...

However an 8" f/5 dob is a very different beastie and more likely to be useful especially if the optics are excellent. On and off over the past 2 years I have contemplated a larger dob, but refrained because I simply don't get out often enough to justify it.

[MortonH]

My Skywatcher Black Diamond 200mm f/5 Newt cost me $280 used. It's the one I take to Katoomba and is my largest scope. My mount is a DSV-3 alt-az and is more than adequate for the load.

[pmrid]

A Celestron SCT with a Farstar (or whatever the Starizona equivalent is these days) fitted - gets you plenty of aperture and a F ration down near 2 somewhere. If that doesn't light your Christmas candles, nothing will.
Peter

[Camelopardalis]

Thanks, I'd love a peek :D I usually use my 40mm with the C8 and last time was getting kicks from using it with the C11 + reducer, still only about 1.3-1.4 degrees, but the views of the Orion Nebula didn't disappoint.

But thinking about it even 8" f/5 is still a lot of focal length...8" f/3 would be much more appealing :help: I guess I was wondering if I was fundamentally missing something...just chasing that unicorn with the scope on it's back.

For those long winter nights, a bigger Dob has gone through my mind more than once...

[Camelopardalis]

Thanks Morton, I've just looked up the mount and it looks interesting, they even claim it will hold 28lb of SCT, which coincidentally is the weight if the 11 :lol:

[Camelopardalis]

Thanks Peter - I'm pretty intrigued by the possibilities of the Starizona kit with a small SCT, so it's on the cards! Just a matter of when :lol: Still in awe of all the shiny new visual objects I've gained this year!