Telescopes: Celestron 14" SCT..Meade 10" ACF/SCT..Stellarvue 4" ED APO Mounts: UA UniStar Deluxe duel clamping saddle on a Celestron CGE tripod...UA UniStar Deluxe on a Meade field tripod and a UA UniStar Light on a UA light surveyor tripod. All with custom made "Manny Miles" eyepiece trays. Binoculars: Garrett Optical 10x50 Oberwerk 15x60. Eyepieces: TV Naglers, and Plossl's. Also Pentax 20XW, a Baader 31 Aspheric and a TMB 40 Paragon.
10" OO VX, 6" iOptron Mak-Cass, Orion 100ED
Quote: the teen is now to just stick in more & more glass. I'm glad at least Celestron is still offering "standard" SCT optics.
LX850 blog: www.LX-850.com
personal website: www.wadsworthobservatory.com
Quote: For visual, I'd rather more photons.-Edit- typo
"The heavens declare the glory of God; the skies proclaim the work of his hands." Psalms 19:1
"Considered as a collector of rare and precious things, the amateur astronomer has a great advantage over amateurs in other fields ... the amateur astronomer has access at all times to the original objects of his study; the masterworks of the heavens belong to him as much as to the great observatories of the world. And there is no privilege like that of being allowed to stand in the presence of the original." --Robert Burnham Jr, Burnham's Celestial Handbook
Quote:Thanks Scott. So, there's an extra set of elements in these. Bit of a shame for me - more glass & surfaces. It's getting to the stage that I may as well as use a brick for a telescope the trend is now to just stick in more & more glass. -Edit- typo
C14 EdgeHD, C11 EdgeHD Zhumell 8" f/6 Newt AP1200GTO, CGEM DX, CG5-ASGT Rob Miller Tri36M tripod Canon Rebel XS, Atik 314L+, DSI pro I,II, QHY5L-II SX 7 FW with Astrodon LRGB, Ha 5nm Hutech OAG5, Rainbow Optics Grating Scorpio Observatory
Quote:that so called microfilter let's just as much dust in as if it was open...
Others may disagree. Your millage may vary. Void where prohibited by law.
Quote: and serious observing is really only done at the centre of the FOV
Quote: If I can have both an excellent image at the center of the field, and an equallly excellent performance at the edge, and I can afford it, and I enjoy it, than that makes the extra money spend on the telescope worth it to me.For you personally, apparently it would be wasted.Not for many of us though.
Clear Skies- Guy
“The first gulp from the glass of natural sciences will turn you into an atheist, but at the bottom of the glass God is waiting for you.” ― Werner Heisenberg
12" LX200 GPS
4" Unitron 150
4" Bosma refractor
Denk Binotron 27, D14's and D21's
Galaxy Note 8 running SkySafari Pro via Bluetooth
Wireless Autostar II
Celestron EDGE 11/CGEM | Stellarvue SVR90T-25FT20MM ES100 | Televue 31MM Nagler T5 | Televue 11mm Nagler T6 | Televue 2X PowerMate Sky Safari 4 | SkyFi
Quote:I really don't understand why anyone would tolerate any distortion or degradation of an image when there's an alternative.
When you buy a 14" scope you are paying a premium for that big mirror. Why would you not want to get the most out of every inch of it? Especially if you're using expensive, wide field eyepieces?
Quote:I realise coma is only along the edge. My original post noted this.But I've never heard of coma being visible at f/10 in a reflector, at least not in an f/10 Newtonian. My f/4.5 & f/4 Newts show some, but then again, echoing Bill's post, it doesn't bother me, so I don't use or need a coma corrector. I also have a couple of little Newts with spherical primaries, so I know what they are capable of.Spherical mirrors (which is what SCT's use as a primary) don't show coma. So how can a scope be described as "coma free" if it isn't there in the first place.I'm glad to read not all SCTs show SA. This implies that there are deficiencies in those designs that exhibit SA. SA would be seen only at high magnification with the whole spectrum of colours not being pulled in to one point. You don't see this at low power which is where you see coma.Hmmm, would a spherical mirror show coma in addition to SA? I can't say I've noticed it when using good quality EPs.The corrector plate deals with SA. The hyperbolic secondary with what edge aberrations there could be with such a fast primary (I think I could be answering some questions for myself).Also, where coma could be seen in an f/10 SCT, it would exceed the field of view afforded by the set of baffles and the f/ratio of the scope. The baffles act as field limiters, so one could never achieve the same true field as a fast Newt. So I'm at the same problem - I don't see where coma comes into an SCT...
I lost count of my scopes. Now I just want mobility. I came, I saw, I bought some interesting accessories, and put names to faces: NEAF 2012, ASAE 2012, SWAP 2013, ASAE 2013.
Quote: My regular C9.25 has some coma but it doesn't prevent me from enjoying 100 FOV eyepieces in it and usually I hardly notice it. That said after looking through Jon's 12.5" Discovery with Paracorr next time I used my SCT the coma seemed much more noticeable. I'm going with SIPS in my new 11" F/5 newt and if I get another SCT someday it will be coma free. David
http://www.faintfuzzy.net Stuff C14, C8, Orion XX14i, Meade 8" ACF, AT6RC, AT102ED, Orion ED80, PST, AP1600GTO, CGE, CG5, ST10-XME/CFW8, QHY8PRO, Optec TCF-s, Microtouch Focuser, Pyxis LE, Hyperstar for C8.
SCOPES: CPC1100; AT66ED; EdgeHD 8";SVR90T RAPTOR
MOUNTS: CGEM; Vixen GP2; iOptron Sky Tracker; Celestron AVX
CAMERAS: Canon 60D;Lodestar
EYEPIECES:TV N31T5;Delos14;Delos8;Pan27; PL20;PL25;PL32;TMB9
The Lord sits enthroned above the circle of the earth...He stretched out the heavens like a canopy.
Quote: I am certainly no expert, but I don't think that coma is necessarily linked to field curvature. I have a Meade ACF scope that has easily measurable field curvature, but no coma. I also have a regular Celestron SCT that has coma.
Quote:A statement was made a few posts above that implies that field curvature itself is the cause of coma. It's that relationship that I don't get.-Wade
Quote:I am certainly no expert, but I don't think that coma is necessarily linked to field curvature. I have a Meade ACF scope that has easily measurable field curvature, but no coma. I also have a regular Celestron SCT that has coma.
The thing with the Celestron scope is that there is no coma on axis, but as you move off axis, it rapidly manifests (the self guiding chip on my ST-10 guides on little comets). Also, as you move off axis, the onset of coma does not seem proportional to field curvature. Coma increases much more aggressively than the field curvature as you move from the center of the field.
I would welcome any correction on the topic.