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Pages: 1 | 2 | 3 | (show all) Widespread sage Reged: 05/11/11 Loc: Bowling Green, Kentucky Re: 1 1/4" or 2" Star Diagonal upgrade for 8SE? [Re: UncleMossy]       #5168220 - 04/12/12 10:23 AM Edit   Reply   Quote Quick Reply   Quote: Thanks Tel. you're always quick with a good answer. I'm enjoying being able to rotate the diagonal now that i've started using a chair. it looks like it would be worth my while to get a 2" diagonal but i'm not sure if the screwing/unscrewing is a viable long term solution for me. so i think i will trade zenith for useful device and get a baader click lock adapter. http://agenaastro.com/baader-2-sct-click-lock-eyepiece-adapter-visual-back-2-sct-thread.html along with either the GSO dielectric or the william optics carbon fiber dielectric. i can always wait for the zenith sky to move into view. jim Televue makes a Shorty version of their refractor-style 2" Everbrite diagonal. They are expensive (I think about $270), but they do combine short length with the ability to easily rotate the diagonal. Best, David P.S. I sold the two Orion Expanse EPs (9mm & 20mm) that came with my new ST80, bringing the effective cost (incl. rings, dovetail bar, finder and diagonal) to $114. Sweet! Post Extras:       dgerow super member Reged: 03/18/12 Loc: Las Vegas, Nv. Re: 1 1/4" or 2" Star Diagonal upgrade for 8SE? [Re: Widespread]       #5169249 - 04/12/12 08:38 PM Edit   Reply   Quote Quick Reply   The new 2" GSO arrived today. What a beautiful piece. Midnight Dan is right. The OTA actually looks a lot tougher now, the 1 1/4" does make the OTA appear quite wimpy. Even if I see no improvement I'll still look better looking. David Post Extras:       Widespread sage Reged: 05/11/11 Loc: Bowling Green, Kentucky Re: 1 1/4" or 2" Star Diagonal upgrade for 8SE? [Re: dgerow]       #5169971 - 04/13/12 10:00 AM Edit   Reply   Quote Quick Reply   Congratulations! That looks like a nice diagonal at a great price! Not that you need any more encouragement, but in explaining my cosmic wimpout <grin>, I omitted mention of one big advantage your 2" 8SE has over my 8SE (1.25")/ ST80 combination: NEBULAS. At very low magnifications (e.g. 35mm Panoptic), the much greater light grasp of the 8SE should give you sufficient brightness to make good use of "nebula filters", such as the UHC Narrowband. Guang Sheng's new jingle: "See great DSOs, with your GSO" (Sung to the tune of, "See the USA, in your Chevrolet") When the groans subside, you may carry on. Post Extras:       cpl43uk sage Reged: 02/09/08 Loc: Bristol, UK Re: 1 1/4" or 2" Star Diagonal upgrade for 8SE? [Re: Widespread]       #5170016 - 04/13/12 10:19 AM Edit   Reply   Quote Quick Reply   Dumb question so sorry in advance for asking, but if i have an 2" diagonal, would i see any difference in using a 1.25" eyepiece or is the view exactly the same as if using a 1.25" diagonal? Thanks Post Extras:       Midnight Dan Postmaster Reged: 01/23/08 Loc: Hilton, NY, Yellow Zone (Bortl... Re: 1 1/4" or 2" Star Diagonal upgrade for 8SE? [Re: cpl43uk]       #5170454 - 04/13/12 01:54 PM Edit   Reply   Quote Quick Reply   Hi Chirs: Not a dumb question at all. No you won't see any difference when using a 1.25" eyepiece. -Dan Post Extras:       Tel Postmaster Reged: 03/31/06 Loc: Wallingford England Re: 1 1/4" or 2" Star Diagonal upgrade for 8SE? [Re: cpl43uk]       #5170495 - 04/13/12 02:19 PM Edit   Reply   Quote Quick Reply   Hi Chris, The short answer is yes. In using a 1.25" EP in a 2" diagonal, the view would be the same: there would be no difference. In using a diagonal, whatever it's size, you are only directing optically unaffected light from an object through either 90 or 45 degrees, (depending on the type of diagonal). Thus, a 1.25"/Xmm EP will only show what it is capable of showing in terms of magnification and field of view irespective of the size of the diagonal. If though, on the other hand, you do wish for greater FOVs, then a 2" diagonal / 2" EP combination will likely give you what you want. Best regards, Tel Post Extras:       Tel Postmaster Reged: 03/31/06 Loc: Wallingford England Re: 1 1/4" or 2" Star Diagonal upgrade for 8SE? [Re: Tel]       #5170506 - 04/13/12 02:27 PM Edit   Reply   Quote Quick Reply   Sorry Dan, we've obviously approached this one from two different ends ! Let's put it to Chris this way: using a 2" diagonal, the view presented by a 1.25" EP will NOT change ! Sorry, Chris, to confuse, if, in fact, I did ! Best regards, Tel Edited by Tel (04/13/12 02:31 PM) Post Extras:       cpl43uk sage Reged: 02/09/08 Loc: Bristol, UK Re: 1 1/4" or 2" Star Diagonal upgrade for 8SE? [Re: Tel]       #5170528 - 04/13/12 02:43 PM Edit   Reply   Quote Quick Reply   Thanks. I had wondered if the 2" are typically 'better quality' so the image might be sharper. One other thing. I have a 1.25” 40mm celestron eyepiece but am told by others that 32mm is the longest eyepiece that works effectively in the 8". A 2" diag would make any difference? Post Extras:       Peter9 Post Laureate Reged: 10/30/08 Loc: Yorkshire - Born & Bred Re: 1 1/4" or 2" Star Diagonal upgrade for 8SE? [Re: cpl43uk]       #5170710 - 04/13/12 04:20 PM Edit   Reply   Quote Quick Reply   Hi Chris, I have the 1.25" 40mm Celestron E.P and it gives me nice sharp low power views of open clusters etc with my 8se. I have switched to 2", but still use the 1.25" 40mm along side my 2" E.Ps. Regards. Peter. Post Extras:       Tel Postmaster Reged: 03/31/06 Loc: Wallingford England Re: 1 1/4" or 2" Star Diagonal upgrade for 8SE? [Re: cpl43uk]       #5170863 - 04/13/12 05:45 PM Edit   Reply   Quote Quick Reply   Hi Chris, I think that, taking sky conditions to be equal while making any comparisons, the sharpness of an image in any EP is determined combinationally by the quality of its own optics, that of the diagonal used and finally, of course, those of the 'scope itself. Given then, that one is satisfied with the quality of the diagonal and performance of the 'scope, one can begin to assess various EPs. As to your second question, we have already established that the size of the diagonal is irrelevant but, to assume that just because the Celestron 40mm has a long focal length it will yield a wide FOV, is erroneous. On the contrary, I think you'll find it has a low, 40 degrees, (or thereabouts), apparent FOV, in which case the true FOV it presents, will only be ca. 0.8 degrees. Compare this perhaps with the standard issue, Celestron 25mm with its apparent FOV of ca. 52 degrees, whereupon its true FOV will be ca. 0.64 degrees: smaller indeed, but arguably, not greatly so. Now finally compare this with a 32mm EP of, say, a not unusual, 70 degrees of apparent FOV as one might expect from a 2" type, then the true FOV will be a raised to ca. 1.1 degrees. So, between the standard issue 25mm/52 degrees AFOV EP and a 32mm/70 AFOV EP, there will be a difference in their respective TFOVs of ca. three quarters of a degree: arguably, a very significant increase ! Hoping this helps, Best regards, Tel BTW. You'll no doubt not see I made no reference to 1.25" or 2" sizes as such is theoretically irrelevant when comparing magnifications and thus, FOVs. Edited by Tel (04/13/12 05:53 PM) Post Extras:       cpl43uk sage Reged: 02/09/08 Loc: Bristol, UK Re: 1 1/4" or 2" Star Diagonal upgrade for 8SE? [Re: Tel]       #5171700 - 04/14/12 10:07 AM Edit   Reply   Quote Quick Reply   Thanks Tel and Peter. Very helpful. Post Extras:       Midnight Dan Postmaster Reged: 01/23/08 Loc: Hilton, NY, Yellow Zone (Bortl... Re: 1 1/4" or 2" Star Diagonal upgrade for 8SE? [Re: cpl43uk]       #5171830 - 04/14/12 11:13 AM Edit   Reply   Quote Quick Reply   Quote: Thanks. I had wondered if the 2" are typically 'better quality' so the image might be sharper. One other thing. I have a 1.25” 40mm celestron eyepiece but am told by others that 32mm is the longest eyepiece that works effectively in the 8". A 2" diag would make any difference? Hi Chris: There is one thing I read about potential differences in the views between the 2 diagonals that might be relevant. When polishing any mirror, even a flat one, it is difficult to maintain the flatness as you move towards the edge. In either a 1.25" or 2" diagonal, there will be an area near the edge which is not as flat as the rest. However, since the 2" diagonal is larger, this area is far outside the circle of light bouncing off the mirror. In the 1.25" the circle of light takes up most of the mirror and so may be affected by this area. So, there is the potential for a slightly better image in a 2" diagonal, but I believe this effect is extremely small. I read about this in a research paper, but I have never heard anyone comment about seeing any differences in the views. As for a 40mm eyepiece, note that a 1.25" light path is limited in size by the barrel of the eyepiece, which restricts the true field of view (TFOV) for the scope. An eyepiece can achieve that maximum field of view with a combination of focal length and apparent field of view (AFOV). Once you've hit the maximum, you can still use longer focal length eyepieces, but the AFOV will be smaller. For example, all the following eyepieces will show the exact same amount of sky (TFOV), and all are at the maximum view for a 1.25" light path: 24mm 68° AFOV 32mm 51° AFOV 40mm 41° AFOV In all three cases, with the 8SE, the TFOV is about 0.8° of the sky. As you move to longer focal lengths, you just see the same view of the sky in a smaller circle, and at a lower magnification. To actually get to a wider TFOV, you need use a focal reducer or move to a 2" optical path, or both. -Dan Post Extras:       cpl43uk sage Reged: 02/09/08 Loc: Bristol, UK Re: 1 1/4" or 2" Star Diagonal upgrade for 8SE? [Re: Midnight Dan]       #5172077 - 04/14/12 01:36 PM Edit   Reply   Quote Quick Reply   OK so at the risk of trying your patience, here is another related question. I do not plan to conduct astrophotography anytime soon however I am thinking of tweaking my 8SE it what it can offer me. I have a hyperion zoom which I have used as my main eyepiece plus a WO binoviewer. I occassionally use the 40mm celestron. Do I go 2" diagonal since I have the pieces with the hyperion to convert it to a 2" eyepiece or do I go the focal reducer route for wider field of views? Since the diagonal costs the same as the FR, but I can only choose one, which would you suggest gives best "viewing experience" options for the longer term? or is it horses for courses? Post Extras:       Midnight Dan Postmaster Reged: 01/23/08 Loc: Hilton, NY, Yellow Zone (Bortl... Re: 1 1/4" or 2" Star Diagonal upgrade for 8SE? [Re: cpl43uk]       #5172099 - 04/14/12 01:49 PM Edit   Reply   Quote Quick Reply   Hmmm ... good question. I guess I can only go by personal experience. I have both and I use the diagonal all the time, but use the focal reducer only occasionally. Getting a 2" diagonal will not, by itself, get you wider views. You'll need wide view 2" eyepieces to see any more than you can see with your current eyepieces. But, the 2" diagonal is a much more secure connection to the scope which is nice with heavier accessories like binoviewers. You get that advantage whether you get new eyepieces or not. In addition, when you do get some wide view EPs, you'll be able to switch them in and out quickly and easily just like any other eyepiece. The FR is rather a pain to put on and off. The threads are very fine and require a lot of turns, so it takes a little time and is not very convenient. If you tend to leave it on all the time as some do, then its not so bad. But it reduces the magnification on your high end making it more difficult to get to higher mags for planetary observations. You can add a barlow in, but then you've got a LOT of glass between you and the image. Just my 2 cents, but I like using the 2" diagonal and wide eyepieces better than using the FR. Even so, to get the the absolute widest views I can get, I need to use both my 36mm 72°AFOV Hyperion Aspheric *and* the FR. But I find that I very rarely need to go that wide. -Dan Post Extras:       Peter9 Post Laureate Reged: 10/30/08 Loc: Yorkshire - Born & Bred Re: 1 1/4" or 2" Star Diagonal upgrade for 8SE? [Re: Midnight Dan]       #5173328 - 04/15/12 09:26 AM Edit   Reply   Quote Quick Reply   Hi Chris, I agree with Dan in that I think you will find a 2" diagonal much more useful. I also find that the F.O.V provided by my 2" wide angle eyepieces, is plenty good enough. I have two 8mm 24mm zooms, so I have my 0.05 focal reducer, which works very well on the zooms, more or less permanantly screwed onto one of them, giving me options, depending on the type of object being viewed. Regards. Peter. Post Extras:       Bob Griffiths Getting Grouchy Reged: 10/10/05 Loc: Frederick Maryland Re: 1 1/4" or 2" Star Diagonal upgrade for 8SE? [Re: Peter9]       #5173620 - 04/15/12 12:25 PM Edit   Reply   Quote Quick Reply   Dan Made the following comment ...quote..>> The FR is rather a pain to put on and off. The threads are very fine and require a lot of turns, so it takes a little time and is not very convenient. If you tend to leave it on all the time as some do, then its not so bad. But it reduces the magnification on your high end making it more difficult to get to higher mags for planetary observations. You can add a barlow in, but then you've got a LOT of glass between you and the image. < end quote.. =========================================== I agree COMPLETELY... so I solved the problem by "investing" in a Denkmeier P/S diagonal...built in 2x barlow as well as a 0.6o (not 0.63) focal reducer... one push on a lever (newer models use sliding buttons) and the focal reducer or barlow is functional..take as of millisecond to go from a normal view to a barlowed view or a reduced ..all without touching the eyepiece... BUT then you are still left with refocusing the scope..lol Least Expensive Denk 2 inc diagonal is like $389.00 but since it does have a barlow as well as a focal reducer it replaces the need to buy either of those items.. The connivance alone in the time and effort and effort is priceless ...each individual eyepiece will give you 3 different magnifications all at the push of a lever or button.. Any-who..I sure could not cope being without it anymore... Bob G Post Extras:       cpl43uk sage Reged: 02/09/08 Loc: Bristol, UK Re: 1 1/4" or 2" Star Diagonal upgrade for 8SE? [Re: Bob Griffiths]       #5174178 - 04/15/12 06:39 PM Edit   Reply   Quote Quick Reply   Interesting Bob. I wonder if anyone sells these in UK. I'll look into it. Do you know how the S1 would work with binoviewers? And the weight? Post Extras:       dgerow super member Reged: 03/18/12 Loc: Las Vegas, Nv. Re: 1 1/4" or 2" Star Diagonal upgrade for 8SE? [Re: cpl43uk]       #5174281 - 04/15/12 07:52 PM Edit   Reply   Quote Quick Reply   Yes, interesting Bob. I had no idea such an animal existed. The things I learn on this forum continue to amaze. David Post Extras:       Terrance professor emeritus Reged: 08/11/04 Loc: Near Portland Or. Re: 1 1/4" or 2" Star Diagonal upgrade for 8SE? [Re: dgerow]       #5174557 - 04/15/12 11:41 PM Edit   Reply   Quote Quick Reply   My denkmeier Powerswitch 1 diagonal only claims a .66 FR, not .60, and it has a narrower clear aperture than .63 celestron. I seem get a slightly wider FOV with the Celestron .63 screw FR, than I do with the Denk Powerswitch S1, but it is more of a pain to use and switch out. Post Extras:       Bob Griffiths Getting Grouchy Reged: 10/10/05 Loc: Frederick Maryland Re: 1 1/4" or 2" Star Diagonal upgrade for 8SE? [Re: Terrance]       #5174857 - 04/16/12 08:23 AM Edit   Reply   Quote Quick Reply   Terrance you are correct,.,.. Brain fade on my part I guess. The Denk S1 is a 0.66 NOT a 0.63 and I agree the to FOV is slightly (and I do mean slightly smaller) but like you the the advantages far far outweigh having to install and remove a focal reduce 10 to 20 times a night.. Bob G. Post Extras:       Pages: 1 | 2 | 3 | (show all)

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