C10NGT, Z8, 150 Rumak, XLT 150, C6, C5, SW5 Newt, 4.5 Ball, C102GT, C90, ST80, A70LF; 15x70, 25x100; Burgess BV; Paracorr II; T6 2.5, XO 2.58/5.1, Ethos-SX 3.7, Delos 4.5, TV Plossl 7.4-26, BCO 10, Hutech HC 12.5, Sterling 12.5-25, ES100 14, CZJ H 16/25, CZJ O 16, M5k UWA 24, T5 31, Ultrascopic 35, Titan-II 40; Bino Pairs M5k UWA 6.7, Baader Zoom 8-24, M5k SWA 24, TV Plossl 26, RKE 28.7; Zooms NZ 2-4, NZ 3-6, Leica ASPH 8.9-17.8, Baader 8-24; Baader Zoom Barlow, VIP Barlow
Indiana for a three more weeks...
14.5" Teeter w/ Richard Fagin mirror, TT #66
EON 120ED on CG-5 ASGT
Lunt LS60THa/B1200 Sky Guy Porta II
Denk Super System with A45 OCS
Nexstar 8SE, SV F60M3 ES 82* 14, 8.8, Meade 5K 24 Constellation Hunter Norther Skies #101 Lunar Club #747 Messier #2629
Quote:Have they shipped any of you guys' orders yet?
Homemade 16"F6.5 dob(Stellafane optical winner 1996) and 22.6" F4.9 homemade mirrors, 10"F7 dob (Stellafane 2nd opt 2009)Celestron Ultima 9.25 dynascope RV6 1973, Orange C14 1975,orangeSupC8,c11/C5orangetube CGEM, CGE, Meade 30 UWA5K,34&28mmSWA 5k,14mmUWA4K 4K/ES9mm&14mm100degree/panoptic 22mm/nagler11mmT6/7mmT1/3.5mmT6/T.V.WF 19mm and 15mm, Cel AXIOM LX 23mm/15mm Sears 80F15 3#4454/sears4-6344 76mmf16
Quote:I plan on removing the blue anodized color from the sides of the diagonal. Vanity has control and I am not going to sport a blue diagonal on an orange scope.
My eyepieces are made from the waste product of exploding stars. 10XTi 102XLT ST80A(2" Focuser) XW: All; XO: 2.58 Televue: Naglers-T1 Smoothside-full set, 17T4,12T4,Ethos 17,4.7; plossels-40,32,20,17,&7.4mm; Pans-22,24mm; Delos-6,8,12,17.3mm ES100: 5.5,9*,14,20 ES82: full set ES68: 16,20,24,34 NLV: 5,9,10,15 Ortho: HD-7,9; OPS-9,12 Meade RG 7mm Other: Pentax 12.5K(.965), 10mm Parks Zoom: Nag3-6 *=on b/o DAS Dark Site
Quote:Hey, here in Colorado, thems our colors......
Quote:I forgot to mention that using a 2" star diagonal on the C6 does lengthen the focal length and narrow the field of view some.
I estimate the adapter and star diagonal have about a 5" light path from the back of the scope to the focal plane at the end of the diagonal (it could be 6"). That length makes the focal length of the scope to 76 to 80", or really f/12.7 to f/13.3
That is one of the negatives of using a 2" star diagonal on the back of the scope.
Meade LS8 ACF Meade 2" Diagonal Apetura 10" Tweakers Package Meade ETX-125, ETX-90 for Solar Celestron 80mm APO PST Meade SWA - 34mm,28mm,24mm,20mm Brandon 32mm, 16mm Vernonscope 40mm Erfle 2" ES 14mm,11mm,6.7mm 8.8 Nagler 13mm T6, Pan 19mm Meade 12.4 Pl,9.7mm, 15mm SP Meade 2x Shorty Barlow Powermate 2.5x WO Bino Viewer, 20mm 66* pair Denkmier 2 Super System Meade Nebula Filters Meade 9x60 Bino Vivitar S1 8x42 Bino Canon T2i, 18-55mm, 50mm 1.8, 55-250mm
Is there anything inherently wrong with increasing the f number of the C6 by using a 2" visual back and 2" diagonal? Shouldn't that make it easier to observe planets and the Moon, since higher magnification can be reached with eyepieces that have somewhat longer focal length, which tend to have longer eye relief?
I suppose there would be vignetting of the image if wide-field 2" eyepieces are used. But if the C6 is mostly used for medium to higher power viewing of the Moon and planets, and the field stop of the eyepieces are kept at or below the clear aperture of the C6, would there still be a problem with vignetting?
I attach a chart showing the change in focal length with back focus distance. On the 6", I see that a 6" back focus results in a focal length of just under 80", which is f/13.3
Quote:the mirror is not designed to operate outside a specific range. So the further you move from the norm, the higher the spherical abberationThe longer (or shorter) the focal lenght the more the aperture becomes obstructed. The more the aperture becomes obstructed the higher the ratio of central obstruction to effective aperture, and therefore the more destructive the result to the contrast function.
Quote:is there any combination of accessories that would allow a Burgess Binoviewer (CA of about 22mm) to be used on the C6 without appreciable increase of SA and decrease of CA
Quote:Quote:Ed,I attach a chart showing the change in focal length with back focus distance. On the 6", I see that a 6" back focus results in a focal length of just under 80", which is f/13.3 This graphic is INCORRECT.I've seen it before and commented on it before, in fact, here in these forums. I get tired of the same old *BLEEP*. That's part of the reason why I walked away from this site for a while, the proliferation of inaccurate data. It assumes all (at least the C5, the C6 and the C8) SCTs have the stated nominal F precisely at the backplate. That is incorrect. That's why I took the trouble to ACTUALLY MEASURE the C5 the C6 and the C8 and posted those plots in the SCT forum. Not only that but it presumes at 6" of backfocus the C6 is operating at 80" F=2032. That's just plain outright wrong. At near 6" of backfocus the C6 is found to be operating near F=1800. The difference may not be due to the slope of the increase. More likely it's due to the fact that the C6 at the backplate is more like F=1300. So, I'm going to ask you Don, Have you ever tested any of this? And if not, why then would you believe that chart is more accurate then my test results and post that chart and ignore my test results?So, for all you other forum members, you can continue to rely on inaccurate assumed data plots, or you can rely on actual data. Your choice. edz
Quote:Ed,I attach a chart showing the change in focal length with back focus distance. On the 6", I see that a 6" back focus results in a focal length of just under 80", which is f/13.3
Quote: A Celestron engineer told me years ago that the 2032mm focal length of the C8 was actually at a distance of 4" (100mm) behind the back plate of the scope, i.e. with the visual back and 1.25" star diagonal in place.