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Pages: 1 NorthCoast Carpal Tunnel Reged: 12/05/04 Posts: 2308 Loc: Westerville, Ohio, U.S.A. Binoviewer and system focal length?       #826027 - 02/15/06 08:41 AM Edit   Reply   Quote Quick Reply   Please help me answer this question (we all like story problems): What magnification am I viewing at? The system is a WO Megrez 80 SD (f/6.25, fl. 500mm); the diagonal is a WO 2" mirror; followed by a TV 2.5x Powermate; the WO binoviewer (without of the WO 1.6x nose piece) and finally 20mm EPs. I want to say that simple math makes it 63x, however, it just seems bigger. Is there an addional "physical" multiplication factor because of the BV and/or length of the optical path? Or, is it just in my head? Thanks, Mark -------------------- Mark Hold the "Alt Key" and type 248 on the number pad for ° Post Extras:       NorthCoast Carpal Tunnel Reged: 12/05/04 Posts: 2308 Loc: Westerville, Ohio, U.S.A. Re: Binoviewer and system focal length? [Re: NorthCoast]       #826580 - 02/15/06 03:04 PM Edit   Reply   Quote Quick Reply   Anyone? -------------------- Mark Hold the "Alt Key" and type 248 on the number pad for ° Post Extras:       TedKord super member Reged: 06/13/04 Posts: 166 Loc: NE USA Re: Binoviewer and system focal length? [Re: NorthCoast]       #826733 - 02/15/06 04:48 PM Edit   Reply   Quote Quick Reply   With everything lined up as you state, I think 63X sounds about right. I have also noticed that two eyed viewing makes the image seem bigger. Many have noticed this effect, and it sounds like it's what you're seeing. The best way to tell is to frame something in the daytime with everything but the binoviewer, then put the binoviewer in and see if the FOV changes. -------------------- "Don't drop the banana!" "Why not?" "Good source of potassium!" Post Extras:       b1gred Enginerd Reged: 04/01/04 Posts: 16902 Loc: Castle Rock, CO 6677' MSL Re: Binoviewer and system focal length? [Re: TedKord]       #826782 - 02/15/06 05:19 PM Edit   Reply   Quote Quick Reply   I think I would ask William of Williams Optical to see if they have any hard and fast numbers on the system. -------------------- "Dark Skies & Great Viewing" RandyR / W0RDR GPS 9.25 XLT/Sky Align /FeatherTouch TV85 w/FeatherTouch Post Extras:       NorthCoast Carpal Tunnel Reged: 12/05/04 Posts: 2308 Loc: Westerville, Ohio, U.S.A. Re: Binoviewer and system focal length? [Re: b1gred]       #827334 - 02/15/06 11:22 PM Edit   Reply   Quote Quick Reply   Thanks, I'll try the daytime comparison, and, if there is a significant difference noted I will then post up to the WO Yahoo Group to see if I can get a response from Wo directly. Later, Mark -------------------- Mark Hold the "Alt Key" and type 248 on the number pad for ° Post Extras:       photonovore Moonatic Reged: 12/24/04 Posts: 2792 Loc: tacoma wa Re: Binoviewer and system focal length? [Re: NorthCoast]       #827441 - 02/16/06 12:59 AM Edit   Reply   Quote Quick Reply   It should be less than 63X actually...about 55X. Using a binoviewer with a 2.5x powermate on the nosepiece increases the distance to the focal plane (located inside the EP) by about ~100mm (check this 100mm figure with your binoviewer for more accuracy if you wish but 100mm should be quite close). Check this chart to see how much a 2.5x Powermate changes with increased focal plane distance. The chart shows the multiplier factor actually decreases !! (totally UNlike what happens with an ordinary Barlow lens BTW) from 2.5x to a factor of ~2.2. So... (500mm*2.2)20mm = 55x -------------------- Mardi 4" achromat, ETX-70, 8"cat. Whitepeak Lunar Observatory Website Post Extras:       b1gred Enginerd Reged: 04/01/04 Posts: 16902 Loc: Castle Rock, CO 6677' MSL Re: Binoviewer and system focal length? [Re: photonovore]       #827612 - 02/16/06 06:10 AM Edit   Reply   Quote Quick Reply   Mardi, Nice explanation. Thanks for that, I was wondering myself. -------------------- "Dark Skies & Great Viewing" RandyR / W0RDR GPS 9.25 XLT/Sky Align /FeatherTouch TV85 w/FeatherTouch Post Extras:       NorthCoast Carpal Tunnel Reged: 12/05/04 Posts: 2308 Loc: Westerville, Ohio, U.S.A. Re: Binoviewer and system focal length? [Re: b1gred]       #829728 - 02/17/06 02:35 PM Edit   Reply   Quote Quick Reply   Mardi, Thanks for the explanation. I did the daytime test mentioned above. Here are the details: System used (same as above): WO Megrez 80 SD (f/6.25, fl. 500mm); the diagonal is a WO 2" mirror; followed by a TV 2.5x Powermate; the WO binoviewer (without of the WO 1.6x nose piece) and finally 20mm EPs. Target: A house donw the street with a wide wall covered with 4" cedar siding. I figured it was uniform enough for this experiment. Observations: I picked a fixed location (edge of the roof -line) to start at the top of the FOV. a) Without binoviewers I counted down 14 boards across my FOV b) with binoviewers inserted I counted down 16 boards accross the FOV This validates Mardi and the TV information. What I experienced was not an increase in magnification, moreover, it was actually a slight decrease. However, there is something else going on. It may just be a two eye, binoviewer thing, and, I try to explain. When viewing with a single EP I can see the entire FOV (e.g. both opposite edges) without moving. When using the BV I have to move my eyes. It now seems wider or more emersed into the image... Perhaps this is what I experienced when viewing M36, M37 and M38 with this same configuration on the 14th? Thanks Again, Mark -------------------- Mark Hold the "Alt Key" and type 248 on the number pad for ° Post Extras:       Pages: 1

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