walter david
member
Reged: 08/02/09
Posts: 21
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I'm using the 70 ED for visual use and not astro photo's. I intend to buy the Stellarvue premium Dialectic 1.25 or 2". What are the advantages and disadvantages of either. Would I gain a lot going to the 2" ? Right now I have only 1.25" eye pieces so any advantage of the 2" would be delayed till I get a few 2" eye pieces. Would the 2" diagonal and 2" eye pieces too heavy for the 70ED? Any advise would be greatly appreciated!
Thanks.
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Phil Frederick
scholastic sledgehammer
Reged: 12/19/05
Posts: 845
Loc: Seattle, WA & La Paz MX
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Hi Walter,
With a 1.25" EP (eg, 32 Plossl or 24 Panoptic) the maximum FOV that you will get is just under 4 degrees--not shabby! If you go to 2" EPs you can approach 6 degrees depending upon the EP you choose. Just depends upon how wide a FOV you really want.
Balance with the SV70ED does become a slight problem with a 2" diagonal and heavy EP. You can overcome this to some degree by reversing the shoe which allows you to slide the scope further forward in the mount. Alternatively, you can attach a longer vixen-style dovetail to the shoe which will give you the same ability to move the scope further forward in the mount.
For many folks the 4 degree FOV is plenty but the 5 or 6 degree FOV with 2" EPs can be quite nice especially for terrestrial viewing.
Hope this helps!
Phil
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Phil
Intes M500 MCT (Teton Mods)
Stellarvue SV115EDT
Stellarvue SVR70ED Raptor
Orion ST80 f/5 w/Crayford
SV F50 Sparrowhawk
SV F60 Biggerhawk
Tak Teeguls, SV MG, SV Stablelock tripod, TV Gibraltar tripod, a rebuilt TV Gibraltar tripod with fixed Walnut/Oak legs, M1 on Bogen475
... Naglers, Panoptics, Stratus'
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DLB242
professor emeritus
Reged: 07/29/08
Posts: 545
Loc: Pen Argyl, PA
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Quote:
I'm using the 70 ED for visual use and not astro photo's. I intend to buy the Stellarvue premium Dialectic 1.25 or 2". What are the advantages and disadvantages of either. Would I gain a lot going to the 2" ? Right now I have only 1.25" eye pieces so any advantage of the 2" would be delayed till I get a few 2" eye pieces. Would the 2" diagonal and 2" eye pieces too heavy for the 70ED? Any advise would be greatly appreciated!
Thanks.
Walt,
I use a 1 1/4" Stellarvue diagonal in my SV70ED because my G&G setup is a Baader 8-24 zoom 2.5X Powermate and a 32mm Plossl. I don't think you need to spend the extra for a 2" diagonal now since you don't have any 2" eyepieces. Use your scope now with your 1 1/4" eyepieces and if you find you have a burning need to go wider than the almost 4 deg view provided by a 32mm Plossl you can add a 2" eyepiece and diagonal later. The SV70ED balances better with the 1 1/4" any way 
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David B
10" f/5 DOB
6" f/8 DOB
Celestron C8
Antares 1529 6" f/6.5 MoonLite Focuser
Orion ShortTube 130mm f/5 Reflector
Stellarvue SV102BV f/8.7 LOMO Doublet APO
Stellarvue SV90T f/7 Fluorite
Synta ShortTube 80
Stellarvue SV70ED
Edited by DLB242 (11/01/09 01:25 PM)
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walter david
member
Reged: 08/02/09
Posts: 21
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Thanks so much for the input. So it is the FOV that is the biggest advantage which would be nice. Since money is a huge thing for me (one is $85.00 more than the other but then add the eye pieces) I may just do the 1.25 since my present EP's are the 1.25. Thanks again!
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johnnyha
Pooh-Bah
Reged: 11/12/06
Posts: 1139
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I have a Pentax 75mm and after using it with a 2" diagonal for awhile I went with a 1 1/4" Astronomy Technologies diagonal (at $65 a steal). My main reason was the extra infocus, the light path on the 1 1/4" is shorter than the 2". The weight and aesthetics are also much better with the smaller diagonal. Generally any 2" EP I have is way too big for this size scope anyway.
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Johnny
Spicewood, TX
Sherman Oaks, CA
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charen
Pooh-Bah
Reged: 05/28/05
Posts: 1083
Loc: New Zealand
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I use a 2in. WO SCT diagonal with my WO 66 Pertzal.
The weight is noticable but the 6 degree FOV views are worth it. I reversed the mounting shoe to aid in balancing as Phil stated above.
I use a 42mm Superview GSO and get 9.5x with no vignetting and an ultra flat, sharp to edge image.
Chris
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35 binos.
80mm Cat.
WO66ED
SV NH 80mm / EQ3
Meade 8in.LX90
Skywatcher Equinox ED120 / Goto HEQ5.
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walter david
member
Reged: 08/02/09
Posts: 21
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I read that Vic uses an over-sized mirror in his 1.25" diagonals for a good edge to edge image. Will I notice a difference from the OPT diagonal and the stellarvue? I was told not to expect dramatic differences but I always planned the upgrade just because I feel the scope and the glass is better than the economy diagonal mirror. I want to wring out all the potential from this 70 mm scope.
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David E
Post Laureate
Reged: 05/25/06
Posts: 3020
Loc: North Carolina
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Quote:
Thanks so much for the input. So it is the FOV that is the biggest advantage which would be nice. Since money is a huge thing for me (one is $85.00 more than the other but then add the eye pieces) I may just do the 1.25 since my present EP's are the 1.25. Thanks again!
That's the strategy I use, even though I have a few 2" eyepieces. Like you, my SV70 is strickly for visual use, and since I get a nice 3.6º true field out of a 32mm Plossl I've found the 1.25" diagonal to work very well.
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David E
If you keep a stack of old Orion catalogs in your bathroom, you might be an astro-redneck.
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DLB242
professor emeritus
Reged: 07/29/08
Posts: 545
Loc: Pen Argyl, PA
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Quote:
Quote:
Thanks so much for the input. So it is the FOV that is the biggest advantage which would be nice. Since money is a huge thing for me (one is $85.00 more than the other but then add the eye pieces) I may just do the 1.25 since my present EP's are the 1.25. Thanks again!
That's the strategy I use, even though I have a few 2" eyepieces. Like you, my SV70 is strickly for visual use, and since I get a nice 3.6º true field out of a 32mm Plossl I've found the 1.25" diagonal to work very well.
The SV70ED is to tail heavy with a 2" eyepiece and diagonal.
My 2" eyepieces are better suited for use in my SV90T and SV102BV.
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David B
10" f/5 DOB
6" f/8 DOB
Celestron C8
Antares 1529 6" f/6.5 MoonLite Focuser
Orion ShortTube 130mm f/5 Reflector
Stellarvue SV102BV f/8.7 LOMO Doublet APO
Stellarvue SV90T f/7 Fluorite
Synta ShortTube 80
Stellarvue SV70ED
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CESDewar
GorillAstronomer
Reged: 01/16/05
Posts: 2069
Loc: Morganton, GA, USA
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I have both 1.25 and 2in. diagonals that I've used in my 70ED, but found little use for the 2in. even though I have several 2in. eyepieces. The 24mm Hyperion I have offers 17.5x with a 3.89° FOV. Yes, my paragon 40 offers 10.5x with a 6.67°FOV, but at this point, a pair of 10.5x70 binoculars such as the Garrett Signature series will provide a much better view with more light-gathering power. So ask yourself how often you might go below 17x.
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Billydee
super member
Reged: 01/23/08
Posts: 186
Loc: Winter Haven, FL
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A 2" diagonal is not a small item. It is very large when placed next to a 1.25" one. With all your EPs being 1.25" the smaller is the way to go.
Luck, Bill
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DLB242
professor emeritus
Reged: 07/29/08
Posts: 545
Loc: Pen Argyl, PA
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Quote:
I have both 1.25 and 2in. diagonals that I've used in my 70ED, but found little use for the 2in. even though I have several 2in. eyepieces. The 24mm Hyperion I have offers 17.5x with a 3.89° FOV. Yes, my paragon 40 offers 10.5x with a 6.67°FOV, but at this point, a pair of 10.5x70 binoculars such as the Garrett Signature series will provide a much better view with more light-gathering power. So ask yourself how often you might go below 17x.
I'm rethinking the 32mm plossl for my G&G in favor of my 24mm Hyperion. About the same Same 3.89° FOV in both the 32mm plossl as the 24mm Hyperion 
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David B
10" f/5 DOB
6" f/8 DOB
Celestron C8
Antares 1529 6" f/6.5 MoonLite Focuser
Orion ShortTube 130mm f/5 Reflector
Stellarvue SV102BV f/8.7 LOMO Doublet APO
Stellarvue SV90T f/7 Fluorite
Synta ShortTube 80
Stellarvue SV70ED
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Phil Frederick
scholastic sledgehammer
Reged: 12/19/05
Posts: 845
Loc: Seattle, WA & La Paz MX
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Quote:
I'm rethinking the 32mm plossl for my G&G in favor of my 24mm Hyperion. About the same Same 3.89° FOV in both the 32mm plossl as the 24mm Hyperion
...and at the same FOV you get a bit more power with the 24mm hence a bit darker sky background offering better contrast! 
Phil
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Phil
Intes M500 MCT (Teton Mods)
Stellarvue SV115EDT
Stellarvue SVR70ED Raptor
Orion ST80 f/5 w/Crayford
SV F50 Sparrowhawk
SV F60 Biggerhawk
Tak Teeguls, SV MG, SV Stablelock tripod, TV Gibraltar tripod, a rebuilt TV Gibraltar tripod with fixed Walnut/Oak legs, M1 on Bogen475
... Naglers, Panoptics, Stratus'
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