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Rogerio
super member
Reged: 09/01/07
Posts: 177
Loc: Soteropolis
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Hi!
By now, I have the following EP setup, plus a TV 2X Barlow and a GSO Ed 3X Barlow, my useful focal lengths are:
24 Pan: 24-12-8
16 NagT5: 16-8-5.3
13 Hyp: 13-6.5-4.3 (yet to arrive)
10 Radian: 10-5-3.3
I’ve got two 8’’ scopes, F6 and F8 (F=1200mm and 1600mm)
I want to search for planetary nebulas, until now, the only one I’ve seen was the ring nebula in Lyrae, but I know that’s an easy target. The old man, my ATM friend, told me that I would need very high magnifications to visualize this kind of object. Here’s the big problem, I live in light polluted skies, and use to observe through a window, with limited field of view, so a can’t use the powerful F8 to this kind of observation here. I need to drive to the semi-desert regions of my state, but I have a small car. I can’t imagine the two scopes inside It or going to clear dark skies without my F6.
My question Is: do I really need magnifications higher than 363X (10Rad + 3XBarlow) to observe most of the nice planetary nebulas In the sky, like Saturn nebula? I don’t want to look for the dimmer ones, just the most beautiful.
If so, which EP would be the best? I thought about a 6mm Radian EP: 200X; 400X and 600X
BTW, my wife Is traveling to USA In November, and It would come without international shipping or importation taxes. My scopes optics are very nice, my state is almost free of light pollution and the skies very clear In the summer.
Thanks, sorry about the english
Rogerio
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Deep13
Pooh-Bah
Reged: 01/25/05
Posts: 1454
Loc: NE Ohio
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400x is your highest theoretical magnification and that is under perfect conditions.
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Preserve the night sky. Join the Internat. Dark Sky Assn. for less than a cheap eyepiece.
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doug76
Carpal Tunnel
Reged: 12/05/07
Posts: 2554
Loc: SE Louisiana
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Yes, and 300x is a realistic maximum, and sometimes, even in the desert, 200x is all your going to be able to use.
Doug
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Doug
The Truckstop Astronomer
Meade 12" Lightbridge/Dob Driver II
Celestron C6 SCT
Celestron C6R/Moonlight focuser
Celestron XLT150
Astro-Tech AT80EDT
Celestron CG5-ASGT, CG-4
Celestron Nexstar SE (large)
Meade SWA 34mm
Televue Panoptic 24mm
Pentax XW 10mm, 7mm
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Astro-Tech AT66ED
Celestron Nexstar SE (small)
Televue Plossl 32mm
Smart Astronomy Solar System 14.5mm
BO/TMB Planetary 9mm, 7mm, 5mm, 4mm, 3.2mm, 2.5mm
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cuir
scholastic sledgehammer
Reged: 03/03/07
Posts: 835
Loc: 45° 1'12. N, 73°56'12. W (Qc)
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Try using this spreadsheet to calculate what you have and what you get from various eyepieces. It should make your life easier, as it will give you result for both your telescopes, all in one easy to read table.
Screen:
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Seb
Latest eyepiece spreadsheet
Choosing the right eyepiece
Main scope: 150mm Skywatcher Maksutov
Favorite ep: 24 Panoptic
Pref'ed filters: Lumicon 0III and UHC
Mounts: EQ6-Pro and Skyview AZ
Just in: C8-S-XLT
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Tom Trusock
Reged: 02/26/02
Posts: 27299
Loc: Alternate Reality (TM)
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Contrary to common wisdom, I've found that very high powers are often useful on planetary nebula. An increase in power alters the view, and often frequently you to dig out the central star.
FWIW, I use my 3-6 zoom in my 18" obsession quite commonly with these targets.
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There are two theories to arguing with my wife. Neither one works.
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AZStarGuy
super member
Reged: 05/05/08
Posts: 152
Loc: Scottsdale AZ
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Tom's dead on. For diffuse objects like PN's you can exceed your theoretical mag limit to whatever extent you'd like - limited by your tolerance for the narrow FOV and dimming image. My issue is I can't focus between EP's. Tom's Zoom is a huge advantage there!
If you're curious about the Radian - pick one up used. They hold their value. Sell it if you're not happy. You'll probably recoup all of your $.
For detailed Planetary like Jupiter etc, everyone's right. 300x is a more realistic max on a good night. I hit that a few times a month here in AZ - but more often stop around 243x (5mm Radian in 8" f6 newt). Go past that and the image fuzzes up and you start loosing detail.
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Ron
8" f6 Eq Newt
24PAN, 13T6,7T1,6RAD,5RAD,4 & 3.2 Planetaries
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Rick Woods
Post Laureate
Reged: 01/27/05
Posts: 4262
Loc: Inner Solar System
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It's like any other tool: you may not get to use it much, but when you do, you'll be glad you have it!
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- Rick
14" LX200GPS
8" Meade 826C
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desertstars
Deja moo
Reged: 11/05/03
Posts: 29970
Loc: Tucson, AZ
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Yes, indeed. I have a 4.8mm Nagler that I very rarely use. But when conditions permit, having it makes all the difference.
Guidelines regarding maximum useful magnification are, well, useful. But I make a habit of pushing it on good nights. The numbers may say I'm wasting my time, but it takes only a few minutes to determine this. Once in a while, I am surprised by the result. And when I'm not, well, no harm done. 
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Tom W.
SVP8 'She turned me into a 3-legged Newt' EQ
Ralph, the All-Purpose 102mm Refractor
Under the Desert Stars
"If we don't change direction soon, we'll end up where we're going." Professor Irwin Corey
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bicparker
Pooh-Bah
Reged: 02/07/05
Posts: 1434
Loc: Plano, TX
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Planetary nebulae generally need magnification to really see and appreciate them. They are small and their details are even smaller. This was a lesson I learned from Barbara Wilson several years ago and it has served me well.
I, like Tom, generally use eyepieces starting with and beyond my 5T6 on my 17.5" dob to really view PN's. That basically means 444x and above, in my case.
On your 8" scopes, I would strive to continually go for the highest magnifications you can on PN's. As a practical matter, I would certainly do what you can to try out that Radian before you buy it, to see if it suits your needs.
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Bic Parker
17.5" f/5 dob
10" f/10 SCT
5" f/8 refractor
80mm f/6 refractor
66mm f/6 refractor
Plus a few others out of the rotation
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Rogerio
super member
Reged: 09/01/07
Posts: 177
Loc: Soteropolis
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Thank tou all for the nice answers! 
So... the old Dario Pires is correct!
My conclusions:
1-I can try higher magnifications, like 500X
2-It would be useful In observing details of PN, like central stars.
3-With my "small" 8'' newt I won't have many oportunities to do that.
4-I'll need to think a while, because I don't know anyone else that has a Radian or any kind of premium EP (astronomy isn't a popular hobby in Brazil)
well, I think It would be more wise to try the 450-500X range, before pushing my scope to 600X. Maybe a less expensive EP, like the WO SPL 6mm, despite the narrower aFOV. Is there too much difference?
Thanks again
Rogerio
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Rogerio
super member
Reged: 09/01/07
Posts: 177
Loc: Soteropolis
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BTW,
Seb,
great spreedsheet, thank you very much
Rogerio
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