toastmaster425
member
Reged: 09/22/09
Posts: 63
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Well, got my new 9 and 4mm plossls today, just put them out as jupiter became visible... jupiter is really big, but its kinda hard to make out the details on the surface. i cant seem to get the views in the 9 and 4 as crystal clear as i can the 25... im sure this has something to do with the useful magnifications of the scope... or something else?
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i'm new at this.
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NerfMonkey
sage
Reged: 06/12/08
Posts: 482
Loc: NE Ohio
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Without knowing the focal length of your scope it's hard to say whether it's because the magnification's too high or there's something wrong with the optics. 4mm and 9mm are pretty short focal lengths so it's probably just too high a magnification to get a sharp view.
The formula for magnification is:
focal length of scope/focal length of eyepiece
So if your telescope has a focal length of 1000mm the 4mm eyepiece would give you 250x and the 9mm would give you 111x. The rule of thumb is to not go over a magnification of double your scope's aperture in millimeters, so if you're using a 200mm scope that would mean a maximum magnification of 400x. And that's on the most stable nights. On most nights you'll never get near that magnification because the turbulence of the atmosphere (the "seeing") will limit you to lower powers.
Cooldown also has an effect on the quality of your views; if your scope hasn't had a chance to reach ambient temperature your views will suffer. And if you're using a Newtonian, collimation is important. A miscollimated scope will give fuzzy views.
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Mike
Zhumell 12", Oberwerk 15x70s
107 Messiers, 247 total DSOs, 6 planets, 1 comet
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toastmaster425
member
Reged: 09/22/09
Posts: 63
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thanks. its an f/6 1200mm xt8
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i'm new at this.
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beachchairbill
professor emeritus
Reged: 11/06/08
Posts: 509
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Toast,
Please give us the make of your telescope and it's focal length.
Thanks
BB
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GUNER
Carpal Tunnel
Reged: 07/19/04
Posts: 1617
Loc: Bedminster,NJ USA
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Well the 4 is 300x so that is pushing the power but it really depends on how good your skies are if you can go that high.
Also how low Jupiter is will affect the viewing a lot. You should look for something between the 9 & the 25 or a 2x barlow with the 25 to give you 12.5 then you try higher power till the image gets bad & back off till it's good & that's the high power you can use at that time for those skies.
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Thomas
17mm ETHOS NEAF Door Prize
THANK-YOU TELEVUE!!!!
12" SuperCharged LX-200 GPS
TAK SKY 90 on a Vixen Skypod
Stacked GOLD!PST/EXT-70AT/DSX-125
Infinity 2-1 CCD Camera with Lucam Recorder
Custom Scientific 1.25" LRGB filters
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toastmaster425
member
Reged: 09/22/09
Posts: 63
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will the 4mm work better on objects that are farther away, say galaxies and clusters?
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i'm new at this.
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Joe Lalumia
Post Laureate
Reged: 01/24/07
Posts: 3616
Loc: Rockwall, Texas, USA
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Too much magnification for the sky conditions. Try 100-150 power.
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LX90 8" LNT, SV Nighthawk & TelePOD, SV 80/9D & M4 mount, ETX 90, Orion XT10i, 20x80 binoculars, SV-BV3s-- www.texasastro.org
"Great minds discuss ideas;Average minds discuss events;Small minds discuss people." Unknown
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dgs©
Postmaster
Reged: 03/29/04
Posts: 15042
Loc: West Monroe, Louisiana
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Try the moon. Often, a really bright, detailed object like that can cut through poor seeing conditions.
The 9mm should do well and the 4mm will occasionally do well particularly for the moon and Saturn. BUT, you'll need to have really steady seeing conditions (little to no high altitude turbulence). Unfortunately, those kind of nights can be few and far between.
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- david
8"Ø Newtonian on SVP, Moonlite CR2, Telrad
PST Oberwerk Ultra 15x70 Orion Ultraview 10×50
Hand-me-down Sears Refractor (Discoverer) 60mm×900mm
"What we have done for ourselves alone dies with us; what we have done for others and the world, remains and is immortal." --Albert Pike
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panhard
Mongo
Reged: 01/20/08
Posts: 5223
Loc: Markham Ontario Canada
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My 10"dob has the same focal length as yours. My 13 mm ep gets the most use 92x. My 8 mm is the second most used 150x. There are nights that I can use 250x but they are rare. For viewing galaxies you don't want to use a lot of power.
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solshaker
Carpal Tunnel
Reged: 06/06/06
Posts: 1836
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i would blame the seeing. we get some very good seeing around here and my old 4mm gso plossl has given me some excellent views of jupiter, saturn, and mars over the years.
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My Gallery
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RonBurgundy
sage
Reged: 06/16/09
Posts: 271
Loc: Philadelphia
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Hey, toastmaster... As silly a question as it may seem, have you taken all of the eyepiece covers off? This has happened to me a few times out in the field, when the manufacturer put transparent eyepiece covers on it. I had no idea until it dawned on me that I was being really absent-minded.
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Kipp Ginsburg
8" LX200-ACF
Orion 120mm F/5.0 Piggybacked Refractor
Meade UWA Set [4.7mm-30mm]
DSI-II
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ebusinesstutor
sage
Reged: 07/01/09
Posts: 468
Loc: Nanaimo, BC, Canada
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I have an Orion XT8i and I usually observe Jupiter around 120x to 150x. I have same focal length as yours, so I am usually using the 8mm to 10mm eyepiece setting on my Hyperion Zoom for this.
You may be able to use others on nights of truly exceptional seeing. Trying them on the moon is also a good idea.
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Garland Coulson
Orion XT8i Dob & Celestron 80 ED on a Vixen Porta Mount Mini
Baader Hyperion 8-24mm Click Zoom & Siebert Observatory 36mm
Siebert Black Knight Binoviewers
SkyWatcher Observing Chair
Celestron Skymaster 15x70mm binos
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ComaB
super member
Reged: 09/22/07
Posts: 106
Loc: Nevada
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Low power views will always be sharper. the 4mm will not work well on distant deep sky objects. the 4mm is for the moon and planets. 1 little trick that i use is to graduate slowly in the use of power,for example look at jupiter with your 25 mm then go to a 15 mm,let your eyes adjust then go to a 9mm,again let your eyes adjust for a few minutes,then go to the 4mm.
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JimmyWong 10 inch schmidt 8 inch schmidt 10 inch schmidt a 2120 lx5 by Meade in 1984 and 6 inch refractor.
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Adrian Lopez
sage
Reged: 10/22/08
Posts: 271
Loc: Puerto Rico
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Quote:
will the 4mm work better on objects that are farther away, say galaxies and clusters?
From Earth, everything in space focuses at infinity. Thus, the object's distance wouldn't make any difference with regard to how hard it is to focus.
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Celestron Omni XLT 120 (f/8.3) Refractor
William Optics 1.25" Dielectric Diagonal
Celestron 4, 6, 9, 15, 25, and 32mm EPs
Nikon Action Extreme 8x40 Binoculars
Canon Digital Rebel XT
RA Sweep Calculator (find objects without GoTo)
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David Castillo
scholastic sledgehammer
Reged: 09/09/06
Posts: 882
Loc: Carmel Valley, Ca
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I'm going to drop the "C" bomb here; have you checked collimation?
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Dave
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Starman1
Vendor - Scope City
Reged: 06/24/03
Posts: 12230
Loc: Los Angeles
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Yes.
The 3 "C"s:
Collimation.
Have you collimated? Do you know how? Do you have a tool to do it? Newtonians never arrive at a person's home collimated perfectly, so that could be a factor.
Cooling.
The 8" mirror could take up to 3 hours to cool down to ambient temperature, or, in steadily falling temps, never arrive at ambient. That warmth creates a boundary layer of warm air in front of the mirror that will distort the images. You should use at least one fan behind the mirror, and don't do any high resolution viewing until the scope has been outside for a few hours. It will help to set the scope out at sunset and not start your observing until it gets dark 90 minutes later.
Conditions.
Seeing conditions (the turbulence in the atmosphere) often limit the maximum magnification of a scope. In most places, on most nights, 200-250X seems to be the limit on all sizes of scopes. On nights of stiller air, the bigger scopes can continue up to maximum and beyond. But if you stick to magnifications below 250, you will see steadier images most of the time and not miss seeing anything except maybe the very closest of double stars (perhaps).
In my experience, most objects in the sky are nicely framed by 50-70X, 100-140X, and 150-210X. It is a rare target on which I see more detail at higher powers. I have viewed Jupiter at 730X in my scope on an exceptional night, but most of the time I can see all the detail I need to see at much lower magnifications.
When I owned an 8", my favorite magnifications were 50x, 100x, and 150X. Sometimes, even when seeing was good enough for me to go to 400X, I still preferred the image quality and brightness at 200X. Remember, the image will grow dimmer with magnification and the turbulence in the sky will also have its effects magnified.
Double stars are often a good excuse for super high powers.
But, in my opinion, magnifications over 350X are more the bailiwick of very large scopes (over 20").
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Don Pensack
12.5" Truss Dob, 5" Maksutov, Fujinon Binos
Sustaining Lifetime IDA member
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