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8 inch dob advice

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Hi and hello my first post:hello2:

i have a sky watcher 8 inch dob and need advice please

when viewing the moon the image is breath taking (for me any way) but viewing saturn is not so good it apaers as a smudged ball and i can make the rings out but only just.....Am i doing anything wrong........ i am using 17 mm plosal i have also tried to colimate it and i think i have done it right ....


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Hi,Welcome to SGL. Super scope.If the moon is cyrstal clear, then to see more of Saturn you might have;

1.0 Poor seeing conditions, try and look at Saturn when it's high in the sky and no fine cloud around.

2.0 You'll need a planetary lens to give you more magnification. Your 17mm eyepiece is giving you x70 magnification. That's your tube length/eyepiece focal length.

You need as much magnification as is useful.The 200p will take a max.of double the mirror width (200x2). But this'll mean your view will be passing very quickly. Dobs are also very hard on eyepieces.

I use a 5mm long releif eyepiece, this gives x240. Enough to give good views of the rings,moons and storm belt on Saturn.

Join the Dob users forum on this site, it's the future.Best wishes, Nick.

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Saturn was 'smudgy' for me too last night, but to be fair, there was some high level cloud in the way. Best view was with my 9mm plossl (133x), but it wasn't great. The other night was better.

There will be other nights to see Saturn.

The Moon was nice, with cloud acting as a natural filter to dim down the brightness a tad. Used four of my EPs (8-24 zoom, 13mm Hyperion, 9 & 6.4mm plossls) with my 2x barlow. The Hyperion gets the whole of the Moon in it's field of view. Watching the Moon drift through reminded me of the Death Star :p All views were good, even up to the 6.4mm with 2x barlow (375x).

But I'm also looking forward to the Moon taking a breather so I can have a good DSO hunt in Leo & Virgo :)

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Has it been colimated? I know when I first got mine and looked at Jupiter it was blurred. When I colimated it I couldn't believe how off it was (the laser didn't even hit the smaller mirror, not sure if that is promary or secondary still.) I lost the chance to test it again on Jupiter but my views of Saturn are crystal clear.

I'll see u in the Dob section. I didn't know how to join either so thanks for asking the question.

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Hi, and as others have said if the seeing conditions are not right no scope will show Saturn clearly, so it is not necessarily down to you or your scope.

Also when it comes to viewing planets you do not have to buy planetary eyepieces as all EP's will show detail, but some are more suited to planetary viewing than others, but what you will need to remember using a dobsonian scope is that the target will drift through your FOV quite quickly at high magnification and although your scope does offer views up to 400x this is by no means practical and more like 200x is realistic with a manually operated dob.

What i find useful are eyepieces with a wide field of view for use with a dob as it allows the target to be visible in the eyepiece longer before having to nudge the scope, Naglers offer 82 degrees fov whilst orthoscopics (planetary EP's) offer 40 - 50 degrees FOV.

Here is a great post from Warthog about EP's HERE.



Edited by GazofCorra
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:) thanks for all the advise

i will keep looking as i think your right as i live on the north downs

and saturn is quiet low in the sky, i have joined the dob owners group so hope to pick up some advice and tips many thanks:hello2:

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ok also can you tell me what make eyepieces to purchase,

i have a set of celestron but would like to purchase an eyepiece per month that will last , as per warthogs post on eye pieces i know which ones to get but not the make,and will 2 inch eye pieces be better

many thanks again:hello2:

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Again you will get different advice from most SGL members, but get the best you can afford and also bear in mind that what one person perceives as the best eyepiece may not be to someone else's taste, if you wear glasses whilst viewing you will want EP's with longer eye relief (Nearly all the manufacturers state how much eye relief a lens has in mm).

Televue and pentax are 2 of the best and you can build an eye piece collection to last you a lifetime of viewing as they can be used on any other scopes you buy in the future and if looked after correctly will always have a decent resale value.

If your focuser can take 2" eyepieces it is wise to have 1 or 2 long focal length EP's in your collection a really good EP is the 27mm Panoptic from televue in 2" i also have a 38mm SkyWatcher Panaview 2" at less than £100, TMB have some so called planetary EP's with decent eye relief and a 58 degree FOV, these get constant good reviews and are less than £50 each, they are for your high powered viewing of planets, lunar and splitting double stars.

But at the end of the day it is your money and solely your choice.

Have fun.

Edited by GazofCorra
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Hey, welcome to SGL :)

1. You want to use the highest practical magnification with an eyepiece for planets.

2. The atmospheric conditions can affect things

3. Any cloud

5. Light pollution in your area

6. Correct collimation of your scope

7. Don't breath or get dew on your eyepieces by mistake which can lead to cloudy views

8. Unless you have expensive eyepiece, keep the object in the center of the view for best views

9. Join the dob clud and ask away :p

10. PM me if you have any questions regarding things


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