Dobsonian 8"

[edelweiss]

Hi guys, recently i bought a dobsonian 8" skywatcher

I've been trying to star gaze through the eyepiece but seems like it's quite hard to do so. The image is so blurred. I've read the manual that we have to let the temperature of telescope stabilized with the outside's temperature first for half an hour and I've did that. Besides, during the day, I try to check the finderscope and the eyepiece lens. Finderscope works excellent but it's still a no for eyepiece.

The question: may I know what can cause the eyepiece to display such blurred image? Is it because the disturbance of air in the tube? Because lately it has been quite windy in my place. Or perhaps because of other reasons.

Besides,can u give any advice/tips how to use dobsonian for the first time. Perhaps u can share how to take care of it (the manual just give the simple one). Thank u so much

[jenchris]

I suppose you have tried the focus knob?
Um removing the end cover?

[omegacrux]

Hi and welcome Eeda
Sounds likely that you still have the 2in eyepiece holder still behind the 1,25 adapter , undo the 1,25 screws then there's two more screws undo them and you should have what looks like a barrel take that out and now put the 1,25 there, leaving out the 2in adapter should focus now

David

[Ryz]

Recently got one too :)

Very helpful forum this one.

[Allan_L]

Hi Eeda, :welcome:

I believe David is correct.
It is a very common mistake with Skywatcher DOB (first time) users.
It comes with an adapter for 2" eyepieces and standard 1.25" eyepieces.

(Unfortunately on newer models) the 1.25 adapter fits into the 2" adapter and looks like it belongs that way.
It does not, only use one at a time.

Remove the 2" adapter (as the supplied eyepieces are normally only 1.25).

Using both together moves the focus point beyond the range of the focuser.

You have chosen a great telescope and it should give you amazing views.
Another hint, always start with the lower magnification eyepiece( the one with the larger number in mm on it) - (probably 20mm or 25mm).
Then move up to the higher magnification (probably a 10 or 12 mm).
Note that this will require a little focus adjustment.

Enjoy, and keep asking questions.

[jenchris]

Cool - I wondered what was going on there
Missed telling you about that off the manual I expect.

[edelweiss]

I see...I thought we have to put both holders (silly me) :rofl::rofl: ...But the image is still blur (but better than before). Well, is it possible the image is blurred because my target is near (less then 500m)..Since my backyard is quite small, I just pointed my telescope towards any tree/house near to my house. I should try to point towards moon but now it's waning crescent and it's rise quite late nowadays.

[edelweiss]

Thank you for the information :thumbsup:! There are lot of things I don't know about this telescope and I'm glad if you guys can help me! It's so fun to explore this telescope and night sky of course.

Mine was supplied with 25mm and 10mm. How those two may differ?

[RAJAH235]

Hi & welcome Eeda,
The eyepieces will give different magnifications.
Here's a site that gives you the low-down.
> http://www.twcac.org/Tutorials/magnify4.htm#Magnification%20Calcul ator

&, not knowing your level of expertise, may I also suggest this site.
> http://www.astronomyforbeginners.com/

Plus, this site has heaps of links at the top LHS to lots of helpful articles etc.
viz; > http://www.iceinspace.com.au/projects.html

[Blue Skies]

Pointing at a close tree definitely wont help, it is too close! You really need to point it skyward. As the Moon will probably not be high enough to try until later in the week, why not try pointing it at Jupiter, the really bright "star" about half-way up in the north at sunset? You should see the big disc of the planet and the 4 Galilean moons around it. Focus the moons to pin points (or as close as) and then if Jupiter is still a bit fuzzy or blurry that is the local atmosphere moving about, but you should at least see two stripes across it, which are the main equatorial belts.

[expon]

wrong thread

[Ryz]

Wondering what the best way to transport one of these is?

[edelweiss]

I'm so sorry for being inactive these past weeks..I've been busy with my examinations and university life. :sadeyes:




I've take a look at jupiter. That is soo awesome!! It's really beautiful! :thumbsup: . So the tiny,shiny 'dots' (through the eyepiece) surrounding jupiter are the Galilien moons?? Wow!

What else can I see/explore with my dobsonian 8"? *truly excited*

[edelweiss]

Last night, I spent most of my time with my telescope. Yup, the night sky is totally awesome through the eyepiece. Even my friends were excited when I showed them the moon and jupiter though. Lol, it's the time to influence them to like astronomy :rofl::rofl:

Here is my first,best moon picture taken last night (others are not good). It's quite hard to take this picture through dobsonian and I was told dobsonian is not suitable for astrophotography. Nevertheless, I'm very satisfied with it!

[edelweiss]

Btw, is there any accessories that I should/need to buy? I'm thinking of buying a moon filter since it's to bright to see directly with telescope.

[Allan_L]

Hi Eeda,
welcome back.
Before buying a moon filter, if your dust cover has a small removable cap, try viewing the moon with the dust cover on (with the small cap removed).

Make sure to position this away from the spider veins (that hold the secondary mirror).

This should cut down the light significantly, while still allowing good viewing.

Also works for Jupiter when it is bright.

If this is not sufficient, you can buy a moon filter, or a NULL filter (which just cuts down light transmission) or a polarising filter arrangement (which is two polarised filters, which you can turn in respect of each other to adjust the amount of light that gets through).

Other things to look at currently may include Eta Carina (nebula), Omega Centauri (Globular cluster), The Jewel Box (Open cluster with various coloured stars); Centaurus A (Galaxy - The Hamburger).

These are all deep Southern objects around the Southern Cross (Crux).

[noeyedeer]

there is plenty to see, just pan around and discover. that's the beauty of a dob, you can do that with ease.

planets are good to wow friends with and so are clusters. especially globular clusters like omega centauri which is in a good position at the moment and getting better as winter moves in. open clusters are good too .. infact the whole sky is good :)

the moon can be your friend with bright objects like solar objects like the moon and some planets, and clusters .. but is your enemy for faint fuzzies like galaxies and nebulae.

enjoy your scope

matt

[edelweiss]

Ahh..it works! It's not too bright when I viewed moon..So I believed I don't need to buy the moon filter. So, the function for the small hole at the removable cap is to cut down the light transmission?

Btw, but how do guys easily managed to spot the stars/clusters in the finderscope (n of course the eyepiece later on). Last night, I tried to take a look at The Jewel Box as I read at the wiki that it's easily spotted once u find the Beta-Crucis. But I got trouble to find the Crux itself inside the finderscope although I can spot its location with my naked eyes. When I viewed the sky with the finderscope, there are lot of stars and I can't spot the Beta-Crucis. Easily lost in the midst of stars :lol:

[edelweiss]

I wonder how the clusters look. I've been pointing my scope towards the southern sky and yup, it's breathtaking scenery :eyepop: . But I don't know how to look at a specific clusters (easily lost by the trillion of stars).

[raymo]

The small dust cap is primarily meant for solar work to avoid heat build up in the optical train, which can be destructive. The sun is so bright that
the small aperture doesn't matter.
What you are experiencing with trouble locating clusters, is exemplified by what happens when at a dark site. There are so many stars visible that
the familiar patterns get swamped. The best thing to do is learn some of
the sky using low power binoculars. 7x at most. It takes quite a while to
become thoroughly familiar with the night sky.
raymo

[noeyedeer]

the jewel box in the finderscope like most open clusters look like a clump of stars or or fuzz, and for globulars a haze, and going to the eyepiece they're resolved into spectacular patterns.

as raymo has said, if you can view the area of sky with binos first it gives you a better feel for navigating with the finderscope.

the jewel box is relatively small in the finderscope .. but is sweet in the eyepiece at low and high power.

some clusters require low power to fit their field of view and some require high powers to really make them punch you in the face.

I still think just scanning with the finderscope and stopping on anything feint and fuzzy usually looks good in the telescope :)

again, using charts or software to star hop to the desiered object is always handy.

matt

edit : if you Google "jewel box sketches in crux" this image comes up in the images.
www.pampaskies.com/gallery3/var/albums/Wide-Field/Crux.JPG?m=1307742077

it is the bright blob of stars near the bottom in the middle

it shows the jewel box as big as becrux in size and not as bright, but when you look at the sketches or closer fields of view you can see it's elegance.

[Allan_L]

Caution.
This could be taken the wrong way by a new user.
Never point the scope at the sun, even with only the small opening exposed.
This will cause serious eye damage.
That is, You still need a special solar filter covering the small opening.
(The eyepiece filters alone are dangerous too.)

[edelweiss]

AH, Thank u for the reminder. So, is it possible to view the sun with the dobsonian?

Btw, what's the purpose of having 'large' eyepiece lens (more than 25mm)? What is it suitable for? WHat about the smaller lens like 6mm or 7mm?
I'm thinking of buying another new lens but not sure which one should I buy, either bigger than my 25mm lens or smaller than 10mm.

Besides, what's the function of barlow lens?

And what's the use of having colored filters?

Oh, another thing. I browse the ozcope website and saw a filter for nebula. How is it works?

THat's quite a lot of questions...Sorry :confused2::confused2:

[Allan_L]

Yes it is possible, but only with the appropriate filter over the opening, preferably the small aperture.
And you must keep the view finder capped (never use it for the sun). better still, remove it.
Also something to consider, all you can see through a regular telescope on the sun is really sun-spots. It usually takes a solar scope to see Solar Flares and such.
You can buy various types, or (carefully) make your own solar aperture filter from Mylar.




A lot of deep sky objects are quite large, and require a smaller magnification (higher number mm) to fit in the eyepiece.
Examples are Eta Carina; Orion Nebular, Pleiades; etc
Smaller (like 6mm) are for high magnification probably mainly for seeing more details in Planets (rings of Saturn, bands of Jupiter, surface marking of Mars).


You can use a Barlow lens to increase magnification. There are x2 and x3 etc barlows. This can reduce the number of eyepieces you need. But some people don't like using them for various reasons (changing focus point; reducing contrast;etc)

coloured filters can enhance the details in some (usually brighter) objects (mainly planets Jupiter Saturn Mars, even Venus)).
But remember, every filter reduces the amount of light that gets through to your eye.

A narrow band filter designed to only let through the wavelength of light coming from certain nebula types can enhance contrast. But again total light is reduced.

Thats OK. Keep asking. :)

[julianh72]

You might want to consider getting a red dot finder - these allow you to target the scope very quickly and easily by just pointing the scope until the 'floating" red dot lands on the centre of your target area. Most people find them much easier to use than a conventional magnifying finderscope for coarse / manual targeting.

This, coupled with a long focal length / low magnification / wide angle eyepiece (32 mm to 40 mm say) can make it very easy to get your target roughly into view; then you can centre it in the wide angle view, and swap out for a higher power eyepiece.

With a properly aligned red dot finder and a wide angle eyepiece, you should be able to land bang-on all visual targets first-time every-time. For the fainter targets, you will need some sort of star chart or planetarium app, and use "star hopping" to locate the "faint fuzzies", but again, targeting with a low-power / wide-angle eyepiece can be easier because you can see more sky at once, so it is easier to make out the star patterns you need to locate your target. Again, get it centred in the wide angle eyepiece first, then swap out for an eyepiece that is more suited for the actual target.

If you have an iPad or Android tablet, a planetarium app that allows you to display "Field of View" rings can be REALLY handy, because with the right settings, it will display a circle that is the approximate Field of View that you will see through your eyepiece, which makes it really easy to match up what you are seeing with what your planetarium app is showing, and help you track down the fainter targets.

[edelweiss]

Thank you for the reply. What is red dot finder n where can I find it?

I already installed stellarium mobile in my phone and it's really helpful!

[edelweiss]

I see. I think it's better for me to buy the 6mm eyepiece as well as the large one (30mm++). But what's the differences between plossl, superview n fmc eyepieces? So confusingg :question: ? And I wonder, can I use any type of eyepiece as long as it's 1.25"?

Btw, what about the zoom eyepiece? I come across the zoom-capable eyepiece in the Bintel website (but the price is quite painful too).

Regarding Barlow lens, doesn't that means it allow me to zoom for example the planet? What do you mean by changing the focus point and reducing contrast?

[edelweiss]

is there any website that provides eyepieces at a reasonable price? Maybe not too expensive?

Btw, I found this one

http://shop.australiangeographic.com.au/Zoom-Eyepiece-75-to-225mm-P2809.aspx#reviews

the price is quite cheap for a zoom eyepiece, so I'm quite hesitated to buy it

[raymo]

I have found that IMHO the best budget zoom is the 8-24mm sold on
ebay by Seben[ a German company]. Performs well, and requires only
slight focal tweaks at various focal lengths. From memory about $60
including postage.
raymo

[edelweiss]

Found it in ebay.. $80 with free shipping. .quite tempting... >○<