Dobsonian 8"

[noeyedeer (Matt)]

Originally Posted by 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

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.
http://www.pampaskies.com/gallery3/v...G?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 (Allan)]

Originally Posted by 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.
...

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 (Eeda)]

Originally Posted by 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.)

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

[Allan_L (Allan)]

Originally Posted by edelweiss

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

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.

Originally Posted by oneminuteastronomer.com

*Metalized glass solar filters mounted at the top of the telescope tube are a superb choice for solar observing. These filters use flat polished glass coated with nickel and chromium to attenuate the sun to 1/1000 of 1% of full intensity. Glass filters give the sun’s image a pleasing orange-yellow tint. And since you use this filter with your telescope or binoculars, you can crank up the magnification to see sunspots and granulation on the sun’s surface. Thousand Oaks perhaps the best-known manufacturer of glass solar filters. Cost is roughly $60-$200, depending on your setup.

* Mylar solar filters cost a little less than glass filters. They fit over the top of your telescope to block most of the sun’s rays. They give the sun an odd blue tint, which some observers don’t like. Make sure you use mylar filters specifically designed for solar observing. Don’t use low-grade Mylar.
(

Originally Posted by edelweiss

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.

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).

Originally Posted by edelweiss

Besides, what's the function of barlow lens?

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)

Originally Posted by edelweiss

And what's the use of having colored filters?

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.

Originally Posted by edelweiss

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

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.

Originally Posted by edelweiss

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

Thats OK. Keep asking.

[julianh72 (Julian)]

Originally Posted by edelweiss

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

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 (Eeda)]

Originally Posted by 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.

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 (Eeda)]

Originally Posted by 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.

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 ? 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 (Eeda)]

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

Btw, I found this one

http://shop.australiangeographic.com...9.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 (Eeda)]

Originally Posted by 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

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