8" Dob

[Frostyricho (Stephen)]

Hi members of IIS,

I can't remember if i asked this already. But I am this weekend going to be buying my telescope. The Guan Sheng 8" Dobsonian. I just want to know if this is a good telescope to see a fair amount of sky objects. Will it be able to let me see the polar caps on Mars and the storm raging of Jupiter. Also I want to know if i can see some deep sky objects. I just want to make sure before i make any payments.

Kind Regard,
Frostyricho

[barx1963 (Malcolm)]

Hi Frostyricho
I think you did ask this before, but that's OK.
This scope will be OK for planets. The thing with planets is they are REALLY small in a scope. They are also strongly affected by seeing conditions. Unfortunately the best way to beat these 2 factors is to either go a bigger scope or be very patient waiting for the moments of still atmosphere. This all particularly applies to Mars as it is so very small.
That said you will be able to make out details on the planets. Just also be aware that Mars and Jupiter are past opposition now so you will have to wait until next year to see them at their best.
That all being said, an 8" dob is a great starter scope for deep space objects. Enough aperture to nab some truly marvellous objects while still being easy to handle and use. Orion is starting to come back into our skies in the mornings so the Great Orion Neb (M42) will start to become easy to see which is simply spectacular through an 8".

Let us know how you get on! Oh and I saw on previous posts some urging you to consider a 10". If it is within your budget and you are comfortable with the size it is worth considering.

Malcolm

[Frostyricho (Stephen)]

Well I think personally this is a good deal. I've looked at 8" dobsonians for $700 and this one is $450. Is this a good deal. It really disappoints me how i can't see that much. Can you possibly list the things I would be able to see. Through it. Would i be able to see star clusters.

By the way my budget is Just $450.

[omegacrux (David)]

Hi Frostyricho
Yes you will see star clusters
It would take too long to list all the things to see
In the thousands I guess , its a lot
Star clusters like Jewel box , Tucana and omega cent look great in a dob
You won't be disappointed

David

[Frostyricho (Stephen)]

Originally Posted by omegacrux

Hi Frostyricho
Yes you will see star clusters
It would take too long to list all the things to see
In the thousands I guess , its a lot
Star clusters like Jewel box , Tucana and omega cent look great in a dob
You won't be disappointed

David

OK good i wont be disappointed. So i will be able to see heaps of things with with my dobsonian. I was worried if I would be disappointed. Thanks for the help guys.

[Steffen]

Check out Bambo's 600, a list of deep-sky targets for southern observers:

http://www.iceinspace.com.au/forum/s...ad.php?t=45678

From this list you should see galaxies and nebulae down to at least 8th or 9th magnitude with an 8" Dob. That'll keep you busy for a while.

You will see a lot more if you leave the city or the suburbs and join other IISers at dark sky sites in the Blue Mountains, Mangrove Mountain, etc.

Cheers
Steffen.

[barx1963 (Malcolm)]

Originally Posted by Frostyricho

Well I think personally this is a good deal. I've looked at 8" dobsonians for $700 and this one is $450. Is this a good deal. It really disappoints me how i can't see that much. Can you possibly list the things I would be able to see. Through it. Would i be able to see star clusters.

By the way my budget is Just $450.

Frosty. Sorry if you thought I was saying your scope wouldn't see much but you asked about planets, and there are only 7 of them (apart from Earth!) and only 3 are really worth looking at with a small scope (Mars, Jupiter and Saturn) IMHO.
As others have said there are 1000's of objects within grasp of an 8". The reason I highlighted M42 is that in my opinion it is the single best object to get with an 8", although Omega Cent and 47Tuc run it a close race!!

Malcolm

[Monstar (Johnny)]

Cheers Steffen,

It's the first time I've seen that list too.

[Frostyricho (Stephen)]

Originally Posted by barx1963

Frosty. Sorry if you thought I was saying your scope wouldn't see much but you asked about planets, and there are only 7 of them (apart from Earth!) and only 3 are really worth looking at with a small scope (Mars, Jupiter and Saturn) IMHO.
As others have said there are 1000's of objects within grasp of an 8". The reason I highlighted M42 is that in my opinion it is the single best object to get with an 8", although Omega Cent and 47Tuc run it a close race!!

Malcolm

Ok. Would investing into some eyepieces make viewing better for me.

[barx1963 (Malcolm)]

Originally Posted by Frostyricho

Ok. Would investing into some eyepieces make viewing better for me.

My usual advice is just use the ones that come with the scope. Do you know what you will be getting? Oh and is this a brand new or second hand scope?

Malcolm

[Frostyricho (Stephen)]

Originally Posted by Steffen

Check out Bambo's 600, a list of deep-sky targets for southern observers:

http://www.iceinspace.com.au/forum/s...ad.php?t=45678

From this list you should see galaxies and nebulae down to at least 8th or 9th magnitude with an 8" Dob. That'll keep you busy for a while.

You will see a lot more if you leave the city or the suburbs and join other IISers at dark sky sites in the Blue Mountains, Mangrove Mountain, etc.

Cheers
Steffen.

Im confused how to use it. I understand the first 5 columns but the rest like Vmag, SB, Max, Min, Pa and onwards.

[Frostyricho (Stephen)]

Originally Posted by barx1963

My usual advice is just use the ones that come with the scope. Do you know what you will be getting? Oh and is this a brand new or second hand scope?

Malcolm

Brand New Telescope, It comes with a moon filter and three GSO Plossl eyepieces.

[barx1963 (Malcolm)]

Originally Posted by Frostyricho

Brand New Telescope, It comes with a moon filter and three GSO Plossl eyepieces.

Cool!
The scope probably comes with a 25mm, 15mm and 9mm eyepiece. You will use the 25mm the most. At this focal length a plossl is not a bad EP, reasonable eye relief, wide enough FOV that you are able to leave the scope and consult a chart without the object leaving the field etc. The other 2 (especially the 9mm) will get less use.
My usual advice with EPs is use the ones you have for a while until you are more familiar with what their strengths and weaknesses are and how they suit your observing style. Good EPs are expensive and with moderate size dobs it is not unusual to see the EP collection being worth several times more than the scope. When I had my 12" I paid $1k for it but at the end I was using a bunch of Ethos EPs in it!!

Malcolm

[Frostyricho (Stephen)]

Originally Posted by barx1963

Cool!
The scope probably comes with a 25mm, 15mm and 9mm eyepiece. You will use the 25mm the most. At this focal length a plossl is not a bad EP, reasonable eye relief, wide enough FOV that you are able to leave the scope and consult a chart without the object leaving the field etc. The other 2 (especially the 9mm) will get less use.
My usual advice with EPs is use the ones you have for a while until you are more familiar with what their strengths and weaknesses are and how they suit your observing style. Good EPs are expensive and with moderate size dobs it is not unusual to see the EP collection being worth several times more than the scope. When I had my 12" I paid $1k for it but at the end I was using a bunch of Ethos EPs in it!!

Malcolm

Ok. So this seems like a good scope. I think this is the scope for me. Getting it on Saturday so excited!!!!!!:starg aze::jawdr op:

Im also thinking of a telrad finder later on. What else do you recommend for me.

[Suzy]

Originally Posted by Frostyricho

Well I think personally this is a good deal. I've looked at 8" dobsonians for $700 and this one is $450. Is this a good deal. It really disappoints me how i can't see that much. Can you possibly list the things I would be able to see. Through it. Would i be able to see star clusters.

By the way my budget is Just $450.

Hi FrostyRicho,

$700 for an 8" dob ????
10" dobs sell between $750 & $800
And they're around $450 - $500 second hand.

V.Mag on that list is "visual magnitude". As Steffen said, the 8" will be quite capable of mag. (magnitude) 9 objects. Especially from a dark site.

Take a look at an article I did- Highlights of the Winter Sky - they are all within reach of an 8" dob. Grab the constellation Carina first as it's setting early.

All the best & have fun with your new toy.

[Dooghan (Dooghan)]

G'day Frostyricho. I've got the same dob your getting and love it. I've had mine for a year now. The 9mm and the 25mm eyepieces are the most used. 9 for planets and 25 for DSO's. I've started to upgrade my eyepieces collection. I've been able to get a couple from the classifieds on this forum. Adding a telrad to the dob has helped a lot in pointing the scope to the general area of interest. Then use the finder scope to locate the object of interest. Locating mag 7 or 8 DSO's are normally not a problem to locate. Anything below that starts to be a challenge for me.

[Frostyricho (Stephen)]

Originally Posted by Dooghan

G'day Frostyricho. I've got the same dob your getting and love it. I've had mine for a year now. The 9mm and the 25mm eyepieces are the most used. 9 for planets and 25 for DSO's. I've started to upgrade my eyepieces collection. I've been able to get a couple from the classifieds on this forum. Adding a telrad to the dob has helped a lot in pointing the scope to the general area of interest. Then use the finder scope to locate the object of interest. Locating mag 7 or 8 DSO's are normally not a problem to locate. Anything below that starts to be a challenge for me.

Omg i thought i was the only one getting this scope on the forum. Thanks now i feel more confident on getting this scope now. 99.9% chance ill be getting it.

Also with mag, how does it work, the higher it is the deeper it is into space. I don't know i still learning.

[barx1963 (Malcolm)]

No the 8" dob is probably the most popular beginners scope. I had one and lots of visual astronomers started off that way.
Magnification is often misunderstood. A more powerful eyepiece (for example a 9mm versus a 25mm) will not make things brighter only bigger. But that is quite often not needed as many deep space objects are already large. Open clusters often exceed the moon in size in the sky so you don't actually need much magnification to view them.
A scope is primarily about gathering light so dim objects become visible and that is primarily a function of aperture. In fact for many dime objects magnification can make them harder to see as you spread the light over a larger area, making it dimmer. Of course magnification also can darken the sky background, increasing the contrast so making them easier to see. That is why we have a range of eyepieces so we can select the eyepiece that suits an object best.
For you reference in your 8" it has a focal length of 1200mm so the magnifications for the EPs you ill have will be 1200/25 = 48x , 1200/15 = 80x and 1200/9 = 133x.

Malcolm

[Frostyricho (Stephen)]

Originally Posted by barx1963

No the 8" dob is probably the most popular beginners scope. I had one and lots of visual astronomers started off that way.
Magnification is often misunderstood. A more powerful eyepiece (for example a 9mm versus a 25mm) will not make things brighter only bigger. But that is quite often not needed as many deep space objects are already large. Open clusters often exceed the moon in size in the sky so you don't actually need much magnification to view them.
A scope is primarily about gathering light so dim objects become visible and that is primarily a function of aperture. In fact for many dime objects magnification can make them harder to see as you spread the light over a larger area, making it dimmer. Of course magnification also can darken the sky background, increasing the contrast so making them easier to see. That is why we have a range of eyepieces so we can select the eyepiece that suits an object best.
For you reference in your 8" it has a focal length of 1200mm so the magnifications for the EPs you ill have will be 1200/25 = 48x , 1200/15 = 80x and 1200/9 = 133x.

Malcolm

Yea i know it doesn't make it bigger. But i know that the Plossl eyepieces make images more crisp. Oh and i also have some eyepieces from my old scope. I think i have a 16mm, 12mm and 4 mm but i dont know if they would fit into the viewing end of the eyepiece.

[madwayne (Wayne)]

Hi Frosty

The Sutherland Astronomical Society (SASI) has a public open night planned for Friday 29 and Saturday 30 August. I see your location is Sydney, maybe worth a trip down to Green Point in the Shire and checking things out for yourself.

I've seen the list of members' telescopes and there will be at least 8, 10 and 12" Dobs, ranging from manual push to to computerised goto models. As well as the dome and other permanent telescopes available for viewing as well as talks and the opportunity to talk to other amateur astronomers about any questions or concerns you may have.

If you are interested you'll find more info at www.sasi.net.au. I'll be there with my 12" goto dob on the Saturday night. I can't get there for the Friday.

Wayne