First Post - Comparing Dobs

[Stu Ward]

Hi
I'm brand new to Amateur Astronomy and have been lurking on this site for some time, using you all for info.
So now i have come to a decision about what type of telescope i want to purchase, and have decided on an 8" Dob

So i've looked at whats available and now need to choose from a

Bintel 8" from Bintel
https://www.bintelshop.com.au/welcome.htm
GSO 8" from Andrews Communications
http://www.andrewscom.com.au/site-section-10.htm

Now my question for all you experienced stargazers.

Is there any difference of note between the two ?
$50 difference in price, but which is the better scope.
I think the package is around the same in the fact you get 90' finder eyepieces and 3 eyepieces (diff mm though)

I appreciate the time taken to help me along my way to purchasing my first scope.

Stu

[barx1963]

They are (apart from badges) the exact same scope. Really the only thjing different is the eyepieces. The Bintel has a 2" 26mm and 1.25" 15mm and 9mm.
From what I can see the GSO at Andrews has the 1.25" 25mm and 9mm. Would probably ring and check with Andrews to make sure as web site is not really clear. FWIW, you will probably end up using the 25mm or thereabouts EPs the most, the shorter ones are only just usable.
If you find yourself really getting into observing, you will very shortly be looking to buy better EP's and the ones that come with the scope will be relegated to the bottom of your kit box anyway!
I have the 12" GSO and it is a great scope for the money. And I have purchased from both companies and found both to have excellent customer service.

[Stu Ward]

Thanks Barx

Can you point me in the general direction of EP types, and how the size dictates what you can see ?

Stu

[barx1963]

OK, the focal length of the EP gives you the magnification in your scope if you do the following

Focal length of scope/Focal length of EP = magnification

So a 25mm ep in one of these 8" scopes (FL = 1200mm) gives you power of 1200/25 = 48x. This is sufficient to see most deep sky objects, remember most DSO are not small, just faint! So you dont need much magnification.

The other important thing is the Field of View. Most stock eps are plossls with an Apparent FOV of 50 degrees. Divide this by the magnification and you get the True FOV which is how wide a slice of the sky you are seeing. So for a 25mm plossl you get 50/48 = 1.042 deg. As many of the better DSOs are fairly large you want a wide FOV to see them well. They also stay in view longer.

This is why you will find you will almost always use your 25mm EP the most in a scope of this size. I had an 8" for 6 months before getting the 12" and I think I used the 10mm EP that came with it about 3 times. Can be used on planets and for splitting doubles but thats about it. Things drift out of view really quickly, hard to get decent focus unl;ess the seeing is very good, and makes many objects dimmer.

On the other hand once you get into premium EPs, its a whole new story. I got a 13mm Nagler that gives me 115x with an 82deg AFOV. Superb views and TFOV of about .71deg. Easily my favourite EP but fairly pricey at about $340. Worth every cent I think.

Hope this helps, I think I have the maths right. Best advice I can give is when you get your scope, get along to a Club night, people are always happy to help and show you some abjects, and give you practical hands on advice as to EPs.

Malcolm

[Stu Ward]

Thanks again barx, great info there !!

Now to look for a club in Wollongong i think !!

Stu

[wavelandscott]

As noted, they are basically the same scope with BINTEL affixing their brand sticker.

There may be one difference, BINTEL do open each box and collimate them as they affix their stickers, this ensures that everything is in working order (which was worth something to me)...I don't know if Andrews does a pre-shipping check or not.

The eypieces that come with the scope will be servicable and should get you started.

[Stu Ward]

Yeah i guess a pre-Collimation is well worth the $50

Unfortunately i have been told that they are both out of stock, so have a 3 week wait whichever way i go :mad2:


Stu

[barx1963]

I would guess that Andrews do nothing to the scopes, as mine appeared to be as shipped from Taiwan.

[erick]

$ has been headed up, you might get a cheaper price on the next shipment??? Worth asking.

[Stu Ward]

I actually asked Bintel if they would be prepared to price match Andrews, and was told a resounding NO !!!

So i doubt they will budge on currency, although my guess is they are paying in $US so $Au is very favourable atm

Stu

[erick]

The prices swing up and down considerably as the exchange rate varies - with some lag time. If you look at the ads in magazines over the last three years you will see how great it can be. 12" dob well under $1k and six months later well over $1k. Part of the fun of living in a world with no single currency!

[paddy510]

i ordered the GSO ASDX 8" Dob from Andrews a couple weeks ago for a mate, it came with 4 EPs, 6/9/25mm 1.25" and 32mm 2", i asked for the 32mm instead of the 26mm 2". the 32mm SP had much nicer/wider view than the std 1.25" plossl but ive never used anything other than the GSO and Andrews EPs that came with my 6" dob. i pretty much just use the 25mm and 9mm but if i could get a 32mm for it i would.
the 10:1 crayford focuser is heaps better than the old R&P one ive got, the roller base bearings are a lot smoother than my old teflon pads and the new alt bearing/tension setup seemed to work pretty well.
you wont need any new EPs for a while the 4 that came with it would be plenty, 32/25mm for just looking around and the 9/6mm for the planets. the 6mm really only on the good seeing nights.
we're in SA and the scope arrived with good enough collimation out the box, the mirror had the center marked too.

[Stu Ward]

Thanks for all the great info guys.

Bintel have told me that the 8" Dob will now not be available till late May :mad2:

But they have offered an 8" Skywatcher bare bones for $449 so a good price.
However if i add the extras to give me the same package as a Bintel it ends up $666.

Is the Skywatcher worth an extra $115 over the Bintel ?

Stu