8" VS 10" Dobsonian

[DRCORTEX (Lance)]

Well, the plot thickens.

I've decided to go with the Bintel BT-252 10" Premium Dob, which includes the fan and 2" CRF. ( $799 ). It is the same Guen Sheng scope.

It's $100 more than the Guan Sheng sold by Andrews, but I've been told it has better eyepieces, and includes a collimation and scope check by Bintel before delivery.

The guys at Bintel are very helpfull, and the after sales service I would receive from them could be the make and break of whether I have an enjoyable experience, or quickly throw the scope into the back of my garage

Don's suggestion re change of mounts later, was basically, just buy a new scope with mount, etc, better suited to photography etc, when the time comes, as a decent computerised mount will cost 4 times the value of the scope anyway - a good point I thought, as decent photography would be well out of my reach for some time.

Anyways, catch you later

Neo ( Lance )

[ving (David)]

yeah its the sme scope as the andrews one. congrats, you'll love it. you will have to learn how to collimate (if you dont already know how to) but once you get the hang of it you'll be fine



as for the mount, theres absolutely no reason you couldnt buy a mount for it further down the track.... none what so ever.

[davidpretorius]

Originally Posted by DRCORTEX

It's $100 more than the Guan Sheng sold by Andrews, but I've been told it has better eyepieces, and includes a collimation and scope check by Bintel before delivery.

The guys at Bintel are very helpfull, and the after sales service I would receive from them could be the make and break of whether I have an enjoyable experience, or quickly throw the scope into the back of my garage

$100 well spent if only for the back up service. The only reason i went andrews was that it was $125 cheaper again to get it to tassie!!!

Eyepieces will be roughly the same i would think, the series 500, bintel and gs versions are all good starting points and will work well. In a few years time, you will work towards starting to get a specialist eyepieces!!

The collimation before hand is great, but hopefully they can help show you how they do it. A few bumps on the way home and the collimation will be out anyway.

Well done, welcome to the extraordinary 10" dobbers club. Find orion, put your 25mm or 30mm or even 12mm and sit back and lap it up.

The other jaw dropper is saturn, hang around for say 1am and you will see a pinkish star, well that is saturn. Put your smallest eyepiece in ie 12mm or 9mm and check it out!!!

[acropolite (Phil)]

Well chosen Neo, keep us posted on your progress.>

[RAJAH235]

A nice choice Lance. You won't regret it until 'aperture fever' hits.
Just to help a little bit with collimation >
http://skyandtelescope.com/printable...rticle_790.asp
http://www.andysshotglass.com/Collimating.html
Clear skies. L.
ps. Did you get a 'Cheshire' collimator, a 'planishere' & red LED torch?

[Dobman (Simon)]

Good Choice Neo. I bought the bintel 12" 8 months ago & its absolutely brilliant !! I went the 12" as I had no transport concerns(falcon station wagon) There is a significant difference in light gathering abilit between the 8" & 10". If my high school maths serves me correctly, if you increase the diameter by 25% (8' to 10") you increase the area by 50%- Area = pi r squared(R=Radius) thus the area of the 8" mirror is approx 50.25 square inches and the 10" is approx 78.5Sq inches- a big difference. Anyone please correct me if I'm wrong
What others have said about EP's is right on, they make a huge difference. My one piece of advice if you want to look at DSO's(deep sky objects) think about a wide angle EP I've just got a 8.8mm 82Degree AFOV EP which gives me 170x mag & its the onle EP i use now. The view is best at 170x but when I barlow it I'm always disapointed with the view I get
Join a club and try out other peoples EP's b4 you buy.
You will love the view you get even from a light polluted backyard
Let us all know what "First light" is like when you get it
Clear skies
Simon

[ballaratdragons (Ken)]

Originally Posted by davidpretorius

i also remember at the november star camp, ken said he hardly ever used his 6.5mm eyepiece in his 12" which gives him 230x. We chucked it in his scope anyway and due to the major factors ie mirror the same temp as ambient and the seeing was 9/10, then out popped the cassini division and 5 or 6 moons of saturn from memory.

That's right Davo!

I hardly ever use my 6.5mm EP coz it just ain't worth it. You need near perfect conditions for it!!! The moment Davo is talking about was at the Camp and Saturn was as clear as a Hubble photograph and it was only about one inch above the horizon!!!! That is exceptional seeing!

Normally the 6.5mm in an f5 (the GS 12" is an f5) is pretty useless and you are pushing the limit at around 9mm. It is not the scope, it's the seeing and that f5's just don't like very high mag. Thay are a Deep Space scope and therefore love 10mm - 32mm and especially widefield. The 12" comes into it's best as a Galaxy Hunter, not so much a Planet Snooper. But that suits me fine as I am a Galaxy & DSO freak.

[janoskiss (Steve H)]

Easy there with the wide angle eyepieces Simon & Neo! There is an overwhelming range of choices and prices. You don't need those yet, Neo. Better spend some time getting an idea of what sort of things you like looking at and what magnifications are the most useful for you. The only accessories that I'd recommend at this stage is a barlow and a Cheshire/sighttube for collimation. A 2x barlow with the Bintel starter EPs (the 15 & 9mm in particular) will be useful for cranking up the magnification when seeing is good.

[janoskiss (Steve H)]

Originally Posted by ballaratdragons

Normally the 6.5mm in an f5 (the GS 12" is an f5) is pretty useless and you are pushing the limit at around 9mm.

The 10" f5 will handle shorter focal length eyepieces than the 12" f5 by virtue of the shorter focal length of the scope itself. I'd say you'd use a 6.5mm more often in the 10". I certainly use the 7mm or a barlowed 12mm (which is like a 5.5mm) quite often in my 8" (1200mm focal length, close to the 1250mm of the 10"). Ah, numbers, numbers, numbers. It matters not, Neo. You will have your own preferences different from ours...

[kosh]

In the past, i have found that using a barlow has made it impossible for me
to achieve a good focus on anything, but this may just be a caused by
bad quality barlows and EP's. I bought the 10" GSO a couple of months
ago, and very happy, however i has the same issue, couldn't see any detail
on mars either, but I, also, am mainly interested in Deep space Objects.

Davidpretorius: Do you have any info on the dob drive? I would like to have a
look at, maybe give it a go.

[ving (David)]

a good barlow wont degrade your seeing, but a bad one will... that help kosh.

[janoskiss (Steve H)]

I could still see plenty of detail on Mars just 3 days ago in my 8", in average seeing conditions. But cooling the mirror is very important, as is collimation. So don't be lazy with collimation and crank those fans! Greyish blue "seas" on the red surface and the polar cap (on top when viewed in the EP) are easily seen. Even a complete newbie could see them after I explained what to look for (and I'm pretty sure they weren't just being polite).

Details are easiest to see with my UO HD orthos or TV Plossl. It seems that the warmer colour tone of the TV plossl (15mm barlowed) actually enhances contrast of the Martian surface compared with the more colour-neutral HD orthos. But just about any old plossl should be fine.

[davidpretorius]

Originally Posted by kosh

Davidpretorius: Do you have any info on the dob drive? I would like to have a
look at, maybe give it a go.

need to cut a few more sections with the coping saw tonight to balance up the other side of the ALT axis and then i will post some more pics. I got mine 2nd hand from Gary in NZ who bought it from AStromart

The other system similiar and probably more well known is Mel Bartels. Do a search on google and he crops up heaps.

I paid $600, so i am very very happy for the investment, not sure what it is worth brand new!

[Gavan Butler]

Get the 10" model if you can. The 10" has approx. 80 sq. ins. of light gathering area compared with 50 sq. ins. for the 8".
If you need to travel regularly for dark skies a refractor may be a better option.

Regards,

G.B.

[ballaratdragons (Ken)]

G'day Gavan, and welcome.

You sound like a Man who knows his scopes!!

[ving (David)]

welcome aboard gavan

[janoskiss (Steve H)]

Welcome Gavan!

Neo, I'd say once you've gone to the trouble of traveling to dark skies, then you might as well make that little extra effort of packing the largest aperture you, your vehicle, and your wallet can manage. I see the refractor's main role as a quick grab-n-go backyard / social scope. I'd say you'd need a minimum of 80mm aperture, max. about 100mm (otherwise you lose the grab-n-go factor).

But personal preferences vary, and I think there is enough info on this thread for you to make a reasonably informed decision. If you can visit a star party or similar amat. astro. get-together for a bit of hands-on experience before buying, that should be helpful.

[kosh]

Welcome Gavin. Good advice.

THanks for the info David, will have a look.

[DRCORTEX (Lance)]

OK,

I've got my 10" Bintel Premium DOB ( with the 2" and fan ). BARELY fit into my car - had to put the rear seats down. Took everyones advice and grabbed the largest aperture my car could accom, plus a redled, and planetsphere. They threw in a pair of Meade 7X50's for 30 bucks - wanted an extra pair for guests/vistors/relos.

Not exactly shopping in comfort - Bintel have got to get out of the city! ( more about that in another post )

Now then, to unpack and put this sucker together.

Wish me luck

Neo

[janoskiss (Steve H)]

Good Luck Neo! And congratulations!
Take your time and it will all go together nicely. You got a ripper deal on the 7x50s.
Come down to Bintel Melbourne, if you don't like to have your scope shop in the middle of the city.
Let us know how it goes and what you can see up there.