Choosing my first 'proper' telescope.

fremanwarrior · #1 19-04-2006, 08:43 PM

Last weekend I thought I had figured out what I wanted.

After reading lots here and visiting the shops and talking with the sales guys (all of them astro enthusiasts). I thought I was about to buy a 10" Dobsonian.

One of the shop guys had told me that buying a dobsonian (we were looking at the 10") would mean that later on down the track it could be hoisted out onto an eq mount to facilitate tracking if I decided later on I wanted to take some snaps of the sky I was visiting.

(Photography looks very appealing to me but certainly not initially, the idea of being able to choose a telescope initially (dobsonian) that is sound enough to do so after being remounted onto a eq tracking mount seems like the way to go.)

The place I was about to buy the 10" from has emailed me with an emphatic NO it is really not feasible to mount the 10" on a eq mount due to 'flex'.

Are 10" dobsonians just too big to mount successfully on a eq mount? Maybe 8" is a better prospect or is the step up to 10" worth it even if mounting in a eq is out of the question?

I understand that the dobsonians are a really good all rounder for viewing purposes, as a beginner I am obviously going to say I want to look at everything

, but my preference initially at least has to be DSO.

Cheers for you advice.

[1ponders] (Paul) · #2 19-04-2006, 08:51 PM

Please don't tell us who said NO as they are likey to get the hay bagged out of them.

Yes you can mount a 10" newtonian/dob on an equatorial mount. Hell you can mount a 20" if you can get an eq big enough.

Which 10" were you looking at? GS, Skywatcher, Meade, Saxon????? They are all pretty good, probably the main difference will be after sales service. Have you spoken to any interstate suppliers. There are some pretty good deals getting around atm. It's alway nice to support the local bloke, unless his prices are rediculus.

janoskiss (Steve H) · #3 19-04-2006, 09:15 PM

It's probably that the shop that sells the Dob does not have a good enough EQ mount to handle a 10" f/5 Newt. Have a look at Bird's scope (in last issue of AS&T). It's a 13" monster Newt and it is rock solid on an EQ mount. Look at the awesome images Bird takes with it!

Flex? Maybe they mean in the steel tube itself rather than the mount? But I find that very hard to believe and that too can be solved with good set of tube rings and maybe some bracing.

fremanwarrior · #4 19-04-2006, 09:59 PM

They were referring to the tube.

I have my eye on the Bintel 10" Premium.

cjmarsh81 · #5 19-04-2006, 10:12 PM

FremanWarrior. It is amazing how many people on this forum are computer gamers!

The good thing about the premium bintel dob you are looking at is it comes with a crayford focuser. Others like Skywatcher (mine) do not and this can be a pain after a while with focusing and will be more important later when you want to image.

Also, I have every intention of taking my 10" dob and putting it on an EQ mount down the track. I have read numerous reviews of others who have done just that without problems. This thread is the first I have heard about any flex problems.

fremanwarrior · #6 19-04-2006, 10:18 PM

Quote:

Originally Posted by cjmarsh81

FremanWarrior. It is amazing how many people on this forum are computer gamers!

Haha.. got hooked very early on... The game that really sucked me me for the first time was StarFlight... Oh and Indy 500.

anyway this is the exact quote..

Quote:

At 10" f/5 the tube is too long to be mounted equatorially successfully. There would always be flexure inthe tube and the mount would need to be very substantial.

I think I'll go with the 10" come what may.

janoskiss (Steve H) · #7 19-04-2006, 10:21 PM

The Skywatcher/Saxon Dob, like CJ's, is one you might want to consider. The Crayford is not such a big deal, especially since you will want to upgrade to the one with the 1:10 slow motion control anyway

, rather than the standard GS Crayford, which is what the "premium" dobs come with. $119 from Bintel for the new fancy crayfords. Try www.myastroshop.com.au for the Skywatcher Dob but there might be dealers for them in Brisvegas too.

[1ponders] (Paul) · #8 19-04-2006, 10:45 PM

a 1250mm FL scope too long to mount on an EQ mount. Bunkum. What's it made out of tissue paper. If you want to image with it then where there is a will there is a way.

I tell you what Fremanwarrior. If you get the scope and a set of rings, come up to Astroron's at Kenilworth one dark weekend, we'll run off a few shot's of some fabulously stunning deep sky object and email them to them. I can tell you now if we can't get a shot it won't be because of tube flexure.

jjjnettie (Jeanette) · #9 19-04-2006, 11:25 PM

You don't need to mount it on a GEM. An eq wedge will work as well. Probably cheaper too.

vespine · #10 20-04-2006, 08:03 AM

You can convert the dobson mount into a equatorial mount with the use of a wedge or by redesigning the mount all together, there are heaps of people that have approached the problem slightly differently, I have had a great time researching different designs.

Then of course the other option is an equatorial table which is looking more and more like the best option, you can buy one ( https://www.bintelshop.com.au/Product.aspx?ID=7186 ) or you can try to make one. There are also heaps of sites about home made Equatorial Tables, just google it.

OneOfOne (Trevor) · #11 20-04-2006, 08:40 AM

Yeah, even though my scope is on an EQ mount, if I had a dob, I would be spending the money on an eq table. That way you keep the benefits of the dob mount and have the ability to have it track simply by placing it on the table, and it would be a lot cheaper.

As for tube flexure, from what I have seen in shops, scopes that come in EQ or Dob versions appear to be pretty much the same tube but with different mounting hardware. I have seen pictures of the Celestron 8" dob and the tube looks identical to my GoTo tube. When you put the rings on the tube to put it on an EQ, it will be held in two widely separated places rather than just two points at the "center of gravity" of the tube. The rings will also have a dovetail bar between which would also help to strengthen the tube. If anything, this would reduce the flexure, perhaps the tube could be modified to have both types of support on the tube and simply take it from one to the other?

rmcpb (Rob) · #12 20-04-2006, 09:07 AM

Go with the dob then worry about getting a really big GEM or an equatorial platform or a dob wedge to allow tracking later. One hell of a "starter" kit no matter which way you look at it.

ving (David) · #13 20-04-2006, 09:29 AM

cant mate a 10" GS dob to an EQ mount! never heard such rubish!
we have a member here who had a 12" GS mounted equatorially!!!

some shope have alot to answer for!

that said you are going to have to get a pretty big mount.
and it will cost you.

but go the 10er, its a great scope!

fremanwarrior · #14 20-04-2006, 11:22 AM

I will indeed be buying the Bintel 10" this weekend really looking forward to looking forward..LOL.

I thought I would ask them again via the telephone about the prospect of mounting it later on, on an eq mount.... I got the same answer + "to mounted properly you would need to buy a $7000+ mount"

Anyway having it track is way down the road so I won't be dwelling on it thanks to the responses here.

Cheers

ving (David) · #15 20-04-2006, 11:31 AM

Quote:

Originally Posted by fremanwarrior

really looking forward to looking forward..LOL.
Cheers

er... hate to corect kyou but you will be looking back in time, not forward

fremanwarrior · #16 20-04-2006, 11:55 AM

Quote:

Originally Posted by ving

er... hate to corect kyou but you will be looking back in time, not forward

only if I was refering to time and not the physical act of looking infront rather than above.

[1ponders] (Paul) · #17 20-04-2006, 12:22 PM

It may be stretching it a bit for 10" scope but you should be able to mount it on an eq6. I'm sure members that have a 6 will be able to clarify that. I've seen a 12" on a 6 but it wasn't for imaging.

what's an EQ6 worth these days, about 1,600 or so.

Here check out this. 252 skywatcher on an eq6 Ignore the price, just shows it can be done for astrophotography. You'd still be advised to talk to users though to see how good it would be in that configuration

Starkler (Geoff) · #18 20-04-2006, 12:32 PM

It is a far simpler proposition to image using a smaller scope and affordable mount.
Its cheaper to own both a 10" dob for visual and say a 6"f5 on an eq5 mount (affordable) than it is to mount the 10" tube.

rmcpb (Rob) · #19 20-04-2006, 02:27 PM

Geoff,

Might be the logical way to go but is sure does not look as impressive

Great idea though, that way both scopes could be tuned for their different tasks.

Miaplacidus (Brian) · #20 20-04-2006, 02:30 PM

Having two scopes means you've still got something to look at while you're recording that three hour exposure in H-gamma.