Is this telescope worth it?

[positron]

I'm planning on my first scope....

Is this one good

www.tejraj.com/offer-of-the-week.html

It's a D=150/F=750 with AZ Mount (table top)

Cost aprox. $210

Is building a scope or buying one better?. Will building a scope give you a more personal attachment with the scope?

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[Putaendo Patrick]

In theory a 150mm reflector is a good telescope.

But, although I am not familiar with Indian marketing methods, this advertisment seems to have a hard sell approach that I find a little suspicious.

As I say, the specifications are good enough - BUT is the quality? It doesn't say anything about certain important features - for example, is the primary mirror parabolic? Is the solar filter really safe? The mount base looks to me to be very small - is it really stable?

Before I spent my money on this I would want to examine it very carefully. Perhaps members of a local astronomy club have one and could comment.

Brands such as Celestron, Orion, Starwatcher etc. are known quantities, with after-sales back up in the event of a problem. Are Indian manufacturers as good as, or better than Chinese? Any information on a guarantee? I know nothing about this brand - but then again, I know nothing about the offer of astronomy equipment in India. Even so, I would recommend caution!

[alan potts]

I would stick to known brands where there is a track record, may cost more at first but could be cheaper in the long run, SkyWatcher make decent stuff aimed at the mass market, I have a couple of their scopes and I am very pleased with them though they are from the upper end of their range.

Alan

[wheresthetorch?]

I think the mount looks disastrously wobbly. It the words of SPM: "as steady as a jelly"!

[brantuk]

Yes that table top mount looks very dodgy to me - never seen anything like it before. Better to invest in a scope with a proper tripod and mount.

A lot of beginners don't realise how stable the whole set up needs to be in order to get good views of objects in the night sky. If the scope/mount combo aren't rock solid then the view just jitters about all over the place - almost as bad as hand held binocs. Hth

[happy-kat]

If you can find a bit more out about the telescope tube the mirror and how good/nice is the focuser unit then surely the mount does not matter. You could build your own dobdonian mount for it from a few bits of board etc. So if the telescope is good and the price is cheap and you can build a mount for the telescope it might work for you. Might need to sort out the telescope mount fixings hard to tell what is going on in the pictures but it looks just one sided mounted.

An example build

http://stargazerslounge.com/topic/255435-a-bargain-dob-project-for-someone/page-1

[Dave Lloyd]

If you can find a bit more out about the telescope tube the mirror and how good/nice is the focuser unit then surely the mount does not matter. You could build your own dobdonian mount for it from a few bits of board etc. So if the telescope is good and the price is cheap and you can build a mount for the telescope it might work for you. Might need to sort out the telescope mount fixings hard to tell what is going on in the pictures but it looks just one sided mounted.

An example build

http://stargazerslounge.com/topic/255435-a-bargain-dob-project-for-someone/page-1

Yeah, I was thinking the same. All boils down to whether it's a parabolic or spherical mirror I suppose.

[John]

Th advert does not mention the scope having a parabolic primary mirror as far as I can tell. The scope is an F/5 newtonian so it really ought to have a parabolic mirror if it's to deliver decent images. The fact that it's not mentioned in the advert and the low price makes me suspicious that it has a spherical mirror which is not too good at F/5. Advertisers are usually very quick to highlight the strenghs of their products so, if it's not mentioned, it's most likely not there.

I'm also not keen on the 1.25" only focuser and the 3 rather thick secondary supports that the scope has and the mount looks like it could be less than stable as well.

I'd not buy that scope, even for it's low price.

As said above, Skywatcher, Celestron and Meade are the brands to look out for, all producing decent instruments are reasonable prices.

[Cornelius Varley]

I have no idea about the quality of the telescope but it does remind me of the cheaper 150/750 telescopes sold exclusively on ebay. The mount looks decidedly weak and would not hold the telescope with sufficient stability to make it usable.

[positron]

I think I'll go to their store sometime next month if I can... What are the things that I should look in... I mean what could tell the difference between a good and bad scope?

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[positron]

What are the problems I'd likely run into with this scope?

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[Dave In Vermont]

I'd be looking for a shop that knows optics and can answer questions such as: "What type of mirror does this telescope have?" "What is the warranty period?" "Does the telescope have 2-inch focuser with a 1.25 adapter?" "Who manufactures this telescope?"

If the telescope is made by any of the outfits already mentioned - such as Meade, Celestron, Skywatcher, or Orion - you are looking at a good quality telescope with a good warranty so you can get your money back if it doesn't perform properly or is outright defective. Buying a telescope with a brand-name no one has heard of, here in SGL, I wouldn't go near it.

You were acting quite intelligently to come to us to ask. Good job!

Keep looking,

Dave

[Alan64]

Hello Positron, and welcome,

If you're looking for a 150mm f/5 Newtonian, you'll want one with a four-vane spider assembly, like this one...

This is my Orion(USA) 6" f/5 Newtonian.  It was made by Suzhou Synta Optical Technology Co., Ltd. of Suzhou, Jiangsu, China.  The company manufactures astronomical equipment for Celestron, Orion and Sky-Watcher...

The curved or bowl-shaped surface of the primary or main mirror, located at the back, has a special type of curve known as a parabola.  The other type of mirror used in Newtonians is a spherical.  You want one with a parabola instead...

http://www.acoustics.salford.ac.uk/feschools/waves/pics/curvedmirrors.jpg

A fast Newtonian's parabolic mirror produces sharper images.  Parabolic mirrors are more difficult to figure, and therefore more expensive to make, but that's the kind you want.  The one within mine is parabolic...

It should be center-dotted, with a white "doughnut", as seen in the center of the mirror.

This is a Meade 6" f/5 Newtonian... http://images1.opticsplanet.com/755-405-ffffff/opplanet-meade-lx70-r6-6in-newt-ref-tele-optical-tube-asm-270021-main.jpg

It's of very good quality, too, and is also made in China.

Try to find one within one of those brand-names(Celestron, Orion, Sky-Watcher or Meade), and you can't go wrong.

If you're wanting an alt-azimuth mount, too, then here are some examples of said mounts that will support said telescope...

http://www.bintel.com.au/Mounts---Tripods/Alt-Az-Mounts/Bintel-SkyView-Alt-Az-Mount/98/productview.aspx

http://www.teleskop-express.de/shop/product_info.php/info/p8069_TS-Altazimuth-Mount-with-Fine-Adjustment-and-Quick-Release.html

http://www.teleskop-express.de/shop/product_info.php/info/p4539_TS-AZ5-Alt-azimuthal-Mount-with-fine-adjustment-in-both-axes.html

If you're wanting an equatorial mount, which will enable the telescope to follow an object in the sky, this is an example of one that would support said telescope...

http://www.bintel.com.au/Mounts---Tripods/EQ-Mounts/SkyWatcher-EQ3-Deluxe-Mount/1560/productview.aspx

[happy-kat]

Surely 3 vanes is adjustable, like a 4 vane arrangement for the secondary mirror.

Should add that there are telescopes made by the listed manufactures that are not parabolic but they tend to be used on slower telescopes. A telescope that is f5 you might expect it to have a parabolic mirror.

The centre spot on the mirror helps with collimation of the mirrors.