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8" Dob or 10" Dob?

Hootsitabernacle

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Bart

Bart

Posted
Posted
the 10" is pushing my budget but i would be prepared to spend that if i was going to reap the benefits...so it looks like its either an 8" or go straight to the 48" megascope!!!!

You'd might as well, stop all the messing with the 20" and 30" tiddlers :0

Barry

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astronymonkey

astronymonkey

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My God, you must have seen some difference!!!

Barry

It was a huge difference but well worth it. The things I would struggle to see in the 6 inch were easy pickings in the 16 and it opens you viewing sessions up to so many more possibilities.

I now try to choose my viewing based on whatever constellation is sue south at the time as I can usually see loads of objects just in this small area of sky.

I agree with the comments though about what are considered reasonable upgrades, based on mirror area:

6 inch = 28 sq inch (150p = £7.67 per inch)

8 inch = 50 sq inch (200p = £5.78 per inch)

10 inch = 78 sq inch (250p = £5.70 per inch)

12 inch = 113 sq inch (300p flextube = £7.52 per inch)

14 inch = 153 sq inch (350p flextube = £8.49 per inch)

16 inch = 201 sq inch (400p flextube = £8.70 per inch)

So as you can see 8 to 10 inch gives a 50% increase in area yet move to a 12 inch and you double it. But aperture increases light gathering and also resolution but as has also been said the F ratio tends to drop as the scopes get bigger which makes them less forgiving on eyepieces .....mind you I have some £40 plossls which I use in my 16inch f4.5 and they give acceptable views, ok not Ethos quality but decent enough for me.

But there is also the price, which Ive taken for the skywatchers from FLOs website and there is definitely a value for money point at 8 and 10 inch, but at 12 inch you start to pay for the cost of the flextube setup. Telescope house do the skyliner range and 12 inch comes out at £6.30 per square inch which is a solid tube but brings down the cost.

I would say get the biggest aperture you can afford, as long as you enjoy it ...and when you upgrade, sell your old scope and get the biggest you can get once again. :smiley:

Clear skies

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Optical Dob

Optical Dob

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oh good lord im dizzy now :huh:

Hi there,

Well as you've found out deciding on a dob is easy but finding the right one is a bit more tricky. Will you be using it at home or slinging it in the back of a car to go to a dark sky site?

As knobby said try and get to see how big they are in a shop or club event.

Good luck with you decision. They are great scopes. :smiley:

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Dude_with_the_tube

Dude_with_the_tube

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instead of asking everyone's opinion on what aperture scope to get as obviously everyone will suggest the one they have or they would like to have in future,better get in touch with the Glasgow astro club what is near to you and see the scopes in flesh and i am sure the lads there will also give you a tour on they scopes and even let them try out.then you can decide what is best for you.One thing is reading opinions and looking at the pictures,seeing the scope in real is a complete different thing.

Collimation is not that big of an issue to do,neither on 8" neither on 10" or 16" scope as such that should not be the main criteria on decision.best scope is the one you will use not the one you bought and its gathering dust only because its either too big to lug out or too small and you dont like it.

good luck on whatever you decide to buy and enjoy it :D

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Bart

Bart

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instead of asking everyone's opinion on what aperture scope to get as obviously everyone will suggest the one they have or they would like to have in future,better get in touch with the Glasgow astro club what is near to you and see the scopes in flesh and i am sure the lads there will also give you a tour on they scopes and even let them try out.then you can decide what is best for you.One thing is reading opinions and looking at the pictures,seeing the scope in real is a complete different thing.

Collimation is not that big of an issue to do,neither on 8" neither on 10" or 16" scope as such that should not be the main criteria on decision.best scope is the one you will use not the one you bought and its gathering dust only because its either too big to lug out or too small and you dont like it.

good luck on whatever you decide to buy and enjoy it :D

Well said. One thing I would say is that I've rarely heard of someone say they're glad they bought the smaller scope of the two choices. Saying that, portability is an issue. Good luck.

Barry

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Moonshane

Moonshane

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just a couple of points. coma is a feature of a fast primary mirror and will not be corrected by even the best eyepieces as they don't do that. I have used a number of scopes (f4, f5, f5.3, f6, f8 and f11) and find that f5 is OK with most decent quality eyepieces. in my f4 scopes, the 32mm TV plossl and even my 26m Nagler show lots of coma in the outer third of the field so I use a coma corrector. my 15mm plossl and shorter focal lengths are quite usable so for higher power a coma corrector is unlikely to be needed with the 10" scope. the 8" scope will be fine with most eyepieces.

I'd not be wishing to carry the 8" scope or the 10" scope very far as a single unit. therefore I see them as being better split and carried as the base and then the tube. they are the same length and not massively different in weight. it's really down to budget. for me the 10" is a better investment long term but the 8" will be perfectly fine and give great views too, especially if your skies are decent which they may well be in Scotland. include in your budget a Telrad finder and perhaps a barlow and this might mean the 8" is better for you.

I have a 12" f4 and this is easily carried through the whole house as two parts.

if you can, go to a shop or visit a local club to see them both in action. they are fairly ubiquitous scopes and there's likely to be one or two at any star party or club meeting.

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Hootsitabernacle

Hootsitabernacle

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i am planning to use the scope out my backdoor and will travel to a couple of dark sites withing an hours travel (so im told) unfortunately the local clubs all meet on a Tuesday..which is a night that i cannot make (pah!)..i certainly cant afford the aforementione 14"+ scopes...weight is not a problem as i am a strapping lad but if there is discernable difference between the 8" and the 10" then i would push the boat out..otherwise the 8" will be good for me..i mean..8 inches!!!!! cor blimey guv..thats a whopper in any mans language! when i thought about buying a scope i was looking at 4.5 inches!!! is there any one or many EP's that would increase my viewing pleasure with the 8"?

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John

John

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...is there any one or many EP's that would increase my viewing pleasure with the 8"?...

There are quite literally dozens of options depending on your budget with prices from £30 to £500+ an eyepiece.

Probably best to sort out the choice of scope first and try it out a few times before diving into the even more bemusing world of eyepiece options :smiley:

There is a discernible difference between a 10" and an 8" on deep sky objects but much less so on the moon and planets I reckon.

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cotterless45

cotterless45

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I'd go with the 8" as being literally grab and go, it's that easy to manage. I'd use Bst explorer eps: 25 mm, 12 mm and 5 mm. I'd get a Cheshire and replace the finder scope with a rdf or Telrad and print these off;

http://www.atmob.org/library/member/skymaps_jsmall.html

That should considerably increase your pleasure as would a copy of the Pocket Sky Atlas and Turn left at

Orion,

Nick.

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Stargazer_00

Stargazer_00

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not really to be honest. It's more of the sort of eyepieces you get with the scope pretty much. Will expand your set a little but wont open the potential of the scope up much. Depends entirely on your budget.

the 32mm has only 44' field of view, which would be like looking through a straw. The suppied 25mm would probably show more sky.

You'd be better of spending the same money on 2 or 3 decent eyepieces, BST starguiders are only £47 each. You wont need filters for a while most likely. You'll want a barlow if you dont intend on buying lots of eyepieces. If the scope comes with one that that one will see you good for quite a while id expect.

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Stargazer_00

Stargazer_00

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Id hold off on the moon filter too. I have the same scope and have no issue looking directly at the moon without a filter, I have a nice baader neodynium too. Dont use it for moon at all even though thats one of its uses.

The moon looks best in all its bright, stunning glory. Use the money for moon filter on a nice red LED torch instead.

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Stargazer_00

Stargazer_00

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Eyepieces are named after the engineer who invented them, and they typically refer to the positioning of the lenses, the number of lenses and so forth.

Plossl eyepieces are typical the lower end of th budget range because they have few elements internally. They are usually limited to 50 degrees apparent field of view. BSTs have a 60 degree aparent field of view. I am not sure what design the BST eyepieces are, I didnt think they were Plossl but I may be wrong. In truth it doesnt much matter what the design is, its the properties of the design that you are shopping for.

BSTs are good because they have an improved AFOV to standard plossl eyepieces. They have good light control due to the ED glass element/s internally. they offer good, sharp views across most of the field of view and good contrast. In short they do a little bit of everything pretty well, hence they are universally regarded as good eyepieces to buy.

They also come in a nice range of focal lengths. The entire set would see you good in nearly all scenarios. I think they may even be parfocal..I cant recall.

I own the 5mm , 18mm and 25mm and enjoy them all. The 12mm is regarded as the best of the bunch I believe.

I would recommend these eyepieces regardless of your specific target interests as these are versatile eyepieces that will allow you to grow in different areas without reinvestment. Once you have a good idea what your main aim is you can start to purchase more specialist eyepieces.

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