Would you buy a 12 year old newtonian/dob?

[R26 oldtimer]

I've been offered a 12 year newt/dob for about 40% of it's current new value. It's a good price and there is no visible degradation on the mirror coating, but I'm afraid that the coating has exhausted most of it's life span, and will need a recoat in the next five years. This eliminates the low price advantage and makes it a no-go.

[CraigT82]

You seem to have answered ypur own question in your post!

I'd say it depends on the coatings, what dob is it? Hilux coatings are suppose to last 25 years. 

[JOC]

11 minutes ago, R26 oldtimer said:

I'm afraid that the coating has exhausted most of it's life span

I suspect a typo in the post.  😉  the 'but' is important, I read the current coating looks are OK, but he is worried it may have reached it's use-by date.

I will be the first to admit I know nothing about telescope mirrors, but I shall be amazed if this is the case.  After all what can happen to a coating on a mirror?  It's not like my spectacles - they get a hard life I rub them with whatever I have to hand several times a day, I wear them doing all sorts of 'particulate' jobs around the farm and they end up predictably scratched and fogged where the coatings wear.  OTH telescopes (esp. well kept ones) are usually kept dry, often covered in stable temperatures and with no physical wear or abrasion to their mirror surfaces - would the coating really just break-down and deteriorate?

Edited June 26, 2019 by JOC

[Mr niall]

There's no definitive timescales. Generally if it looks fine; then it is fine. If it looks iffy then it is iffy. If you get one that is fine right now it could last 100 years. Conversely you could get one that is brand new right now and needs to be recoated in 10 years. It's difficult to say and depends on the conditions it lives in itself, but also luck to a certain extent.

If it were me I'd probably go for it. If it looks great now then chances are its been in a happy condition thus far.

edit: Just googled to make sure I wasn't imagining it, here's Gary's (sky and telescope) take:

While it’s true that the aluminized surface of a telescope mirror will deteriorate over time, there is no hard and fast rule about how long this will take. Some coatings last only a few years, while others will outlast you. Indeed, the coating on my very first reflector telescope looks absolutely perfect in spite of being more than 30 years old. When it comes to coating life, the main determinants are the environment in which the telescope is used and how it is stored. In both situations, preventing condensation of moisture from the air is a top priority.

So how will you know when your telescope’s mirror needs recoating? In short, if you have to ask the question, the answer is “not yet.” By the time the coating has deteriorated to the point where it actually affects the telescope’s performance, the mirror will look bad enough that you’ll have no doubt. Until then, the best advice is to stop worrying and enjoy the views.

— Gary Seronik

Edited June 26, 2019 by Mr niall

[Paul73]

There isn’t much to go wrong in a Dob. If, it moves freely, the focuser works smoothly and the mirrors are clear, i’d Go for it.

Paul

[Nigella Bryant]

I bought a13 year old 12inch f4 Newtonian orion UK telescope for £350 brilliant telescope and I love it. I've had 10 and 12inch SCT, 8inch Mak, 6inch frac, and this current scope out ways those that I've used in the past. So yes, go for it. 

[Paul M]

I'd not be inclined to think of the lifespan of the coatings as an inherent property.

Most important is how the optics have been stored and cleaned. Unadulterated coatings of any age aren't going to suddenly deteriorate for no reason other than their age. So if this scope's optics have been looked after, no unnecessary cleaning etc then they'll remain serviceable for  plenty more years.

If the scope has been sat in a damp shed for years and/or the mirrors abused by rough cleaning then it may already be past its best.

So as others say, if its ok now then its ok!

[R26 oldtimer]

Thank you for your replies so far. So, essentially what you say is that any mirror degradation should be visually obvious, or if it looks good then it is good! I'll arrange to go and take a look before committing to buy.

Does shining a strong light down the tube while checking the rear of the mirror for pin holes or light passing, make any sense?

[John]

My 12 inch orion optics newtonian dates from 2006 but the primary was re-coated by Orion Optics in 2010. The coatings still seem to be in excellent nick but the reflectivity will have decreased slightly year on year since the new coatings were applied. If I still have the scope in 5 years time I will probably have it re-coated again then.

Shining a torch onto the front surface might show pinholes and thin coatings but will also make the mirror look filthy when it isn't.

What make of scope are we talking about ?. The coatings on GSO made scopes for a certain period do seem to wear out rather more quickly and you might expect. There were rumours that for a period, certain GSO made scopes did not have over-coated mirrors so the aluminising did not last too long.

[R26 oldtimer]

Thanks John. Actually it is a GSO.... Hmm....

[R26 oldtimer]

Just to make sure we're on the same wavelength, when we say recoating, I assume we're talking about realuminising and new protective coating?

[John]

If it's a Revelation or a Meade Lightbridge and it has not been re-coated for 12 years I would look long and hard at the conditions of the coatings and think hard about the price being asked. Recoating a 12 inch mirror costs around £150 I think.

 

[John]

5 minutes ago, R26 oldtimer said:

Just to make sure we're on the same wavelength, when we say recoating, I assume we're talking about realuminising and new protective coating?

Yes. Removing the old coating is also part of the work involved.

[fiestazetecmk2]

Oh yes.fabulous scope. 

[haitch]

Of course, another consideration when recoating is OO's Hilux coatings, whilst pricey, are rumoured to have a 25+ year life

Edit: oops - should read the whole thread!

Edited June 27, 2019 by haitch

[Mr niall]

3 minutes ago, haitch said:

Of course, another consideration when recoating is OO's Hilux coatings, whilst pricey, are rumoured to have a 25+ year life

 

They're not actually that pricey at all (all things considered); again about £160 to £170 for the whole package including stripping for a 12". You don't even have to remove it from the cell!

[R26 oldtimer]

57 minutes ago, Mr niall said:

They're not actually that pricey at all (all things considered); again about £160 to £170 for the whole package including stripping for a 12".

That's a tiny bit under the asking price...

[Mr niall]

Yes... but a new 12" scope would be at least £800. It's all relative. And all I'm saying is if you needed it doing (and it sounds like you don't) - the best of the best is about £170. And then you'd not need any further maintenance for at least another two decades. 

[John]

I saw a Skywatcher 12 flextube dob (non-goto) a few days back on e.bay with a "Buy it now" price of £350.00. It looked to be in very nice condition but of course needed collecting.

 

[Mr niall]

I saw that one too. I only paid £360 for mine now come to think of it...

[R26 oldtimer]

23 minutes ago, Mr niall said:

Yes... but a new 12" scope would be at least £800. It's all relative. 

Yes, I totally get your point. Even if it will need a recoat in the near future -god forbids- I will still get a brand new (optically) scope for half the price.

20 minutes ago, John said:

I saw a Skywatcher 12 flextube dob (non-goto) a few days back on e.bay with a "Buy it now" price of £350.00. It looked to be in very nice condition but of course needed collecting.

 

 

14 minutes ago, Mr niall said:

I saw that one too. I only paid £360 for mine now come to think of it...

Now, now.... You've had your share of local bargains, It's my turn for a local listing that I won't have to pay my kidney for shipping.

[Mr niall]

5 minutes ago, R26 oldtimer said:

Yes, I totally get your point. Even if it will need a recoat in the near future -god forbids- I will still get a brand new (optically) scope for half the price.

 

Now, now.... You've had your share of local bargains, It's my turn for a local listing that I won't have to pay my kidney for shipping.

Ha ha fair enough - but your find has the potential to eclipse anything I've seen in a while if its a good one. Even if you got it recoated it would still be less than I paid for mine. Worth considering...

[John]

I've owned a couple of GSO made dobsonians of around that age. The mirrors in both were OK but nothing special in terms of optical quality both and were in good condition re: coatings etc. I paid £100 for the 8 inch and £300 for the 12 inch.

The Revelation 12 inch dobs were around £500 to buy new a couple of years back.

Personally, I've felt that the Skywatcher dobs that I've owned and used had better mirrors in them and the coatings certainly seem to last on them.

If it were an Orion Optics scope with one of their better mirrors in then that might be worth making more effort to acquire even if re-coating was required.

 

 

 

[cletrac1922]

For a 12yo, and first scope, I would go for it

Down the track, if interest still there, and wants to expand into AP, then get something like ED120 on HEQ5 mount

I have had my 10" flextube Dob now over 10 years, and I am also out couple times per month with my club doing presentations in primary schools/scout groups

The attached pics are my Dob, and ED80

With the Dob, there is also a small detachable cap, hard cover lid

If you sticky tape some baader visual solar film underside hard cover, then be able to do solar viewing

Make sure leave finder scope off

With respect to finder scope, you will find better to have right angle, rather than straight through, as saves having to lay on the ground, to view through

As the base is also only chipboard, I also put down a small waterproof tarp, to protect the base from ground moisture

 

John

 

PS

Something for him and his friends

Early next year, NASA is sending another Rover to Mars

The attached link will enable you to register, and have your name included on the Rover, and can also download Boarding Pass

https://mars.nasa.gov/news/8440/nasa-invites-public-to-submit-names-to-fly-aboard-next-mars-rover/

 

 

[John]

Nice Skywatcher 12 inch for sale here (not my advert I ought to say):

https://www.astrobuysell.com/uk/propview.php?view=151231