ED lens tools (tools? I wonder what I meant to type...)

[Stub Mandrel]

I have to admit, many 'fracs are things of beauty. I'd like to try my hand at making one from scratch (I have a good supply of scratch).

It strikes me that to be worth the effort, I ought to start with a decent lens but I'm struggling to find a source of, say, ED doublets for less than the cost of a whole scope!

I realise demand for these is probably low = high prices, but can anyone suggest a reasonable source.

Size not critical, 60-80mm diameter, F/L about 300-500mm.

Taking one from a damaged scope is an option, but that will raise the temptation of repair rather than make everything.

[Peter Drew]

I'm just making a 6" F10 refractor for Ha solar using an Istar objective. As you say, difficult to find an ED objective at a reasonable price, specially large ones. Tubing, in the larger sizes without "ton an inch" wall thickness is also scarce.   

[John]

APM in Germany sell some (not low cost !)

http://www.apm-telescopes.de/en/optical-accessories/optical-sets/lenses-cell.html

Here is the Istar UK website with contact details:

http://www.istartelescopes.co.uk/

There have some "specials" towards the bottom of this page:

http://www.istartelescopes.co.uk/page_2413941.html

Another alternative would be to look out for a low cost ED doublet OTA such as the Celestron ED80 or ED100. These are the same objective as the Skywatcher ED Pro's but they are not quite so popular because of their mediocre focusers. I've seen the Celestron ED100 OTA go for not much more than £200 in the past. You can then re-home the very nice ED doublets in a fine tube !

 

[xtreemchaos]

bresser ARs have very fine glass in them, id say near as darn to ed spec, you can pick used scopes up cheap. charl.

[John]

15 minutes ago, xtreemchaos said:

bresser ARs have very fine glass in them, id say near as darn to ed spec, you can pick used scopes up cheap. charl.

Do they ?

They are good scopes but crown / flint achromats as far as I'm aware. Quite a different spec from ED glass.

 

[xtreemchaos]

yes thay are different John, I am looking at performance wise not the numbers mate. charl.

[Ben the Ignorant]

https://www.teleskop-express.de/shop/index.php/cat/c91_Selbstbau-----Optiken---Spiegel--Linsen-.html

TS has a 70mm and an 80mm that fill your bill.

[Stub Mandrel]

Ow! I may need to lie down. The cheapest APM at 150€ looked reasonable, then I read it was just an adaptor... 549€ for an 80mm is a bit beyond the budget.

The Istar lenses start at 150mm, and the 'affordable special is a scope with no lens - the wrong way around.

Might have to wait for someone to accidentally drive over their prize scope...

 

[Stub Mandrel]

2 minutes ago, Ben the Ignorant said:

https://www.teleskop-express.de/shop/index.php/cat/c91_Selbstbau-----Optiken---Spiegel--Linsen-.html

TS has a 70mm and an 80mm that fill your bill.

Thanks Ben, that's getting a lot closer to my budget, still more than an impulse buy but might happen

[John]

3 minutes ago, Stub Mandrel said:

...Might have to wait for someone to accidentally drive over their prize scope...

 

Try a "wanted" advert here and on UK Astro Buy & Sell - you never know what might be out there !

[MarsG76]

Try Edmund Optical... their prices were good and they ship world wide.

 

[John]

16 minutes ago, xtreemchaos said:

yes thay are different John, I am looking at performance wise not the numbers mate. charl.

The Bresser 127L that I used to have was pretty good - but an F/9.5 achromat won't show much CA. Compare it with an ED120 and the difference is obvious though.

Having said that I liked the big Bresser 127 - a proper 5 inch achromat at a very affordable price

[xtreemchaos]

i totally agree with you john, I was just thinking of something near without spending ED money, my 127l shows a small bit of CA but with a contrast booster filter in its on par with my ed80 for CA and imaging wise it shows a tiny bit more but nothing photoshop carnt sort out. charl.

[Stub Mandrel]

Well I've got the ED doublet lens cell from a Skywatcher Equinox 66 400mm on its way.

I hope I can rise to the challenge!