Long Length Achromatic Refractors

[johnt]

I am thinking of buying one or two long focal length refractors. It seems to me a good way of getting something unique, mainly for planet viewing, in my city location. Being interested in the older stuff, I also find them quite appealing in a nostalgic sense.

Firstly I thought of buying an old classic, but it seems they are restricted to mainly 4” aperture or less.

I then started looking at the ISTAR scopes after seeing one being available for sale. But I then got really attracted to the D&G range of achromatic refractors for the more classic (white tube) look, and lighter weight. Ones that interest me are the D&G 6" F15 & D&G 6" F12. These seem to be within the payload range an easily obtainable larger mount, if a longer tripod or pier is added. The D&G 8" F12 would also be great to own, but it seems outside the range of the easy to obtain mounts. I am not planning to build my own scope, so I’m planning to buy the whole OTA tubes, rather than the lenses. The D&G website indicates about $600 freight for Australia, and I am aware there is a waiting time of several months. Has anyone had experience in bringing these into Australia?

Also, on the older (classic) scopes, am I correct in thinking that anything over 4” aperture would be almost impossible to find? (Again, I’m not talking short scopes, such as APO’s or short Achromatic, I’m talking the classic long focal length F12 –F15 Achromatic scopes. )

Thank you,
John

[Merlin66]

The long focal lengths look great, but seriously...what "easily obtainable mount" are you thinking of - NEQ6pro? It would be close to it's limit.....

[johnt]

The 6" D&G scopes are not that heavy. The D&G 6" F15 is 28 pounds (under 13Kg). So, with the extra stuff, it should be under 20Kg. Remember, I’m talking about observing, not photography. So, yes, the AZEQ6GT or perhaps the IEQ45, with longer tripod or long pier.

I know most are attracted to shorter scopes, that’s understandable. However, I've asked the question from the point of view of getting something different, apart from the easily obtainable short scopes.

As for looking great, I agree, they do. However, from the reviews, they seem to work great as well, and the advantages of long focal lengths have been discussed by others. And reading the technical stuff regarding Apochromatics vs. Achromatics, once the focal length/aperture ratio is high enough, the achromatic design does work well, in the past that was usually the only choice.

[Wavytone]

Hi John,

I'll suggest you need to think carefully about why you're buying this.

Firstly if you want an ornament for the lounge, a 4"-6" at f/12 - f/15 is going to be pretty big for any room and something smaller might be a better idea.

Instead I'd suggest something more compact such as the brass antique table telescope someone recently sold here on IIS, very pretty and it actually did function. Another rather more masculine lounge telescope is a Questar 3.5".

Secondly if you want to do some observing from the city I'll suggest you should consider an f/12-f/15 Maksutov, with a small secondary than the usual SCT's have - a Intes Micro (7" or 8") or SkyWatcher (180mm) will match a 6" refractor for resolution. Moreover they provide a brighter image and are a far more convenient size to manage; for casual use a cheap isostatic altaz mount is fine.

Personally I have a 4" f/7 refractor (sometimes its in the lounge for visitors) and a 7" f/15 Mak for the nights when i really want to look at something. And I'm in Sydney, FWIW.

[PRejto]

Hi John,

I built a 5" f15 refractor in Los Angeles in the mid 60s. It has a quite nice Edmund lens and I've upgraded the scope with a Moonlite focuser, repainted, etc. It's huge and it's heavy, probably more than the scope you are considering. Optically it is pretty darn good. I know you are not looking at an APO but my TEC140 is in an entirely different league and at f7 is quite manageable in comparison. I've had both scopes on my PMX mount....an incredible mount that can easily take these weights, but the f15 refractor will still shake a bit and take much longer to dampen out than the TEC. Weight is only part of your problem; the other is moment from such a long arm. I don't know much about the mounts you are considering, but I'd say no matter what you buy you can expect the shakes...or more shake than you will get from a folded scope like the Intess. I'm not trying to discourage you from this quest. I think refractors are amazingly instruments but you do pay a big price and not always in $$. Just go into this with your eyes wide open. If you are in Sydney I'm happy to show you mine and you can get a sense of what you will be dealing with!'

Peter

PS If you want a classic mount, I've got a Cave Astrola mount on an aluminium pedestal complete with a frequency generator and adapted for the Southern Hemisphere. You might talk me into parting with the whole kit (scope and mount) for a song if you want to deal with this!

[Merlin66]

I've recently bought a TS102 (102/1100) dedicated to solar observing.
It's a great scope and I'm having fun....It will sit nicely on the HEQ5pro but better on the NEQ6pro.....

[johnt]

Thanks to all for your replies. Although I did not get any specific information from someone who has brought a large D&G into Australia, I now have more understanding on what to buy.

Thanks again,
John

[brian nordstrom]

:)Hi John , I have a friend in NZ with a Zeiss 6 inch f/15 refractor in a perminent observatory and the views of the moon and planets thru that long throw refractor are 2nd to none , I have seen mars in that scope like nothing else using Zeiss Othhoscopic eyepieces of .965mm ( better than my old clubs C14 ) .
Thats where these long refractors shine , just beautiful .
Good luck on your journey , sounds like it will be a good one .
Oh yes I have an Istar 127mm lense in a scope I built last year and its very very good , they give awsome service , 10 days from payement to delivery here in Darwin give them a call via e/mail .
Brian.

[doppler]

Hi John,
Have a look at this web site they have some classics available from time to time and its in au. http://www.astronomyalive.com.au/
Cheers Rick

[johnt]

Thanks Rick,
I have looked at that webpage. I think Chris is a very helpful man, a master, and must have a great collection of old scopes. Yes, there are some older "long" scopes there for sale, and although they are all 4" or smaller, I may still consider one of them in addition to something larger.
Regards,
John

[doppler]

Here is one he had for sale last year 150mm objective I was pretty keen but didnt have the funds

[brian nordstrom]

:D Agian shoddy photos .
Brian.

[Poita]

I had a 6" F15 D&G and a similar Istar side by side a few years ago in the US. Less CA through the Istar and all who were there placed it ahead of the D&G. But that is just two samples, both were very good, but man, you want a sturdy mount, the slightest breeze can play havok with them, and they are unwieldy buggers.

[chris lewis]

I acquired a SYC Yamamoto 108mm/ 1600 F/15 approx 6 months ago. Its approx. 30 years old and in mint condition. I sold my SW Equinox ED120 to help finance it. These are rare 108mm Fraunhofer doublets.
The OTA are the same as the equally rare Professional Tacso TE20. I have no regrets trading my ED120. Optically the views are 'similar' to the ED120m, however fine detail resolution is superior. CA is minimal and only seen when in the 200x + magnification on bright objects. The image is flat with no aberrations. Needless to say it excels on detailed planetary and lunar viewing. It can take 300x with no image deterioration. It has the 1.25 in focuser. Even the long tube 50mm finder gives good planetary and lunar images up to 60x. The whole set up is around 170lbs yet I can manage it in two lifts. It looks superb and has that 'wow' factor and one has to see it to realize the build quality. There is something very special with these long tube achromatics.

Chris

[johnt]

Hi Chris,
Thanks for showing the telescope, it looks great. Fantastic looking mount/pier! The photo with you standing next to it really puts it in perspective. Regardless of anything else I get, I would like to get one of those also! If I can find one.

John