Do I need a 5” ED doublet?

[MartianHill]

11 minutes ago, John said:

Over the years I've been in the astronomy hobby I've found the best cure for an "itch" is to scratch it. I read a lot of different view points from a lot of different sources but there comes a time when only "seeing for yourself" will do. 

Occasionally I have regretted that, and the example of the 6 inch F/12 achromat refractor that I acquired, as mentioned by @Stu earlier in the thread is one of those. But I learned from it and it's quite possible that had I not actually tried it, I would still have that itch of curiosity for a really long, large aperture refractor. They do look so alluring 🤩

 

 

 

 

 

 

 

  

Wow !!!

[johnturley]

1 hour ago, John said:

Over the years I've been in the astronomy hobby I've found the best cure for an "itch" is to scratch it. I read a lot of different view points from a lot of different sources but there comes a time when only "seeing for yourself" will do. 

Occasionally I have regretted that, and the example of the 6 inch F/12 achromat refractor that I acquired, as mentioned by @Stu earlier in the thread is one of those. But I learned from it and it's quite possible that had I not actually tried it, I would still have that itch of curiosity for a really long, large aperture refractor. They do look so alluring 🤩

 

 

 

 

 

 

 

  

There are several excellent 6 in f7ish Refractors on the market now though, and which will probably give better results than that f12 Achromat

John 

Edited December 10, 2023 by johnturley

[F15Rules]

7 hours ago, Mr Spock said:

I keep looking at these 120 - 125s class of scopes and fancying one. Then reason hits and I remember why I have a 100. It's light, small, fits an EQ5 without struggling and in terms of performance only a shade behind a 120 - only 0.19" less resolution and 0.4 mag less faint. I conclude each time the extra size and weight isn't worth the difference.

See, I just talked myself out of one again 

That's completely your choice.

But having owned excellent 4" apos for some 7 years and my current full 5" apo (and a 120mm scope is NOT a full 5"), for almost 7 years, I concluded that the larger size and weight of my setup, at around 20-22kg including mount, scope and tripod, IS worth it. 

The sheer number of stars visible in a 5" lens versus a 4" grows exponentially, see table below showing global totals of stars visible at a given magnitude.

I mentioned previously M13 in Hercules as an example. The more you look, the more you see, and at 5" you can see a whole lot more stars with direct vision than with a 4". That matters to me.

Similarly, bright nebulae such as M42 in Orion are significantly more impressive at 5".

For planets, and the moon, the difference to my eyes is less obvious: planets, because they vary so much in apparent diameter, plane orientation and orbital variations from one apparition to the next, and the moon, well, because it's the moon, and always shows massiive amounts of detail in either aperture!

I hope any or all of the above is helpful to the OP. And for the record, I'd happily accept the Stellalyra 125mm as a proper 5"..whats 2mm between friends??😊

Dave

 

[John]

1 hour ago, johnturley said:

There are several excellent 6 in f7ish Refractors on the market now though, and which will probably give better results than that f12 Achromat

John 

Yes, and I have still not completely ruled out another 6 inch refractor at some point. But it will be an F/7 or F/8 I think. Back then I was smitten with the idea of a long and larger aperture refractor. The Istar Perseus AT150 that I acquired was optically very good but it was a beast of a scope to find a suitable mount for. It rather dwarfed my ED120 and ED102SS:

Still, we live and learn 🙂

I still rather like long refractors as my avatar testifies. 

Edited December 10, 2023 by John

[Bivanus]

Well, having been to the promise land and having seen there up close and personal some largish scopes ( 5 / 5.5 / 6 / 7 in)  I had an epiphany: my next refractor is going to be a 5.5in / 140mm one. Hands on it looked to me like a goldilocks size  where aperture is still not offset by weight or rather the weight is ok-ish for the aperture. Regarding F ratio probably an F/7 or thereabout , a tad shorter even. Now, if only those pesky Euromilions would hit in so a proper mount can also be in the books...  😂

[MartianHill]

24 minutes ago, John said:

Yes, and I have still not completely ruled out another 6 inch refractor at some point. But it will be an F/7 or F/8 I think. Back then I was smitten with the idea of a long and larger aperture refractor. The Istar Perseus AT150 that I acquired was optically very good but it was a beast of a scope to find a suitable mount for. It rather dwarfed my ED120 and ED102SS:

Still, we live and learn 🙂

I still rather like long refractors as my avatar testifies. 

That Istar is really impressive John, you must have needed an equally impressive mount  ?

[Xilman]

I have two 150mm (6 inch) refractors from which I may be persuaded to part. No mount, just the OTA,

[John]

53 minutes ago, MartianHill said:

That Istar is really impressive John, you must have needed an equally impressive mount  ?

I ended up with an EQ6 mounted on a Meade Giant field tripod with 3 inch steel tubed legs. Even that was not really stable enough. I would have really needed something like an EQ8, a Losmandy G11 or even one of the old Fullerscopes Mk IV's. Probably a massive pillar to put the mount on as well.

Putting a 7 foot long 30 lbs optical tube onto a mount head that is over 6 feet off the ground is no joke either. 

I concluded that scopes like this need to be permanently mounted in observatories. No possibility of that where I am 😒

[MartianHill]

That’s a shame @John but you have other great refractors 👍

[Sunshine]

5 hours ago, John said:

Over the years I've been in the astronomy hobby I've found the best cure for an "itch" is to scratch it. I read a lot of different view points from a lot of different sources but there comes a time when only "seeing for yourself" will do. 

Occasionally I have regretted that, and the example of the 6 inch F/12 achromat refractor that I acquired, as mentioned by @Stu earlier in the thread is one of those. But I learned from it and it's quite possible that had I not actually tried it, I would still have that itch of curiosity for a really long, large aperture refractor. They do look so alluring 🤩

 

 

 

 

 

 

 

  

You would beed to buy the house next door to keep that in.

[John]

1 minute ago, Sunshine said:

You would beed to buy the house next door to keep that in.

I'm sure glad that I did not go for the F/15 version of the Istar 6 inch. There was one available from the same source at the time that I acquired the F/12. I saw the F/15 in it's box and decided that there was no way that I could handle it. I would also have needed to cut a hole in the ceiling to stand the thing on end !

 

[Sunshine]

7 minutes ago, John said:

I'm sure glad that I did not go for the F/15 version of the Istar 6 inch. There was one available from the same source at the time that I acquired the F/12. I saw the F/15 in it's box and decided that there was no way that I could handle it. I would also have needed to cut a hole in the ceiling to stand the thing on end !

 

That’s not necessarily a bad thing, you can observe from the comfort of your sofa.

[Mr Spock]

It goes without saying a 150mm f15 Mak is only about a foot long  

[StuartT]

On 05/12/2023 at 18:59, Peter Drew said:

After all my years in astronomy I'm still puzzled by the hype surrounding Takahashi telescopes as an OTA.  Granted the performance is legendary but this is due to the excellence of the Canon made objective, so shouldn't Canon deserve the accolades?.  In reality, what is Takahashi's contribution to the hype? a fairly ordinary looking tube assembly, yukky colour (ymmv) and a so-so  focuser which those who can still afford it replace with something better.  Wouldn't another telescope, say an Askar, with the same Canon objective, be a better telescope overall? or are Canon objectives available only to Takahashi ? I'm not knocking refractors, I have at least 20 including 7 150's and a 220.   🙂   

That's fighting talk, sir! And you know it.

(but someone had to say it 🤣)

Edited December 10, 2023 by StuartT

[SCANS]

5 hours ago, F15Rules said:

That's completely your choice.

But . . .

You sir, are evil 😂

[IB20]

Maybe I should change the title to “I have a 5” ED doublet”… 😁😁

Thanks for all the input and hurry up postie!

[globular]

oooo congratulations 

[SCANS]

1 hour ago, IB20 said:

Maybe I should change the title to “I have a 5” ED doublet”… 😁😁

Thanks for all the input and hurry up postie!

So happy for you. Santa will have a tough time topping that 😁 Best wishes for many years of enjoyment ahead 👍

[johnturley]

1 hour ago, IB20 said:

Maybe I should change the title to “I have a 5” ED doublet”… 😁😁

Thanks for all the input and hurry up postie!

Did you go for the StellaMira ED 125 Doublet then?

Would be interested to hear the First Light reports.

John 

Edited December 11, 2023 by johnturley

[Cjg]

1 hour ago, IB20 said:

Maybe I should change the title to “I have a 5” ED doublet”… 😁😁

Thanks for all the input and hurry up postie!

No wonder the forecast has gone to pot for Thursday and the peak of the Geminids.🤣

Congratulations, look forward to seeing your 1st light report in due course. (Asking should I get a 5 inch 'frac on an astronomy forum was really and truly only going to give you 1 answer, wasn't it! 🤣)

Good luck with your new scope

Chris

 

 

[IB20]

1 hour ago, johnturley said:

Did you go for the StellaMira ED 125 Doublet then?

Would be interested to hear the First Light reports.

John 

Sure did. Too good an offer to refuse and Jupiter, Orion and Sirius are and will be superbly placed in my observing location. Can’t wait to give it first light, apologies all for the impending 100% cloud cover.

 

[IB20]

1 hour ago, Cjg said:

No wonder the forecast has gone to pot for Thursday and the peak of the Geminids.🤣

Congratulations, look forward to seeing your 1st light report in due course. (Asking should I get a 5 inch 'frac on an astronomy forum was really and truly only going to give you 1 answer, wasn't it! 🤣)

Good luck with your new scope

Chris

 

 

Well I liked that answer better than the one I’d have gotten off the wife. 🫣

[F15Rules]

23 hours ago, John said:

Yes, and I have still not completely ruled out another 6 inch refractor at some point. But it will be an F/7 or F/8 I think. Back then I was smitten with the idea of a long and larger aperture refractor. The Istar Perseus AT150 that I acquired was optically very good but it was a beast of a scope to find a suitable mount for. It rather dwarfed my ED120 and ED102SS:

Still, we live and learn 🙂

I still rather like long refractors as my avatar testifies. 

I really like 6" F8 refractors, as you do, John. Having owned a couple of really rather good 6" achromats, a Celestron C6r and a Helios 150mm, both F8 achromats made by Synta, I know what great images they can put up.

There was one for sale last week for £195, a lot of scope for not a lot of money! Quite heavy though, and need a GPDX or Eq6 to mount them properly.

There are more modern ED 150mm doublets available, such as the APM  6".. I know that Steve (@Saganite) has one that he is very pleased with.. Steve has the best of both worlds, having the 6" and a superb Vixen ED103s 4" apo mounted side by side on his excellent Rowan AZ100 altaz mount..(pictures please, Steve!😅)..

Dave

[Cjg]

On 10/12/2023 at 17:07, John said:

Occasionally I have regretted that, and the example of the 6 inch F/12 achromat refractor that I acquired, as mentioned by @Stu earlier in the thread is one of those. But I learned from it and it's quite possible that had I not actually tried it, I would still have that itch of curiosity for a really long, large aperture refractor. They do look so alluring 🤩

  

So many questions, what were the views like? 
How on earth did you store / transport and fit it onto the mount?

Quite certain that’s not a scope you could slip past the other half unnoticed🤣

That’s a lot of commitment, well done!

Chris

[John]

48 minutes ago, Cjg said:

So many questions, what were the views like? 
How on earth did you store / transport and fit it onto the mount?

Quite certain that’s not a scope you could slip past the other half unnoticed🤣

That’s a lot of commitment, well done!

Chris

That scope is not mine - I just used it as an example of the appeal of a large aperture, long refractor.

My Istar 6 inch F/12 was still quite a beast though and, once setup, there it stayed for the session. I think the whole setup weighed somewhere around 50kg.

 

Edited December 11, 2023 by John