What have you seen in a 5" Refractor, that you've not seen in an 8" newt?

[dweller25]

But angular diameter at opposition will not be the best 🙁

[John]

19 minutes ago, Flame Nebula said:

Do you think a used SW120ED will be as good as newest version? I've heard some things about different coatings? 

 

I have only briefly looked through a newish ED120. Mine is one of the very early ones (gold tube / cream trim) and is an excellent scope. The newer one seemed good too but it was only a short look that I had. No chance of a proper comparison.

It's quite possible that the coatings have changed during the life of the model (around 18 years and counting I think) but I don't think the glass types used in the objective will have changed.

 

 

[John]

7 minutes ago, dweller25 said:

But angular diameter at opposition will not be the best 🙁

Plus, there might be a martian dust storm to obscure the features, as there was in 2018 🙄

 

[dweller25]

14 minutes ago, John said:

Plus, there might be a martian dust storm to obscure the features, as there was in 2018 🙄

 

That’s Astronomy for ya 🤣

[mikeDnight]

1 hour ago, Alan White said:

You would be building a larger observatory first Mike.

Yes, it would need to be a redesigned obsey for a Parks Newtonian. I'd probably build a rotating building. It wouldn't take me long if a Parks came my way.

 At present my Newtonian collection is quite minimal. I have a 4.5" Newt' which is a nice little scope, made by a long gone local telescope company, yet the telescope itself is still going strong more than 30 years down the line. And I have a 6" given to me by paulastro.  I have also had a couple of lovely larger apertures, a 10" on loan from Peter Drew which was very nice optically, though I didn't enjoy the OO dob mount one bit, and a 8" F6 which I used on my observatory equatorial. It was very nice but my 4" apo was more pleasurable to use so the 8" was moved on.

The best Newtonian I've ever owned was a 6" F10 made by my friend Phil. I told him I didn't want a spider, so he made it with an optically flat window to hold the secondary. Double stars in that scope were droolworthy! The problem with it was I'd mounted it on a steel pier with three welded feet. The pier itself was an sizeable old oxygen bottle that the chunky equatorial was bolted to. The whole thing was dragged out of my garage onto my drive, which was a bit of a task. Phil also painted the tube with black hammerite using a brush. It looked crubish and couldn't love it despite trying hard.

My current 6".

 

[bosun21]

52 minutes ago, John said:

I think) but I don't think the glass types used in the objective will have changed.

Didn't they used to be FPL53 ? They are now stated as being an equivalent glass type. I mention this as I was considering a SW150ED and noticed this. Needless to say the 150 is just too big and heavy for me 🙄.

[Flame Nebula]

57 minutes ago, John said:

I have only briefly looked through a newish ED120. Mine is one of the very early ones (gold tube / cream trim) and is an excellent scope. The newer one seemed good too but it was only a short look that I had. No chance of a proper comparison.

It's quite possible that the coatings have changed during the life of the model (around 18 years and counting I think) but I don't think the glass types used in the objective will have changed.

 

 

OK, that sounds encouraging. I'd rather get a used one, as usually much cheaper than new

[John]

19 minutes ago, bosun21 said:

Didn't they used to be FPL53 ? They are now stated as being an equivalent glass type. I mention this as I was considering a SW150ED and noticed this. Needless to say the 150 is just too big and heavy for me 🙄.

My understanding is that the ED80, ED100 and ED120 still use an Ohara FPL-53 ED element mated with a Schott glass element. The ED72 and ED150 use undisclosed glass types. Changing the glass type used in the long established aperture models would, IMHO, be complex and risky for the brand. 

The decision by Skywatcher not to disclose the ED glass type used in the 72mm and 150mm models initially caused some angst from potential customers judging by the comments made on forums but it seems to be accepted now and those models seem to be judged on their merits.

 

 

[bosun21]

1 minute ago, John said:

My understanding is that the ED80, ED100 and ED120 still use an Ohara FPL-53 ED element mated with a Schott glass element. The ED72 and ED150 use undisclosed glass types. Changing the glass type used in the long established aperture models would, IMHO, be complex and risky for the brand. 

The decision by Skywatcher not to disclose the ED glass type used in the 72mm and 150mm models initially caused some angst from potential customers judging by the comments made on forums but it seems to be accepted now and those models seem to be judged on their merits.

 

 

No longer the case it would appear John.

[paulastro]

2 hours ago, John said:

Something else that has occurred to me is that we are reaching the end of a period of several years when the planets that we love to observe most (ie: Mars, Saturn and Jupiter) have not been well placed for observing from the UK - generally low in the sky. 

Jupiter is looking better now and Saturn and Mars will slowly get better placed as well. 

I found that observing the planets when they were low in the sky was quite a different proposition, scope choice-wise, than when they were high in the sky, as they were when I was observing them 20 years or so back. My refractors took over from my 10 and 12 inch dobsonians because they were able to provide better views and cut through the shaky seeing and the additional atmosphere thickness. There was a period of a couple of years when I gave up using my 12 inch dob for observing these planets altogether.

I guess what I'm suggesting is that what has delivered the best planetary observing for the past 5-6 years or so may not be the optimum instruments for the future, or at least might have any edge that they had in the past few years removed by more favourable planet positions allowing newtonians, SCT's and maks to deliver more of the benefits that their additional aperture suggests they have the potential to do.

Just a thought 🙂

 

Are you saying we need more than one telescope John? 😊

Edited April 19 by paulastro

[mikeDnight]

37 minutes ago, bosun21 said:

No longer the case it would appear John.

Having used a number of old ED's, even from long established top end manufacturers, knowing the glass type isn't a big thing to be honest. The old Vixen 102ED didn't disclose the glass type as far as I'm aware, yet when my friend Derek bought a 102ED F9 we were both blown away by its stunning definition on Saturn (c2004). The colour correction on that scope was equally impressive and almost indistinguishable from the legendary FL102. When Derek told me he was about to exchange his 102 ED F9 for a 102SS ED F6.5 I was convinced he was making the biggest mistake of his life. He made the change anyway and I was proved wrong yet again. The 102EDSS was stunning both as a rich field scope and for lunar and planetary. I'm not sure if the Vixen ED's used FPL51 or an equivalent but the point is it didn't make a jot of difference. The scope was a jewel. So I think we should trust the choices made by the optical designers and the skill of the optical engineers and just enjoy the great scopes they provide us with.

Edited April 19 by mikeDnight

[bosun21]

2 minutes ago, mikeDnight said:

Having used a number of old ED's, even from long established top end manufacturers, knowing the glass type isn't a big thing to be honest. The old Vixen 102ED didn't disclose the glass type as far as I'm aware, yet when my friend Derek bought a 102ED F9 we were both blown away by its stunning definition on Saturn (c2004). The colour correction on that scope was equally impressive and almost indistinguishable from the legendary FL102. When Derek told me he was about to exchange his 102 ED F9 for a 102SS ED F6.5 I was convinced he was making the biggest mistake of his life. He made the change anyway and I was proved wrong yet again. The 102EDSS was stunning both as a rich field scope and for lunar and planetary. I'm not sure if the Vixen ED's used FPL51 or an equivalent but the point is it didn't make a jot of difference. The scope was a jewel.

I totally agree with you regarding this. More often it's  matching the element types together that proves to be more crucial. There's apparently little difference between the refractive index of FPL53 and FCD100 anyway.

[John]

29 minutes ago, bosun21 said:

No longer the case it would appear John.

I think the ED80, 100 and 120 will still use FPL-53 plus a schott element, despite the above 🙂

 

 

[paulastro]

2 hours ago, John said:

I have only briefly looked through a newish ED120. Mine is one of the very early ones (gold tube / cream trim) and is an excellent scope. The newer one seemed good too but it was only a short look that I had. No chance of a proper comparison.

It's quite possible that the coatings have changed during the life of the model (around 18 years and counting I think) but I don't think the glass types used in the objective will have changed.

 

 

John.  Many years ago my first SW120ED was the gold version, an ex-demo one from Widescreen.  In fact I was comparing it with Mike's TV101 at my home with Mike shortly after I bought it.  The next day he advertised his TV and bought a new 120ED!

In my memory it was excellent, as good as all the later editions  including the Equinox which I've had at some time.

Edited April 19 by paulastro

[JeremyS]

1 hour ago, mikeDnight said:

Yes, it would need to be a redesigned obsey for a Parks Newtonian. I'd probably build a rotating building. It wouldn't take me long if a Parks came my way.

 At present my Newtonian collection is quite minimal. I have a 4.5" Newt' which is a nice little scope, made by a long gone local telescope company, yet the telescope itself is still going strong more than 30 years down the line. And I have a 6" given to me by paulastro.  I have also had a couple of lovely larger apertures, a 10" on loan from Peter Drew which was very nice optically, though I didn't enjoy the OO dob mount one bit, and a 8" F6 which I used on my observatory equatorial. It was very nice but my 4" apo was more pleasurable to use so the 8" was moved on.

The best Newtonian I've ever owned was a 6" F10 made by my friend Phil. I told him I didn't want a spider, so he made it with an optically flat window to hold the secondary. Double stars in that scope were droolworthy! The problem with it was I'd mounted it on a steel pier with three welded feet. The pier itself was an sizeable old oxygen bottle that the chunky equatorial was bolted to. The whole thing was dragged out of my garage onto my drive, which was a bit of a task. Phil also painted the tube with black hammerite using a brush. It looked crubish and couldn't love it despite trying hard.

My current 6".

 

Warning! I think someone might have hacked Mike’s account 🫣

[Flame Nebula]

8 minutes ago, JeremyS said:

Warning! I think someone might have hacked Mike’s account 🫣

Actually, this is very interesting, as I've wondered why manufacturers don't do the same to avoid spiders in commercial scopes. 

[dweller25]

35 minutes ago, JeremyS said:

Warning! I think someone might have hacked Mike’s account 🫣

He caught covid - it’s badly affected his logic, memory and love of lens licking 🙂

Get well soon Mike 👍

[John]

44 minutes ago, Flame Nebula said:

Actually, this is very interesting, as I've wondered why manufacturers don't do the same to avoid spiders in commercial scopes. 

I believe that making an optically flat window, properly flat that is, is quite difficult. I have seen it offered as an option in the past but it was quite an expensive option. 

I used to have a 6 inch F/6 maksutov-newtonian but the meniscus on that had a figure of course, to correct the spherical primary. Nearest thing to refractor images that I've seen from a reflecting design though. Tiny secondary - just 18% of the aperture of the primary. 

 

 

 

[melsmore]

Sirius B in my Vixen SD115S. Never had a hint of it in my 8" newt nor C8. Never tried with an aperture mask though.

Edited April 19 by melsmore
Aperture mask bit added.

[Flame Nebula]

25 minutes ago, melsmore said:

Sirius B in my Vixen SD115S. Never had a hint of it in my 8" newt nor C8. Never tried with an aperture mask though.

Mmm, very interesting, 

This was actually a specific example I did wonder might be easier in the frac., without diffraction spikes, and very uneven brightness. 

[Gfamily]

Can I show something that I unexpectedly did see in a 5" Mak that I would have normally expected to see in an 8" Newt? 

A spider. 

[Flame Nebula]

48 minutes ago, Gfamily said:

Can I show something that I unexpectedly did see in a 5" Mak that I would have normally expected to see in an 8" Newt? 

A spider. 

Ultra thin too. 

[Flame Nebula]

9 hours ago, Mr Spock said:

Approximate view of Jupiter without and with a polariser in a large aperture. Not entirely accurate but you get the idea.

It's especially important for Venus with almost any aperture.

Hi Mr Spock 

Do you mind me asking which brand of variable polariser you used? 

From reading other threads it also looks like having a O-III and UHC filter can enhance certain objects like nebula and planetary nebula. Do you have either of these? 

Thanks 

 

[Deadlake]

3 hours ago, mikeDnight said:

Doesn't this go to show there's nothing written in stone when it comes to one aperture or scope design vs another!  A number of years ago I'd been loaned a very nice SW 8" Dob which I'd set up in my garden at around 3pm on a clear afternoon. Alongside the Dob was my Equinox 120ED and both spent a good six hours standing in the cool air before being aimed at the Moon. My friend Derek witnessed this event as we looked at the Moon using the 8" and both genuinely felt the view was quite literally as good as it could ever possibly be. I knew in my heart that the 120ED would be hard pushed to get anywhere close to the 8", but when we looked at the Moon through the 120ED standing alongside, we were both in awe at the improved sharpness. The night had excellent seeing and both scopes were giving their best.  It would have been very easy to assume the 8" would be unbeatable by a smaller scope had the smaller scope not been standing right alongside, and anyone with that 8" would have had a seriously great scope.  

 It didn't stop there however, as we next aimed the 8" at Saturn which was high in the south east, and again the 8" gave what appeared to be another unbeatable view of the planet and its rings. Again I felt that the 120ED would struggle to get close to the view given by the 8" as it was perfection. Anyone seeing that 8" perform as it did on Saturn would be convinced it wouldn't be possible to get a better view through a smaller scope, as the A ring, Enke minima, Cassini's division, variations in the brilliance of the B ring, and the Crepe ring were all visible with ease, as well as globe detail. Nervously I aimed the 120ED at Saturn and Derek took the first look. His response to what he saw was littered with expletives which made me want to push him out of the way and look for myself. Instead I patiently waited for my turn to look, and when it came I was gobsmacked at the improved definition. The rings in the 120ED were as in the 8", but unlike the 8" were littered with the finest grooves similar in appearance to the grooves on a vynil record.  Derek likened the view to a Voyager image! 

I think there is a wish that everything is simple however we know that many things are not.

In this case the MTF of the scope and not just the aperture needs to be taken into account. 

The C11 although good, its mirror cannot really compare with the optics of a top tier APO and if the C11's mirror was manufactured to the same tolerance I'm sure it would be a 12K scope.

Having said all of that the C11 is a great light bucket, but to get contrast and detail on objects needs a better mirror....

 

[Stu]

6 hours ago, Flame Nebula said:

O-III and UHC filter can enhance certain objects like nebula and planetary nebula

They certainly can. It is specifically emission nebulae (and planetary nebulae) which are enhanced as the emit light at specific frequencies so that filters can be produced which just allow these frequencies to pass, blocking out most of the rest. This does dim the image a bit, but increases contrast by increasing the difference in brightness between background and target. They still perform best under dark skies and with good dark adaptation but will allow views of some objects under relatively light polluted skies.

Reflection nebulae, and galaxies generally don’t benefit from filters as their light is broadband in nature so a filter just decreases the brightness of the whole image.

Don’t listen to the ‘you can only use them in 8” or larger scopes’ comments, they are not true. Yes, you do need some dark adaptation and dark skies but filtering can give amazing views of some objects like the Veil in 4” scopes, smaller even.

Actually, you haven’t talked about a 4” scope as far as I recall. If the same question was asked about 8” vs 4” you could add wider files views to the list. If you stick a 31mm Nagler in a Starfield 102mm you get a 3.5 degree field, enough for the whole Veil just about, whereas an 8” gives just over 2.1 degrees.