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Stu

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2 hours ago, josefk said:

This link posted by Dan Pensack in another thread on here has a group review of 10mm wide angles including the Tak UW. It may mitigate disappointment at their (i think) non availability in the UK @MalcolmM

https://web.archive.org/web/20130829052725/http://www.cieletespace.fr:80/files/InstrumentTest/201306__6_oculaires_10mm.pdf

Cheers 

Joe

Thanks for the link and a great chance to practice my French 🙂

Certainly easier than trying to translate the Japanese brochure that @JeremyS posted 🙂

Malcolm

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  • 3 weeks later...

During a few weeks round late August of 2015, we experienced a drought, and as I'm experiencing again, at present.  I then decided to take my FS-102, 102mm f/8 out to the Moon...

083115i.jpg.5d7f1dd610a515965beee5d3c6c952ab.jpg

 

857224302_fluoritedoublet2b.jpg.6c3ffeb37dc6acfb9cf9c5841e716409.jpg

The image of its doublet there has always reminded me of these...

spacer.png

The blue light from the power indicator of my desktop PC from across the room entering the doublet...

1012886527_fluoritedoublet7.jpg.eed0ab92abb579a7f59475a6c654d396.jpg

Here, blue and green are seen...

1295027096_fluoritedoublet8b.jpg.6801faeb9f96dee29fea1f3b91ab533e.jpg

An afocal shot of the Moon through a medium-grade ocular; nothing fancy...

083115h.jpg.fbfeed0fa2615d506e774c3725d3c82c.jpg

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On 30/09/2022 at 12:49, JeremyS said:

Congratulations Malcolm. A fine scope if ever there was one.

It’s probably bad form to link to another Forum, but if you have not read the first post in this thread, you should (and I suspect you’ll read the whole thread). It’s not specifically about this scope, but summarises by high quality small scopes can be so attractive.

https://www.cloudynights.com/topic/633339-put-your-stars-on-a-diet/

Also have a look at what this guy does: https://www.fzu.cz/~kupco/astro/equipment/FOA60.html

 

Great link, Jeremy, thanks👍.

Very thought provoking and a great read (which I will read in full later this evening)..at 50mm aperture my FS128 would be over F20..😱😁..

..but if I made a 69.3mm mask, it would be an exactly F15 apochromat..👏😎.

As the saying goes, F15RULES!

Watch this space!😂

Dave

 

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I had an interesting hour outside last night..

Picking up on Jeremy's link to the (excellent and fascinating) CN thread where a member was extolling the virtue of small aperture objectives, and how he "masked" down his FS128 to just 50mm by removing the centre section of the dew shield, I decided to have a try myself. 

I'll write that up this evening all being well, but for now suffice it to say that it was quite an eye opening experience!

Here's a couple of shots of "Trinity" at full 128mm aperture and also masked down to 50mm😊.

DaveIMG_20221028_195745613.thumb.jpg.ff3c43fb604effa9b6bafd220bee1642.jpgIMG_20221028_195754772.thumb.jpg.7bc82a6f2fee08e377374d5e15d24bdc.jpgIMG_20221028_195953674.thumb.jpg.bddb8fe076dfc9f4bf617c7197f0c08b.jpgIMG_20221028_204954962.thumb.jpg.7d0943a0d9f3fbe51690dd1f8d3c014b.jpg

Edited by F15Rules
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😱😱😱😱😱😱

Throttling down all that beautiful Fluorite performance to just 50mm should be against the law 😂 

 

(but I’m waiting for your writeup……….🙂)

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I often stop down my TSA-120 too -  to get slower focal ratios for solar Ha. There’s a ridiculously expensive Baader diaphragm available which allows you to choose a precise aperture (I think from around 110mm down to circa 50mm), but I just use cardboard cutouts. Never tried it for night astronomy though. 

E76C5091-3911-45B7-92BD-1AE661C9C597.jpeg

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Rather belatedly, here are my Part 1 thoughts from my session on Friday night. Part 2 to follow😊

Equipment used:

FS128 scope on Tak EM2 driven equatorial mount.

Eyepieces: TMB/Burgess 5mm Planetary series, Morpheus 9mm, Pentax XL 10.5mm, Morpheus 17.5mm, Axiom LX 23mm. All used in 2" sleeve mode.

Also used, Baader Zoom barlow 2.25x.

Conditions: Seeing poor to fair..after days of very changeable weather, and more rain in a week than for 5 months, the atmosphere is very active and unsettled. Transparency was good, however, with the Milky Way showing well right overhead.

Aims of session: to test and compare my FS128 apo at full 128mm F8.1 aperture, and at 50mm F20 stopped down aperture. This was following a link posted by Jeremy S from CN claiming that small c50-60 mm apertures can, on the right objects and under the right conditions get much closer to larger aperture performance. Here's the link in question:

https://www.cloudynights.com/topic/633339-put-your-stars-on-a-diet/ Author Credit: this article was published by Daniel Mounsey, and makes fascinating and thought provoking reading.

The central "challenge" of Daniel's article is for us to not be so conditioned to observing the way we have always done that we can't or won't look seriously at other ways of observing and using our existing equipment.

In my own case, I confess it didn't really occur to me that it could be worthwhile using my 5" apo at 2" aperture..and indeed why would it? (Even though the scope's maker, Takahashi, had seen fit to supply the scope with a 2" aperture removable disk in the centre of the dew shield)..if I had ever thought anything about this feature, it was probably that it would/could only be useful for solar projection or some such thing that didn't interest me.

But reading Daniel's piece, and his detailed and well argued reasoning, I was intrigued enough to give it a go..

I didn't have that much time, so I selected several targets, with the aim of comparing the 5" and 2" views through the same scope, with the same eyepieces, and trying to assess and describe the key differences and similarities that I saw.

Targets ( in the order I observed them):

Jupiter, Pleiades, Vega, Epsilon Lyrae (double double), M57 Ring Nebula in Lyra,  M13 great globular cluster in Hercules.

Jupiter:

At 128mm F8 - very bright at low power (too bright), 45 x and 60x. Very sharp. Two main equatorial belts seen and of a darkish brown colour. At higher power ( 99x and 115x), larger, fainter disk but few additional details seen as seeing was not cooperating. The main two belts did just hint at some structure, but the atmosphere would hold still long enough for this to be satisfying. The 4 main moons were clearly shown as tiny disks at all powers. I tried the TMB Burgess 5mm for 208x but just far too much for the conditions and a wobbly mess.

At 50mm F20. At the same powers as per full aperture, the disk was noticeably fainter, but more comfortable to look at as there was less sheer brightness. The same two bands were visible, but paler in tone. The satellites were fainter, but pin sharp - not seen so much as disks but tight stellar points..more than once I felt I saw a single diffraction ring around a couple of the points. At the medium powers the view did become more "woolly"..but apart from the different brightness level, I could see as much (or as little) detail on Jupiter as I could at full aperture.

Pleiades: I felt that this object was the one where on this night the views were most similar..at 45x at F8 (82deg Axiom 23mm LX) I could almost get the whole asterism in the fov, at both apertures..but what really surprised me was how similar the two views were, despite the 5" to 2" difference in aperture! Sure, the 2" view was clearly fainter, but the stellar images were pin sharp, and easier to fine focus (due to the long F20 focal length adding depth of focus?). The little asterism of 6 main stars leading off in a line was visible with direct vision at both apertures, and 2 of the 3 fainter stars close to this line were visible with averted vision at 2" as well! No sign of nebulosity at either aperture, but the cluster was still quite low down at this point.

Vega: a beautiful star at any power or aperture, this was a joy at both apertures..and I could see Vega's faint (optical double?) 10th mag companion star at c 5 o'clock position with both apertures..direct every time at 5" and with averted vision and some direct glimpses at 2". No false colour at all, just a lovely pure white point.

To be continued, with conclusions..🙂

Dave

IMG_20221029_170328047.jpg

Edited by F15Rules
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2 hours ago, JeremyS said:

Fully Tak baby blue livery on the FC 76DCU, now restored that’s to proper colour finder handle

CCC99AB0-EBA9-4F9F-9C04-A470F04B96B5.thumb.jpeg.3fa56ccbf40b5570eaa44610e3730529.jpeg

Looking good, glad it's all matching again now 👍

I've just noticed that you have your tube cradle "upside down" compared to how I have mine... I normally loosen mine for balancing (not so much now with a limited set of eyepieces), and would worry that the screw knob might fall down in this configuration 😮 However, I suppose there is little chance that the cradle would actually open with in your configuration... intriguing 🤔

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53 minutes ago, HollyHound said:

Looking good, glad it's all matching again now 👍

I've just noticed that you have your tube cradle "upside down" compared to how I have mine... I normally loosen mine for balancing (not so much now with a limited set of eyepieces), and would worry that the screw knob might fall down in this configuration 😮 However, I suppose there is little chance that the cradle would actually open with in your configuration... intriguing 🤔

Yes, I normally have it the other way up, Gary - I had just been testing in another configuration.

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46 minutes ago, JeremyS said:

Yes, I normally have it the other way up, Gary - I had just been testing in another configuration.

Ah thanks, apologies... I thought you had some special configuration and was very curious... situation normal, nothing unusual to see here 😁

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15 hours ago, F15Rules said:

Rather belatedly, here are my Part 1 thoughts from my session on Friday night. Part 2 to follow😊

Equipment used:

FS128 scope on Tak EM2 driven equatorial mount.

Eyepieces: TMB/Burgess 5mm Planetary series, Morpheus 9mm, Pentax XL 10.5mm, Morpheus 17.5mm, Axiom LX 23mm. All used in 2" sleeve mode.

Also used, Baader Zoom barlow 2.25x.

Conditions: Seeing poor to fair..after days of very changeable weather, and more rain in a week than for 5 months, the atmosphere is very active and unsettled. Transparency was good, however, with the Milky Way showing well right overhead.

Aims of session: to test and compare my FS128 apo at full 128mm F8.1 aperture, and at 50mm F20 stopped down aperture. This was following a link posted by Jeremy S from CN claiming that small c50-60 mm apertures can, on the right objects and under the right conditions get much closer to larger aperture performance. Here's the link in question:

https://www.cloudynights.com/topic/633339-put-your-stars-on-a-diet/ Author Credit: this article was published by Daniel Mounsey, and makes fascinating and thought provoking reading.

The central "challenge" of Daniel's article is for us to not be so conditioned to observing the way we have always done that we can't or won't look seriously at other ways of observing and using our existing equipment.

In my own case, I confess it didn't really occur to me that it could be worthwhile using my 5" apo at 2" aperture..and indeed why would it? (Even though the scope's maker, Takahashi, had seen fit to supply the scope with a 2" aperture removable disk in the centre of the dew shield)..if I had ever thought anything about this feature, it was probably that it would/could only be useful for solar projection or some such thing that didn't interest me.

But reading Daniel's piece, and his detailed and well argued reasoning, I was intrigued enough to give it a go..

I didn't have that much time, so I selected several targets, with the aim of comparing the 5" and 2" views through the same scope, with the same eyepieces, and trying to assess and describe the key differences and similarities that I saw.

Targets ( in the order I observed them):

Jupiter, Pleiades, Vega, Epsilon Lyrae (double double), M57 Ring Nebula in Lyra,  M13 great globular cluster in Hercules.

Jupiter:

At 128mm F8 - very bright at low power (too bright), 45 x and 60x. Very sharp. Two main equatorial belts seen and of a darkish brown colour. At higher power ( 99x and 115x), larger, fainter disk but few additional details seen as seeing was not cooperating. The main two belts did just hint at some structure, but the atmosphere would hold still long enough for this to be satisfying. The 4 main moons were clearly shown as tiny disks at all powers. I tried the TMB Burgess 5mm for 208x but just far too much for the conditions and a wobbly mess.

At 50mm F20. At the same powers as per full aperture, the disk was noticeably fainter, but more comfortable to look at as there was less sheer brightness. The same two bands were visible, but paler in tone. The satellites were fainter, but pin sharp - not seen so much as disks but tight stellar points..more than once I felt I saw a single diffraction ring around a couple of the points. At the medium powers the view did become more "woolly"..but apart from the different brightness level, I could see as much (or as little) detail on Jupiter as I could at full aperture.

Pleiades: I felt that this object was the one where on this night the views were most similar..at 45x at F8 (82deg Axiom 23mm LX) I could almost get the whole asterism in the fov, at both apertures..but what really surprised me was how similar the two views were, despite the 5" to 2" difference in aperture! Sure, the 2" view was clearly fainter, but the stellar images were pin sharp, and easier to fine focus (due to the long F20 focal length adding depth of focus?). The little asterism of 6 main stars leading off in a line was visible with direct vision at both apertures, and 2 of the 3 fainter stars close to this line were visible with averted vision at 2" as well! No sign of nebulosity at either aperture, but the cluster was still quite low down at this point.

Vega: a beautiful star at any power or aperture, this was a joy at both apertures..and I could see Vega's faint (optical double?) 10th mag companion star at c 5 o'clock position with both apertures..direct every time at 5" and with averted vision and some direct glimpses at 2". No false colour at all, just a lovely pure white point.

To be continued, with conclusions..🙂

Dave

IMG_20221029_170328047.jpg

Interesting experiment! Will read that full article you linked to. Although it is not exactly the same, I'm currently exploring how much you can do with high quality, very small aperture scopes for ultra grab-and-go, and it's surprising how well modern optics perform at tiny apertures. The scope in my case is a very fast SW Evoguide and I'm just awaiting an adaptor for visual use but also considering adding a Powermate in the optical train as a focal extender. 

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Stopped down aperture experiment Part 2..

Part 1 looked at the first 3 targets on my list, now Part 2 looks at the remaining 3 targets:

- Epsilon Lyrae (double double), M57 Ring Nebula in Lyra,  M13 great globular cluster in Hercules.

- Epsilon Lyrae: the famous double double is a classic "celestial lollipop" often recommended for new observers as it's such a showpiece double star..each component of which is itself double. 

Keen eyed observers can, I believe, split each pair at c 60-70x magnification..I don't think I have ever managed the split at much under 80x, and nowadays I find  I need 90-10x to get a comfortable split🥴.. but it's a lovely system, with each pair at more or less right angles to the other, and all 4 components of similar brightness.

I do remember splitting epsilon with my Prinz 550 60mm F15 refractor at the age of 15..in those days I only had 0.965" eyepieces with narrow fields of view, but the two pairs were nevertheless stunning. And long focus fracs do throw up beautiful stellar images, with fine airy disks with usually a single diffraction ring on half decent nights..and so it proved with the FS128 stopped down to 50mm F20. Due to the poorish seeing, the sharpest image was seen at the 50mm aperture, although it clearly was a good deal dimmer than at 128mm. On a good night of seeing, the full aperture would definitely have been more pleasing, but tonight the F20 view was definitely the best.

M57 Ring Nebula in Lyra. Perhaps not surprisingly, this object can prove a bit disappointing at first look..it's quite faint in small to medium scopes like mine, and being below 9th magnitude. Moreover, it's not a big object, although I find it quite easy to locate: I usually use a low power wide angle eyepiece as a finder in the main scope as my 50mm Raci is only 9x magnification and so doesn't always show it.

This object gave the most "expected" view..ie the 50mm aperture view was the faintest, although it was obvious as a faint donut shape..I've always found that the Ring takes magnification well, surprisingly, despite it's faintness..higher power darkens the sky background, so increasing contrast. Moving to full aperture then, the donut shaped ring stood out well, even up to 200x, although little detail was visible, and I've never seen the central star..at c mag 13.5 it's beyond a 5" scope, certainly to my eyes!

Finally, M13, the Great Globular cluster in Hercules. A long time favourite target of mine, now fast sinking in the north west.

I looked firstly at full aperture to get my bearings so to speak..I know what to expect of this object..a small but quite bright nebulous disk at low power (50x or so), and in my Axiom LX 23mm at 82 deg fov it was a lovely sight, framed against a background of fainter stars..

What I love with M13 is that you can start at low power, and gradually move up through higher powers and see more detail at each step..beyond c100x the views become more detailed as more individual stars begin to resolve, beginning with mag c10, then increasing numbers of scintillating faint but distinct tiny points of light popping into view around mag 11-12 with each successive magnification. 

By 200x, the sky background is black, and many individual stars are resolved - this is the joy of refractors! - both with direct and averted vision. And the cluster grows in apparent size, giving a real 3D effect as the resolving stars seem to be in front of the unresolved main body of the cluster in the background.

Moving to 50mm aperture I had to manage my expectations, but in fact the image, although small and much fainter was sharp and clear. As I racked up to c 115x I still got the improved contrast, just to a much less degree..a small number of individual stars of c mag 9.5-10 did begin to resolve, but only with averted vision, and intermittently. I didn't see the Propeller in either mode tonight, although I have seen it at 127mm several times, albeit not clearly (more my ageing eyes than the scope, I think). But I really enjoyed the views at both apertures.

So, what conclusions did I draw from this one session?

1. IMHO, Daniel's reports are based on good observing experience. I was pleasantly surprised at what I saw in my one scope used at very different apertures.

2. I think that local sky conditions will affect how the lower (and higher) apertures work here in the UK. But I am sure that it's worth experimenting and great fun to do so ..almost like discovering a new scope within your scope!

3. In order purely of my own experience in this one session, this is the order in which I would place my 6 targets in order of observing satisfaction at the 50mm aperture:

 a) (best) - Epsilon Lyrae   b) Pleiades                c) Vega, d) Jupiter                                              e) M13 Globular, Hercules f)  Ring Nebula M57 Lyra.                   

4. Many of our younger friends on SGL (say under 45years) may very well have never looked through a long focal length refractor before..I know that many are intrigued, but put off by the thought of using and balancing a long scope tube, and whether their mount will be steady enough? Well, here is a great way to bypass those concerns..just making a simple mask of say 50-60mm from card etc..on a 100mm F7 scope this will give you at 60mm an almost F12 focal length - plenty sufficient for you to see how good stellar images especially can be at a long focal length..sure, the fov will be narrower, but for observing doubles etc and planets this won't matter at all. Just remember, aperture always rules on fainter objects, but on nights of poor seeing but good transparency you may just find that that " it's not worth going outside tonight" night might just become very worthwhile indeed!

I, for one, intend to make such a mask and do more of this kind of observing this winter..as suggested by Jeremy previously Polaris and Mizar will be on my next list.

Thanks for sticking with this and do share your experiences if you have a go..(maybe on the observing forum..Mods, please move this post if you feel it should be over there?).

Clear Skies,

Dave

 

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1 hour ago, F15Rules said:

this will give you at 60mm an almost F12 focal length - plenty sufficient for you to see how good stellar images especially can be at a long focal length..sure, the fov will be narrower, but for observing doubles etc and planets this won't matter at all. Just remember, aperture always rules on fainter objects, but on nights of poor seeing but good transparency you may just find that that " it's not worth going outside tonight" night might just become very worthwhile indeed!

This makes me really glad I've chosen to keep my FOA-60Q (60mm f/15) 😁

Thanks for the really great reports 👍

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22 minutes ago, HollyHound said:

This makes me really glad I've chosen to keep my FOA-60Q (60mm f/15) 😁

Thanks for the really great reports 👍

Yup, F15 rules 😊

If something dreadful happened and I had to shift my larger Tak scopes, I think I could be very happy with my FOA 60Q. Especially when I look at these drawings: https://www.fzu.cz/~kupco/astro/equipment/FOA60.html

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1 hour ago, F15Rules said:

Stopped down aperture experiment Part 2..

Part 1 looked at the first 3 targets on my list, now Part 2 looks at the remaining 3 targets:

- Epsilon Lyrae (double double), M57 Ring Nebula in Lyra,  M13 great globular cluster in Hercules.

- Epsilon Lyrae: the famous double double is a classic "celestial lollipop" often recommended for new observers as it's such a showpiece double star..each component of which is itself double. 

Keen eyed observers can, I believe, split each pair at c 60-70x magnification..I don't think I have ever managed the split at much under 80x, and nowadays I find  I need 90-10x to get a comfortable split🥴.. but it's a lovely system, with each pair at more or less right angles to the other, and all 4 components of similar brightness.

I do remember splitting epsilon with my Prinz 550 60mm F15 refractor at the age of 15..in those days I only had 0.965" eyepieces with narrow fields of view, but the two pairs were nevertheless stunning. And long focus fracs do throw up beautiful stellar images, with fine airy disks with usually a single diffraction ring on half decent nights..and so it proved with the FS128 stopped down to 50mm F20. Due to the poorish seeing, the sharpest image was seen at the 50mm aperture, although it clearly was a good deal dimmer than at 128mm. On a good night of seeing, the full aperture would definitely have been more pleasing, but tonight the F20 view was definitely the best.

M57 Ring Nebula in Lyra. Perhaps not surprisingly, this object can prove a bit disappointing at first look..it's quite faint in small to medium scope like mine, and being below 9th magnitude. Moreover, it's not a big object, although I find it quite easy to find: I usually use a low power wide angle eyepiece as a finder in the main scope as my 50mm Raci is only 9x magnification and so doesn't always show it.

This object gave the most "expected" view..ie the 50mm aperture view was the faintest, although it was obvious as a faint donut shape..I've always found that the Ring takes magnification well, surprisingly, despite it's faintness..higher power darkens the sky background, so increasing contrast. Moving to full aperture then, the donut shaped ring stood out well, even up to 200x, although little detail was visible, and I've never seen the central star..at c mag 13.5 it's beyond a 5" scope, certainly to my eyes!

Finally, M13, the Great Globular cluster in Hercules. A long time favourite target of mine, now fast sinking in the north west.

I looked firstly at full aperture to get my bearings" so to speak..I know what to expect of this object..a small but quite bright nebulous disk at low power (50x or so), and in my Axiom LX 23mm at 82 deg fov it was a lovely sight, framed against a background of fainter stars..

What I live with M13 us that you can start at low power, and gradually move up through higher powers and see more detail at each step..beyond c109x the views become more detailed as more individual stars begin to resolve, beginning with mag C10, then increasing numbers of scintillating faint but distinct tiny points of light popping into view with each successive higher magnification. By 200x, the sky background is black, and many individual stars are resolved - this is the joy of refractors! - both with direct and averted vision. And the cluster grows in apparent size, giving a real 3D effect as the resolving stars seem to be in front of the unresolved main body of the cluster in the background.

Moving to 50mm aperture I had to manage my expectations, but in fact the image, although small and much fainter was sharp and clear. As I racked up to c 115x I still got the improved contrast, just to a much less degree..a small number of individual stars of c mag 9.5-10 did begin to resolve, but only with averted vision, and intermittently. I didn't see the Propeller in either mode tonight, although I have seen it at 127mm several times, albeit not clearly (more my ageing eyes than the scope, I think). But I really enjoyed the views at both apertures.

So, what conclusions did I draw from this one session?

1. IMHO, Daniel's reports are based on good observing experience. I was pleasantly surprised at what I saw in my one scope used at very different apertures.

2. I think that local sky conditions will affect how the lower (and higher) apertures work here in the UK. But I am sure that it's worth experimenting and great fun to do so ..almost like discovering a new scope within your scope!

3. In order purely of my own experience in this one session, this is the order in which I would place my 6 targets in order of observing satisfaction at the 50mm aperture:

 a) (best) - Epsilon Lyrae   b) Pleiades                c) Vega, d) Jupiter                                              e) M13 Globular, Hercules f)  Ring Nebula M57 Lyra.                   

4. Many of our younger friends on SGL (say under 45years) may very well have never looked through a long focal length refractor before..I know that many are intrigued, but put off by the thought of using and balancing a long scope tube, and whether their mount will be steady enough? Well, here is a great way to bypass those concerns..just making a simple mask of say 50-60mm from card etc..on a 100mm F7 scope this will give you at 60mm an almost F12 focal length - plenty sufficient for you to see how good stellar images especially can be at a long focal length..sure, the fov will be narrower, but for observing doubles etc and planets this won't matter at all. Just remember, aperture always rules on fainter objects, but on nights of poor seeing but good transparency you may just find that that " it's not worth going outside tonight" night might just become very worthwhile indeed!

I, for one, intend to make such a mask and do more of this kind of observing this winter. 

Thanks for sticking with this and do share your experiences if you have a go..(maybe on the observing forum..Mods, please move this post if you feel it should be over there?).

Clear Skies,

Dave

 

Many thanks for part 2 of your very worthwhile experiment, Dave. 
I must admit I rather enjoy the views of M57 and its field in my 60mm.

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On 01/11/2022 at 10:47, F15Rules said:

Stopped down aperture experiment Part 2..

Part 1 looked at the first 3 targets on my list, now Part 2 looks at the remaining 3 targets:

- Epsilon Lyrae (double double), M57 Ring Nebula in Lyra,  M13 great globular cluster in Hercules.

- Epsilon Lyrae: the famous double double is a classic "celestial lollipop" often recommended for new observers as it's such a showpiece double star..each component of which is itself double. 

Keen eyed observers can, I believe, split each pair at c 60-70x magnification..I don't think I have ever managed the split at much under 80x, and nowadays I find  I need 90-10x to get a comfortable split🥴.. but it's a lovely system, with each pair at more or less right angles to the other, and all 4 components of similar brightness.

I do remember splitting epsilon with my Prinz 550 60mm F15 refractor at the age of 15..in those days I only had 0.965" eyepieces with narrow fields of view, but the two pairs were nevertheless stunning. And long focus fracs do throw up beautiful stellar images, with fine airy disks with usually a single diffraction ring on half decent nights..and so it proved with the FS128 stopped down to 50mm F20. Due to the poorish seeing, the sharpest image was seen at the 50mm aperture, although it clearly was a good deal dimmer than at 128mm. On a good night of seeing, the full aperture would definitely have been more pleasing, but tonight the F20 view was definitely the best.

M57 Ring Nebula in Lyra. Perhaps not surprisingly, this object can prove a bit disappointing at first look..it's quite faint in small to medium scopes like mine, and being below 9th magnitude. Moreover, it's not a big object, although I find it quite easy to locate: I usually use a low power wide angle eyepiece as a finder in the main scope as my 50mm Raci is only 9x magnification and so doesn't always show it.

This object gave the most "expected" view..ie the 50mm aperture view was the faintest, although it was obvious as a faint donut shape..I've always found that the Ring takes magnification well, surprisingly, despite it's faintness..higher power darkens the sky background, so increasing contrast. Moving to full aperture then, the donut shaped ring stood out well, even up to 200x, although little detail was visible, and I've never seen the central star..at c mag 13.5 it's beyond a 5" scope, certainly to my eyes!

Finally, M13, the Great Globular cluster in Hercules. A long time favourite target of mine, now fast sinking in the north west.

I looked firstly at full aperture to get my bearings so to speak..I know what to expect of this object..a small but quite bright nebulous disk at low power (50x or so), and in my Axiom LX 23mm at 82 deg fov it was a lovely sight, framed against a background of fainter stars..

What I love with M13 is that you can start at low power, and gradually move up through higher powers and see more detail at each step..beyond c100x the views become more detailed as more individual stars begin to resolve, beginning with mag c10, then increasing numbers of scintillating faint but distinct tiny points of light popping into view around mag 11-12 with each successive magnification. 

By 200x, the sky background is black, and many individual stars are resolved - this is the joy of refractors! - both with direct and averted vision. And the cluster grows in apparent size, giving a real 3D effect as the resolving stars seem to be in front of the unresolved main body of the cluster in the background.

Moving to 50mm aperture I had to manage my expectations, but in fact the image, although small and much fainter was sharp and clear. As I racked up to c 115x I still got the improved contrast, just to a much less degree..a small number of individual stars of c mag 9.5-10 did begin to resolve, but only with averted vision, and intermittently. I didn't see the Propeller in either mode tonight, although I have seen it at 127mm several times, albeit not clearly (more my ageing eyes than the scope, I think). But I really enjoyed the views at both apertures.

So, what conclusions did I draw from this one session?

1. IMHO, Daniel's reports are based on good observing experience. I was pleasantly surprised at what I saw in my one scope used at very different apertures.

2. I think that local sky conditions will affect how the lower (and higher) apertures work here in the UK. But I am sure that it's worth experimenting and great fun to do so ..almost like discovering a new scope within your scope!

3. In order purely of my own experience in this one session, this is the order in which I would place my 6 targets in order of observing satisfaction at the 50mm aperture:

 a) (best) - Epsilon Lyrae   b) Pleiades                c) Vega, d) Jupiter                                              e) M13 Globular, Hercules f)  Ring Nebula M57 Lyra.                   

4. Many of our younger friends on SGL (say under 45years) may very well have never looked through a long focal length refractor before..I know that many are intrigued, but put off by the thought of using and balancing a long scope tube, and whether their mount will be steady enough? Well, here is a great way to bypass those concerns..just making a simple mask of say 50-60mm from card etc..on a 100mm F7 scope this will give you at 60mm an almost F12 focal length - plenty sufficient for you to see how good stellar images especially can be at a long focal length..sure, the fov will be narrower, but for observing doubles etc and planets this won't matter at all. Just remember, aperture always rules on fainter objects, but on nights of poor seeing but good transparency you may just find that that " it's not worth going outside tonight" night might just become very worthwhile indeed!

I, for one, intend to make such a mask and do more of this kind of observing this winter..as suggested by Jeremy previously Polaris and Mizar will be on my next list.

Thanks for sticking with this and do share your experiences if you have a go..(maybe on the observing forum..Mods, please move this post if you feel it should be over there?).

Clear Skies,

Dave

 

Thanks for this! Most illuminating so to speak. I am currently playing around with my Evostar 80ED which also has an aperture mask (I think 50mm, which would make it F12) built in to the end cap, so based in your reports perhaps I'll have a play with that too. 

I've also noticed @HollyHound has an FS60-CB up for sale, which would go nicely with a Q extender! If I were in the UK I would be sorely tempted by that 😅

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2 hours ago, badhex said:

Thanks for this! Most illuminating so to speak. I am currently playing around with my Evostar 80ED which also has an aperture mask (I think 50mm, which would make it F12) built in to the end cap, so based in your reports perhaps I'll have a play with that too. 

I've also noticed @HollyHound has an FS60-CB up for sale, which would go nicely with a Q extender! If I were in the UK I would be sorely tempted by that 😅

Well, F12 would be a lovely focal length..about 10-12 years ago I had a Pentax Japan J80 F12 achromat..it was a truly wonderful scope, and gave me a view of the double double in Lyra which has only been matched my my FS128 and a D&G 128mm F15 achromat..a 2 metre long scope!!

The ED80 is a very nice scope, so at 50mm  F12 it should be a very interesting comparison!

Dave

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10 minutes ago, F15Rules said:

Well, F12 would be a lovely focal length..about 10-12 years ago I had a Pentax Japan J80 F12 achromat..it was a truly wonderful scope, and gave me a view of the double double in Lyra which has only been matched my my FS128 and a D&G 128mm F15 achromat..a 2 metre long scope!!

The ED80 is a very nice scope, so at 50mm  F12 it should be a very interesting comparison!

The FC-76DCU with Extender is also f/12.5, and that has been a great scope for me (and @Stu too I believe) 👍

I've only dropped mine back to normal configuration (f/7.5) as I'm wanting it to be super portable again, and I'm intending to use my FOA-60Q (f/15) a lot more now (can't believe I thought about selling it 😬)... particularly as I'm moving on the FS-60CB 😁

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On 01/11/2022 at 11:18, JeremyS said:

Yup, F15 rules 😊

If something dreadful happened and I had to shift my larger Tak scopes, I think I could be very happy with my FOA 60Q. Especially when I look at these drawings: https://www.fzu.cz/~kupco/astro/equipment/FOA60.html

Those drawings are amazing! And interestingly, some of the drawings with North at the bottom and West to the left seem to have been made while straight through viewing?

So there's another question..how many of you have tried, or regularly do, straight through observing? I've often heard it suggested that Takahashi have resisted offering RACI finders because straight through observing is the preferred norm by it's main (Japanese) user base?

Discuss!😊

Dave

 

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2 hours ago, F15Rules said:

Well, F12 would be a lovely focal length..about 10-12 years ago I had a Pentax Japan J80 F12 achromat..it was a truly wonderful scope, and gave me a view of the double double in Lyra which has only been matched my my FS128 and a D&G 128mm F15 achromat..a 2 metre long scope!!

The ED80 is a very nice scope, so at 50mm  F12 it should be a very interesting comparison!

Dave

I had a dig around and found my original post ref the Pentax J80 F12 in case anyone's interested..the scope was a 1990 model.

Dave

 

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