Again TS 152 F5.9- does it worth over ST 120 achro? I am using bino or ultrawides

[Marian M]

Hi friends!

 

It seems that I have developed on obsession over this fast achromat in the past months. I have read probably almost all of the reviews here on SGL and other websites, I know same version is sold under various brands, but not yet clear..

In a nutshell, I have TS 72 FPL53 (ultra GnG), TS 102 FPL53 and SW 120 F5 achro, with video head/ tripod, Skytee and AZEQ6. Most of the times with MB bino and Morpheus, or on cyclop with APM XWAs. Very often quick sessions on the balcon/ city with the 72, once in a month outside the city, with whole arsenal. I had a Mak 127 which I sold after getting the 102 APO, which I found superior on everything. Only visual, I like everything, moon, DSOs and planets, every single observation is giving me that smile and happiness as probably to most of you

Last evening I had the chance to compare pretty well on a variety of DSOs my 102 APO, with my friends SW 150/ 1200 ED and C8. My personal and very objective opinion is that most of the things which I see in 150 are visible in 102 as well, but better and brighter, is not necessary a fundamental difference. C8 sometimes shows more that 150ED but I like the APO view more than the C8- wider views and crisper images. Once again, just my personal impression, others could be different. So don't shoot me.

The 120 ST was not here to compare but in a previous session I did an 102 APO vs 120- on up to 50-60x magnification, not a huge difference. Stars maybe crisper, cleaner image in APO but DSO brighter in 120. Above that magnification, the APO is gorgeous, the SW 120 fail

 

Setting up the context, my question to you is where would be 152 F5.9 between the 120 ST and the 150 SW ED, only for DSO and up to 100x magnification? Would be better than 120 F5, would be similar to SW 150ED for wide low/ medium power? Is a big difference between 120 F5 achro and 152? from my preliminary computations, the 152 can accommodate bino without GCP easily, with some adapters change. TS give clear data on backfocus, which I found true for the 72 and 102.

 

There are also some observations planned when a friend will come with a 300 Dobson, maybe that will be a gamer change. In between, if I will sell the 120, the difference to 152 F5.9 will be manageable as cost, but does it worth?

 

PS the 120 F5 is changed completely on focuser part, now works at full aperture and can accommodate bino without GCP

[Stu]

I’ve not used a 120 f5, but have looked through a few 152 f5.9s and they are very nice, well corrected scopes considering their fast focal ratio. Definitely worth the upgrade I reckon given the increased aperture and better quality optics.

[Mr Spock]

A 152mm at low power will go a lot deeper than you might imagine. I reckon your 17.5mm Morpheus would be a perfect match and give fabulous wide field views. 
Yes, the apo can give higher magnifications, but at x51 you aren't going to notice any CA from the 152mm and that kind of aperture in a refractor can tease out faint nebulosity really well.
One of my best views of M42 came from my 120mm f8.33 achro with a 22mm T4 Nagler I used to have (x45). Quite spectacular.

[Louis D]

I recently picked up both the KUO 152mm fast achromat and a GSO 6" f/5 Newtonian.  Side by side, I much prefer the Newtonian.  The false color on the achromat is excessive on bright objects.  It doesn't go any deeper on DSOs than the reflector that I could see.  It's also way heavier and much more expensive.  On bright solar system objects, the reflector stomps all over the fast frac with sharp images.  The fast frac's unfocused violet and red ruin its solar system views.  I have to heavily green filter the frac to see anything sharply.

In summary, on dim objects, the fast frac shows nothing more than the fast reflector (which doesn't show diffraction spikes on dim objects) while the reflector shows sharp images on solar system objects compared to flaring messes in the fast frac.  To see DSOs best, just get a large, fast reflector.

I have no idea what to do with the fast frac now.  It doesn't really fit into my observing style at all.  Maybe I'll save up for a 150 ED to see if it shows anything more than a fast 6" or 8" Newtonian.

[The60mmKid]

2 minutes ago, Louis D said:

I recently picked up both the KUO 152mm fast achromat and a GSO 6" f/5 Newtonian.  Side by side, I much prefer the Newtonian.  The false color on the achromat is excessive on bright objects.  It doesn't go any deeper on DSOs than the reflector that I could see.  It's also way heavier and much more expensive.  On bright solar system objects, the reflector stomps all over the fast frac with sharp images.  The fast frac's unfocused violet and red ruin its solar system views.  I have to heavily green filter the frac to see anything sharply.

In summary, on dim objects, the fast frac shows nothing more than the fast reflector (which doesn't show diffraction spikes on dim objects) while the reflector shows sharp images on solar system objects compared to flaring messes in the fast frac.  To see DSOs best, just get a large, fast reflector.

I have no idea what to do with the fast frac now.  It doesn't really fit into my observing style at all.  Maybe I'll save up for a 150 ED to see if it shows anything more than a fast 6" or 8" Newtonian.

I was going to reply with something similar. I think that the 152mm refractor will, of course, go deeper than the 120mm refractor. But a 250mm f/4 reflector will provide a rather similar FOV to the 6" achro and will go far deeper than either of the refractors. Plus, you can't eliminate the fast achro's CA, but you can eliminate the fast reflector's coma. I had a 10" f/4 dob that was a lovely, lovely rich field instrument.

I've often considered one of the 6" achros but have never gone with one for these reasons.

[Alan White]

The 152 5.9 is a lovely scope for what you want, I know as I recently had one for a short while.

Be warned it’s a far bigger lump than a 120 and heavier, mounting may become a challenge with the step up.

Wide or Richfield in the right conditions is so much fun, but if it’s for use in town, then the light pollution may just spoil the party.

 

[Marian M]

Hi friends again, any many thanks for your messages!

 

Last evening, I had the chance to compare my 102 F7 FPL53 with the same 150 F8 SW ED and with a 300mm Dobson, for 1.5 hours time observation only, all without goto.

The sky was decent, allowing magnification up to 200x-250x, outside the city. Around 21.30, we had all equipment installed and ready to go.

 

First target was the Moon, with striking details in all 3 instruments. 102 had MB bino with Morpheus 9 and GPC (around 200x), SW 150 ED MB bino with Nikon NAV SW 17.5mm and Barlow (250x) and Omegon Dobson with APM UFF 24. We spent some time on Posidonius crater (hope my memory is good), where Posidonius C (around 3km diameter) was visible in 150 but just maybe/ with peripheral vision in 102, from time to time. Not necessary the best atmosphere to go higher on magnification.

 

Next targets were Wild Duck, Double cluster, Omega nebula, Ring Nebula, mostly on low power. Just as a personal very subjective opinion, I felt the jump from 102 to 150 was lesser than the jump from 150 to 300, but not that much. Whatever was visible in one instrument, was brighter and richer in the second one. Whatever was barely visible on the first instrument, was clearer in the second one. 102 has enjoyable views by up to 200x, 150 ED and Dobson may go for sure more. The view in the APOs seems sharper vs Dobson. Anyway, much more time is required to compare properly the Apo vs Dobson

 

I was wondering which one is suiting better my observation style. Last evening, being in hurry, I took only the APO on a video fluid head/ photo tripod, all at once, in one single trip. Setup time- 5 min. If would had the 152 achro, which should be similar on low power/ wide fields with the 150 ED, I should have taken the Skytee at least, more trips from the flat to the car, but quick setup time. With a 300 DOB, probably more trips would have been required but a quick setup time. Storage- the first 2 easy in the furniture, 300 Dobson- a little issue here. Binoviewer (which I enjoy a lot)- easy in the 2 Apos, challenging in Dobson- probably I have to look for the SW version which is collapsible, with the price of some aperture loss.

 

All these years I have learned that the hurry of acquisition leads to later selling, hence more time spent to study, and experiment is required  

 

On the short list still there is the 152 Achro but it seems that a Newton/ Dobson has a good chance to win

[Alan White]

7 minutes ago, Marian M said:

All these years I have learned that the hurry of acquisition leads to later selling, hence more time spent to study, and experiment is required  

Marian, that is such a spot on statment.

[Marian M]

Well, to be honest, I suppose is mostly my wife statement 😄😄

I am just closing my eyes, easy come, easy go 😄

[Mr Spock]

36 minutes ago, Marian M said:

All these years I have learned that the hurry of acquisition leads to later selling, hence more time spent to study, and experiment is required  

A sensible course of action. As always for DSO the more aperture you can get, the better the view.

At the cost of size - my 12" is huge and only moves from the shed to the patio. Cracking views though and can spank any apo you'd care to name at a fraction of the price 

[Stu]

It seems the original question has changed, from a choice between a 120mm f5 achro and the 152mm f5.9 achro to a choice between the 152mm f5.9 and a 300mm dob…. Different questions get different answers! No problem, these things evolve as we discuss them 👍

To me they are not comparable in that they both do what they do very well. Talk of one ‘spanking’ the other seems a little simplistic to me, even on DSOs. The 300mm of course excels on all sorts of DSOs but its limitation is field of view and coma. If you want widefield fields of open clusters with pinpoint stars to the edge then the frac is the way to go. If you want to see the whole of the Veil in one field of view then again a frac is the tool for the job (although not the 152mm as its focal length is too long still), but if you want close up detail and to really see what’s in there, the Dob wins of course so each on has its place.

For Lunar and planetary again a dob will show you much more under excellent seeing conditions, but often a decent frac will run them close when conditions are more variable. The 152 f5.9 isn’t necessarily the right tool for the lunar planetary job, but the question I was answering was would it be better than a 120mm f5, answer: Yes!

So, it’s horses for courses really, in many ways these two complement each other well so owning both would be a lot of fun I reckon 👍

Some screen grabs to illustrate the point. Kemble’s Cascade pretty much fits in the frac fov with a 31mm Nagler. The Veil is a bit of a squeeze and would be better in a shorter focal length frac. The whole of the Eastern Veil fits very nicely in the fov of the Dob with the big nag which would be a great view, and it will of course take higher power too to see the finer detail.

As an aside, the 152mm would also do a great job for Solar Ha observing with a Quark and also for white light with a Herschel Wedge.

Just as a further reference, the Moon shots were taken through a 128mm f8.1 frac (FS-128), so decent lunar views are very possible with this size of scope. Single smartphone shots, visually it was much better of course.

[Louis D]

On 22/07/2023 at 09:44, Marian M said:

my question to you is where would be 152 F5.9 between the 120 ST and the 150 SW ED, only for DSO and up to 100x magnification?

 

7 hours ago, Marian M said:

I had the chance to compare my 102 F7 FPL53 with the same 150 F8 SW ED and with a 300mm Dobson

I haven't looked through a 150 ED, but I have compared my 80mm f/5 achro to my 72 ED, and the views are not comparable at all.  The unfocused violet and red ends of the spectrum (spherochromatism) along with spherical aberration ruin the overall sharpness of the ST80 compared to the 72ED at all but the lowest powers.  I haven't had a chance to check for SA on my 152 achro yet.

My point is, don't draw conclusions for how an achromat at a particular aperture might perform based on a similarly sized ED scope.

[Louis D]

4 hours ago, Stu said:

the Moon shots were taken through a 128mm f8.1 frac (FS-128)

Those shots in your achromat look way better than what I'm seeing through my 152 achromat.  The purple wash and orange/red highlights really cut down on the contrast in my scope.  There's only a hint of purple wash in the darkest shadows in your scope by way of comparison.

[Stu]

12 minutes ago, Louis D said:

Those shots in your achromat look way better than what I'm seeing through my 152 achromat.  The purple wash and orange/red highlights really cut down on the contrast in my scope.  There's only a hint of purple wash in the darkest shadows in your scope by way of comparison.

These were through an apo (Tak FS-128), I guess I was just trying to show the kinds of detail that can be seen in a 5/6” class scope. Sorry for the confusion.

[Mr Spock]

If you are looking at planets rather than DSOs then a good 4" apo is not out of it's depth. I reckon a good 4" apo and a 12" Newt is the ideal combination. Each has its strengths.

A (noisy) snap of Petavius with the 4"

Scopes like this FC-100 and the FS-128 mentioned above are of the highest quality and relatively free of CA - they do come with a hefty price tag of course  There are others almost as good though for much less.

There are so many choices it's difficult to know what to do and mistakes can be expensive. I've swapped scopes quite a few times to get what I want. If only I'd been able to sit back and have a good think about it before committing!

[Louis D]

9 hours ago, Stu said:

These were through an apo (Tak FS-128), I guess I was just trying to show the kinds of detail that can be seen in a 5/6” class scope. Sorry for the confusion.

Roughly what power was that image taken at?  I can try to capture an image of the moon with the 152 achromat at a similar power sometime for comparison.

[Stu]

5 hours ago, Louis D said:

Roughly what power was that image taken at?  I can try to capture an image of the moon with the 152 achromat at a similar power sometime for comparison.

Looks like it was around x100 but using the x2 camera.

[Marian M]

Missing one single day and very excited to see so many comments here! 😄

 

@Stu, yes, your remark is well received- if the sum of Dobson benefits will be larger than the 152’s, I may change my mind. I would like to go more in aperture and checking a lot of boxes at once. Probably the best ever telescope will be the largest one possible, with all time access, in the darkest possible place but in front of my house and the most- belonging to someone else for the rest of headaches. In real life, there is no scope to meet all requirements at once. Many thanks for the simulations you have posted, very often I am doing the same through Stellarium app installed on the laptop, where I can choose the setup and simulate the view. What is missing there, is the visual experience. How far can you push the 152, for DSO only, still having a good view? For 120 ST- I would say max to 60x, for 152 some says even up to 120-150x, which seems a good achievement

 

@Louis D, I have compared the 120 achro with the 102 FPL53. During the day, as spotting scope, there is no comparison at all. On bright objects, there is a mess of colours in the 120, challenging the focus point, while 102 has a crisp, clear, colour free view. On the other hand, during the night/ DSO only/ low to low-medium power, the difference, for my eyes, is very small and non-disturbing. The 120 is brighter on the same magnification. The question is- you have been so disappointed of 152 for his only role- DSO/ low to medium power? If you can revert with few pictures of the Moon, would be great!

 

@Mr Spock- very happy with so many choices on scopes and eyepieces. Just to give more headaches while planning which to buy, wondering after purchase why I took this. And the most frustrating- even after all the people here told that you better take a different one. Some of the joy maybe is to buy it and convince yourself that this is not the right choice

[Stu]

34 minutes ago, Marian M said:

Probably the best ever telescope will be the largest one possible

Well it is oft said that the best telescope is the one you are looking through ie the one you use most. If you have easy access to dark skies and can pop a 300mm dob outside easily then it will be a good candidate. If you can lift/ move them easily then a dob can be quicker to setup than lugging mount, refractor and other bits and pieces out. However, if the size/weight/effort makes it less likely to be used then the balance shifts to smaller/light scopes. That’s why my most used scope is a Tak FC100DC on a ScopeTech mount and Gitzo tripod. Easy lift into the garden even for the quickest of sessions.

[The60mmKid]

I'd also recommend considering dobs smaller than 300mm if portability/deployability is a concern. A smaller (i.e., 6-10") fast dob can be a wonderful rich-field scope if that's still what we're after. And well collimated, it will also show more detail on planets than a smaller refractor does when conditions allow for it. But then other questions become relevant... thermal acclimation, local seeing conditions, preferences for mount/tracking, etc. If it's still a matter of "x vs. y rich-field scope," then I consider fast dobs quite worthy of consideration... and I'm sort of a refractor guy... or maybe I'm not... maybe I'm confused about my identity... but I digress. All of that aside, if I were to move to a place with dark skies, I'd be itching to get my hands on a fast 10" or 12" dob. One glimpse of the Double Cluster through a 10" f/4 is all it takes...

Edited July 25, 2023 by The60mmKid

[Mr Spock]

Here's my two ready for action. The Dob is next to the shed, and the Tak can go anywhere. Especially useful as my house blocks the East so I can only see there from the top of the garden. The garden runs exactly East to West - North to the right and South to the left 

[Louis D]

44 minutes ago, Marian M said:

The question is- you have been so disappointed of 152 for his only role- DSO/ low to medium power?

At low to medium powers on dimmer stars and DSOs, both the 6" achro and 6" fast Newt show similar views.  The Newt doesn't show diffraction spikes on dimmer objects, so that advantage of the refractor is lost.  The unfocused light in the frac is hard to detect, so that advantage of the Newt is lost.

I like having the eyepiece up nice and high on the Newt.  I refuse to extend the legs on my tripod due to the inherent shakiness in so doing, so the refractor's eyepiece ends up a foot or two off the ground which is really uncomfortable.

On DSOs in particular, I see no advantage to the frac over the Newt when you figure in cost, weight, and cool down time (the frac has more glass to cool).

[Marian M]

On 25/07/2023 at 14:56, Stu said:

Well it is oft said that the best telescope is the one you are looking through ie the one you use most. If you have easy access to dark skies and can pop a 300mm dob outside easily then it will be a good candidate. If you can lift/ move them easily then a dob can be quicker to setup than lugging mount, refractor and other bits and pieces out. However, if the size/weight/effort makes it less likely to be used then the balance shifts to smaller/light scopes. That’s why my most used scope is a Tak FC100DC on a ScopeTech mount and Gitzo tripod. Easy lift into the garden even for the quickest of sessions.

After the acquisition of the 72 APO, it become my most used scope. 20 minutes today, 15 tomorrow- the time spent in a month is more than a full night of observations once in a month

Later I discovered that 102 APO stays well with a William Optics plate on the video head, hence I presume it will become no 1

 

 

[Marian M]

On 25/07/2023 at 15:16, The60mmKid said:

I'd also recommend considering dobs smaller than 300mm if portability/deployability is a concern. A smaller (i.e., 6-10") fast dob can be a wonderful rich-field scope if that's still what we're after. And well collimated, it will also show more detail on planets than a smaller refractor does when conditions allow for it. But then other questions become relevant... thermal acclimation, local seeing conditions, preferences for mount/tracking, etc. If it's still a matter of "x vs. y rich-field scope," then I consider fast dobs quite worthy of consideration... and I'm sort of a refractor guy... or maybe I'm not... maybe I'm confused about my identity... but I digress. All of that aside, if I were to move to a place with dark skies, I'd be itching to get my hands on a fast 10" or 12" dob. One glimpse of the Double Cluster through a 10" f/4 is all it takes...

I love refractors; but reflectors seems winning on the benefits. Here it is my internal debate- one part of the mind is pushing against the rationale towards a bigger, heavier, colorful scope, while the logic part keep pushing back- largest aperture, similar effort to get out. Well, maybe the easiest way is to buy both 

[Marian M]

On 25/07/2023 at 15:27, Mr Spock said:

Here's my two ready for action. The Dob is next to the shed, and the Tak can go anywhere. Especially useful as my house blocks the East so I can only see there from the top of the garden. The garden runs exactly East to West - North to the right and South to the left 

Wonderful setup, peaceful place, amazing views...