51 replies to this topic

[jml79]

I am just sorting out my new 8" f/4 newt so my experience is very limited. From my long research phase;

 

The TS-Optics GPU is a good coma corrector and many believe it is a re-branded SharpStar 1x 4 element corrector which has shown performance on par with many well regarded correctors.

 

The common upgrades to the Quattro 200 and PDS are;

 

-Rigid spider

-rear mirror cover

-mirror mask

-light seal the focuser baseplate where it meets the the scope

 

Many also replace the focuser, Cuiv has a video on a very interesting R&P focuser from AliExpress that is designed to fit that scope. I wish it would fit on mine.

 

I was almost ready to just pay the extra for a TS-Optics UNC scope when a new, old stock ES208 came available for a screaming deal ($675 Cdn which is about 450 Euro) and I decided to jump. It has an integrated rear mirror cover (not a piece of cardboard) and a much nicer spider but the focuser is still meh and it's missing the baffles that the quattro has. Still hunting for a replacement focuser and deciding on the coma corrector, I think it will be the SharpStar (apertura, Ts-optics etc.) 0.95 for the smaller size and price over the 4 element 1x correctors available.

Edited by jml79, 17 August 2024 - 10:46 PM.

[grasklippare]

So, here is where I am at the moment.

 

As the discount for the 10 inch Quattro no longer is active, that scope is now a lot more expensive than the 8 inch Quattro. For that reason alone I would have gone for the latter. But, also some of the experiences and thoughts brought up in thread has brought me to the conclusion that the 8 Inch Quattro is the one to go for.

 

While The TS Optics GPU coma corrector seem to have a great reputation, there are also some negative opinions about it, specifically regarding it vignetting severly on APS-C size sensors. As the TS Optics GPU consists of a quite long tube, that also seems to protrude into the telescope tube, it should be the coma corrector, and not the size of the focuser that causes most of the vignetting.

 

Anybody have any actual experience with this? Does the TS Optics GPU introduce heavy vignetting for sensors of that size? Any unedited frames to share? It calibrates out nicely when using flat frames?

[Andros246]

So, here is where I am at the moment.

 

As the discount for the 10 inch Quattro no longer is active, that scope is now a lot more expensive than the 8 inch Quattro. For that reason alone I would have gone for the latter. But, also some of the experiences and thoughts brought up in thread has brought me to the conclusion that the 8 Inch Quattro is the one to go for.

 

While The TS Optics GPU coma corrector seem to have a great reputation, there are also some negative opinions about it, specifically regarding it vignetting severly on APS-C size sensors. As the TS Optics GPU consists of a quite long tube, that also seems to protrude into the telescope tube, it should be the coma corrector, and not the size of the focuser that causes most of the vignetting.

 

Anybody have any actual experience with this? Does the TS Optics GPU introduce heavy vignetting for sensors of that size? Any unedited frames to share? It calibrates out nicely when using flat frames?

Little off topic and unsure if it was mentioned already but make sure you flock the tube well, a stock quattro is a like a hallway full of mirrors for reflections.

Edited by Andros246, 26 August 2024 - 10:59 AM.

[grasklippare]

Little off topic and unsure if it was mentioned already but make sure you flock the tube well, a stock quattro is a like a hallway full of mirrors for reflections.

Okay, I guess that one should only flock the part before the baffles start, and not in between the baffles or something like that? The baffles should be left as is?

[Andros246]

Okay, I guess that one should only flock the part before the baffles start, and not in between the baffles or something like that? The baffles should be left as is?

That's a good question I was under the assumption it shared the PDS line those do not have baffles.

[Spaceman 56]

 

I will mostly do DSO imaging, but I would also very much like to be able to do some planetary imaging, this is the main reason why I am considering the 10 inch scope. 

can I ask your experience level with regard to imaging ?

 

is the 10 inch Newtonian your first imaging scope ?

 

have you used smaller refractors successfully ?

[grasklippare]

can I ask your experience level with regard to imaging ?

 

is the 10 inch Newtonian your first imaging scope ?

 

have you used smaller refractors successfully ?

Yes, you can.

 

Like I have mentioned before in this thread I am currently using a 70 mm refractor telescope. I got all of my equipment up and running in march 2022. So, I have about two and a half years of experience imaging. I would say it has been quite succesfully, though, I have had some doubts regarding the guiding performance, which I am quite sure is down to there being some klind of problem with my mount. 

 

As you can see a few posts up, the 10 inch is no longer an option, so there is only the 8 inch Quattro left as an alternative. And of course, the option of not getting a newtonian at all.

[Spaceman 56]

 I am currently using a 70 mm refractor

ok. thanks.  

 

when I moved up from my 80mm refractor (448mm focal) I went to a 106mm refractor (530mm focal)

the change was not too difficult, in terms of focal length and guiding requirements. same type of images but with a bit more zoom, and slightly faster due to F Ratio.

later I tried a 102mm refractor which is 714mm focal. more zoom but slower (slightly) each step getting a bit closer to the small details I was chasing.

 

about then (after considerable success) I decided to try Galaxy imaging and bought a big CEM-120 mount and the 10 inch RC, which is set up for 1484mm focal length. this gets me way way closer to those smaller targets and I have been happy with the progress and the outcomes.

 

I say all this because its clear to me that small steps in AP are good and most people benefit from doing this. there are individual exceptions to this.

 

Q. what do you want to image specifically ?    

Edited by Spaceman 56, 28 August 2024 - 05:05 AM.

[grasklippare]

ok. thanks.  

 

when I moved up from my 80mm refractor (448mm focal) I went to a 106mm refractor (530mm focal)

the change was not too difficult, in terms of focal length and guiding requirements. same type of images but with a bit more zoom, and slightly faster due to F Ratio.

later I tried a 102mm refractor which is 714mm focal. more zoom but slower (slightly) each step getting a bit closer to the small details I was chasing.

 

about then (after considerable success) I decided to try Galaxy imaging and bought a big CEM-120 mount and the 10 inch RC, which is set up for 1484mm focal length. this gets me way way closer to those smaller targets and I have been happy with the progress and the outcomes.

 

I say all this because its clear to me that small steps in AP are good and most people benefit from doing this. there are individual exceptions to this.

 

Q. what do you want to image specifically ?    

I actually would like to image galaxies, and some star clusters too. Do you reckon that I will feel that the 800 mm focal length of the Quattro 8 inch is a tad bit short for the galaxies?

[Spaceman 56]

I actually would like to image galaxies, and some star clusters too. Do you reckon that I will feel that the 800 mm focal length of the Quattro 8 inch is a tad bit short for the galaxies?

you can certainly image the Larger Galaxies at 800mm and some of the Medium sized ones too.

 

using my Takahashi which is 530mm focal length I get shots like this.

 

click to enlarge.

 

 

 

using my 1484mm RC I get shots like this.

 

 

as you can see focal length is an advantage.

 

whilst I have not shot at 800mm, and cant speak from personal experience, I think you could get some lovely galaxy shots of Large and Medium size galaxies at that focal length.

 

you can crop in the images to make them look closer.

 

this is Centaurus A wide field. taken with the 530mm Takahashi.

 

 

this is a cropped in version of Centaurus A galaxy shown above.

 

 

as you can see its more spectacular.  

 

800mm is a pretty good focal length for many targets, but probably not enough for Small Galaxies. understand that Small Galaxies are Very Small. Hard Targets. 

 

 

Edited by Spaceman 56, 30 August 2024 - 02:53 AM.

[Oort Cloud]

you can certainly image the Larger Galaxies at 800mm and some of the Medium sized ones too.

using my Takahashi which is 530mm focal length I get shots like this.

click to enlarge.





using my 1484mm RC I get shots like this.




as you can see focal length is an advantage.

whilst I have not shot at 800mm, and cant speak from personal experience, I think you could get some lovely galaxy shots of Large and Medium size galaxies at that focal length.

you can crop in the images to make them look closer.

this is Centaurus A wide field. taken with the 530mm Takahashi.




this is a cropped in version of Centaurus A galaxy shown above.




as you can see its more spectacular.

800mm is a pretty good focal length for many targets, but probably not enough for Small Galaxies. understand that Small Galaxies are Very Small. Hard Targets.

Dave, do you have any examples where you shot the same galaxy with both a refractor and the RC? Preferably with the same camera, as that would really put the difference into perspective.

[grasklippare]

 

you can certainly image the Larger Galaxies at 800mm and some of the Medium sized ones too.

 

using my Takahashi which is 530mm focal length I get shots like this.

 

click to enlarge.

 

 

 

 

 

using my 1484mm RC I get shots like this.

 

 

 

as you can see focal length is an advantage.

 

whilst I have not shot at 800mm, and cant speak from personal experience, I think you could get some lovely galaxy shots of Large and Medium size galaxies at that focal length.

 

you can crop in the images to make them look closer.

 

this is Centaurus A wide field. taken with the 530mm Takahashi.

 

 

 

this is a cropped in version of Centaurus A galaxy shown above.

 

 

 

as you can see its more spectacular.  

 

800mm is a pretty good focal length for many targets, but probably not enough for Small Galaxies. understand that Small Galaxies are Very Small. Hard Targets. 

 

 

 

Those are some glorious galaxies you have right there!

 

I do not believe I can go for any longer focal lengths than 800 mm with my EQ6-R, it has never seemed to behave as well as the EQ6-Rs of other users. Now that I just recieved it back after warranty repairs it performs even worse than before. Maybe I should scrap my dreams for galaxies and go widefield for the large nebulas instead.

 

Dave, do you have any examples where you shot the same galaxy with both a refractor and the RC? Preferably with the same camera, as that would really put the difference into perspective.

Yes, that could be nice to see!

[Spaceman 56]

Dave, do you have any examples where you shot the same galaxy with both a refractor and the RC? Preferably with the same camera, as that would really put the difference into perspective.

not so far Oort Cloud.

 

right now I am shooting Helix nebula, with the RC10, that I previously shot with the smaller refractors. 

 

but I could shoot NGC55 or NGC-300 again with the 10 inch if you want me too. would it be useful ?

[Dan_I]

I actually would like to image galaxies, and some star clusters too. Do you reckon that I will feel that the 800 mm focal length of the Quattro 8 inch is a tad bit short for the galaxies?

It's not too short with a small pixels camera (more specifically, cameras based on the IMX183 or IMX294 sensor )

 

Small galaxies are no problem:

https://www.cloudyni...axies-in-draco/

https://www.cloudyni...-galaxy-arp-84/

https://www.cloudyni...-1-and-arp-285/

neither are gravitationnal arcs of galaxies 7billions light-years away

https://www.cloudyni...bortle-7-skies/

 

Clear skies,

 

Dan

 

Regarding planetary imaging, an f/4 newtonian is not more obstructed than an SCT, and has no chromatic aberrations unlike SCTs, so with a good 5x barlow it should work well.

Edited by Dan_I, 01 September 2024 - 06:37 AM.

[ntph]

An 8 inch (200mm) f/4 will be a great scope for DSOs in general. Dan shows us some very nice images above. Another good place to see what this scope can do is Kathy Walker's A-bin--a lot of her images are with this size scope. I shoot at around 850 mm with a 130mm refractor and I like what I can get from galaxies. If I want to go bigger, I can use the 1000mm FL 250mm (10 inch) but it is a bit of a beast to get on and off, so I kind of reserve it for "small and faint". Go for the 8 inch would be my advice. 

[grasklippare]

It's not too short with a small pixels camera (more specifically, cameras based on the IMX183 or IMX294 sensor )

 

Small galaxies are no problem:

https://www.cloudyni...axies-in-draco/

https://www.cloudyni...-galaxy-arp-84/

https://www.cloudyni...-1-and-arp-285/

neither are gravitationnal arcs of galaxies 7billions light-years away

https://www.cloudyni...bortle-7-skies/

 

Clear skies,

 

Dan

 

Regarding planetary imaging, an f/4 newtonian is not more obstructed than an SCT, and has no chromatic aberrations unlike SCTs, so with a good 5x barlow it should work well.

Unfortunately I just recently treated myself a new camera, with larger 3,76 micrometer pixels. For the pixel scales your were referring to I would need a new camera  and the camera budget is completely drained for the foreseeable future. That means then that I would need to go for a scope with a longer focal length than the Quattro, in the 1300 mm range. A newtonian of that length would probably not be held steady enough for deep sky imaing by my poor EQ6-R?

 

I do have an 8 inch f/6 dob, that I can adapt to put on the EQ mount for some occasional planetary imaging. Then I just need a 2,5x barlow for reaching the optimal focal ratio for my IMX585 equipped planetary camera. I gues that should work just fine.

 

An 8 inch (200mm) f/4 will be a great scope for DSOs in general. Dan shows us some very nice images above. Another good place to see what this scope can do is Kathy Walker's A-bin--a lot of her images are with this size scope. I shoot at around 850 mm with a 130mm refractor and I like what I can get from galaxies. If I want to go bigger, I can use the 1000mm FL 250mm (10 inch) but it is a bit of a beast to get on and off, so I kind of reserve it for "small and faint". Go for the 8 inch would be my advice. 

Yes, those were some nice examples shown by Dan. I had a look at some images of Kathy's, and she seems to use a camera that has even larger pixels than my camera. So my with my camera, and an 8 inch Quattro, I would land between the pixel scales of Dan and Kathy.

 

I find it a little bit curious that 10 inch vs 8 inch does not sound like that much of a difference. But it does entail close to a doubling in weight with a 10 inch newtonian and I imagine that that plus the increased size does make it quite cumbersome to handle.

 

Maybe I should just go ahead with the 8 inch Quattro then. I have been offered a great discount on having it modified and improved for DSO imaging.

[ntph]

Don't obsess over the numbers for image scale and such. Get the 8 inch and get on with it! It will be just fine. Too many people do this--worry about second decimal place numbers--your local seeing is going to trump everything else if you are anywhere near the right ball park which is somewhere between 1 and 2 for all intents and purposes. You will do amazing things with it--if you get over your paralysis by overanalysis!

[Spaceman 56]

I find it a little bit curious that 10 inch vs 8 inch does not sound like that much of a difference.

 

But it does entail close to a doubling in weight with a 10 inch newtonian and I imagine that that plus the increased size does make it quite cumbersome to handle.

when I was considering a Galaxy imaging scope I looked at 8 inch and 10 inch Newtonians as being an option. the advantage would be the low F Ratios.

 

then I learnt that a Newtonian basically doubles the OTA assemble tube length and has a 2x focal Length, but an RC basically triples the OTA assembly tube length

so we end up with a focal length 3x the Tube assembly length.

 

the weight between a 10 inch Newtonian and a 10 inch RC wont be such a great difference, but the focal length differences are considerable.  

 

That and the elimination of Coma Correctors, and the Flat Field from the RC was why I chose an RC.

 

either way you will need a big mount for anything 10 inch, and even the 8 inch newtonian is a pretty sizeable beast. 

[grasklippare]

Don't obsess over the numbers for image scale and such. Get the 8 inch and get on with it! It will be just fine. Too many people do this--worry about second decimal place numbers--your local seeing is going to trump everything else if you are anywhere near the right ball park which is somewhere between 1 and 2 for all intents and purposes. You will do amazing things with it--if you get over your paralysis by overanalysis!

Thank you! I am ALWAYS bogged down from suffering from that affliction. Not the info I asked for with starting this thread, but what I actually needed to hear.

 

when I was considering a Galaxy imaging scope I looked at 8 inch and 10 inch Newtonians as being an option. the advantage would be the low F Ratios.

 

then I learnt that a Newtonian basically doubles the OTA assemble tube length and has a 2x focal Length, but an RC basically triples the OTA assembly tube length

so we end up with a focal length 3x the Tube assembly length.

 

the weight between a 10 inch Newtonian and a 10 inch RC wont be such a great difference, but the focal length differences are considerable.  

 

That and the elimination of Coma Correctors, and the Flat Field from the RC was why I chose an RC.

 

either way you will need a big mount for anything 10 inch, and even the 8 inch newtonian is a pretty sizeable beast. 

That does not sound correct to me. Am I missing something?

 

For instance, my 1200 mm focal length f/6 dobsonian newtonian has a tube length of around 1100 mm. The focal length is the distance from the primary mirror up to and via the secondary mirror and out the side to the focal point. There's no doubling involved there?

 

An RC would be primary-secondary-through the primary with the focal point somewhere behind the primary.

 

Anyway, my EQ6-R can not deal with those longer focal length anyway. Even the 800 mm of the 8 inch quattro might be too much.

[Spaceman 56]

Thank you!

 

That does not sound correct to me. Am I missing something?

 

I simplified the theory.

 

a Newtonian takes the light from the front of the OTA, bounces it off the Primary to the secondary, which is like doubling the light path. folding it twice.

 

an RC does the same thing except it bounces it it off the Primary, to the secondary, then back through the centre of the primary and well beyond this point.

so in simple terms it can be looked at as bouncing the light or folding it 3 times.

 

the distance that the camera sensor is beyond the Primary can also be substantial.

 

thats why an 8 inch Newtonian (Skywatcher Quatro)  might be focal length of 800mm, but an 8 inch RC is over 1500mm.

 

anyway as you said the EQ6-R wont hold the RC focal length, so something else is required.  

[Dan_I]

 

 

Anyway, my EQ6-R can not deal with those longer focal length anyway. Even the 800 mm of the 8 inch quattro might be too much.

An EQ6-R is perfectly adequate to handle a 8" f/4, there're plenty of great images taken with this combo.

 

And don't let the OTA length differences fool you. It is true than an 8" RC OTA is shorter than an 8" f/4 newt but:

 

With the newt the imaging train load is very close to the axes of the mount:

 

 

While the RC needs several extension tubes to reach focus, so a large moment arm with a heavy camera:

 

 

Clear skies,

 

Dan

 

 

 

 

 

 

[Oort Cloud]

An EQ6-R is perfectly adequate to handle a 8" f/4, there're plenty of great images taken with this combo.

And don't let the OTA length differences fool you. It is true than an 8" RC OTA is shorter than an 8" f/4 newt but:

With the newt the imaging train load is very close to the axes of the mount:



While the RC needs several extension tubes to reach focus, so a large moment arm with a heavy camera:



Clear skies,

Dan

I agree, the EQ6-r can definitely handle an 8" Newtonian. But unlike a small refractor, it will need precise balance, and relatively low wind speed, or shelter from wind in an obsy. An 8" newt is like a giant sail compared to, for example, a small to medium sized refractor.

Moment arm, aerodynamics, balance. They all have a hand to play too, not just weight and focal length.

[grasklippare]

I simplified the theory.

 

a Newtonian takes the light from the front of the OTA, bounces it off the Primary to the secondary, which is like doubling the light path. folding it twice.

 

an RC does the same thing except it bounces it it off the Primary, to the secondary, then back through the centre of the primary and well beyond this point.

so in simple terms it can be looked at as bouncing the light or folding it 3 times.

 

the distance that the camera sensor is beyond the Primary can also be substantial.

 

thats why an 8 inch Newtonian (Skywatcher Quatro)  might be focal length of 800mm, but an 8 inch RC is over 1500mm.

 

anyway as you said the EQ6-R wont hold the RC focal length, so something else is required.  

Well, if it works for you it works for you I guess.

 

An EQ6-R is perfectly adequate to handle a 8" f/4, there're plenty of great images taken with this combo.

 

And don't let the OTA length differences fool you. It is true than an 8" RC OTA is shorter than an 8" f/4 newt but:

 

With the newt the imaging train load is very close to the axes of the mount:

 

 

While the RC needs several extension tubes to reach focus, so a large moment arm with a heavy camera:

 

 

Clear skies,

 

Dan

Yes, sure, an EQ6-R should be able to handle that, but I was specifically talking about my EQ6-R. It is not like other EQ6-Rs. And I just recieved it back from the mount mechanics after some repairs were done under warranty, and now it is performs even worse than before. The store where I bought it from no longer replies to my email. My frustration knows no bounds.

 

I hadn't really though about how the weight actually is distributed on an RC telescope set up for imaging. That is  a good point.

 

I agree, the EQ6-r can definitely handle an 8" Newtonian. But unlike a small refractor, it will need precise balance, and relatively low wind speed, or shelter from wind in an obsy. An 8" newt is like a giant sail compared to, for example, a small to medium sized refractor.

Moment arm, aerodynamics, balance. They all have a hand to play too, not just weight and focal length.

My hope is that the relatively short tube of the 8 inch quattro, only 72 cm, still is small enough not to catch every single autumn breeze. And that even my EQ6-R will be able to handle it reasonably well.

[Oort Cloud]

Well, if it works for you it works for you I guess.

Yes, sure, an EQ6-R should be able to handle that, but I was specifically talking about my EQ6-R. It is not like other EQ6-Rs. And I just recieved it back from the mount mechanics after some repairs were done under warranty, and now it is performs even worse than before. The store where I bought it from no longer replies to my email. My frustration knows no bounds.

I hadn't really though about how the weight actually is distributed on an RC telescope set up for imaging. That is a good point.

My hope is that the relatively short tube of the 8 inch quattro, only 72 cm, still is small enough not to catch every single autumn breeze. And that even my EQ6-R will be able to handle it reasonably well.

I can definitely see the effects of even small gusts on my C8 with dew shield, which is roughly equivalent dimensions to an 8" quattro. And my scope is flanked by 2 enormous hedges, and a house on the 3rd side, so it is already pretty well sheltered. The 65PHQ on the other hand, can image in 20mph winds and it's no different than 0mph. The diameter makes a huge difference, probably moreso than the length.

[Spaceman 56]

 EQ6-R.

 

I just recieved it back from the mount mechanics after some repairs were done under warranty, and now it is performs even worse than before.

 

 

well thats a seperate issue and a seperate problem.

 

you need to get it working good with a small refractor, and when its working good consider larger OTAs.

 

putting a large OTA before the mounts working well is not going to work.

 

what is the Mount Problem ?

 

Do you have Guiding Logs ?