Next scope question

[Bikingbill]

My main interest is astrophotography but I'm relatively new to it. I bought a Horizon 60ed (360mm FL) with a tracker mount about 18 months ago. Soon after up-graded to a HEQ5 mount with DSLR. The last thing a bought was a ZWO asi533mc camera. Now that I'm completely hooked I'm eyeing up a better scope. 

My question is, will I notice a substantial improvement in the quality/ resolution of my images with a new scope? I'm looking at a 90mm triplet such as the StellaMira 90mm ED Triplet or the William Optics Fluorostar FLT 91, basically the biggest, fastest scope my mount will cope with. Am I on the right lines? 

 

Edited September 4, 2022 by Bikingbill

[dan_adi]

10 hours ago, Bikingbill said:

My main interest is astrophotography but I'm relatively new to it. I bought a Horizon 60ed (360mm FL) with a tracker mount about 18 months ago. Soon after up-graded to a HEQ5 mount with DSLR. The last thing a bought was a ZWO asi533mc camera. Now that I'm completely hooked I'm eyeing up a better scope. 

My question is, will I notice a substantial improvement in the quality/ resolution of my images with a new scope? I'm looking at a 90mm triplet such as the StellaMira 90mm ED Triplet or the William Optics Fluorostar FLT 91, basically the biggest, fastest scope my mount will cope with. Am I on the right lines? 

 

With small increase in aperture the difference will not be so big. So get the biggest scope your mount could properly handle, but from 60 mm to 90 mm there won't be an earthshatering improvement.

[Dan_Paris]

If you're looking for big and fast, a 150/750 Newtonian is a perfect match for an HEQ5 mount. Its focal length (more than twice that you have) would open the door for many objects that are too small for your current refractor, in particular galaxies, while keeping integration times reasonable with its low f/ratio. Even the most  expensive models, like this one:

https://www.teleskop-express.de/shop/product_info.php/info/p13462_TS-Optics-6--f-5-UNC-Newtonian-Telescope---Carbon-Tube---made-in-Germany.html

are significantly cheaper than the 90mm APOs that you suggested.

Edited September 5, 2022 by Dan_Paris

[wvrfish]

I recently acquired a StellaLyra 8" RC (1600mm focal length) to complement my Horizon 72ED. Very pleased with it so far, and found guiding to work well with a ~230mm guidescope. I thought I might need to switch to OAG but not found it to be necessary.

I should probably mention that my HEQ5 has had the belt mod so that may have helped as the 8" RC is probably at the top tend of the mount capacity.

I must admit I'm now contemplating getting something with a FL of around 8-900mm so I've got all bases covered!

[Bikingbill]

2 hours ago, Dan_Paris said:

If you're looking for big and fast, a 150/750 Newtonian is a perfect match for an HEQ5 mount. Its focal length (more than twice that you have) would open the door for many objects that are too small for your current refractor, in particular galaxies, while keeping integration times reasonable with its low f/ratio. Even the most  expensive models, like this one:

https://www.teleskop-express.de/shop/product_info.php/info/p13462_TS-Optics-6--f-5-UNC-Newtonian-Telescope---Carbon-Tube---made-in-Germany.html

are significantly cheaper than the 90mm APOs that you suggested.

Like the idea of a small Newtonian, looks well suited to my mount. Also, like you say, cheaper! Thanks for all the replies, lots to think about.

[Stu]

24 minutes ago, Bikingbill said:

Like the idea of a small Newtonian, looks well suited to my mount. Also, like you say, cheaper! Thanks for all the replies, lots to think about.

Don’t forget that you will likely need a coma corrector to get sharp stars across the field view, and likely other bits and bobs. I’m not an imager though so others should advise.

[Dan_Paris]

1 hour ago, Stu said:

Don’t forget that you will likely need a coma corrector to get sharp stars across the field view, and likely other bits and bobs. I’m not an imager though so others should advise.

 

You're right, its an important point. This one is good for an f/5 scope and not very expensive :

https://www.firstlightoptics.com/coma-correctors/ts-95x-maxfield-coma-corrector.html

 

 

 

 

 

[ONIKKINEN]

6 minutes ago, Dan_Paris said:

 

You're right, its an important point. This one is good for an f/5 scope and not very expensive :

https://www.firstlightoptics.com/coma-correctors/ts-95x-maxfield-coma-corrector.html

 

 

 

 

 

I had the Maxfield 0.95x with an F/4.4 scope and was not satisfied with it. Does not correct coma up to APS-C and has noticeable field curvature/star shape issues in the corners along with just producing generally soft stars all across the field (including center). Could be better with an F/5 primary, but if given the choice i would not buy this corrector again. The Skywatcher aplanatic or the various GPU correctors would probably be better value for money judging from released spot diagrams found online.

Edited September 5, 2022 by ONIKKINEN

[Bikingbill]

Anyone had experience imaging with this?

https://www.firstlightoptics.com/reflectors/sky-watcher-quattro-150p-f4-newtonian-modified-aplanatic-super-coma-corrector.html

 

[ONIKKINEN]

5 minutes ago, Bikingbill said:

Anyone had experience imaging with this?

https://www.firstlightoptics.com/reflectors/sky-watcher-quattro-150p-f4-newtonian-modified-aplanatic-super-coma-corrector.html

 

Its a new item, not many of them out there. Astrobin search only comes up with a handful of images taken with the thing, but they look good to me.
https://www.astrobin.com/search/?d=i&sort=-likes&q="Sky-Watcher Quattro 150P"
 

The price seems very competitive with the corrector included. Not sure if its a good or a bad thing, but if everything works its very well priced.

[Dan_Paris]

50 minutes ago, ONIKKINEN said:

just producing generally soft stars all across the field (including center). Could be better with an F/5 primary,

This is precisely the issue with this corrector, it introduces a hint of spherical aberration at f/4 (I tried it) but at f/5 it should be fine.  The GPU is good but more expensive, and its length could be an issue if the focal plane is not far enough (which is likely the case for a 150/750).

[Bikingbill]

23 minutes ago, ONIKKINEN said:

Its a new item, not many of them out there. Astrobin search only comes up with a handful of images taken with the thing, but they look good to me.
https://www.astrobin.com/search/?d=i&sort=-likes&q="Sky-Watcher Quattro 150P"
 

The price seems very competitive with the corrector included. Not sure if its a good or a bad thing, but if everything works its very well priced.

I agree, those images look very good. Very tempting...😬

[newbie alert]

Make sure that you like images with diffraction spikes in rather than a frac that doesn't before you part with any hard earned 

[900SL]

Personally I'd go for the 90mm TS CF APO, sharp scope and less bother than a Reflector, no spikes, not a big increase in focal length but better resolution and more than twice the area

[davies07]

14 hours ago, 900SL said:

Personally I'd go for the 90mm TS CF APO, sharp scope and less bother than a Reflector, no spikes, not a big increase in focal length but better resolution and more than twice the area

I agree. Newtonians are good value for money per aperture but need a lot of maintenance, and you will be constantly checking collimation. The secondary mirror obstruction diminishes contrast, and I never liked the diffraction spikes - having used a 200P and a 10" Quattro. A good refractor is a lot less trouble, and you can concentrate on enjoying using it rather than fixing it. 

 

[Dan_Paris]

5 hours ago, davies07 said:

and you will be constantly checking collimation. The secondary mirror obstruction diminishes contrast, and I never liked the diffraction spikes - having used a 200P and a 10" Quattro. A good refractor is a lot less trouble, and you can concentrate on enjoying using it rather than fixing it. 

My  personal experience differs from yours.

It is true that you need to spend a couple of minutes, not more, to check collimation and tweak if needed each time you set up your gear. Nothing else to fix or tweak.

In exchange, you literally save hours compared to a refractor since you collect your data in much less time, to reach a certain SNR ratio.

Adding to that that the newt is significantly cheaper than the refractor, in my opinion collimation does not weigh a lot in the balance.

Of course I compare a common Newtonian astrograph (say 200/800) to a typical refractor of similar focal length (say 120/900).

Regarding spikes it is a question of taste, so a newt is indeed a poor choice for someone that does not like them (some solutions exist though).

Edited September 7, 2022 by Dan_Paris

[CraigT82]

5 hours ago, davies07 said:

A good refractor is a lot less trouble

 

And a lot more money!