Sky-Watcher Evostar 72ED DS-Pro much better than my DSLR lenses?

[MKHACHFE]

Hi all, basically, contemplating buying a Sky-Watcher Evostar 72ED DS-Pro to use with my canon DSLR and star adventurer 2i and was wondering if the images will be that much better than my current crop of lenses, which include a 70-300mm f5.6 canon, a few 50mm f2.8 nikor and a few others.

I get pretty bad chromatic aberration on all of them, but other than that, I've been very satisfied with what I've achieved with them (see below).

Would this scope be a good next step? I'm not really interested in perfection and elongated stars on the edges of my images are not a concern for me at this stage. I just want a noticeable increase in quality. 

Or would a good coma corrector give me the same result as the scope would.?

My budget is no more than 400 quid. Absolutely not a penny more, and preferably less.

I've read that it's easier to focus the scope, which isn't hard as the difference on the 70-300mm between in focus and bokeh is a movement so slight, I can barely feel I'm doing it. 

 

Thanks for your help

[Elp]

I don't have the 72 Evo, but I do have a WO Z61. The images you've produced so far are excellent, I think the difference with a scope is that you'll have more focal length so what you've imaged thus far will be slightly more magnified and you'll get better focus across the whole field of view with the use of a field flattener. The 72 is supposed to be a good scope though personally I'd try to stretch to an 80mm apochromatic.

Another option is a 5-6 inch Newtonian though it's a big size difference but I found they are much brighter due to the increase in aperture. You will need a coma corrector for it though which adds to the cost.

[ONIKKINEN]

Take a look at astrobin to see what others have done with the scope: https://www.astrobin.com/groups/162/skywatcher-evostar-72ed/

Some have fat stars, some dont. Some have purple halos, some dont. Its hard to say from just looking at pictures posted by others because processing is key anyway, but i would say its going to be an improvement. If for nothing else, the focal length and the ease of using an actual telescope with a focuser instead of fiddling with a lens.

[vlaiv]

Scope will be diffraction limited while camera lens are not.

This simply means that it is possible to get far sharper images of some targets with telescope than it is with lens.

Telescope will gather more light as well - which can be translated into "speed" - but will have narrower field of view than all of your lens. Even with reducer 72ED will have 360mm of FL - while your "longest" lens has 300mm of FL.

This means that all errors in focusing / guiding and so on will be more visible with telescope.

Will you be able to exploit the sharpness of the telescope - depends on your whole setup. If your mount does not track particularly well, or you don't pay attention to focusing very precisely - then you won't have very sharp image.

Just to give you idea of sharpness difference:

This is your M31 taken with lens:

That is as good as good lens goes - I have similar image taken with Samyang 85mm wide open (stopping it down will probably fix some of issues):

But here is what 380mm FL scope (80mm F/6 scope with reducer) can produce:

In fact - it will go much more in detail and remain sharp - above is just scaled to match size of lens made images:

[alacant]

On 19/11/2021 at 12:32, MKHACHFE said:

Absolutely not a penny more

You may just be able to get the 72 with the not-really-optional corrector. If the latter puts you over budget, perhaps stick with the lenses.

To avoid fat, coloured stars with cheap refractors and camera lenses, don't use a focusing mask.

Cheers and HTH

Edited November 22, 2021 by alacant
Gramática

[MKHACHFE]

13 hours ago, Elp said:

I don't have the 72 Evo, but I do have a WO Z61. The images you've produced so far are excellent, I think the difference with a scope is that you'll have more focal length so what you've imaged thus far will be slightly more magnified and you'll get better focus across the whole field of view with the use of a field flattener. The 72 is supposed to be a good scope though personally I'd try to stretch to an 80mm apochromatic.

Another option is a 5-6 inch Newtonian though it's a big size difference but I found they are much brighter due to the increase in aperture. You will need a coma corrector for it though which adds to the cost.

Thanks for the compliment. When i started AP, i really didn't expect to get images like this, i've found it so incredibly rewarding,  and hard work! 

Your comment about the focal length is pretty much the main reason for buying it, id like to tackle smaller targets and get a bit more detail. Regarding the Newtonian, im not sure that my SA 2i would cope with the weight. Its got a 5kg limit, so lets assume 4kg, that's 3 for the 2 and 1 and a bit for the DSLR and guide cam. I think im already pushing it as it is. 

[MKHACHFE]

12 hours ago, alacant said:

You may just be able to get the 72 and corrector. If the latter puts you over budget, I'd stick with your lenses.

To avoid fat, coloured stars with cheap refractors and camera lenses, just don't use a mask.

Cheers and HTH

Actually a member has messaged me and has the 2 and flatenner possibly for sale within my budget. So, fingers crossed he decides to sell.

 

Thanks for your reply

[MKHACHFE]

12 hours ago, vlaiv said:

Scope will be diffraction limited while camera lens are not.

This simply means that it is possible to get far sharper images of some targets with telescope than it is with lens.

Telescope will gather more light as well - which can be translated into "speed" - but will have narrower field of view than all of your lens. Even with reducer 72ED will have 360mm of FL - while your "longest" lens has 300mm of FL.

This means that all errors in focusing / guiding and so on will be more visible with telescope.

Will you be able to exploit the sharpness of the telescope - depends on your whole setup. If your mount does not track particularly well, or you don't pay attention to focusing very precisely - then you won't have very sharp image.

Just to give you idea of sharpness difference:

This is your M31 taken with lens:

That is as good as good lens goes - I have similar image taken with Samyang 85mm wide open (stopping it down will probably fix some of issues):

But here is what 380mm FL scope (80mm F/6 scope with reducer) can produce:

In fact - it will go much more in detail and remain sharp - above is just scaled to match size of lens made images:

I see what yo mean entirely, although i really wish you hadn't highlighted my rubbish noise reduction and pixelated image to everyone! Come on dude... Just kidding. Yours is exactly the reply i was hoping to get. It seems that it would be a good next step for me, as well as more challenging at 420mm FL, as well as being one of the very few scopes my mount can handle in terms of weight, this seems like the right choice for me. 

Thanks for posting your images and thanks to everyone for your advice

[MKHACHFE]

13 hours ago, ONIKKINEN said:

Take a look at astrobin to see what others have done with the scope: https://www.astrobin.com/groups/162/skywatcher-evostar-72ed/

Some have fat stars, some dont. Some have purple halos, some dont. Its hard to say from just looking at pictures posted by others because processing is key anyway, but i would say its going to be an improvement. If for nothing else, the focal length and the ease of using an actual telescope with a focuser instead of fiddling with a lens.

I did look there, but i feel i cant really rely on astrobin as a guide since everyone is at a different level, even with the same equipment and as you say, processing is the clincher.

As far as easier focusing....god, yes please. ANYTHING has to be easier than trying to turn a lens by a hairs width. Its so hard that i sometimes put up with less than perfect focus as i just cant bring myself to struggle with it anymore. 

Its like being on a game show and deciding whether to keep the money or risk it all. Yes, i could get better focus and win, but i can also (more likely) lose it and have to start again. No thanks! 😂

[Clarkey]

@MKHACHFE There is an ED80 and flattener of Astro Buy and Sell at the moment for £350. I says collection only but you might be able to negotiate arranging you own courier. It is a bit bigger, but a good deal.

U.K. Astronomy Buy & Sell (astrobuysell.com)

In fact having had a closer look there are some other options such as an ED66 and some other ED scopes within your budget.

Edited November 20, 2021 by Clarkey

[vlaiv]

5 minutes ago, Clarkey said:

@MKHACHFE There is an ED80 and flattener of Astro Buy and Sell at the moment for £350. I says collection only but you might be able to negotiate arranging you own courier. It is a bit bigger, but a good deal.

U.K. Astronomy Buy & Sell (astrobuysell.com)

I think that is too much scope for SA.

[900SL]

On 20/11/2021 at 05:04, MKHACHFE said:

Thanks for the compliment. When i started AP, i really didn't expect to get images like this, i've found it so incredibly rewarding,  and hard work! 

Your comment about the focal length is pretty much the main reason for buying it, id like to tackle smaller targets and get a bit more detail. Regarding the Newtonian, im not sure that my SA 2i would cope with the weight. Its got a 5kg limit, so lets assume 4kg, that's 3 for the 2 and 1 and a bit for the DSLR and guide cam. I think im already pushing it as it is. 

I think you will be pushing the capability of the SWSA2i for a bunch of reasons. Aperture will require longer exposures, focal length requires better tracking and guiding, weight of image train, sensitivity to wind and vibration, etc

I had a SWSA2i, usable limit was 200mm on a crop sensor

 

 

 

[MKHACHFE]

27 minutes ago, 900SL said:

I think you will be pushing the capability of the SWSA2i for a bunch of reasons. Aperture will require longer exposures, focal length requires better tracking and guiding, weight of image train, sensitivity to wind and vibration, etc

I had a SWSA2i, usable limit was 200mm on a crop sensor

 

 

 

I understand what you are saying, but im finding my 300mm absoluely fine to use on my SA2i. As i said, im not that interested in perfection at this stage...if i can get a nice image , im happy to put up with elongated stars at the edges or chromatic aberration. 

I am a little concerned about the 400mm FL, 300mm is hard enough, but hey, you got to challenge yourself. I think my polar aligning is pretty decent and i have an autoguiding cam and scope, so while it may be tricky, i think ill be fine at 400mm.

As for he weight...well yes, thats an issue, fingers crossed

Im not sure i understand why i would need longer exposures. Its an f/5.8, only slightly slower than my 0-300mm f/5.6.

Thanks for your advice mate. Very much appreciated

[900SL]

Be sure to post your results 

I use a GT71 with reducer on a Fornax LT2 (330mm on a cropped sensor). It's on the limit but doable when counterbalanced, no wind, accurate polar alignment.

It's on a rock solid tripod, no slack or movement in the set up, and the LT2 tracks better than 2 arc sec PE. I'd never try it with my old SWSA but you might be lucky

Example image here 

https://stargazerslounge.com/topic/385555-sgl-2021-challenge-8-all-about-orion/?do=findComment&comment=4165162

 

Edited November 21, 2021 by 900SL

[Whistlin Bob]

Good luck if you do go ahead with it.

I do have both a 72ed and a Star Adventurer and the comments above are more or less reflective of my experiences with it.

I do a bit of mucking round with vintage lenses- the 72 blows them out of the water for optical quality, probably for the reasons @vlaiv says. However- it isn't perfect optically. When I use it with a mono camera the focus and sharpness in blue is significantly poorer than green and red, and this can lead to a blue bloaty appearance in stars. There lots you can do in processing to mitigate this, so for me it's not a deal breaker, but there's a reason truly apo diffraction limited optics cost quite a bit more than the 72!

The other question about whether your mount can handle it- it's pretty marginal, but it can. I mainly use mine on an HEQ5,  but I've tried it on the Star Adventurer as well using an Altair 183c. The read noise is very low on these cameras, so you can stay with short subs and get away without guiding- doing 30 seconds gets me good results. I think there's still a bit of risk for you as the DSLR will be heavier, but hopefully you'll get away with it.

And if you ever decide to upgrade your mount and camera, you'll find that the 72 rocks at narrowband!!!

[Whistlin Bob]

....oh, and as for trying a small newt instead, I can confirm that the Star Adventurer definitely can't cope with a 130pds. Tried that too. It's not just the weight, it's the size and shape. Shame, because optically the 130 is fantastic.

[MKHACHFE]

21 hours ago, Whistlin Bob said:

....oh, and as for trying a small newt instead, I can confirm that the Star Adventurer definitely can't cope with a 130pds. Tried that too. It's not just the weight, it's the size and shape. Shame, because optically the 130 is fantastic.

Thanks for your reply. I definitely am taking on board all the cautionary advice being given here.

I am a little daunted by moving to 400mm and the extra precision that will require, but I figure since I'm pretty relaxed about not achieving perfect images, it should be fine. I got to grips with the 300mm very quickly. In fact, the bigger worry is targeting, as it already takes me ages to centre with the 300mm.

I really just would like something that will allow me to image smaller objects. 

I did look at the 130, looks awesome for AP, but yes, won't work with the SA2i sadly.

 

Thanks everyone.

[MKHACHFE]

23 hours ago, 900SL said:

Be sure to post your results 

I use a GT71 with reducer on a Fornax LT2 (330mm on a cropped sensor). It's on the limit but doable when counterbalanced, no wind, accurate polar alignment.

It's on a rock solid tripod, no slack or movement in the set up, and the LT2 tracks better than 2 arc sec PE. I'd never try it with my old SWSA but you might be lucky

Example image here 

https://stargazerslounge.com/topic/385555-sgl-2021-challenge-8-all-about-orion/?do=findComment&comment=4165162

 

I've so far surpassed what I ever thought I would achieve with my kit that I'm willing to take the leap and risk on the 72 with my mount.

 

Lovely image by the way. Incredible detail.

[Whistlin Bob]

23 hours ago, MKHACHFE said:

I am a little daunted by moving to 400mm and the extra precision that will require

Yeah, I've found that tricky too. The solution for me was to take a leaf out of the visual observers book and put an rdf plus the finder on the 72, whilst aiming it, and then take them off to reduce weight once I'd got the framing right.