Refractor or reflector help.

[Ray Mondo]

Hi,

This is my first post as I’ve just joined. 

I have been interested in the solar system and beyond for many years but I am now thinking of buying a telescope. 

I have been using DSLRs for quite a few years and I know my way around photoshop and lightroom proficiently. 

I have been looking at quite a few telescopes that seem to have good reviews but I’m still stuck on what to do. 

I have around £450 to spend. 

I would like to take photos of the deep sky objects and I don’t mind the work involved as I edit photos quite a lot anyway. 

The only problem I have is that my son loves the moon and the scope I am looking at is a refractor https://www.harrisontelescopes.co.uk/acatalog/skywatcher-startravel-120mm-eq3-2-telescope.html#tab-3

The reviews seem to say that this scope has quite a lot of CA. 

I know how to counter it in photoshop but I want to see a good image through the eyepiece. 

Am I better off with this scope?

https://www.wexphotovideo.com/sky-watcher-explorer-150pds-eq3-2-parabolic-dual-speed-newtonian-reflector-1524187/

I would like to have the best of both but I can’t afford more than £500  

Please can someone help  

Thanks

Ray

 

[Stu]

Welcome to the forum. I'm sure you will get plenty of good advice on here.

One of the problems is that you are trying to cover too much with one scope. The requirements for an imaging scope are different from a visual scope, and deep sky Astrophotography has quite different requirements to solar system imaging.

One suggestion would be to read the book 'Making Every Photon Count' which explains all there is to know about deep sky AP.

[Ray Mondo]

11 minutes ago, Stu said:

Welcome to the forum. I'm sure you will get plenty of good advice on here.

One of the problems is that you are trying to cover too much with one scope. The requirements for an imaging scope are different from a visual scope, and deep sky Astrophotography has quite different requirements to solar system imaging.

One suggestion would be to read the book 'Making Every Photon Count' which explains all there is to know about deep sky AP.

Thanks for the welcome. 

I know I’m mad for trying to do everything with one scope, I’m probably leaning towards the refractor but I don’t want to look at a purple edged moon or any other planet. Do you think the CA will be that bad?

Thanks for the pointer on the book. 

[Owmuchonomy]

To counteract CA in a refractor for DSO imaging is going to quadruple your budget. If you are really strapped and you really want to image then go for the 130P DS. Second hand they are around £100. You will need to spend a lot more on a decent equatorial mount too such as the HEQ5 Pro for DSO work. Sorry but imaging can require deep pockets. Other folks will be along with suggestions.

[pipnina]

Hello and welcome to the forum!

For imaging planets, especially for a beginner, I would wholly recommend a reflecting telescope (at least to start) for a few reasons:

1. Reflecting telescopes do not suffer from chromatic abberation
2. Reflecting telescopes below 12" are fairly cheap by themselves (compared to good quality refractors of the same size) and generally self-sufficient for visual observing and planetary.

Of course if you went up-market you will find areas where refracors will be more suitable than reflectors (I mention that before someone like Olly gets on my case!)

 

One point to note is that even the cheap reflectors (bar a few) will have parabolic mirrors. Why does this matter? Well, the curve of a parabolic mirror is such that any ray of light coming at the mirror in the center of the field of view is focused at exactly the focal point of the mirror (i.e. the center is always "perfectly" focused). This benefit wanes the further from the center you get but since planets use only a small part of the field of view they effectively only use the golden area of these mirrors. Lenses do not have this benefit, and suffer from the additional chromatic aberration unless compensated for (added expense).

The biggest downside to a reflector is that the mirrors must be aligned. The secondary usually once (but only if you suspect there is a problem with it out-of-the-box!) and the primary (i.e. the big one) perhaps every session, though it is far easier to align. This process does not typically cause problems once you understand it.

[Ray Mondo]

6 minutes ago, Owmuchonomy said:

To counteract CA in a refractor for DSO imaging is going to quadruple your budget. If you are really strapped and you really want to image then go for the 130P DS. Second hand they are around £100. You will need to spend a lot more on a decent equatorial mount too such as the HEQ5 Pro for DSO work. Sorry but imaging can require deep pockets. Other folks will be along with suggestions.

Thanks for your reply, I know I’m trying to do too much for my budget. I’m just hoping that the CA from the 120 isn’t bad enough to make the planets look odd. 

[John]

Hi and welcome to the forum.

The ST120 is an F/5 achromatic refractor. They are great for low to medium power deep sky observing but they do show quite a lot of CA around bright objects such as planets and the Moon. This is unavoidable with the F/5 achromat design. They were not designed to be high power instruments. The 150mm newtonian that you also mention in your 1st post will not show any CA and will, in my opinion, be a better all round scope than the 120mm F/5 refractor. The larger aperture will show deep sky objects slightly better and the lack of CA will show the moon and planets crisply.

The one snag with the newtonian is that the eyepiece position might not be that easy for your son to reach.

As has been said, it is really not easy to find a scope design that will do everything well. It's a matter of knowing where each designs compromises lie and seeing how those fit within your priorities.

 

 

 

[Ray Mondo]

31 minutes ago, pipnina said:

Hello and welcome to the forum!

For imaging planets, especially for a beginner, I would wholly recommend a reflecting telescope (at least to start) for a few reasons:

1. Reflecting telescopes do not suffer from chromatic abberation
2. Reflecting telescopes below 12" are fairly cheap by themselves (compared to good quality refractors of the same size) and generally self-sufficient for visual observing and planetary.

Of course if you went up-market you will find areas where refracors will be more suitable than reflectors (I mention that before someone like Olly gets on my case!)

 

One point to note is that even the cheap reflectors (bar a few) will have parabolic mirrors. Why does this matter? Well, the curve of a parabolic mirror is such that any ray of light coming at the mirror in the center of the field of view is focused at exactly the focal point of the mirror (i.e. the center is always "perfectly" focused). This benefit wanes the further from the center you get but since planets use only a small part of the field of view they effectively only use the golden area of these mirrors. Lenses do not have this benefit, and suffer from the additional chromatic aberration unless compensated for (added expense).

The biggest downside to a reflector is that the mirrors must be aligned. The secondary usually once (but only if you suspect there is a problem with it out-of-the-box!) and the primary (i.e. the big one) perhaps every session, though it is far easier to align. This process does not typically cause problems once you understand it.

Thanks for the detailed reply. 

The 150PDS was my first choice until the 120 was mentioned to me. 

I’m an aircraft airframe inspector so I’m not too bothered about technical adjustments (hear the trumpet). 

The 150PDS comes with a recommendation that a coma corrector is needed which will add another £100+ to the bill. 

I’m  also stuck on what eyepieces I will need and what are the good ones vs the throw in the bin type. 

Thanks again

[Ray Mondo]

28 minutes ago, Owmuchonomy said:

To counteract CA in a refractor for DSO imaging is going to quadruple your budget. If you are really strapped and you really want to image then go for the 130P DS. Second hand they are around £100. You will need to spend a lot more on a decent equatorial mount too such as the HEQ5 Pro for DSO work. Sorry but imaging can require deep pockets. Other folks will be along with suggestions.

Thanks for your reply 

[Cosmic Geoff]

9 minutes ago, Ray Mondo said:

Thanks for your reply, I know I’m trying to do too much for my budget. I’m just hoping that the CA from the 120 isn’t bad enough to make the planets look odd.  

The Startravel is not a suitable telescope for looking at planets, With a f5 focal ratio, it is really intended for widefield views of the night sky.

What would be more suitable for looking at planets? Almost anything else - opinions on the best telescope for planetary viewing vary.   I suggest buying a telescope you could also use for deep-space astrophotography.  

The Explorer 150 in your link would make a nice visual scope but AFAIK is not particularly suitable for deep-space astrophotography -  for the latter the telescope probably does not need to be that big and the mount should be heavier.

[Owmuchonomy]

Planets are a bit of an issue right now. The positions of the gas giants are poor for several years, Mars is low in the sky but will put on a good show in October 2020 and the ice giants are just a long long way away. Imaging planets requires serious  focal length and high frame rate planetary cameras or a DSLR with movie crop mode and decent frame rate. In my case I image planets at about 5 metres focal length using a 9.25” SCT design scope.

[Ray Mondo]

8 minutes ago, John said:

Hi and welcome to the forum.

The ST120 is an F/5 achromatic refractor. They are great for low to medium power deep sky observing but they do show quite a lot of CA around bright objects such as planets and the Moon. This is unavoidable with the F/5 achromat design. They were not designed to be high power instruments. The 150mm newtonian that you also mention in your 1st post will not show any CA and will, in my opinion, be a better all round scope than the 120mm F/5 refractor. The larger aperture will show deep sky objects slightly better and the lack of CA will show the moon and planets crisply.

The one snag with the newtonian is that the eyepiece position might not be that easy for your son to reach.

As has been said, it is really not easy to find a scope design that will do everything well. It's a matter of knowing where each designs compromises lie and seeing how those fit within your priorities.

 

 

 

Thanks for the advice, I didn’t think about the height issue with my son. 

I see CA in most images quite easily so i think the 120 is out as it will drive me mad. 

Thanks again

[vlaiv]

Getting AP kit, even if you already own a camera, for £500 is going to be next to impossible.

Sorry, that is just the way it is.

I might offer another approach. Split your cash between two things: AP capable mount (and that in itself will be a stretch) - that you can use to mount your camera with regular lens and just do long exposure wide field ap. (so no scope for that yet). Get a good Moon scope (almost any scope is good for Moon if optics are decent- except mentioned fast achromat refractor) for your son.

I have ST102 - so a bit smaller scope than ST120, but overall same thing. Planets are just not it's thing. You can observe moon, and planets with it if you use aperture mask to help with CA, or filters - and it sort of works, but I bet that decent 50mm refractor would beat it at this task. You can also do AP with such scope, it's not something that I would recommend, but it is doable, I've done it, again using all sorts of trick to get half decent image.

 

[Ray Mondo]

3 minutes ago, Cosmic Geoff said:

The Startravel is not a suitable telescope for looking at planets, With a f5 focal ratio, it is really intended for widefield views of the night sky.

What would be more suitable for looking at planets? Almost anything else - opinions on the best telescope for planetary viewing vary.   I suggest buying a telescope you could also use for deep-space astrophotography.  

The Explorer 150 in your link would make a nice visual scope but AFAIK is not particularly suitable for deep-space astrophotography -  for the latter the telescope probably does not need to be that big and the mount should be heavier.

Thanks for the information, there is a lot of good help coming in. 

[Ray Mondo]

2 minutes ago, vlaiv said:

Getting AP kit, even if you already own a camera, for £500 is going to be next to impossible.

Sorry, that is just the way it is.

I might offer another approach. Split your cash between two things: AP capable mount (and that in itself will be a stretch) - that you can use to mount your camera with regular lens and just do long exposure wide field ap. (so no scope for that yet). Get a good Moon scope (almost any scope is good for Moon if optics are decent- except mentioned fast achromat refractor) for your son.

I have ST102 - so a bit smaller scope than ST120, but overall same thing. Planets are just not it's thing. You can observe moon, and planets with it if you use aperture mask to help with CA, or filters - and it sort of works, but I bet that decent 50mm refractor would beat it at this task. You can also do AP with such scope, it's not something that I would recommend, but it is doable, I've done it, again using all sorts of trick to get half decent image.

 

That’s probably the answer I was hoping for really, I don’t want to wast money on a scope I can’t use for planets. 

I cant believe how many helpful replies I’ve had in a short space of time. 

Thanks

[Owmuchonomy]

May I suggest you take a look at this type of offering. It won’t do DSO long exposure capture but it will fulfill most of your other needs. You could easily do Lunar imaging with this set up.

https://www.firstlightoptics.com/maksutov/skywatcher-skymax-127-synscan-az-goto.html

[vlaiv]

+1 for Maksutov suggestion

Besides going AZ goto, there is another option (stretches budget a bit):

https://www.firstlightoptics.com/skywatcher-mounts/skywatcher-eq3-pro-synscan-goto.html

+

https://www.firstlightoptics.com/maksutov/skywatcher-skymax-102-ota.html

it will be over £500 by about 40 or 50.

This way you will have EQ mount that you can use to do AP with just your camera and some lens that you already own (just need suitable dovetail bar with appropriate camera holder). Or you can put Maksutov on the mount and enjoy the Planets.

This mak is just a tad less "powerful" than one suggested above on AZ mount. If you want one of those, you can get it on EQ mount as a bundle, but it will cost a bit more:

https://www.firstlightoptics.com/maksutov/skywatcher-skymax-127-eq3-2.html

(at £639 when goto mount is selected)

Third option would be to get mentioned Skymax 127 on EQ3-2 manual mount and then fit RA/DEC motors to it - it will be cheaper but you will loose GOTO and not sure how much in terms of quality you will be giving up.

BTW you can attach your DSLR to both of these Maksutovs with suitable T2/Lens mount adapter and take images thru the scope if you like to try it out (prepare for modest results, but it is doable).

[Ray Mondo]

35 minutes ago, Owmuchonomy said:

Planets are a bit of an issue right now. The positions of the gas giants are poor for several years, Mars is low in the sky but will put on a good show in October 2020 and the ice giants are just a long long way away. Imaging planets requires serious  focal length and high frame rate planetary cameras or a DSLR with movie crop mode and decent frame rate. In my case I image planets at about 5 metres focal length using a 9.25” SCT design scope.

Nice information, thanks. 

[Ray Mondo]

27 minutes ago, Owmuchonomy said:

May I suggest you take a look at this type of offering. It won’t do DSO long exposure capture but it will fulfill most of your other needs. You could easily do Lunar imaging with this set up.

https://www.firstlightoptics.com/maksutov/skywatcher-skymax-127-synscan-az-goto.html

This looks like a lot for the money!

Thanks, I will have a good look at it. 

[Ray Mondo]

22 minutes ago, vlaiv said:

+1 for Maksutov suggestion

Besides going AZ goto, there is another option (stretches budget a bit):

https://www.firstlightoptics.com/skywatcher-mounts/skywatcher-eq3-pro-synscan-goto.html

+

https://www.firstlightoptics.com/maksutov/skywatcher-skymax-102-ota.html

it will be over £500 by about 40 or 50.

This way you will have EQ mount that you can use to do AP with just your camera and some lens that you already own (just need suitable dovetail bar with appropriate camera holder). Or you can put Maksutov on the mount and enjoy the Planets.

This mak is just a tad less "powerful" than one suggested above on AZ mount. If you want one of those, you can get it on EQ mount as a bundle, but it will cost a bit more:

https://www.firstlightoptics.com/maksutov/skywatcher-skymax-127-eq3-2.html

(at £639 when goto mount is selected)

Third option would be to get mentioned Skymax 127 on EQ3-2 manual mount and then fit RA/DEC motors to it - it will be cheaper but you will loose GOTO and not sure how much in terms of quality you will be giving up.

BTW you can attach your DSLR to both of these Maksutovs with suitable T2/Lens mount adapter and take images thru the scope if you like to try it out (prepare for modest results, but it is doable).

Thanks for the detailed advice. 

I will certainly do a bit of research on them. 

Thanks

[pipnina]

1 hour ago, Ray Mondo said:

The 150PDS comes with a recommendation that a coma corrector is needed which will add another £100+ to the bill. 

I’m  also stuck on what eyepieces I will need and what are the good ones vs the throw in the bin type.

The coma corrector is a useful piece of kit - if you are taking images of deep-sky (and so wish to use the scope at the maximum possible field of view). It is not so necessary for visual observing or planetary imaging. In fact, it is almost certain that even a very expensive coma corrector would worsen the image quality at the center of the image (where you place planets!) though likely not by a noticeable margin in the vast majority of cases.

I have misplaced (likely deleted) a set of images that would highlight the effect of a coma corrector very nicely (since it is for the 130PDS, which it would have the same effect for as the 150PDS). They would have shown that the center of the field is very sharp, whether coma corrector is present or not. However, the coma corrector improves the quality of the image (most noticeable in the shape of the stars) massively further afield from the center. The net result is still that the stars at the edge are not shaped entirely correctly but far better than without the corrector - however since planetary does not need wide angles, the coma corrector is not necessary.

 

As for eyepieces, the one that comes with the PDS line is OK (certainly not "throw in the bin" quality!), given you can find a suitable thing to protect it from dust (it only comes with a lens cap for one side!). If you wanted to expand the viewing capabilities of the scope you would want to look for anything ranging from a budget plossl, orthographic, to more premium Celestron X-cel, Vixen SLV, or very expensive Pentax or Tele Vue. Which one is right for you? It is hard to say with such choice, especially for one who does not yet know whether they will enjoy the hobby or not long-term.

It may be better to have a telescope, with default eyepiece and a basic alt-az mount, see if you enjoy a few viewing sessions (with the 28mm eyepiece it will be the moon, the easiest doubles and the bright galaxies, clusters and nebulae). Then decide if you wish to invest further.

 

I do ramble a bit, but I hope this helps you somehow

[Z3roCool]

Can I ask what camera lenses you have? I started at the end of last year and ended up using my Canon 400 5.6 lens and buying a decent EQ Mount. Taken some really nice, in my eyes, DSO photos that I am really happy with. Saving up for a scope now and a dedicated camera. If you have anything with some decent focal length maybe worth a go to begin with.

[Ray Mondo]

1 hour ago, pipnina said:

The coma corrector is a useful piece of kit - if you are taking images of deep-sky (and so wish to use the scope at the maximum possible field of view). It is not so necessary for visual observing or planetary imaging. In fact, it is almost certain that even a very expensive coma corrector would worsen the image quality at the center of the image (where you place planets!) though likely not by a noticeable margin in the vast majority of cases.

I have misplaced (likely deleted) a set of images that would highlight the effect of a coma corrector very nicely (since it is for the 130PDS, which it would have the same effect for as the 150PDS). They would have shown that the center of the field is very sharp, whether coma corrector is present or not. However, the coma corrector improves the quality of the image (most noticeable in the shape of the stars) massively further afield from the center. The net result is still that the stars at the edge are not shaped entirely correctly but far better than without the corrector - however since planetary does not need wide angles, the coma corrector is not necessary.

 

As for eyepieces, the one that comes with the PDS line is OK (certainly not "throw in the bin" quality!), given you can find a suitable thing to protect it from dust (it only comes with a lens cap for one side!). If you wanted to expand the viewing capabilities of the scope you would want to look for anything ranging from a budget plossl, orthographic, to more premium Celestron X-cel, Vixen SLV, or very expensive Pentax or Tele Vue. Which one is right for you? It is hard to say with such choice, especially for one who does not yet know whether they will enjoy the hobby or not long-term.

It may be better to have a telescope, with default eyepiece and a basic alt-az mount, see if you enjoy a few viewing sessions (with the 28mm eyepiece it will be the moon, the easiest doubles and the bright galaxies, clusters and nebulae). Then decide if you wish to invest further.

 

I do ramble a bit, but I hope this helps you somehow

Thanks for the help and I totally appreciate your help.

The way Sky-Watcher make it sound is like you need the corrector. 

I know I will enjoy the hobby as I love photography and anything to do with the universe. I just don’t want to waste any money. 

Thanks

[Ray Mondo]

54 minutes ago, Z3roCool said:

Can I ask what camera lenses you have? I started at the end of last year and ended up using my Canon 400 5.6 lens and buying a decent EQ Mount. Taken some really nice, in my eyes, DSO photos that I am really happy with. Saving up for a scope now and a dedicated camera. If you have anything with some decent focal length maybe worth a go to begin with.

I have a Nikon D7000 with a 18-105mm f3.5-5.6 kit lense and a 50mm f1.8 standard. I also use a Sony a6000 with a kit lense but I haven’t got the details to hand. 

Thanks for your reply 

[Stu]

11 hours ago, Ray Mondo said:

Thanks for the welcome. 

I know I’m mad for trying to do everything with one scope, I’m probably leaning towards the refractor but I don’t want to look at a purple edged moon or any other planet. Do you think the CA will be that bad?

Thanks for the pointer on the book. 

An Startravel 120 is a fast achromatic scope so will show a fair amount of CA on the moon and bright objects. It will be ok on deep sky for visual but I suspect it may struggle a bit for imaging

I think if you limited yourself to achieving some but not all of your objectives then you are more likely to have success.

The SkyMax 127mm for instance would allow good visual views on the moon, planets and most of the smaller DSOs. The field of view would be too narrow for some of the larger nebulae and open clusters. It would also allow lunar and planetary imaging, but would struggle on DSOs because of its slow speed and long focal length, needing careful guiding and longer exposures.

One suggestion of the 130PDS reflector is, I think, a good one on you budget. There is a thread on here some showing the imaging results people get with them and they are very capable scopes. Visually they would be pretty handy too, perhaps a little limited on planets but lunar should be fun and DSOs quite doable too.