First scope advice – Evostar 102 v 120?

[Mr Thingy]

On 15/02/2021 at 19:57, Basementboy said:

How important is the focuser? I'm not quite sure how much to pay attention to this factor

A focuser with dual speed/fine focus is nice to have and eliminates some of the challenge finding the perfect focus, but it's not the be-all and end-all. My grab and go scope has a basic focuser and works fine. Not as nice as my scopes with dual speed focusers but not an encumbrance really.

I'd be tempted to spend that money on the scope itself or the mount and upgrade later if you find yourself wanting to. There are always DIY options to improve fine focusing anyway, like increasing the focus wheel diameter.

[Ricochet]

4 hours ago, Basementboy said:

I suppose the question is whether the Startravel 120 is much worse on planets than the Evostar 102?

Yes, it will be. Fast achromats are not planetary scopes due to the amount of chromatic aberration they exhibit. 

[Stu1smartcookie]

As , Ricochet mentioned ... the longer the focal length the less CA you will see ... FLO sell an 80mm refractor by Scoptech that is F15 !!! apparently suffers from barely any CA. 

Long refractors were very traditional , but ED Glass has become "the thing " and shorter refractors awith ED glass are more common , especially for astro photography Very expensive though . But , there is no better sight in my opinion  than a long refractor sitting on an AZ or a EQ mount.  The thing is , you may be winding yourself up here ... and i do understand it , honestly ( cos its happened to me ) . You are , quite rightly doing your homework and searching for the best beginner scope , but you could still be searching this time next year ! If you want to look at planets and the moon , a Mak or SCT are great ( but do take longer to cool down , whereas a refractor will be a "mount and Go option ... short tube refractors are great but will suffer more from CA ... whether thats an issue for you is something only you can answer, a Dob isnt very portable ( for walking with )  , so thats out of the equation . So that leaves a small (ish ) reflector or a refractor on a portable mount . The choice is yours of course . I think portability is key for you . Its often said that aperture is king ... thats a fair point but not if it comes at the expense of not being able to lug the scope to a site to observe . A four inch refractor is a great start ... and for some people thats all they need . 

Sorry for the sermon ... once i get going etc etc .  

 

[Tiny Clanger]

10 minutes ago, Stu1smartcookie said:

As , Ricochet mentioned ... the longer the focal length the less CA you will see ... FLO sell an 80mm refractor by Scoptech that is F15 !!! apparently suffers from barely any CA. 

Long refractors were very traditional , but ED Glass has become "the thing " and shorter refractors awith ED glass are more common , especially for astro photography Very expensive though . But , there is no better sight in my opinion  than a long refractor sitting on an AZ or a EQ mount.  The thing is , you may be winding yourself up here ... and i do understand it , honestly ( cos its happened to me ) . You are , quite rightly doing your homework and searching for the best beginner scope , but you could still be searching this time next year ! If you want to look at planets and the moon , a Mak or SCT are great ( but do take longer to cool down , whereas a refractor will be a "mount and Go option ... short tube refractors are great but will suffer more from CA ... whether thats an issue for you is something only you can answer, a Dob isnt very portable ( for walking with )  , so thats out of the equation . So that leaves a small (ish ) reflector or a refractor on a portable mount . The choice is yours of course . I think portability is key for you . Its often said that aperture is king ... thats a fair point but not if it comes at the expense of not being able to lug the scope to a site to observe . A four inch refractor is a great start ... and for some people thats all they need . 

Sorry for the sermon ... once i get going etc etc .  

 

That's not a sermon by my standards, that's a precis ! 🙂  

There just is no easy answer to the 'one best scope' question as far as I can see,  price constraints and physical size/portability limitations mean major compromises have to be made. The question is , where do you make those compromises when you are a beginner with no idea of what will catch your interest once you get further into observing, and need kit that is good for that specific purpose . Or for that matter how far into observing you will get, or if it will be a passing phase, and the 'scope will sit in the corner being an ornament and wasted money. It's easy to concentrate on the kit and lose sight of the fact it is nothing more than a tool .

As with cameras, and hi fi and camping gear, I'm only interested enough in the intricacies of the kit to try to make sensible, cost effective, informed decisions for myself about purchases . I want to use these things as tools to facilitate activities I enjoy , I don't want to fall into the trap of thinking the tool is the activity, something it is all too easy to do in this kind of forum where one can just get carried along . 

Heather

[Basementboy]

Yep – this is exactly what I'm starting to realise. There's no perfect all-rounder starter scope.

And until I actually get out there, I'm not going to know WHAT I really want to do!

All I DO know for certain is that it needs to be:

-portable (ideally in a backpack, for visual security while walking through dark London parks at 2am)

-easy to set up and use, with no collimation or fussing about in the dark

-Forgiving enough FOV that I can actually find things while I'm just getting started.

I think that rules out the Evostar 102, because it's just too long; reflectors because of collimation issues; and probably the Mak for now, until I'm more comfortable finding things in the sky.

SO!

I'm thinking to start with a decent widefield scope like a Startravel 80 or 102, to get my bearings in the sky, with an AZ mount – maybe the AZ5, or even a smaller Pronto?

And then soonish buy a second scope – probably a Mak 127, also extremely small – for better views of planets. 

...... and if all of that sounds insane to plan for two scopes before I even have one, well – I blame it all on the advice I'm getting here.

(Just kidding. You guys have been amazing.)

 

[vlaiv]

13 minutes ago, Basementboy said:

And then soonish buy a second scope – probably a Mak 127, also extremely small – for better views of planets. 

...... and if all of that sounds insane to plan for two scopes before I even have one, well – I blame it all on the advice I'm getting here.

(Just kidding. You guys have been amazing.)

Well, there is scope that is half way between the two. It will provide you with planetary views similar to that Mak 127 and is "short" enough to provide you with wide fields.

It is also more expensive - but when you factor in the price of two scopes - it's actually not that much more expensive.

Get yourself 4" F/7 ED doublet.

https://www.altairastro.com/starwave-ascent-102ed-f7-refractor-telescope-geared-focuser-468-p.asp

That one will have a just a tiny bit of chromatic aberration. If you want to get rid of that too - get a bit more expensive version:

https://www.altairastro.com/starwave-102ed-r-fpl53-refractor-459-p.asp

[Basementboy]

1 minute ago, vlaiv said:

Well, there is scope that is half way between the two. It will provide you with planetary views similar to that Mak 127 and is "short" enough to provide you with wide fields.

 

I actually wouldn't mind – it seems like a great scope – except that it says it's 100cm long?

Which is basically the same as the Evostar 102

Unless that's a misprint?

[vlaiv]

4 minutes ago, Basementboy said:

I actually wouldn't mind – it seems like a great scope – except that it says it's 100cm long?

Which is basically the same as the Evostar 102

Unless that's a misprint?

Yes that is probably misprint or some other type of error. It is F/7 scope and has 714mm of focal length. It has retractable dew shield so it's even shorter for transport.

According to TS website (same scope branded differently) is 73cm in length:

https://www.teleskop-express.de/shop/product_info.php/info/p4964_TS-Optics-ED-102-mm-f-7-Refractor-Telescope-with-2-5--R-P-focuser.html

On Altair Astro website - more expensive version (same scope just different glass elements) ED-R version is quoted to be:

Quote

Weight approx. 4kg, OTA length with dewshield retracted, 68cm.

less than 70cm long when dewshield is retracted.

ST102 is both lighter and is probably going to be shorter at least 10cm - but if you want to observe both types of targets - one scope is easier to carry and mount.

[KP82]

13 minutes ago, Basementboy said:

I actually wouldn't mind – it seems like a great scope – except that it says it's 100cm long?

Which is basically the same as the Evostar 102

Unless that's a misprint?

That has to be a typo.

Most 4" f/7 ED doublets on the market are no longer than 60 - 70cm with the dew shield retracted. They also weigh about only 4kg.

If you've already been planning for two scopes, I'd assume you've got the budget for the ED doublet. It will give you the best of both worlds (short-tube refractor and small Mak).

Edited February 17, 2021 by KP82

[Basementboy]

Ah

2 minutes ago, vlaiv said:

ST102 is both lighter and is probably going to be shorter at least 10cm - but if you want to observe both types of targets - one scope is easier to carry and mount.

Ah! Yes, of course I'd prefer one – that's great advice.

 

1 minute ago, KP82 said:

If you've already been planning for two scopes, I'd assume you've got the budget for the ED doublet. It will give you the best of both world (short-tube refractor and small Mak).

It's definitely a bit outside my budget – which was £500 to get started – but this whole thread began when FLO kicked up the price of the Evostar 120 I was eyeing to £679 and I began to wonder what else I could get for that price that was better ...

... which sent me down the rabbit hole of getting good advice from human beings, rather than from shops – which has helped immeasurably.

Of course the ED Doublet is £500 before any extras at all – and I gather I'd need a few, no?  Plus the cost of a mount (AZ5?) Starting to get up there...

 

 

[Basementboy]

Though it definitely says Optical Tube Length: 100cm / I metre

Maybe I'll contact Altair and get them to clarify

[KP82]

4 minutes ago, Basementboy said:

Though it definitely says Optical Tube Length: 100cm / I metre

Maybe I'll contact Altair and get them to clarify

For a standard refractor, the physical length of the OTA has to be shorter than its focal length. Usually at least 100 - 135mm shorter to accomodate a star diagonal, but often much more (180mm - 220mm) on premium models to allow bino-view.

If you go with an Altair or TS Optics ED doublet, you will also need to price in a star diagonal, a finder and a couple of eyepieces as the scope itself is sold OTA + tube ring + dovetail bar only. As you said you would also need a mount. These extras + the mount will probably add about another £400 to the total cost.

[vlaiv]

4 minutes ago, Basementboy said:

It's definitely a bit outside my budget – which was £500 to get started

Ok, I get that. I did not pay attention to budget limit.

I guess some creative thinking is in order then. Here is another idea.

ST120 for example. Most people will say that it will fare poorly on planets and they are right. However - what they often forget is that you can have ST120 - with 120mm of aperture on deep sky and say 3" F/7.9 scope for planets in the same scope? That is very close to Sidgwick standard. In fact - it has the same color correction of say 102mm F/10 (or even a bit better).

All you need to do is make 76mm aperture mask and use it when observing planets and moon with higher powers.

 

 

[Basementboy]

11 minutes ago, KP82 said:

For a standard refractor, the physical length of the OTA has to be shorter than its focal length. Usually at least 100 - 135mm shorter to accomodate a star diagonal, but often much more (180mm - 220mm) on premium models to allow bino-view.

If you go with an Altair or TS Optics ED doublet, you will also need to price in a star diagonal, a finder and a couple of eyepieces as the scope itself is sold OTA + tube ring + dovetail bar only. As you said you would also need a mount. These extras + the mount will probably add about another £400 to the total cost.

Gulp. I'd do it if I was 100% sure I'd love it and it was the right scope. (My life costs in the pandemic have basically dropped to zero.) As a beginner, though, I feel I'm in just a few steps past my depth spending £900 on something I haven't even touched, let alone looked through ... Hmmm

[Basementboy]

12 minutes ago, vlaiv said:

Ok, I get that. I did not pay attention to budget limit.

I guess some creative thinking is in order then. Here is another idea.

ST120 for example. Most people will say that it will fare poorly on planets and they are right. However - what they often forget is that you can have ST120 - with 120mm of aperture on deep sky and say 3" F/7.9 scope for planets in the same scope? That is very close to Sidgwick standard. In fact - it has the same color correction of say 102mm F/10 (or even a bit better).

All you need to do is make 76mm aperture mask and use it when observing planets and moon with higher powers.

 

 

OK – so I have to admit here that I don't understand what you mean. Are you saying by putting some kind of mask over the front of the aperture, it reduces the amount of light – which makes the viewing better on planets? (I'm guessing you mean it reduces the CA that people have said makes the 120 a poor planetary viewer)

If that's right – how does one make a mask? 

[ScouseSpaceCadet]

SGL's very own @Lockie may help you decide. His Youtube channel is a terrific resource for beginners.

D.I.Y. Astro

Just One Telescope for Everything!

 

[KP82]

4 hours ago, Basementboy said:

Gulp. I'd do it if I was 100% sure I'd love it and it was the right scope. (My life costs in the pandemic have basically dropped to zero.) As a beginner, though, I feel I'm in just a few steps past my depth spending £900 on something I haven't even touched, let alone looked through ... Hmmm

I kind of agree. I'd also be skeptical about spending nearly a grand on something I have zero experience with at all. My first scope was a cheap Tasco 60mm gifted to me by my aunt.

On the other at hand the portable aperture size we're talking about at the moment (5" or less), nothing beats an apo refractor for views.

Edited February 17, 2021 by KP82

[vlaiv]

13 minutes ago, Basementboy said:

OK – so I have to admit here that I don't understand what you mean. Are you saying by putting some kind of mask over the front of the aperture, it reduces the amount of light – which makes the viewing better on planets? (I'm guessing you mean it reduces the CA that people have said makes the 120 a poor planetary viewer)

If that's right – how does one make a mask? 

Indeed - it is about masking front end of the scope. Outer parts of the lens bend the light much more than inner part of the lens - they have to so that light reach the same point in focal plane. Chromatic aberration is due to the fact that not all wavelengths of light are equally bent - and more you bend the light - more this difference shows.

By masking outer parts of the lens - you remove "worst" part of it in terms of chromatic aberration.

Down side of it is that you are both reducing light gathering of telescope - very bad idea for DSO observing and you are reducing planetary resolution. Good thing is - it costs you almost nothing, it is not permanent modification (if we can call it modification at all) and you can put it on and remove it faster than you change eyepiece.

With fast achromats - resolution loss due to CA is actually much worse then loosing resolution by using smaller aperture and you can try out few different sizes of aperture mask to find your sweet spot - most CA reduced with the least planetary detail lost.

You can make mask out of anything - even cardboard. Preferred way is to make plastic mask. You only need to cut smaller hole in central region and find some way to attach the mask. Refractors have dew shield - and that is perfect for "plug" type aperture masks.

For example, here is PVC 4" pipe plug that I adapted to be aperture mask on ST102 that I used to own:

But people do make it out of cardboard like this:

Or plastic lids like this one:

If you have access to 3D printer - it is very easy to print one to size.

I wanted to point out with regards to original topic - Evostar 120 will provide you with equal planetary performance to Evostar 102 - regardless of the fact that it is faster achromat - both have same focal length and all you need to do is make 102mm aperture mask to go on 120 to get the same performance.

It also shows that Evostar 150 can be very potent instrument. It will provide you with 6" of unobstructed aperture, same FOV as 8" F/6 scope and excellent 4" F/12 planetary performer - for the price of one scope (which really needs monster mount to hold it - but that is another topic )

 

[Roy Challen]

1 hour ago, vlaiv said:

 

 

 

Unusual focuser arrangement. Is that yours @vlaiv?

[vlaiv]

6 minutes ago, Roy Challen said:

Unusual focuser arrangement. Is that yours @vlaiv?

No, just an image I found online - it shows nicely lid type aperture mask. In fact, I think there is a blog dedicated to making and using mask - maybe it has make of scope and details.

https://10minuteastronomy.wordpress.com/2017/02/11/why-and-how-to-make-a-sub-aperture-mask-for-a-refractor/

Yep, it seems to be Bresser Messier AR102S Comet Edition. Not sure if it is available any more.

[Basementboy]

2 hours ago, KP82 said:

On the other hand at the portable aperture size we're talking about at the moment (5" or less), nothing beats an apo refractor for views.

Well hey – that's the goal! (For me. Not much of a photographer yet. I just want to blow my own mind in a healthy way)

 

2 hours ago, vlaiv said:

By masking outer parts of the lens - you remove "worst" part of it in terms of chromatic aberration.

 

Ah, I see – quite clever. Worth considering! Though I'm terrible at making anything.

 

2 hours ago, ScouseSpaceCadet said:

SGL's very own @Lockie may help you decide. His Youtube channel is a terrific resource for beginners.

I watched the 17 minute video – really great. And what a surprise, he opts for a f7 ed 4" refractor lol. Argh, maybe I will need to save up ........ It does seem like pretty much the perfect option for me.

..... for now though, I'm taking Tiny Clanger's advice and heading out with a pair of binoculars and a little star guide to find my way around. It's not like I can actually buy any of these things new anyway right now, not until the ships reach the distant shores of Albion. 🚢

 

[ScouseSpaceCadet]

41 minutes ago, Basementboy said:

Well hey – that's the goal! (For me. Not much of a photographer yet. I just want to blow my own mind in a healthy way)

 

Ah, I see – quite clever. Worth considering! Though I'm terrible at making anything.

 

I watched the 17 minute video – really great. And what a surprise, he opts for a f7 ed 4" refractor lol. Argh, maybe I will need to save up ........ It does seem like pretty much the perfect option for me.

..... for now though, I'm taking Tiny Clanger's advice and heading out with a pair of binoculars and a little star guide to find my way around. It's not like I can actually buy any of these things new anyway right now, not until the ships reach the distant shores of Albion. 🚢

 

Binoculars are a good starting point. I wish I'd bought mine first & saved up rather than hopping around telescopes until I settled.

If post lock down you can get out to somewhere rural, the binocular view will blow you away I'm sure.

 

[KP82]

1 hour ago, Basementboy said:

Well hey – that's the goal! (For me. Not much of a photographer yet. I just want to blow my own mind in a healthy way)

 

Ah, I see – quite clever. Worth considering! Though I'm terrible at making anything.

 

I watched the 17 minute video – really great. And what a surprise, he opts for a f7 ed 4" refractor lol. Argh, maybe I will need to save up ........ It does seem like pretty much the perfect option for me.

..... for now though, I'm taking Tiny Clanger's advice and heading out with a pair of binoculars and a little star guide to find my way around. It's not like I can actually buy any of these things new anyway right now, not until the ships reach the distant shores of Albion. 🚢

 

Binoculars are a good way to start especially if you're worried about equipment safety in some public parks in London.

Some of these 4" f/7 ED doublets are actually in stock unlike many Skywatcher & Celestron stuffs which are still months away from reaching the shore of UK. But since you also need a mount, you won't be able to get the full kit in a couple of months.

Edited February 17, 2021 by KP82

[ecuador]

I will agree with some users above, that given your requirements the solution is definitely a little ED doublet. I would say not even a 4", I'd go with an 80mm (e.g. Evostar 80ED), which is very portable and surprisingly capable. For example, I had 2 of my scopes set up side by side one night, the Evostar 80ED and the Celestron 127 Mak, aimed at Jupiter and not a single one of the dozen or so people there thought the Mak was better. A trained observer would be able to get some extra faint details, but the much more colour and contrast of the ED make the visual experience easily superior - the Mak is quite "flat" in comparison, although it is definitely the best planetary performer for imaging. You can get an idea of what I am talking about here.
As for the discussion about the ST120 and aperture masks etc, CA is above all a matter of preference, as it is a very "special" kind of artefact, so some users would actually prefer the unobstructed 120mm view, others might not. The 80ED or similar offers better views, it is just a matter of price, which is why I'd try to get one second hand (here, astrobuysell UK, FB etc).

[ecuador]

Oh my! I just checked online prices and the Evostar 80ED is £480 new now! I am sure it was just under £350 when I got it... Well, of course back then I could also buy almost $2 with a pound sterling... 😪