Plugging the bino-dob gap

[Size9Hex]

I'm looking for advice/experience on the gap in my kit please.

I currently use 10x50 binos and a 10 inch, 1200mm, f4.7 dob (Skywatcher 250px). Intended use for the new scope is primarily wide field visual of big nebulae and clusters, which the dob just punches through, while the binos are a bit inflexible, and don't take filters or handle zenith viewing well. Ideally, I'd like it to work with my current heavyish 2" 24mm ES82 eyepiece. I'm not sure if it's too much to ask, but I'd be delighted if could double up for solar duty with a wedge one day (using solar film in the dob makes me nervous), and (assuming it becames my general "quick fix" scope) have a little versatility depending on whether the fickle UK conditions suit DSOs, planets, doubles, etc.

My initial thought was a cheap and cheerful fast achro (though I wouldn't know what size might be the sweet spot compared to my current kit, and not sure how good it would be for solar or general versatility). I also see a lot of folks are getting great results with small high quality refractors, and I wondered if this would be more versatile. However, I also wonder if I was spending that much, then maybe a super cheap table top reflector, with a separate longer slower refractor would be the way to go. Or maybe none of these ideas are any good!

What a muddle...

 

 

[Stu]

Come on them, give us an idea of budget at least!! ??

Personally, I would go for an 80 to 120mm ED Apo with a middling focal ratio. This will get you widefield views whilst still enough quality for lovely double splits, planetary, lunar and solar with a wedge

Ideas?

ED80

TV85

120ED

just for starters, there are some nice ones from TS too such as...

http://www.teleskop-express.de/shop/product_info.php/info/p7169_TS-ED-80mm-f-7-refractor-telescope-with-2--Crayford-focuser.html

http://www.teleskop-express.de/shop/product_info.php/info/p4964_TS-ED-102mm-f-7-Refractor-Telescope-with-2--Crayford-focuser.html

You would obviously need a mount.... Choices include AZ4, Giro-Wr, Mini-Ercole etc etc

[John]

As an example, the scope that I have in that role is my Vixen ED102SS which is a 4" ED doublet with a focal ratio of F/6.5. I can get up to a 4 degree true field for wide field which picks up where big binos leave off and I can exceed 200x when required on the moon planets and double stars. It's also lightweight (around 4kg) and cools quickly.

The Vixen's are no longer made but there are other scopes of similar specs available today.

I also have an ED120 but I feel the 102 is possibly more of an "all rounder".

[Size9Hex]

Sorry yes, budget wise maybe a few hundred pounds. I know that's really vague, but I'd view this as a purchase to last me years to come, and I'd happily tighten my belt for a few months if it made the difference. I'd like to get something that I'm not going to grow out of, but equally I don't really want to be going into the very top end area of rapidly diminishing returns for double the cost. Definitely not thousands though!

Thanks for the thoughts on the scopes above. I'll take a look through. Do you think these are worth the extra above a cheerful f5 achromat for example?

[Stu]

51 minutes ago, Size9Hex said:

Sorry yes, budget wise maybe a few hundred pounds. I know that's really vague, but I'd view this as a purchase to last me years to come, and I'd happily tighten my belt for a few months if it made the difference. I'd like to get something that I'm not going to grow out of, but equally I don't really want to be going into the very top end area of rapidly diminishing returns for double the cost. Definitely not thousands though!

Thanks for the thoughts on the scopes above. I'll take a look through. Do you think these are worth the extra above a cheerful f5 achromat for example?

Regarding your last question, personally I do think an ED doublet is worth the cost over an achro. As a generalization, I think the figure of the optics is usually better and this, combined with the lack of CA makes them much more versatile. They will take higher power, show lovely double star splits, decent planetary views whilst also, as John says, offering lovely widefield capability such as showing the entire Veil complex or North America Nebula, under dark skies of course.

Never forget I'm biased though ??

[Size9Hex]

Thank you both John and Stu. Getting such clear advice based on your experience is brilliant. A few words here is so much better than half a page of detailed scope specs on the commercial websites!

[JG777]

How about a used SW APO 100ED? Nicely corrected optics with FL53 glass and they are usually supplied with a focal reducer which gives you the option of viewing at F9 or F7.65. You see these pop up here and on other sites second hand, maybe £300 - £400. I use mine a fair bit for grab n go visual but also with a 1.25 Lunt wedge for solar. With the wedge I think 100mm is about the maximum you can go up to, maybe someone else can confirm as I am not home at the moment. Lunt do a 2 inch one as well, not sure of the spec though.

[Size9Hex]

On 10 April 2016 at 17:32, JG777 said:

How about a used SW APO 100ED?

Thanks John, that does look like a really nice scope. I'm wondering if it a little larger and slower than I had in mind, but it's interesting that it comes with a reducer. How do you find it performs with wide field?

[Size9Hex]

On 9 April 2016 at 17:06, John said:

As an example, the scope that I have in that role is my Vixen ED102SS which is a 4" ED doublet with a focal ratio of F/6.5. I can get up to a 4 degree true field for wide field which picks up where big binos leave off and I can exceed 200x when required on the moon planets and double stars. It's also lightweight (around 4kg) and cools quickly.

The Vixen's are no longer made but there are other scopes of similar specs available today.

I also have an ED120 but I feel the 102 is possibly more of an "all rounder".

 

On 9 April 2016 at 17:19, Stu said:

Regarding your last question, personally I do think an ED doublet is worth the cost over an achro. As a generalization, I think the figure of the optics is usually better and this, combined with the lack of CA makes them much more versatile. They will take higher power, show lovely double star splits, decent planetary views whilst also, as John says, offering lovely widefield capability such as showing the entire Veil complex or North America Nebula, under dark skies of course.

Never forget I'm biased though ??

Hi John, Stu,

Just wanted to say thanks again for your advice, and ask a follow question if I may, having had a look through the recommendations you've made.

It looks like the well corrected scopes smash the fast achromats at high power, but how do you think they compare at low magnifications? Would it be reasonable to expect great things from the achromat performance at low magnification (say below 50x), and to just accept that beyond that, it is what it is? With the well corrected scopes at perhaps 3 times the price, I guess I'm wondering if I'd notice a difference for the main intended low power usage, or was paying largely for the versatility (which I appreciate is something I asked about in my first post). I've not made up my mind yet - just trying to learn what I'd notice for extra spend.

Thanks once again :-)

[Stu]

A few comments from me, covering a number of the topics discussed.

As far as I'm aware, the 1.25" Lunt would be fine in a 120mm scope and potentially larger. It will get a little warmer but I believe it's fine in these scopes. Pretty sure Shane uses one in a 120ED.

The 100ED is a great scope by all accounts, very sharp, but personally I would either go for the 80 or 120ED as they are a little faster at f7.5 and more versatile. The 80 has the potential for very wide field views, whilst the 120 has the same focal length as the 100 but with the extra aperture.

I suspect the differences between achro and Apo at low power are less noticeable although I've never done side by side tests between an apo and an achro. My experience is limited to an ST80, ST150 and a 150 f8. I didn't enjoy the CA in any of them but never used them at low power under a dark sky. I think that Apo optics tend to be better figured in terms of other aberrations particularly in faster scopes so you may run into spherical aberration for instance. This isn't the case with slower achros, scopes like the 102mm f11 Lyra Optics for instance are very nice indeed but I think you are after something more flexible and versatile.

One scope which has got my attention is the 152mm f5.9 Starwave. This is a well corrected achro with a nicely figured lens and I expect it would perform very well in a deep sky widefield role. BUT...... It's a big scope and needs a big mount. I think for grab and go sessions and travel an 80ED would do you very nicely.

Enough rambling ?

[JG777]

Yep Stu is correct, the Lunt wedge can be used in bigger refractors to 150mm, not sure why I thought it topped out at 100mm, beer and tiredness could be to blame.......but I have 2 refractors the 100 ED which as mentioned is F9 and F7.65 with FR fitted and is excellent on planets and the moon, and of course solar. For wide field I use the 80 Equinox at F6.25 which is a beautiful scope for grab n go and visual on wide field. I did have a 120ST achro but to me the CA on planets and moon was bothersome although WF was very good. I knew I need 2 refractors to complement the C9.25!! I found that I was using the 100ED over the 120 purely down to the quality of the view rather the amount you could see through the latter. It just shows that one scope is never enough when your interests lie in a variety of things.

[Size9Hex]

On 11/04/2016 at 20:16, JG777 said:

It just shows that one scope is never enough when your interests lie in a variety of things.

Thank you once again John and Stu. I originally though the dob would be the only scope I'd ever need, but I'm starting to see this is true. This hobby could very easily become a money pit! Thanks for all the help though. I'll mull it over (and of course judge how much I can spend without finding myself sleeping on the sofa!), but I've got a much better understanding dea of the choices now. Thanks again!

[GimmeAMoonlite]

I was in a similar situation to yourself, and I went with an ED80.

Don't forget that you will need a suitable mount and tripod and possibly a diagonal if the scope does not come with one included.

[Commanderfish]

If you can get a used ED scope, grab one. Preferrably a 120/127.  If there are none around, you could get a Skywatcher ST120, which is an achro, and only costs a couple of hundred quid.  ED is sharper though.

 

WARNING:  once you have an ED, you may find it spoils the view through your other scopes and makes you hanker after impossibly large and pricey big EDs.

[scarp15]

I notice that there is a nice looking TV76 on ABS, reduced (I believe) to £575 delivered, very good, if your budget can stretch this far. I have one of these and find it very complementary with my two dobs. Heavy eyepieces balance very well with this scope on a Porta II mount, which tensions well and slow mo controls are great - though the flexible handles as an extra cost are preferable. 

[Stu]

1 minute ago, scarp15 said:

I notice that there is a nice looking TV76 on ABS, reduced (I believe) to £575 delivered, very good, if your budget can stretch this far. I have one of these and find it very complementary with my two dobs. Heavy eyepieces balance very well with this scope on a Porta II mount, which tensions well and slow mo controls are great - though the flexible handles as an extra cost are preferable. 

That's been up for a while and I can't believe it hasn't sold, lovely little scope.

[scarp15]

Yes I have noticed that there has been two or three  TV 76's that have been quite slow to sell, including the one I had the good fortune to purchase, quite unfathomable really it ought to be sold, particularly at that price. They are really very nice optically and of excellent build quality, will complement 10x50 bino's to.

[Size9Hex]

Thanks for the latest replies everyone. I've just had a quick look at the TV76 and it's showing as Sale Pending. It wasn't me! Maybe the fact it was mentioned here caught someone's attention!

These ED scopes have obviously got a lot of support. The ED80s look like they're among the best value of bunch, but I'm comparing £450 for the scope, plus maybe £100 to £200 for a mount (would be nice if an AZ3 would be suitable?). One of the things that I didn't think of when I started this post was that a slower (than the f4.7 dob) ED scope would need a longer eyepiece than I currently own to give the large exit pupil that I would want to use for nebula hunting (my 24mm gives a modest 3.2mm pupil in the ED80). If I stick with my prefered brand, that could be another £200! That's a tough fight against a 4" f5 achro for £250 including mount and a 2" diagonal when the main usage would be low mag. Appreciate those are prices for new not second hand, but just trying to judge the relative cost. Do you think this reasoning on the eyepiece exit pupil is sensible, as this feels like the final straw that would break the budget.

I've got to confess, since considering the eyepieces I own, and thinking again about what I'm most likely to use this scope for, I am leaning towards a fast achro despite the positive comments above. I hope it doesn't look like I've ignored any advice. I've had a look through the options you've suggested, and I think I've got a better understand of what folks (with more experience than me) are using and the reasons why. It feels like the dream scope might be something like a 120ED one day which would cover me nicely for wide fields, DSOs, planetary and lunar, and then I'll never, ever need to ever buy anything more, ever...

[Commanderfish]

Totally understand.  It is an expensive passtime!   I suspect one day at some point in the future you'll be enjoying an Apo, but a decent achro will do you for now    On the other hand, achros do exihibit Chromatic Aberation on bright objects unless you use longer focal lengths (say over F6 ish), so you will probably still need a longer focal length scope and also a longer focal length eyepiece (to get a wide field).  I see you like ES eyepieces, I can highly recommend the ES 30mm 82 degree, it is really an excellent eyepiece, sharp edge to edge with no aberations (though all my scopes are F6 or higher).  It is my widest field eyepiece and is in use at all times when I am observing (though I do run three scopes at the same time so that's three eyepieces!).  ES are on sale this month (April)  so I'd bag one while they're cheaper.  You can get them a bit cheaper from the US, or from Telescope House in the UK who are very fast dispatchers.

[Moonshane]

I am really a Newtonian man but over the years have tried several achromats, even slow ones and was never satisfied due to CA. I eventually got into solar observing and for this I find refractors along with a Lunt wedge really excel. I do though tend to use f10 achromats for my pst mods for Ha solar. I now have a 80mm f6 apo and a 120mm f7.5 ED and enjoy them greatly for solar with my 1.25" Lunt wedge. I have considered a few times though consolidationg to one more expensive scope, possibly a f7 100mm but have never committed to this as I really enjoy the differences between the scopes I have.

My view on scopes is that I like them to provide nicely aesthetic and well detailed views of the objects I like. I like lunar and planetary observing as well as doubles at home but when I take the scope caravanning, I enjoy mainly solar (I hope!) and wide field low power, but also make use of lunar / planetary if that's all that's available so it's important  it does everything well. To me an ED is well worth the additional money. If you are both patient and quick on your keyboard, watch out for (or place a wanted ad) for a Celestron ED80mm as they are every bit as good as the SW for visual albeit with a older style R&P focuser - still very usable though and they god for maybe £160-180 used.