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menacegtr

FIRST TIME WITH THE STARTRAVEL-120 (AZ3)

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Dave. My recommendation was based on experience. I have 80mm, 102mm and 150mm ST refractors and 90mm, 102mm, 125mm, 180mm and 203mm Maksutovs. I have used these extensively for astro and terrestrial use. IMO for high power observation there is no contest between them, the Maksutovs win hands down. The short focus refractors are exceptional value for wide angle low power use, a combination of a 80mm ST and a 10mm-150mm would cover all bases.

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Dave

I have a ST120 and bought it for public outreach events under dark skies in places like Northumberland.  It excels at wide field views and is really easy to use.  Mate it with an expensive wide field eyepiece and the effect on big objects like the Andromeda Galaxy is jaw-dropping. But here are few points to consider. If you want to look at planets and the moon a five inch mak would be better.  In the synscan flavours you get tracking which makes viewing at higher magnifications much easier. Yes you will have to provide power and use a good dew shield/dew controller. Also the AZ3 is not a good match for the larger ST120 tube, especially if you start adding a heavier diagonal and eyepieces.  Not only is the whole thing shaky but you will find it very difficult to adjust the altitude bolt to the right tension.  Do yourself a favour and plump for the AZ4.   I picked up a mint condition second hand one for just £80.  The tube balances really well.   One more suggestion.  I also have a Celestron version 80mm ED scope (F7) - come up second hand for about £170 - also used with the AZ4.  Very little false colour, good on solar system, but still wide field enough to get lovely views.  

Rich

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I have been doing some research and trying to learn about eyepieces and overpowering the telescope. Is this equation right as I understand. The ST 120 is a 600mm focal length and 120mm aperture? so to get an eyepiece to work inside the scopes capacity is to A x the 120 by 2 to give the maximum magnification at 240x. So the standard aperture of the ST 120mm is 600mm, so do I divide that by the 10mm lens that comes with it to get 60x and the 25mm lens would be 24x so there is massive room for improvement. Now if I add a good 2 or three element 2x Barlow does that effectively give me double the focal length now, so I should have 1200mm focal length so a 10mm lens should now give me 120x. So from that I can squeeze out more mag and go to 1200% by a 7mm lens to give me around 171x magnification, if I go to a 6mm lens I would get 200x mag so still not going over the 240x mag with the 2x Barlow but maybe to strong for the scope. Is this how it works out so as not to overpower your telescope. And if I take the Barlow out and just use eyepieces I would get at the extreme end, 600 aperture % a 3mm lens would get me I would think an unusable 200x magnification.  I don't want people saying that the scope is Rubbish with a Barlow or just use a 3mm lens to get 200x mag is bad, I just want to no is this how you work it out

                                                                                         Regards. Dave

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Yes divide focal length by eyepiece length to get magnification for a given eyepiece/scope combination. Twice the aperture in mm is regarded as a reasonable guide to maximum useful mag - it's also usually stated in the scope specs. I generally find working under 80% of that gives best results. Be careful using barlows - yes they will double the mag, but depending on the scope, eyepiece, and barlow quality, they don't always give improved higher mag views. :)

 

 

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Yes I am going to be as careful as I can. I have purchased a Celestron 7mm X-Cel LX eyepiece 1.25" and either a Baader Planetarium 2.25x Q Barlow Lens 1.25" or a Celestron X-CEL LX 2x Barlow Lens 1.25" to order this week. I have also purchased a Baader Semi Apo filter 1.25" to cut down  CA effect and it seems to work as I know somebody locally to me that has the same filter on a ST 150mm and it works really well, it cuts out most of the blue fringe around the outside especially in the day. I will also swap out the stock 25mm for a quality equivalent, not sure which one though. The scope I will be getting for my birthday on 13/2/16. I thank everyone on this site because 3 weeks ago I new nothing about telescopes and astronomy in general, and now am feeling quiet confident in buying my first telescope and extras after reading loads of comments from you guys, also its great to get all your feedback and take it all in

                                                                                                                  regards. Dave:

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There's a couple of Youtube reviews of the scope in daytime here Dave:

 

Edited by brantuk

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@Super brantuk . thanks for that. The ST 120mm looks a very nice piece of kit so am looking FWD to getting one

                                                                                                                               Regards. Dave:

Edited by menacegtr
wrong name
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6 hours ago, menacegtr said:

I have been doing some research and trying to learn about eyepieces and overpowering the telescope. Is this equation right as I understand. The ST 120 is a 600mm focal length and 120mm aperture? so to get an eyepiece to work inside the scopes capacity is to A x the 120 by 2 to give the maximum magnification at 240x. So the standard aperture of the ST 120mm is 600mm, so do I divide that by the 10mm lens that comes with it to get 60x and the 25mm lens would be 24x so there is massive room for improvement. Now if I add a good 2 or three element 2x Barlow does that effectively give me double the focal length now, so I should have 1200mm focal length so a 10mm lens should now give me 120x. So from that I can squeeze out more mag and go to 1200% by a 7mm lens to give me around 171x magnification, if I go to a 6mm lens I would get 200x mag so still not going over the 240x mag with the 2x Barlow but maybe to strong for the scope. Is this how it works out so as not to overpower your telescope. And if I take the Barlow out and just use eyepieces I would get at the extreme end, 600 aperture % a 3mm lens would get me I would think an unusable 200x magnification.  I don't want people saying that the scope is Rubbish with a Barlow or just use a 3mm lens to get 200x mag is bad, I just want to no is this how you work it out

                                                                                         Regards. Dave

The 120mm f/5 will gather a lot of light, and the Baader semi-apo filter sounds to be effective, per research: win-win.   

The achromat has a focal-length of 600mm.  That's all that's needed when choosing eyepieces and a barlow.  The lowest-power eyepiece, and for great wide-field views, will be a 32mm, and since the focusser is able to accept 2" eyepieces, this 2" 70° 32mm, combined with a 2" 90° mirrored star-diagonal, would be a great performer, and pictured at right...

http://www.firstlightoptics.com/skywatcher-eyepieces/skywatcher-panaview-2-eyepieces.html

600mm ÷ 32mm = 19x, and quite close to that of a pair of 20x80(20x) binoculars.

I have the same 32mm, and illustrated here alongside my Synta 1.25" 25mm...

comparison9.jpg.3026c11601a00ce3dfc0ac96

Just by looking at it, one can get a sense of its performance.  The 1.25" 45° Amici-prism terrestrial/daytime diagonal supplied with the kit can be used at night, but it is not designed for astronomical use, therefore its performance will be lacking.  The kit is sold with one, and in a terrestrial/daytime configuration.  A 90° mirrored star-diagonal is recommended for fast refractors, for astronomical/nighttime use, and for best performance...

http://www.firstlightoptics.com/diagonals/skywatcher-di-electric-star-diagonal.html

 

A 2" eyepiece and diagonal is not required however.  For examples...

A 1.25" 50° 30mm(20x) Plossl... http://www.firstlightoptics.com/vixen-eyepieces/vixen-npl-eyepieces.html

I have it, too, and it's a great performer.  I chose it over the GSO and Baader 32mm Plossls, and after careful research...

56b161fac321c_VixenNPL30mm2.jpg.cac0b06c

...and a 1.25" 90° mirrored star-diagonal, for example... http://www.rothervalleyoptics.co.uk/altair-astro-125-dielectric-star-diagonal.html

 

600mm ÷ 30mm = 20x(2x barlow: simulated 15mm/40x), (3x: 10mm/60x)

600mm ÷ 25mm = 24x(2x barlow: 12.5mm/48x), (3x: 8.3mm/72x)

600mm ÷ 10mm = 60x(2x barlow: 5mm/120x), (3x: 3.3mm/180x)

Examples of better-quality barlows...

2x:  http://www.rothervalleyoptics.co.uk/antares-x2-twist-lock-barlow-lens-125.html

2.25x: http://www.firstlightoptics.com/baader-planetarium/baader-classic-q-225x-barlow.html

3x:  http://www.rothervalleyoptics.co.uk/antares-x3-twist-lock-barlow-lens-125.html

A barlow is placed into the optical train, and therefore needs to at least match the quality of the refractor's doublet-lens and the eyepieces, and for better performance.  The lens element of the Baader Classic Q 2.25x, listed above, is removable, and at 1.3x.  I recently read of a fellow amateur with a GSO 2x/1.5x.  As he removed the element to place it on an eyepiece, he dropped it and chipped the lens, therefore extra care is needed when handling.

Barlows are used for visual, and imaging.  For visual, its use is two-fold...

1. To multiply the number focal-lengths within a small eyepiece set, as demonstrated above.

2. To reach a higher magnification without having to resort to using an eyepiece with a tiny eye-lens and short eye-relief.  For example, this is a 4mm orthoscopic...

56b16b64a41ef_4mmOrthoscopic7.jpg.ac142b

You know that one has to be difficult and even painful to look through, eh?

Instead of using it, 3x-barlowing a 12mm, and for a simulated 4mm, makes for much greater eye comfort...

56b16c39ca618_12mm-Klee2.8x.jpg.dc01d51d

That combination of a 60° 12mm and a 2.8x barlow actually simulates a 4.3mm; but close enough, and O! the wonderful things I've seen with it!

Then, there are eyepieces that have a built-in barlow, with said greater eye comfort, and when compared to a standard 4mm orthoscopic or Plossl...

http://www.firstlightoptics.com/skywatcher-eyepieces/skywatcher-uwa-planetary-eyepieces.html

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@ ALAN64 Thanks for that reply. I will take a look at those vixen eyepieces, they seem like good value for money for replacing my 25mm lens. Also would I be better off getting the Skywatcher 2" Di-Electric Star Diagonal. with the included 1.25" adapter. Or a dedicated 2" Star Diagonal.

                                                                                          Regards. Dave:

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@Alan64 . Again thanks for your time to post, your detailed information is well received and I will take note of all you have said. There seems to be a lot of good eyepieces around the £40-50 mark

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The prisms in the 45 degree erecting diagonal are quite small, they might vignet the field of wide angle long focus eyepieces. Worth checking.

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Finally had a proper first light session with my ST120 last night.

I was very impressed. Especially for the £120 i paid for it.

Andromeda looked stunning in a 2" 28mm eyepiece. Certaqinly close to or indeed maybe the best view i have ever had of it.

I also managed to find comet catalina which had eluded me on other occasions with the ST102.

Orion nebula looked as glorious as ever but i am sure more of the extent of the nebulosity was visible.

M1, although still a smudge in the eyepiece was a clearer more defined smudge again in comparison to the ST102

M81 and M82 also were much easier to locate and the views were clearer with the 120. I even managed to spot (using averted vision) some small NGC object, the number of which escapes me, just to the south of these two.

All in all a great few hours were spent.

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Hello Dave,

A 2" 32mm, as described, would probably be the only 2" eyepiece in your collection.  Some get a 2" ocular in the 25mm-ish range, too.  But the 1.25" oculars are more than adequate from 4mm to 25mm, for most people.  My 2" 32mm is the only one I have, and I don't really feel the need for any more.  If you plan on getting that 2" 70° 32mm eyepiece in future, then it would need a 2" mirrored star-diagonal, and with a 1.25" adaptor as it never hurts to have a spare.  Although I'm unaware of 2" diagonals being sold without 1.25" adaptors.  Most come with one in any event.

On the other hand, if you decide on the 1.25" Vixen NPL 50° 30mm instead as your lowest-power eyepiece, then consider a 1.25" mirrored star-diagonal.

Yes, one doesn't have to spend a fortune on eyepieces to have a rewarding experience 'neath the starry void. 

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Is it ok to use the  Skywatcher 2" Di-Electric Star Diagonal which Includes 2"-1.25" adapter, can I use 1.25 eyepiece's as stated above for my ST 120mm, I hope so as I have purchased one from FLO. I did not want to have to buy 2 diagonals (2" and 1.25") as I want to get a PanaView 2" eyepiece so was informed a good 2" diagonal with adaptor would be the ticket for both types of eyepieces. Thanks again for all your help.

                                                                      Regards. Dave:

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3 hours ago, menacegtr said:

Is it ok to use the  Skywatcher 2" Di-Electric Star Diagonal which Includes 2"-1.25" adapter, can I use 1.25 eyepiece's as stated above for my ST 120mm, I hope so as I have purchased one from FLO. I did not want to have to buy 2 diagonals (2" and 1.25") as I want to get a PanaView 2" eyepiece so was informed a good 2" diagonal with adaptor would be the ticket for both types of eyepieces. Thanks again for all your help.

                                                                      Regards. Dave:

...splendid choice...

diagonals.jpg.f4058619a40445964aa21f8465

A 2" diagonal with a 1.25" adaptor accommodates 1.25" eyepieces as well...

diagonals2.jpg.cda474c050e56f11e7b325c72

In addition, by inserting a .965" adaptor into the 1.25" adaptor, one can use old-school .965" eyepieces even...

diagonals3.jpg.933cdd5524e4239b45813db19

 

A short-tube 120mm refractor is a bit much for the included AZ3 alt-azimuth mount within said kit, and when extra weight is added in the form of eyepieces and accessories, well.  Give it a go with the AZ3 for a spell, and see how it works out.  There is the option, however, of getting the OTA separately...

http://www.firstlightoptics.com/startravel/skywatcher-startravel-120t-ota.html

The OTA is £30 less than the kit, therefore the AZ3 is thrown in at a £67 discount.

A more robust alt-azimuth mount... http://www.rothervalleyoptics.co.uk/skywatcher-az4-1-alt-az-mount-with-aluminium-tripod.html

Whilst that one would easily handle the refractor, and any and all eyepieces and accessories, it does not have slow-motion controls, as the AZ3 does, for some inexplicable reason.

http://www.teleskop-express.de/shop/product_info.php/info/p8069_TS-Altazimuth-Mount-with-Fine-Adjustment-and-Quick-Release.html 

...and ideal, but for yet another inexplicable reason, it's not sold in the UK.  It's very popular for smaller telescopes throughout the rest of the world.

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@happy-kat . Thanks for supplying that, I have just sent the chap that did the mod an email to ask if he can do it for me. It looks like a brilliant idea to counter balance the weight of more gear added to the ST 120m

                                                            Regards. Dave;

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@Alan64 , Thanks for that, its eased my mind knowing I have not wasted my money. The 2" diagonal does look nice though.

                                                                                                          Regards. Dave;

                                                

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Ok the only thing I need  now is a good eyepiece to view the moon, I have the low power and mid sorted but I need some advice on a good high power eyepiece. And yes I no I will be getting the ST 120mm and people slating its higher power usage. But I have seen close up video's and pics of the moon through this scope so I no it is capable of viewing the moon, so I need to no the absolute limit of eyepiece to use, be it a 9/8/7/6mm eyepiece, a good eyepiece is what I want. you can see from earlier post of what I have already purchased. And to add to that I have purchased the Revelation Astro 2.5x Barlow Lens 1.25" to add to my list.

                                                                                    Regards. Dave:

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The mod is easy to do I read that and did it to my az3. I got the weights from astroboot as I didn't have any already. There are several threads on this site where others have done similar to their az3. 

Or go the quick route and fit a nylock.  Here

 

 

What is the budget for the eyepiece?

Edited by happy-kat

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Anyware from £30to50 unless anyone says otherwise , as I said earlier I have the baader apo filter and a nice 2.5 revelation 3 element Barlow. I also will be doing that AZ-3 mod, It looks very good , just need to find a good piece of metal too mount the rod and counter weight . Any ideas?

        Regards. Dave:

Edited by menacegtr

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i'd definitely go for the 32mm panaview ep and 2" 90deg diagonal. having had a go of a st102 with the same ep and diagonal I can say the views were lovely!

 As for lunar, dont go overboard with mag!

your mount isnt sturdy enough, moving the scope to track the moon will induce tears of frustration at over x150 and it'll wobble like hell giving jittery views.

personally I would stick with a max of x100 - even in my 12" dob i rarely go over x100 for lunar viewing! You arent going to see the lunar lander, so accept it and view the craters and rilles with a bit of the surrounding scenery and enjoy the view! A rock steady view of copernicus thats fairly small in the eyepiece will still yield much more detail and enjoyment than a jiggly view that fills the field of vision where you cant make out anything!

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@nicks90, thanks for reply. if I go to a AZ4 Alt-Az Mount with Steel Tripod would that get me steadier view

                                                         Regards. Dave:

 

 

 

 

 

 

 

 

 

 

 

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If your scope was lighter I would say the staradventurer weight bar is fairly inexpensi but I don't know if a kilo will be enough. Sometimes astroboot sell weight bars. I won't advocate the bar I used as it does but fiddlier than it needs to be.

Having never used an Az4 I can't comment on your questions.

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