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DevonSkies

Thoughts on the Startravel 102

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I have been using a Skywatcher Startravel 102 for about a month now as a grab-and-go scope. I also intend to use it as a travel scope for holidays, but I've yet to try it in that capacity. So I thought I'd record some of my thoughts about this scope.

Initially I purchased the ST102 with an AZ3 alt-azimuth mount, but I quickly found I didn't get on with the AZ3. On the plus side, it is very compact and lightweight and would make an excellent travel mount. However, I found the friction bolt arrangement for setting the altitude tension to be unreliable, and the mount was difficult to use near zenith. So, I changed the mount to a Vixen Porta II, which is much more comfortable to use. The Porta II tripod does seem to vibrate a bit more than the AZ3 though (especially on concrete), so maybe I will change the legs for something more substantial one day.

Onto the telescope itself. The optical tube feels very solid and substantial. There is a large dew shield fitted, which is held on with a simple push fitting held in place by a felt band. Removing the dew shield reduces the OTA length significantly, but unfortunately the supplied lens cap won't fit over the front cell without the dew shield in place. This is a pity, as removing the dew shield would make the scope very compact for travel.

The 102mm doublet objective has a blueish-looking coating, that seems evenly applied. The OTA assembly is supplied with decent tube rings and a dovetail. If you buy the scope in a kit with the AZ3 mount it comes without a dovetail, and the tube rings bolt straight onto the mount.

The focuser felt quite smooth but a little tight straight out of the box. Initially there was no play in the focuser and the drawtube was well aligned. However, the focuser does prove to be a weak point on these scopes and I will return to this later.

Now on to the important bit - performance! The OTA came supplied with the usual 25mm and 10mm MA eyepieces. The 25mm is quite a good budget eyepiece, but the 10mm could be better. However, since I already have a set of reasonably good eyepieces I put the supplied EPs to one side. Also supplied with the OTA and AZ3 kits is a 45-degree erecting prism. This is useful for terrestrial observation, but not really of sufficient quality for astronomical work (although it is OK at low magnifications). I replaced this with the excellent Revelation 2" Quartz Dielectric diagonal.

This scope excels at wide-field views of open clusters and brighter DSOs. With a 25mm X-Cel LX eyepiece the whole of the Pleiades can fit in the field of view, which is a stunning sight. I also have a 32mm Panaview 2" eyepiece, which offers a whopping 4.4 degree field of view, framing the Pleiades beautifully within the surrounding sky. Under a dark sky the view is quite breathtaking. Other open clusters such as the Beehive also look superb with such a wide field. Best of all, this scope gives me the best view I've had of the Double Cluster in Perseus, with both parts of the cluster beautifully framed within the FOV.

Large DSOs are also a strong point for this scope. M31 (Andromeda) looks fantastic under a dark sky, and dust lanes are visible. Dimmer DSOs are quite within the reach of this instrument, with M1 (Crab Nebula), M33 and M51 all visible under dark skies. Globular clusters also make good targets, although perhaps a little more aperture would be useful here to see them at their best.

Working at high magnification, the ST102 is quite capable of splitting the "easier" double stars such as Castor and Sigma Orionis. A 5mm EP works well here, and a Barlow can help to increase the separation on brighter doubles. The dim companion to Rigel can just about be made out under good seeing conditions.

You may notice that I haven't mentioned CA (chromatic aberration) yet. That's because, for clusters, DSOs and most double stars it simply isn't an issue. For planets and lunar observation, however, it's a different matter. Yes, the dreaded purple haze is there, especially noticable on the limb of the moon and on bright planets such as Jupiter. In fact, the ST102 is quite capable for casual lunar and planetary observing, but if the solar system is a primary interest for you then you might look elsewhere. Although the optics are pretty sharp at high magnification, I really feel that the CA damages the contrast for planetary and lunar observation.

This is my first refractor (my other scope is a 10" Dob). I have to say I'm now a refractor fan! There's something about the ease of setup and the contrasty, pinpoint stars that appeals to me. I also like the short-tube concept from a portability point of view, and these scopes are very capable deep sky instruments. Yes, CA is a problem on bright objects at high magnification, so it's not an all-rounder like an APO, but for the price it's fantastic value for money.

I mentioned the focuser earlier. After some use, the focus tube developed some vertical play. There are two grub screws on the top of the focuser which are used to tension the drawtube. I needed to tighten the front (i.e. closest to the objective) screw to take up the slop, and also tighten the rear screw to remove any remaining image shift. After this adjustment the focuser worked fine again. I have now had to do this twice, so it seems that periodic adjustment is required. After the second adjustment cycle the focuser was very stiff, which I resolved by slackening off the screws that tension the spring in the focus pinion assembly. Now the focuser is nice and light and smooth, but I anticipate further adjustments will be necessary in future. We shall see! This is really a faff and the only real annoyance with this scope. There is a dual-speed Crayford focuser available which is a drop-in-replacement for the original R&P focuser, but at around £129 I'm not sure it's worth it on an OTA costing £169!

All in all, I really like this scope, apart from the cheap focuser. In fact, I like it so much I'm wondering what the 6-inch ST150 would be like on DSOs and clusters!

Ed

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Great review and a great read. i have the 120mm Evostar which is a great scope and i absolutely love it. it has sligh Ca but i can handle that. all the best and enjoy. Scott

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Excellent review Ed - really brings out the charactistics of this scope very clearly :icon_biggrin:

I think the 150mm F/5 would show substantially more CA as that increases as the aperture increases. It would still be a very nice deep sky / rich field type scope though.

According to this table, your 102mm F/5 will be showing about as much CA as my 150mm F/8 shows:

 

CA-ratio-chart-achro.jpg

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10 minutes ago, John said:

Excellent review Ed - really brings out the charactistics of this scope very clearly :icon_biggrin:

I think the 150mm F/5 would show substantially more CA as that increases as the aperture increases. It would still be a very nice deep sky / rich field type scope though.

According to this table, your 102mm F/5 will be showing about as much CA as my 150mm F/8 shows...

 

mmmm.... 150mm f/8... now there's a thought! Not sure I could justify it alongside the 10" Dob though!

 

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A good field review of these short tube refractors, they have a lot going for them.  Especially with our climate being so changeable, as you often have a short viewing window before the clouds roll in.  For really bright objects like Venus or the Moon, the inbuilt mask works well at reducing excessive glare.  What i did with my porta mount, was to cut a slit in some tennis balls, although it looks it bit odd, they did cut the vibrations down !

 

andrew

porta.jpg

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Thats a nice review.

I had an 102 and was quite pleased with it. I did buy a fringe killer filter which helped on Lunar and planetary.

If you look at most Skywatcher reviews the 10mm stock EP always seems to be the one that gets criticised.

I mod'd the focuser on mine for a 10:1 type from Telescope Service in Germany. It worked well but I had to add an extra spacer as there was not quite enough backward focus with a DSLR.

 

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1 hour ago, andrew63 said:

A good field review of these short tube refractors, they have a lot going for them.  Especially with our climate being so changeable, as you often have a short viewing window before the clouds roll in.  For really bright objects like Venus or the Moon, the inbuilt mask works well at reducing excessive glare.  What i did with my porta mount, was to cut a slit in some tennis balls, although it looks it bit odd, they did cut the vibrations down !

 

Good idea, I might try something like that.

Also a good point about the aperture mask for moon and planets. I've found it virtually eliminates CA, but it does cause some loss of resolution.

I forgot to add that I have also tried the Baader Contrast Booster filter, which is supposed to be the most aggressive of the CA-reducing filters. Although it did noticeably reduce the CA, it left a yellow cast which I found unpleasant and also noticeably reduced the sharpness of the view at high magnification. In the end I decided I preferred the unfiltered view! At some point I will probably buy a dedicated grab-n-go for lunar/planetary work (maybe a Mak or an f/10-ish refractor).

Edited by DevonSkies
Typos

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Great review and sums up pretty much how i feel about my ST102. I have had it for a good number of years now and in fact use it on a Porta II mount myself.

However, it is going to be surplus to requirements shortly as i am waiting for............................an ST120 to arrive :-)

I use a semi-apo filter in my diagonal and it works quite well, it does impart a slightly yellow cast to the view though. But i can live with that.

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49 minutes ago, Bobby1970 said:

Great review and sums up pretty much how i feel about my ST102. I have had it for a good number of years now and in fact use it on a Porta II mount myself.

However, it is going to be surplus to requirements shortly as i am waiting for............................an ST120 to arrive :-)

I use a semi-apo filter in my diagonal and it works quite well, it does impart a slightly yellow cast to the view though. But i can live with that.

I do wonder whether I actually should have got the ST120 in the first place. I was undecided between the two when I made the purchase, and decided on the 102 because I thought it would be more portable. But in the end the ST120 is only 10cm longer and 2cm wider, and for DSOs one needs all the aperture one can get!

I'd be interested to hear how you think it compares to the 102 when you get it. Will you have the chance to compare side by side?

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58 minutes ago, DevonSkies said:

I do wonder whether I actually should have got the ST120 in the first place. I was undecided between the two when I made the purchase, and decided on the 102 because I thought it would be more portable. But in the end the ST120 is only 10cm longer and 2cm wider, and for DSOs one needs all the aperture one can get!

I'd be interested to hear how you think it compares to the 102 when you get it. Will you have the chance to compare side by side?

Yes. I will. I am very much looking forward to comparing all aspects of the two scopes. I will let you know how it goes. 

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55 minutes ago, Bobby1970 said:

Yes. I will. I am very much looking forward to comparing all aspects of the two scopes. I will let you know how it goes. 

Thanks. I'll look forward to hearing how you get on! 

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On 1/26/2016 at 05:00, andrew63 said:

A good field review of these short tube refractors, they have a lot going for them.  Especially with our climate being so changeable, as you often have a short viewing window before the clouds roll in.  For really bright objects like Venus or the Moon, the inbuilt mask works well at reducing excessive glare.  What i did with my porta mount, was to cut a slit in some tennis balls, although it looks it bit odd, they did cut the vibrations down !

 

andrew

porta.jpg

I put tennis balls on the bottom of my Celestron 127 SLT tripod and they do seem to help dampen vibrations. Another side benefit is that the tennis balls are visible in the dark so I don't trip on my own mount!

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Concur with all you've said about the 102. Great little scope although it does produce a little more CA than my evo 120 achro.

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Good little scopes these. I went for the 80mm as I wanted something really portable and have been pleased with it. It's poor on planets, but with the Baader semi apo filter the lunar views are actually quite good. 

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I've had a 102 for a couple of months now. Bought it to use for solar observing, but also use it for a grab and go option. I really like it. Lovely FOV for extended objects and really good for some doubles. CA is there, but I do not find it too obtrusive.

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Just seen this thread and , just in case it’s still relevant , I have a 102 , which I bought about 6 years ago . It didn’t get too much use at the time but I’m completely hooked on astronomy now and , although I’ve bought another refractor (wo z73) which is ultra portable , I still use my 102 , with its goto az mount . I think this  scope is one of the most practical I’ve used . Good for DSO and planets (despite the ca) ... i purchased an eq5 mount which now aids stability , I agree about the focuser , mine seemed to “jump” a bit which can be annoying . I also thought about dropping in a Crayford , but , as I now have the z73 I don’t think it’s going to happen . 

A great review 

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