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Grab and go refractor: SW Startravel 120 or 102 thoughts


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Hi all: just thinking about possible grab-n-go scopes at not too high cost, does anyone have any knowledge of the Sky Watcher Startravel series, particularly the 120, or possibly the 102 on a slightly better mount? I'm referring to this model offered by FLO: http://www.firstlightoptics.com/startravel/skywatcher-startravel-120-az3.html ... It looks like a portable and quite attractive package.

I understand that the short tube 600mm f5 120 has limitations in terms of CA etc, but I have also read re reviews in which users say this isn't really a problem. So I wondered if this forum had any comments on this, and whether, for example the 1000mm f8.3 SW Evostar would be much better... Though it is more expensive.

Also, do you think there would be a significant difference in the 'ability' of a 102 model compared with a 120mm, say when trading off an AZ3 mount against an EQ1 ?

Hope you don't mind me asking all these questions!

Thanks, Julian

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I just got the ST102 on an AZ3 mount as a grab n' go. Set up time is seconds! The AZ3 mount is fine for grab n' go - when you start going to EQ mounts I felt it sort of goes against the concept of "grabbing n' going" with increased weight, faffing about etc. I got the scope for taking to dark skies or taking camping or for times I just can't be bothered setting up my CPC. I've really enjoyed using it. Views are widefield and low mag so its really easy to find objects - just point in the general direction and its there!

Yes there is CA but its only noticeable on brighter objects like Jupiter. I had it round the edge of the moon but when I used the end cap with the smaller cap removed to drop down the aperture it eliminated it. You can get filters to reduce it. 

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Thanks for the quick replies. What low-mag eyepieces do you think might suit this type of scope? My existing EPs of that type I guess are 24mm and 18mm ... And perhaps the 15mm?

If the AZ mount will do, that is fine for me ... I would be looking for something simple and quick to take out when I don't have time to set up the Dob and let it cool down (ie like last night for me).

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+1 for these short focus refractors.

They are brilliant for lo-tech no hassle very portable astronomy.  Ideal for a grab n go in the back garden, or to take on holiday.

Not the best for the planets, but good enough for many.

At their best for low to medium power deep sky, and for many of these dimmer objects, the CA will not be an issue.

If you can get to a dark site, it's amazing what one of these scopes will do, if you are patient.

Depending on your requirements, one of these could perhaps be the only scope you need.

Regards, Ed.

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I have the ST120 and it makes an excellent grab n go scope. I cant say how it compares to a 102 because I have not used one but there are one or two threads here that "suggest" the CA may be ever so slightly increased. In use it is excellent for widefield views, pretty good for contrast and detail with the moon but do expect the orange glow around the edge. For DSO it is not too shabby either the limitation being the aperture but you will easily pick off the main objects in the sky. For planets especially Jupiter it is not so good, views in mine were not much to write home about but this is what I expected.

I really did not care much for the AZ3, I found it quite limiting to be honest and only just about up to the task with the 120. In my view It really belongs on a AZ4 which is what I got for grab n go as I have a 127 mak as well, see this thread for some pics http://stargazerslounge.com/topic/177993-scope-shoot-out-120st-v-130-pds/ My AZ3 currently resides in the loft and following on from that I always wondered why the 120 is not offered as a package with the AZ4.

For EPs I mostly use the 25 and 18 BST when out with the ST120. The combo of ST120 and AZ4 is an excelllent gab n go, not too heavy to cart around assembled as well. No collimation or cool down worries you are viewing in seconds from setup.Yes the scope has its limitations but if you can live with that and you want to grab an hour here or there its a very good option.

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The ST120 is very big compared to the 102 and right at the limit of the AZ3's ability to carry it (some would probably say beyond it).  I do still use the ST120 on the AZ3 though, and can put the whole lot over one shoulder to carry into the field in front of our house quite comfortably.  The ST102 is far more convenient however.  If I wanted a scope to keep in a bag that I could put in the car to take with me anywhere I happened to be going, it wouldn't be the ST120.  The ST102 would probably do that easily.

James

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Thanks for the quick replies. What low-mag eyepieces do you think might suit this type of scope? My existing EPs of that type I guess are 24mm and 18mm ... And perhaps the 15mm?If the AZ mount will do, that is fine for me ... I would be looking for something simple and quick to take out when I don't have time to set up the Dob and let it cool down (ie like last night for me).

I'm not very knowledgeable about eyepieces but yes they should be good. So far I've only been using the 10 and 22mm eyepieces it came with and they seem to give a good range. I haven't tried my others yet.

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Thumbs-up for the short-tube refractor. I use the ST80 and have really enjoyed it, however I do wonder if I'd have been better off with the ST102 on the AZ mount. Even the ST80 on the EQ1 is very portable - I now remove diagonal and slow-motion controls, sling it over my shoulder and stroll down to the park. It also takes up barely any space in the boot of a car and I'm planning to get a more portable mount to take it on trains and planes.

DD

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This is all great information and feedback ... Thanks. Well, I've been and gone and ordered the 120 from FLO. I read elsewhere that the mount was at its limit for the 120 so if it turns out to be I thought I could look for a better second-hand mount later.

I see that this model will have its limitations but I'm open to the drawbacks if it means I can have a scope I can use quickly and simply when I don't have time to set up my beloved Dob. I sense it will be heavier than I imagine, and probably bulkier but I need the exercise!

I do have 15x70 Celestron binoculars and am really happy with them but I do find using these for extended periods, if I can't use the Dob, quite limited ... I admit a better mount for them would help (I only use a photo tripod at the mo).

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Sadly it's been raining since the telescope arrived! Quick further question though... I have an SW 9x50 finder scope from my SW 200mm Dob (I replaced it with a right-angled 9x50). Is there any technical reason why I shouldn't use this spare 9x50 on the new 120mm refractor? I'm not sure if there is an optimum size for a finder scope for each size of telescope.

If it is not suitable I can still use the red dot finder

that came with it of course.

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Thanks John, good to know. It's actually the straight 9x50 (the new RA version is on the Dob) but I assume that doesn,'t matter as they are essentially the same finder.

Yes, it's another wet and windy Wiltshire night here ... Hoping for some clear sky soon.

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Hi Julian. Hope you enjoy the new scope. I have the 120 and have had some great viewing sessions with it. Yes it does suffer from some CA on the planets and moon but nothing a decent filter couldn't contend with. I've managed to see some lovely detail on Jupiter at just x120 ( with x2 Barlow ).

The AZ3 can be a pain and the arms do get in the way when the scope is pointing more vertical, managed to hit my forehead against them a few times, even been slapped by them once or twice. But as a piece of kit to grab, go and be viewing in 2 mins flat, it's brilliant.

Enjoy ...... Eventually.

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Found an interesting (sort-of quantitative) table re. Chromatic Aberration:

http://www.cityastronomy.com/CA-ratio-chart-achro.jpg

No absolutes, but perhaps why f-number might increase with aperture.

102mm = f/5 ... 120mm = f/6... 150mm = f/8. For broadly similar results. :)

P.S. Once did a daylight side-by-side- test of an ST102 and a MAK127...

The MAK showed better detail. But the 'Frac was much more contrasty?

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I considered a fringe killer but if you search around there was not many favorable reviews for it, same for similar filters, seemed inconclusive as to what the gain was if there was actually any. It is difficult make a £200 short F refractor perform like a £700 Apo or similar. Enjoy the scope it is good at what it does, you will soon know if you need to divorce it :smiley:

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Semi APO is considered the better filter to reduce CA.

http://www.firstlightoptics.com/achromat-semi-apo-filters/baader-semi-apo-filter.html

However it isn't cheap and while a bit distracting, CA won't ruin your viewing sessions so I'd say get out and enjoy the views and add the filter as a luxury item later.

Fingers crossed for an hour of starry night soon.....

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