Skywatcher SW102 Refractor Telescope

[nsfx]

Hi guys,

I am fairly new to astronomy and would like to get a simple and small telescope due to space issues (apartment).

Did my research and have narrowed it down to the Skywatcher SW102 because we live by the harbour and we could use it to look at boats from our apartment as well when not stargazing. I noticed the ones on Andrew Communication and Bintel looks different in color but similar in prices. Are they the same product?

http://www.bintel.com.au/Telescopes/Refractor/Sky-Watcher-SW102/140/productview.aspx
http://www.andrewscom.com.au/optical-telescopes

This aside, are there any other refractors that i should be considering? Or any other better alternatives for around the same price? :confused2:

Thanks

[Wavytone]

Key distinction with refractors: Unless it states the objective is an "ED" I would steer clear as it means its an ordinary achromatic doublet and these are only good at f/15, not f/5.

The short-focus achromatic refractors like the Bintel one you linked are only suitable as "finderscopes" to be used as low-power. This will be OK at low magnification say 10-20X, but as soon as you crank up the magnification to ~ 50X you will start to notice coloured edges around bright things like the moon. To solve this, the old-fashioned achromatic refractors were very long things (typically f/15) which makes for a long and unwieldy tube (which would be 1.5 metres long in your case). Space here is too limited to go into why this works, optically.

The key discriminator with this will be the views of the moon and the bright planets (Venus, Jupiter, Saturn and Mars) where it will fare rather poorly if lined up side by side with the next scope...

The optimum travel-scope for visual use IMHO is an f/7 ED Apochromatic objective, this will give you the low-power wide-field views, and at the same time the ED glass is capable of giving excellent diffraction limited images at high power, 100 - 120X is realistic. This type of scope can easily handle magnifications spanning 17X (42mm eyepiece) to 120X (6mm eyepiece). Orion, Stellarvue and many others made excellent ED f/7 apo refractors around the 102mm aperture (it's a fair guess all used the same lenses made in China).

Example http://www.iceinspace.com.au/forum/showthread.php?t=100763

The ultimate are the triplets and fluorite types, more for those into photography. A beginner won't spot the improvement over ED apochromatic doublets, but a photographer will.

[raymo]

Just a little addition to Wavytone's post. You can find a used SW ED80 for
not much more than you would pay for the SW 102 package, but you
would need to pick up a new or used altazimuth mount for it, [similar to
the one the SW102 comes with.] Objects in the night sky would however
be a little brighter through the SW 102. It's really a compromise; a
better quality image in exchange for a slightly dimmer one. Your choice.
It would be good if you could get along to a club night and try a couple
of refractors before buying.
raymo

[cometcatcher]

What's a little CA here and there for visual use? :P I have the SW120 and it's a great little grab and go scope. ED refractors are more expensive and make little difference for terrestrial use. And if you really hate that fringe around Sirius, filter it with a minus violet or semi-apo filter. Of course if you can get a cheap second hand ED100 go for it. But they usually get snapped up faster than the speed of light.

Alternatively what about a 4, 5 or 6" SCT or Mak? Compact, cheap, no CA and still good for looking at boats.

[Amaranthus]

I've found my SW120 apo to be a wonderful rich field telescope, with very little colour and sharp views. In this specific role, I like it better than my 80mm triplet. Caveats: I was using TeleVue eyepieces at mid to low power, and observing from dark skies.

[Tropo-Bob]

Consider:
http://www.myastroshop.com.au/products/details.asp?id=MAS-043A

This is a Vixen70mm scope on a more versatile mount for a about the same $ and looks attractive.

For land viewing, it may be best ask for a lower power eyepiece (25 or 30mm), else the view may be a little over-magnified.

This telescope will give far better views of the Moon and the planets than the suggested 102mm F5 scope, with little false colour.

However, expect to see only the very brightest galaxies and deep sky objects.

[nsfx]

Thank you very much everyone for your input. It is a lot of information to process! Given i am a beginner. :eyepop:

I will have a look at the Vixen (looks to be very good value for money!) and keep my eyes peeled for used ED80 and ED100 as well. I'm assuming if i want images to not be upside down, my easiest choice will still be a refractor.

Also, will it be hard if i want to mount my Canon 5D Mark II or Canon 70D on the telescope? Thanks.

[Wavytone]

Turning the image upright requires an erecting prism... These fit any scope, the question is whether the scope has enough backfocus distance to reach the focus with one of these - some scopes can, many cannot.

Ask the vendor before you buy.

[Hoges]

I made a pair of binos out of two of the 102mm F5 acromats that you're considering. They're fine if you keep the power down below 40x and don't mind a bit of purple fringing. You won't see the purple fringing much on faint deep sky stuff which is what I mainly use the binos for but start pushing the power up past 50x on the planets and the image starts to suffer. The ED80 is a much nicer scope - but more expensive, as is the ED100.

You'll notice the purple outlines on stuff in the daytime too with the cheaper scope, but again, low power is not so much of a problem.

I also have the Vixen porta II mount which I find very smooth and excellent to use (my ED80 usually lives on top of it).

Factor in the price of a nice eyepiece and a good 45 degree erecting prism for daytime use - I got the Orion premium erecting prism for $100 and really like it.

On the three scopes I mentioned, there is a thread on the end of the 2" to 1 1/4" eyepiece adapter - you just need the correct T-ring adapter for your camera.

If you're thinking of using the scope as a camera lens, then hold out for the ED80. It will give you much nicer photos. The cheaper 102mm F5 will have electric blue 'edges' on anything with a bit of contrast and you tend to have a bit of 'blue haze' over the entire picture. If you want, I can email photos from the K50 through both scopes during daytime. I've never regretted buying the ED80. One of the best value scopes around.

[Regulus]

The fast 100 achromats are unsatisfying. It will annoy you with the chromatic aberration around the moon, Saturn, Jupiter etc., as well as high contrast views over land.
If budget is low then the Vixen 80/900 is excellent at f11.4 and I know from experience there is no red/blue fringing.
http://www.myastroshop.com.au/products/details.asp?id=MAS-046A
That said you can try that focal length for $60+freight with the Celestron version that Mental4Astro is selling here: http://www.iceinspace.com.au/forum/showthread.php?t=129263

If you end up getting something bigger/better for astro you will keep this for the ocean views.

A good quality Alt-Az mount for $289 in the Vixen Mini Port, but there are other choices around.
http://www.myastroshop.com.au/products/details.asp?id=MAS-033A3

Trev

[jenchris]

I use my sw 102 as a guide scope ... magic
also used it as a grab and go optical for uk trip this year.
also made quite a decent nature lens on my dslr

[OzStarGazer]

Apparently a #8 light yellow filter helps with chromatic aberration, although of course it also adds a bit of yellow to the image.

[Wavytone]

Here's one rather better than the achromatic doublet http://www.iceinspace.com.au/forum/showthread.php?t=129338

[nsfx]

This looks like a good one! Anyone knows a suitable mount for this? Thanks for the help.

P.S Thanks everyone for the advise. I have learned something new again after reading through the posts. :eyepop:

[Wavytone]

Another scope: http://www.iceinspace.com.au/forum/showthread.php?t=127896

As for a mount ... IMHO only reason to use an Equatorial mount with a small scope like this is for photography. Otherwise an altaz mount is fine and a lot more convenient to use.

[LightningNZ]

I sure if anyone cares but I have a 102mm F/5 achromat that I'd be quite willing to part with. Personally I used it deep-sky viewing and loved the bright views through it of the brighter nebulae and star clusters. I even used a bino-viewer with it and had amazing low-power views of the Moon (it looks truly spherical with the bino-viewer).

It has an erecting prism and that stuff. No mounting though. I was going to use it as a big guide-scope but really it's overkill. I'm happy to take an offer on it.

[Hoges]

I could take a photo of a 'sort of' dobsonian mount I made for mine. Very smooth and easy to use but you'd need to put it on a table or heavy tripod. If you're up for cutting up some 3/4 inch craftwood or similar and some gluing and screwing, I can post up some photos.

I have the Vixen porta II but the 4" f9 is a bit too much for it in my opinion. A 4" f5 or f6 would be ok though.

[brian nordstrom]

:thumbsup: Sin this is one seriousely good APO scope , on the mount an EQ3.2 would be perfect for this .
Brian.