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Author Topic: ST80 vs ST102  (Read 6968 times)

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Offline GordonCopestake

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ST80 vs ST102
« on: 15:05:39, 24 January, 2007 »
I recently wanted to purchase an ST80 or an ST102. I was undecided which to purchase and a wanted advert for an ST80 turned up 2 people wanting to sell me an ST80 AND an ST102. In such a pickle I decided to buy both so I could compare and then sell the one I liked least. I thought I'd share my findings here for those interested.

The ST80 is an 80mm f/5 (400mm) OTA and the ST102 is 102mm f/4.9 (500mm)

Both examples are made by Synta and are in Skywatcher blue. You can see the difference in size isn't massive, with the ST102 being slightly larger. The weight of both tubes is comparable although when weighed "in the hand" I could tell the ST102 was slightly heavier.



Removing the dew shield revealed the lens cells. The ST80 seems to be made from plastic which perhaps isn't a bad thing as it makes it lighter but it gives me concerns about the durability of the 'scope. The ST102 lens cell seems to be a combination of metal and plastic, which is perhaps SLIGHTLY better than the ST80. Neither seem to be collimatable.



The lens cell on the ST80 is screwed to the tube whilst the ST102 (I presume) is screwed a la the ED80.



Viewing down the barrel the ST80 is well baffled and whilst the lens is coated it isn't fantastic. That being said these are nice and cheap so I can't really complain.



The ST102 is equally well baffled, but again the coatings leave something to be desired. I think the ST102 appeared a little better than the ST80 but thats subjective with both examples being second hand (although in good condition)



The ST80 has a cast aluminum 1.25" rack and pinion focuser whilst the ST102 has a 2" cast rack and pinion focuser. (Note the focus wheels on the ST102 have been replaced at some point, but this is a small modification). Both have been regreased but experience tells me that if brought new would be full of "syntaglue". Easily fixed but god knows what the engineers were thinking when they used this "grease"



All the following shots were taken with my Nikon D70 DSLR at prime focus. I've not had the opportunity to test both 'scopes at night yet due to the weather (snowing here!)

The chimney was fairly close, about 300 meters. You can see the difference in focal length immediately with the ST102 giving more magnification from the outset. You can also see that the ST80 image appears to be washed out a lot more than the ST102. I'm not sure if this was a function of the weather or if it's due to the change in aperture. The ST102 definitely seems clearer though and despite it's fast f/4.9 focal ratio in these daytime shots I can't see much colour in either shot. I didn't get a chance to barlow up to take a closer shot with both scopes but perhaps I need to test in that configuration too.


ST80


ST102

Taking a 100% crop of both these images from the 6 mega pixel originals gives more information. Again the ST102 seems MUCH clearer than the ST102 and I'm beginning t think that the added resolution of the 4" compared to the 3" lens makes a big difference, at least for these daytime shots. I was expecting the ST102 to show more colour as it's f/4.9 not f/5 but to my eyes I can't see much difference. Perhaps some moon limb shots will tell more.


ST80 Crop


ST102 Crop

All in all at the moment the ST102 is winning due to the larger aperture, however the ST80 is still the more portable OTA. Night time tests to follow as the weather allows! That being said it's all academic as I have a Stellarvue AT1010 coming now which I'm hoping will wipe the floor with both of these hehe

Offline the fordster

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Re: ST80 vs ST102
« Reply #1 on: 15:10:07, 24 January, 2007 »
Love your reviews, Gordon - They always cover just the right things!

Seems the 102 gets it, not only on contrast, but having the 2" focuser and a better cell holder too. Was there much of a difference in price?

Offline GordonCopestake

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Re: ST80 vs ST102
« Reply #2 on: 15:11:22, 24 January, 2007 »
Knew i'de miss something hehe, the ST80 was £65 and the ST102 was £85, pretty similar second hand

Offline ro

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Re: ST80 vs ST102
« Reply #3 on: 15:17:12, 24 January, 2007 »
Nice review there Gordon!
On those last 2 photos the purple fringing seems much worse on the ST102. I have an ST80 and the fringing on theat is a pain in the behind. If the fringing it that much worse on the 102 it's going to be a nightmare to do any form of imaging with!
EQ1 mount, 350D and lots of old camera lenses

Offline GordonCopestake

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Re: ST80 vs ST102
« Reply #4 on: 15:19:12, 24 January, 2007 »
Both are achros so wouldn't consider them for imaging really. Mostly for guiding and grab and go. If I can afford to I'll compare against the Stellarvue from Arthur too, should be here tomorrow :D

RogerB

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Re: ST80 vs ST102
« Reply #5 on: 15:20:46, 24 January, 2007 »
Yeah, the 102 image definitely has more colour abberation. Did u take them thru the window?? Can see patches on both larger images in the same place..
Rog

Offline ro

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Re: ST80 vs ST102
« Reply #6 on: 15:21:15, 24 January, 2007 »
Both are achros so wouldn't consider them for imaging really.
Some of us can't afford a nice APO *sob*
EQ1 mount, 350D and lots of old camera lenses

Offline GordonCopestake

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Re: ST80 vs ST102
« Reply #7 on: 15:22:02, 24 January, 2007 »
No was out in the open. They are taken through trees though, so it might be that.

Offline GordonCopestake

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Re: ST80 vs ST102
« Reply #8 on: 15:23:03, 24 January, 2007 »
Both are achros so wouldn't consider them for imaging really.
Some of us can't afford a nice APO *sob*

Well the ED80 is about £200 so about twice the price of the ST80 but it's physically MUCH larger which is the appeal of the ST80. (at least to me)

RogerB

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Re: ST80 vs ST102
« Reply #9 on: 15:24:40, 24 January, 2007 »
Could be sunlight getting in?? Seems weird that it's exactly the same on both images!

Offline NickH

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Re: ST80 vs ST102
« Reply #10 on: 15:30:39, 24 January, 2007 »
£85 for a 102...and I thought i was the bargain king...

nice one

Have both myself, st80 as a guider for the c11., st102 as a guider or main imager in parallel with the ed80..all good for what they do..
Celestron C11: DSI-C/Toucam Pro 2 ICX mod and SC1.5 mod/ Meade LPI/EOS300D/ED80/WO80ZS/Shoestring guider. PST/PST CaK/ART285

No time....always bloomin cloudy...need to build the Obsy..

Offline GordonCopestake

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Re: ST80 vs ST102
« Reply #11 on: 08:38:09, 25 January, 2007 »
I had about 10 mins last night with both 'scopes in between the snow! All this did was confirm that the ST80 shows less colour but less contrast than the ST102, whilst the ST102 shows more colour and more contrast than the ST80. I think if I had to chose between the two for astronomy I would go for the ST80 due to the lack of colour. However for daytime use the ST102's extra contrast wins through. The extra aperture really does make a difference.

Offline GordonCopestake

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Re: ST80 vs ST102
« Reply #12 on: 20:22:51, 25 January, 2007 »
Took a few shots of the moon tonight through the clouds (at least it's stopped snowing!). The results between the 2 Synta scopes were actually surprising. On the moon limb slightly over exposed to make the effect worse (1/100th at prime focus with my D70) the ST80 actually showed more colour. These shots are 100% crops of the results:


ST80 crop (400mm Focal length)


ST102 crop (500mm Focal length)

For reference I have also purchased a Stellarvue AT1010 which as I had hoped was better than both the Synta 'scopes although the image quality was closer to the ST102 than the ST80.


AT1010 crop (480mm Focal length)

The SV won on build quality hands down, so thats the one thats the keeper:



Best of 3

Offline Ambermile

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Re: ST80 vs ST102
« Reply #13 on: 20:59:05, 25 January, 2007 »
Quote from: GordonCopestake

The SV won on build quality hands down, so thats the one thats the keeper

You gotta love that focus movement  :-*

arthur

Offline GordonCopestake

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Re: ST80 vs ST102
« Reply #14 on: 21:02:26, 25 January, 2007 »
It is a nicer focuser, rack and pinion too! Shows a well made r&p is better than a poor crayford

 

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