ED72 Vs 102st Vs 102ed

[johnnyp]

Hi all.  

I currently own an evostar 72ed. I've got it mounted on a azt6 travel mount with counterweight and I like the set up. I mostly use it for wide field low power stuff and occasionally as a spotting scope.  I'm after abit more aperture though, and was thinking of an st102 startravel as its not much heavier than the ED72, and I'm thinking I won't suffer too much chromatic aberration with mostly using it for low power wide field.  My other thought was to treat myself to a starfield 102ed for Christmas if it's worth it ?. My thinking with that is that I get the best of both worlds (aperture and no CA), but the azt6 may be at its limit, and I do want to keep using that particular mount. Decisions decisions. 

Your thoughts please ? 

Thanks in advance

John 

[mikeDnight]

The 102ED is definitely  worth it. The ST 102 is a nice little scope which will give you pleasing low power views but the 102ED is in a whole different league in my view, being a much more capable all round scope.

[Louis D]

As my move-up scope from my AT72ED, I bought a used TS-Optics 90mm FPL-53 APO f/6.6 Triplet used a few years back for about $900 shipped.  It has been fantastic.  I love the 2.5" focuser, the camera angle adjuster (beats loosening the diagonal retention screws to angle the diagonal to the side), and the complete lack of false color in focus.  I will say I've not been happy with the slow cool down time of the triplet objective.  Based on this, I'd recommend a doublet.  Getting even an FPL-51 equivalent doublet would be a major improvement over an achromat at these short f-ratios.  Thus, I'd say go for a 102ED over a ST102.  Certainly, an FPL-53 doublet would have correction comparable to an FPL-51 triplet, but the cost is considerably higher than an FPL-51 doublet.  TS-Optics has 102mm ED doublets in both FPL-51 and FPL-53 if you want to compare prices.

[vlaiv]

I think that @Victor Boesen has 102mm F/7 (tecnosky version) on AZ6T and can offer some insight in how it holds up?

[Moonlit Knight]

The Starfield is an outstanding refractor, and very versatile too. I have owned the Altair Astro version and have done for 3 years, it’s a keeper. A very well regarded telescope 🔭 on this forum I think you will find.

[Victor Boesen]

As mentioned by @vlaiv, I own a Tecnosky 102mm F/7 and have used it a lot on my AZ6T both on a manfrotto photo tripod and on a Skywatcher stainless steel tripod. I consider it fine for grab-and-go, but have also purchased a Berlebach Castor II as the AZ6T is, quite frankly, not quite stable enough for high magnification observing.

The biggest problem/issue I had with the AZ6T was, that I found it quite bad at vibration dampening, which is also why I think it's not up to the task of high magnification observation. Using the stainless steel Skywatcher tripod of course helps, so I'd recommend you to use the most stable tripod you have. With that said, I actually got along with the AZ6T for quite some time before I finally bought the Castor, so the AZ6T should certainly be usable for the 102mm, as long as you don't load it with a heavy 2" prism, large 2" eyepiece, finderscope (use a red dot or no finder) and etc.

With regards to the 102mm scope, it's excellent! I thoroughly enjoy mine and have never regretted purchasing it. I use it for everything really - Deep sky, planetary, lunar, double stars and solar (white light and H-alpha).

Feel free to ask me any further questions:)

Kind regards, Victor

[Louis D]

I bought a pair of new old stock 100% Sorbothane insoles from the 90s off of ebay and cut vibration absorption pads to put under each tripod foot.  It cut settling time with my 127 Mak from 3-4 seconds to 1/2 second.  It went from unbearable to completely usable.  This was with a Manfrotto 058B tripod and DSV-2B mount.

[Paz]

I use a 72mm f6 apo with an AZT6 for travel, and I mostly observe at home with a 102mm f7 apo with a skytee 2 mount.

The 102mm apo is great and I would recommend it over the 102mm star travel. The star travel is a fine scope for what it is and I've observed for years with the 120mm version and have had lots of great times but since I've owned both it is almost always the 102mm apo that gets picked for action.

I don't use the 102mm with the AZT6 as the vibes are too much for my liking, but then I put the AZT6 on a very light tripod, it might fare better on a heavy and solid tripod.

[Moonlit Knight]

It would work very well on the highly underrated but rock solid steel legged AZ4. A fine mount for short tube 4 inch refractors.

Cheap too…..

Edited December 10, 2022 by Moonlit Knight

[johnnyp]

@Victor Boesen  thank you ,very useful info.

how did you find the scope without the counterweight and bar for the azt6? ..even with the ED72 I find alot smoother with it added. I only really use my azt6 for low power views.(I have a azgti for higher power observing)  What's the vibrations like at lower powers ?.

Cheers

John 

[johnnyp]

Some great replies so far thanks chaps. I have much to ponder ,but that's the best part for me

[Sunshine]

If my opinion is worth a squirt I did see the Starfield scopes on display at a local star party and they were impressive in their fit and finish.

[Victor Boesen]

1 hour ago, johnnyp said:

@Victor Boesen  thank you ,very useful info.

how did you find the scope without the counterweight and bar for the azt6? ..even with the ED72 I find alot smoother with it added. I only really use my azt6 for low power views.(I have a azgti for higher power observing)  What's the vibrations like at lower powers ?.

Cheers

John 

I have actually never used the AZT6 with a counterweight as I originally bought it without a counterweight for my 72ED and figured I didn't need it It should perform better with one though! Depending on the tripod the vibrations at low power (<50X) is roughly 2-4 seconds from what I can recall from memory. So not great, not terrible I shall emphasize that the tripod it's mounted on is just as, if not more, important than the AZT6 itself!

Victor

[johnnyp]

@Victor Boesen with the counterweight and bar it's silky smooth. But as you say it's still usable without it . Interesting regarding the vibrations. I absolutely hate them 😂

I have minimal  vibrations with my current set up (but as mentioned I very rarely go above 35x. ) I only use a Skywatcher tripod and pillar that come with my azgti, and I have been meaning to upgrade to a decent carbon fibre one when I upgrade the scope. 

Many thanks for your insights it's very useful

[jjohnson3803]

Somewhat related, I have an ST120, bought an 102ED last spring, and just bought an 72ED because the 102ED is more than my AZ5 or ScopeTech Zero mounts can handle.  There's much more vibration on focusing that I care for.  The ST120 is a bit less shaky with a new 2-speed Crayford, but still isn't ideal IMO.  I'm wondering if an achro 90mm or 102mm would be worth considering.

Anyway, the EDs seem to  be much more bulky and heavy (yes, I read the specs before ordering) than I expected, so I'd advise careful consideration of mount capacity.

 

Edited December 11, 2022 by jjohnson3803

[johnnyp]

@Victor Boesen a question if you don't mind. I see you used the tak prism diagonal with the 72ed. Was you able to reach focus with your eyepieces ? 

Cheers

John 

Edited December 11, 2022 by johnnyp

[Victor Boesen]

55 minutes ago, johnnyp said:

@Victor Boesen a question if you don't mind. I see you used the tak prism diagonal with the 72ed. Was you able to reach focus with your eyepieces ? 

Cheers

John 

Don't mind at all! Yes, I used a Tak prism back then, but I don't anymore (wish I hadn't sold it). I had no problems reaching focus with my Explorer Scientific 82 degree eyepieces, however, I didn't have my Baader Classic Orthos back then so I don't know if they would also reach focus.

Victor

[johnnyp]

Thanks alot victor. I have been using a 2inch diagonal with the ED72 but I find that it balances much better with a 1.25inch diagonal. The tak has been on my wanted list for a while now

[Franklin]

When I had my  SW72ED I used to take it up as high as 140x on the Moon and planets and it held up well, they're very nice small scopes. Great on a small mount like your AZT6 for grab and go low power, wide field views, but for higher powers on luna and planetary I'd use my Porta II for the slo-mo's. Regards your scope upgrade plans, I would say that an ED102 F7 is well ahead of the achro, but as others have said, it will want a more capable mount to fully appreciate the scopes capabilities. Slo-mo's are a godsend at higher powers and you WILL push the ED102 F7 as high as 200x or there abouts on good nights.

[Alkaid]

I have an ST102.  At low power x20, it's a very nice image visually on starfields, with minimal CA.   Anything above that power and it's very colourful!

On the moon, even at low power the CA is present.

You can use it as a spotter by removing the central cap, this turns it into a 50mm F10 scope, the CA disappears even at higher powers and the 50mm aperture doesn't matter as it's daylight, the view is still bright.

It's a nice skysweeper however, as long as the limitations are understood.

[vlaiv]

3 minutes ago, Alkaid said:

Anything above that power and it's very colourful!

I think that you are very harsh on little ST102.

It does have some color (a lot if you attempt high power planetary) - but it is very usable even at powers above x20.

Following images were taken with ST102 and DSLR attached to it (at full aperture):

Only when you zoom in - you can see traces of CA on the edges (granted - this is not very high contrast target):

Here is moon shoot with ST102 and DSLR:

Yes, there is yellow and blue fringing on limb, but it is rather decent image.

[Alkaid]

53 minutes ago, vlaiv said:

I think that you are very harsh on little ST102.

 

 

 

I'll try and be a bit nicer   😀

As a general thing, I've had mine for 5 years and still like it.  It's a great little scope.