TheSkySearchers

My 8" Vixen VMC200L and Astro Tech AT80EDT complement each other very well. The Vixen gives great views of nebulae, globs, and open clusters. I wouldn't mind a little more aperture for distant galaxies, but it's unlikely that I will invest in a bigger scope at this point in my life.

The Vixen is fine on planets, but I prefer the refractor on the planets. The color and contrast on the planets, open clusters, and doubles is remarkable to my eyes. Ease of use means I use it more as well.

In short, I really fell in love with the refractor. I don't need another scope. But I keep looking at them online anyway.

Here's what I have been looking at:

The Astro-Tech AT115EDT: f/7 triplet. Price is $1399. Weight 13 lbs. I have two very good star diagonals and would likely add a GLP, maybe a Telrad, so not much more $ or weight.

Sky Watcher offers a "premium" doublet, the Evostar 120mm f/7.5 ED doublet, which includes a diagonal and finder, on sale now at $1775, $150 off. Weight 11.3 lbs

What if any advantage is there to the doublet? I've been so happy with the AT, I would be inclined to get another. There is no real weight advantage. The triplet is less expensive. As a CN member, I will get a small discount on either scope at Astonomics.

12-15 lbs is probably about as big an OTA as I or my mounts can handle.

Just for comparison, there is a Takahashi FS-102 for sale on astromart, with a lot of extras, for $1950. Although smaller aperture than the ones I've already mentioned, these scopes are classics, highly-regarded for visual use. If I ever decide to do any AP or more likely EAA, I would use the 80mm f/6 anyway.

I am not ready to whip out my wallet yet. Just interested in your thoughts.

For visual a doublet will do fine and with most of the better quality doublets they will give pleasing views with EAA as well.

Image scale takes a noticeable jump at a 20mm increase in aperture so anything over 100mm compared to your 80mm.
When I was selling equipment a couple of years ago my intent was to only keep the Stellarvue 80mm, Vixen 115mm and the Celestron 150mm.
Jumps of 35mm in aperture.

Benefit of doublets is the weight is lighter than a same sized triplet and they will cool down faster than the triplet.
If a lens goes out of collimation you can typically re-align them yourself but triplets will need to be sent back for alignment.

At 100mm to 120mm your view is typically smaller than the average sized air cell so the telescope will be capable of holding a steadier image longer if skies are less than great.

The AT 115mm seems to have a good following as well as the Skywatcher Evostar. The Takahashi can be considered a lifetime scope,
New Vixen refractors are considered as the poor mans Takahashi for the 103mm and 115mm ED refractors.
Exceptional views with these and lightweight as well. My 115mm fully outfitted is right around 6.3kg (14lb)

Sorry for the rambling posting, if I think of any other benefits I will post them.

Lady Fraktor wrote: ↑Sun Aug 09, 2020 5:48 pm For visual a doublet will do fine and with most of the better quality doublets they will give pleasing views with EAA as well.

Image scale takes a noticeable jump at a 20mm increase in aperture so anything over 100mm compared to your 80mm.
When I was selling equipment a couple of years ago my intent was to only keep the Stellarvue 80mm, Vixen 115mm and the Celestron 150mm.
Jumps of 35mm in aperture.

Benefit of doublets is the weight is lighter than a same sized triplet and they will cool down faster than the triplet.
If a lens goes out of collimation you can typically re-align them yourself but triplets will need to be sent back for alignment.

At 100mm to 120mm your view is typically smaller than the average sized air cell so the telescope will be capable of holding a steadier image longer if skies are less than great.

The AT 115mm seems to have a good following as well as the Skywatcher Evostar. The Takahashi can be considered a lifetime scope,
New Vixen refractors are considered as the poor mans Takahashi for the 103mm and 115mm ED refractors.
Exceptional views with these and lightweight as well. My 115mm fully outfitted is right around 6.3kg (14lb)

Sorry for the rambling posting, if I think of any other benefits I will post them.

Thanks so much for your thoughts, Gabrielle. I would love the Vixen 115ED as I am a fan of their products, but it is priced way out of my range at $2699. The AT115 at $1399 is comfortable. $1795 for the Skywatcher is manageable, especially as it includes diagonal and finder, but I am not sure I see how it is worth several hundred dollars more than the AT.

$1950 is pushing things right now with uncertainty due to COVID and what the future holds for the winter, but that Takahashi is a beautiful scope. Less aperture but it is kind of a legendary scope, a lifetime scope as you say. Due to its hefty construction, the Tak weight is comparable to the larger scopes I'v mentioned, 5.3 kg vs 5.1 for the SW and 5.9 for the AT.

How do you think the fluorite FS 102mm would compare to a larger aperture scope like your Vixen 115 or the other two I mentioned? Aperture is aperture, and I don't want to regret not getting something larger. Do you have reservations about an older fluorite objective?

On the difference between cost of the AT and the Skywatcher, that becomes one of those thorny conversations that I normally hate to get involved with.

The AT was built to a price point and Astro-Tech did not hide this point even going as far as to post how and where they cut corners to keep costs down but produce a good telescope.
I love vendors that have a degree of transparency.
Skywatcher has done the opposite and will no longer state what glass it uses or where they are made. Synta/ Skywatcher/ Celestron refractors are not made in house but contracted out.
The older ones used FPL-53 (here we go ) but I suspect that they have gone to a much cheaper to produce glass like FCD-1 which is considerably cheaper to make and figure but not passing the savings on to consumer. (Price has stayed the same)
Synta has to pay off their lawsuit to Orion somehow

Skywatcher is quite common here and I have looked through them many times and they are good telescopes, I unfortunately have not looked through the AT offering but opinions of people I give credence to have used them and they like them.

A well made Fluorite lens (with proper mating lens) has the ability to essentially give the most corrected view. Fluorite has virtually no light scatter of itself so colour blur becomes a non issue, as JG has shown before in the past, a laser passing through Fluorite the beam disappears.
I have debated quite a bit on finding a TSA-102 for myself but I keep finding more affordable refractors in the meantime.

In comparrison side by side I would expect my Vixen 115mm to keep up with the Takahashi quite well until the skies really started to deteriorate.
At that point the Takahashi should show a good image for longer.
The combination of 100mm aperture and Fluorite lens is what makes these such a potent refractor.

Another excellent line to check for new or used is the TS Photoline series (Teleskop-Service) very good quality of glass and mechanicals and usually cheaper than the equivalent Skywatcher.

Thank you; a lot of good food for thought. I appreciate the time you took to reply.

I too am skeptical of the benefits of a triplet for visual use. In addition to LF's considerations above, a doublet is more easily serviceable if some collimation is needed. I wouldn't mess with a triplet at home.

Nevertheless there is one triplet that I find tempting. https://www.teleskop-express.de/shop/pr ... cuser.html

It would provide a nice-fish aperture jump from my TS 102mm ED f\11 doublet (which is a MIGHTY fine scope for only $500-600) and the SV ED80A. It has a very nice reputation and I've found the TS folks good to deal with.

TS also provides a Long Perng made 120mm f/7.5 doublet. https://www.teleskop-express.de/shop/pr ... cuser.html

Thanks, nFA. The 115mm triplet looks very interesting, and at an attractive price, even with shipping. The doublet is lovely but getting up there in price for my current situation. Like most other people, I am being cautious in uncertain times, but I also need to make the most of life for the same reason.

I wish I had an opportunity to look through a good doublet refractor.

Voyageur wrote: ↑Mon Aug 10, 2020 2:03 am Thanks, nFA. The 115mm triplet looks very interesting, and at an attractive price, even with shipping. The doublet is lovely but getting up there in price for my current situation. Like most other people, I am being cautious in uncertain times, but I also need to make the most of life for the same reason.

I wish I had an opportunity to look through a good doublet refractor.

If you're not doing broad band or one shot color astrophotography there is no need for a triplet. I had the Orion 80mm triplet and, truth be told, my Stellarvue 80mm f7 doublet is a huge improvement at 2/3 the price. I sold the Orion. The SV and my new TS 102mm ED f11 are both excellent.

viewtopic.php?f=65&t=9641

I'm hoping to set up for planetary fun tonight with it. (Shhhhh don't tell the cloud demons. )

PS I had the Skywatcher 120mm ED doublet as well as the Orion version of the same scope. Both are gone. I prefer the longer 102mm ED f11.

I have both the SW120ed and the TS 115 triple. The TS is far better on the planets. Glass matters. A triple matters. The AT is -51 equivalent which means it would probably be about the same as the SW120.

Jones wrote: ↑Mon Aug 10, 2020 8:24 am I have both the SW120ed and the TS 115 triple. The TS is far better on the planets. Glass matters. A triple matters. The AT is -51 equivalent which means it would probably be about the same as the SW120.

Thank you. That's two thumbs up for the TS 115. I'm getting interested.

I had ES 127mm triplet for a while. Loved the views on a good night. However, due to weight/size and acclimation time, setting it up was more chores than 8" SCT. It was CF version of 127mm, so by weight close to 120/115mm aluminum tube triplet.

I often ended up skipping it for 80mm doublet for quick views on bad nights, or 8" SCT for more aperture on good nights.

After I realized that 127mm is sitting unused, I have sold it and got Stellarvue 102mm doublet instead. I feel this is a perfect size for APO/ED visual. Still compact and lightweight for grab and go, and more light gathering compared to 80mm.

For visual I would put Astrotech 102mm ED doublet as a contender. I almost pulled plug on one, but SV 102ED went on sale.

Voyageur wrote: ↑Sun Aug 09, 2020 3:47 pm Sky Watcher offers a "premium" doublet, the Evostar 120mm f/7.5 ED doublet, which includes a diagonal and finder, on sale now at $1775, $150 off. Weight 11.3 lbs

I have two Evostar ED doublets that I use exclusively for solar imaging... 80 & 100mm. The diagonals are great, and the ED glass is equal to my Vixen ED scope. Both fit my imaging needs perfectly.

I liked the 80mm so well that I have a second one that serves as my grab-and-go for visual use.

The price of the 120mm you mentioned above is still over-priced, even with the $150 off offer. Keep an eye on Ocean Pacific Telescopes for better "deals". https://optcorp.com/ They are "tied at the hip" with SkyWatcher and are literally next-door to the SW warehouse, and often can offer better prices than other suppliers.

Clear Skies & Stay Safe

John, thanks for the advice on the SW. I thought the price was high compared to offerings on other brands.

My decision now is whether to go with 100/102 or move up to 115/120. I'm starting to think the larger sizes might be too big for my needs. Thanks for the perspective on that, Andres.

And maybe I will hold off for awhile to see if I am able to travel this fall, and whether my astro club will start having in-person observing once more for club members, if not public outreach. Most of the members are in their 60's and 70s, and some have significant health problems, so we must be very careful.

I have a 107 mmx700mmf.l. made in China 53 triple, and the 115 T.S. is significantly better on the planets. You would not think 8mm diameter would not make that much difference. Things that are barely seen in the 107, are more clearly defined in the 115. The weights are nearly the same. Both work well on the M2 mount I have. My 107 is a very early model. Might not be as good as the later ones.

Jones wrote: ↑Thu Aug 13, 2020 1:51 am I have a 107 mmx700mmf.l. made in China 53 triple, and the 115 T.S. is significantly better on the planets. You would not think 8mm diameter would not make that much difference. Things that are barely seen in the 107, are more clearly defined in the 115. The weights are nearly the same. Both work well on the M2 mount I have. My 107 is a very early model. Might not be as good as the later ones.

I don't believe the difference you see comes from 7% difference in aperture. More likely 115 T.S. is just better configured.

As you know I own a 120mm Evostar APO. And I had a 120mm f/8 achromat in my possession very shortly.
I only had two encounters with the SW line. Both times they had to be sent back to the optical shop for both had some coma. Once the Evostar came back it generated very fine images, an independend optical shop quaranteed Strehl 0.97. So the SW has good potential, but still it is obvious that SW has some work to do in their final control. For that reason only I would not recommend the SW.

My Vixen 102 f/9 ED gives great images of the planets. I would say the 120 has a small advantage here, not much though. You don't need the refractor for deep sky, so that helps.
As I am growing older I sometimes play the following little game with myself; I ask myself: "What if I had to move to another home when I grow older and was allowed to take only one telescope with me?" It is an easy way to force an answer. The answer would be simple: The 102mm . For its weight, versatility and good allround qualities.

So....my 102mm will still be around when all others are long gone...

I hope this helps.
John

Ive owned some good doublets but Im pretty sensitive to false color so a triplet made sense for me. I got a "good one/good example" with my ES 102mm and its optics are really solid. No color on any objects at any focal length. For visual, I am tending to prefer triplets but a well-made doublet is certainly a great choice too. They are lighter, thermally settle in faster and are usually lower in cost model for model.