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Paz

Altair Starwave 102ED-R

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I recently acquired a 102mm ed scope and having learned a lot from reading posts from others about their scopes thought I should share some comments on this one. I've observed previously with achromats, maksutovs, SCTs, and newtonians, but never an ed/apo. The headline specifications are: 

- 102mm aperture, 714mm focal length, focal ratio f7

- Air spaced ed doublet with fpl53 glass

- 2.5" rack and pinion dual speed rotating focuser, with a retractable dew shield.

This happens to be an Altair Astro Starwave 102ED-R scope. I believe you can get similar scopes from other suppliers, however my comments are intended to be more about this scope compared to my expectations and compared to other types of scope than about this scope compared to other 4" apochromats as I have not tried any others.

I bought this as I would like to experience different types of scope for myself and in the hope that I can simplify to a smaller collection of scopes. In particular this scope is planned to be mostly grab and go in nature - potentially replacing both a Star Travel ST120 f5 Achromat and a Bresser MC127 f15 Maksutov. I will be doing some comparisons of these and it will be interesting to see how it goes... the ED102 has quality on its side but the ST120 and the MC127 have more aperture, lower cost, and are no slouches at what they are designed to so.

Here it is with a typical set up I am using - just an RDF, a 6x30 RACI finder, and 1.25" diagonal and most of the time I'll probably be using light eyepieces (SLV's) or a MkIV zoom eyepiece. I don't use 2" gear on small scopes to keep the size/weight down, and with finders I've downsized from a Telrad and a 9x50 RACI also to reduce the size and weight of the kit I am using.

I've started accumulating notes and will post some when I have sensible chunks of commentary to add - fingers crossed!

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Always fun to get something new.

Look forward to your impressions.

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Looking forward to hearing more on this, do let us know your experiences.

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Here's a few initial notes on this scope.

Weight

The scope with no accessories on its own weighs 4.1kg but it feels lighter. In comparison in standard form with no accessories my MC127 weighs 3.3kg and the ST120 weighs 3.9kg.

So the 102ed-r looks heavy at first, especially given its smaller aperture, but if you were to add dual speed focusing capability to the other scopes that would add around 1kg to the ST10 and more than that to the Maksutov, and if you add a means to hold a second finder which the 102ed-r has built in that adds more weight. On the Maksutov a dew shield adds a bit more and when it is back heavy with a dual speed focuser the Maksutov needs a front end dovetail counterweight that adds more weight still. So if you make all the scopes like for like with the same facilities both the MC127 and ST120 would end up well over 5kg like for like.

Size

Size wise the 102ed-r packs down quite short if it needs to with the sliding dew shield retracted. It goes shorter than the ST 120 but the Maksutov is much more compact and it is tough (or should I say impossible?) for a refactor to beat when it comes to the ratio of tube length to focal length. The photos below show them in comparison - the first is how big they are when observing, the second is how small they can pack down.

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Cool Down Time

I have found that it cools quite quickly as expected and quicker that the ST120 or Maksutov. In addition I find that whilst it is cooling down the effect on the views is not as significant and I can use higher magnifications sooner. I haven't got out the stop watch but the Maksutov takes the longest, then the ST120 probably takes 3/4 or less of that time and the 102ed-r maybe takes 2/3 or less of the time the Mak takes. However all these scopes are quite small and none take hours to cool down - the Maksutov takes half an hour usually, maybe 45 mins if it is a big change in temperature.

Set Up and Take Down Time

The 102ed-r and the ST120 are on a par for fast set up and take down, there's nothing to have to do except add finders and a diagonal and eyepiece. The Maksutov requires an add on dew shield which is an extra bit of kit to have to carry out and put on/take off. However there's not a lot in it.

Finder Scopes

The 102ed-r has two finder shoe mounts. This is a very important feature for me. I always like a red dot or red circle finder to get close and a 6x or 9x raci finder to get spot on. Any scope that only has one finder shoe I have to upgrade or modify to get the 2 finder set up which adds weight and complication.

Vibrations

This might seem like an odd or specialist criteria but vibes reduce quality viewing time and can make focusing a nightmare. and getting the focus dead-on makes a huge difference (at least for me). Although light, the 102ed-r is a longer scope and it vibrates at a slower frequency than other 2 scopes. Interestingly I've found that when it vibes as I am focusing the lower speed vibes are less of a problem.  However the Maksutov when not weighed down with accessories gives the least vibes of these 3 scopes by far, and the ST120 vibes the most. I am mostly using it on a Porta 2 mount hence minimizing vibes is a consideration. With an AZ4 or an EQ5 vibes are not really an issue.

Focusing

The dual speed focuser works well - but any dual speed focuser is a big bonus, so in stock form the 102ed-r is much more accurate in getting to focus than the ST102 or Maksutov.  With a dual speed focuser on the other two scopes the Maksutov is as good at focusing but the ST120 remains a bit harder - I wonder if that is because its faster to pass through focus at f5 compared to f7. The 102ed-r focuser is a bit lighter in feel than I like but it is adjustable - I just don't dare to adjust anything if it is functionally working!

The 102ed-focuser is rotatable and this is beneficial as it means I can rotate the position of the finders - sometimes to make them easier to use and sometimes in effect using them as counter weights by placing them opposite to the direction the eyepiece is pointing whenever that is possible.

The 102ed-r has more focuser in-travel available than the ST120, I can use a Herschel Wedge with some room to spare, and I hope I can use a filter wheel which is not possible with the ST120 - I will be testing this. Obviously the focusing range of the Maksutov beats both refractors by a long way.

Practicalities

The 102ed-r is a long scope and  the eyepiece height and position swings around more with differently located targets with the 102ed-r but that's just the nature of the scope. The compact size of the Maksutov makes it really practical in this respect.

The dew shield being attached and retractable is a big benefit - it is one less thing to carry around and you can't lose it in the dark!

The tube rings and dovetail can be positioned so that I can balance it with light or heavy eyepieces without having to move the rings up and down and this saves a bit of hassle. To achieve this I have the rings located as far back as possible.

Having a white OTA has been beneficial and wasn't something I had thought about before. At night it's easier to see things when handling the scope and in daylight looking at the sun I think the white tube reduces the tube currents caused by heat from the sun. whenever the scope is not pointing straight at it.

Summary

Overall the 102ed-r looks to be very good for grab and go from home.  The next step is comparing the views in the field - I have had a few sessions but not enough to draw conclusions yet - I will add further comments once I have had enough field time.

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3 hours ago, Paz said:

Size

Size wise the 102ed-r packs down quite short if it needs to with the sliding dew shield retracted. It goes shorter than the ST 120 but the Maksutov is much more compact and it is tough (or should I say impossible?) for a refactor to beat when it comes to the ratio of tube length to focal length. The photos below show them in comparison - the first is how big they are when observing, the second is how small they can pack down.

Hi Paz,

Thank you for the detailed information! It's in my plans to have a scope like this or something similar. Your pictures about the size are really helpful as this is a crucial point for me (meet airplane cabin bag size, mount capabilities, etc). Could you please tell me what is the exact transport size in length when the dewshield is fully retracted? Without diagonal & eyepiece, of course :) Many thanks in advance!

Clear skies,
Tamas

Edited by nakiazaki
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1 hour ago, nakiazaki said:

Hi Paz,

Thank you for the detailed information! It's in my plans to have a scope like this or something similar. Your pictures about the size are really helpful as this is a crucial point for me (meet airplane cabin bag size, mount capabilities, etc). Could you please tell me what is the exact transport size in length when the dewshield is fully retracted? Without diagonal & eyepiece, of course :) Many thanks in advance!

Clear skies,
Tamas

With the dewshield retracted I make it 61cm long as it is shown in the photo above. It is 74.5cm with the dew shield extended.

I note that the Altair Astro site says it is 68cm with the dew shield retracted but I've measured it myself and all I know is my tape measure says it is 61cm.

The only thing I can think of is if you have the tube rings placed a long way up the tube you won't be able to retract the dew shield all the way hence maybe the difference as I have the tube rings as far back as they will go?

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1 hour ago, Paz said:

With the dewshield retracted I make it 61cm long as it is shown in the photo above. It is 74.5cm with the dew shield extended.

I note that the Altair Astro site says it is 68cm with the dew shield retracted but I've measured it myself and all I know is my tape measure says it is 61cm.

The only thing I can think of is if you have the tube rings placed a long way up the tube you won't be able to retract the dew shield all the way hence maybe the difference as I have the tube rings as far back as they will go?

Oh yeah, that's why I asked. I know that SW 120/600 is quite short and I was wondering how could be this 102ED-R tube 60 cm long. Thank you for the accurate answer!

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Today I've ordered one. Hope it will arrive soon and all the clouds will go away from above Central Europe :)

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Yesterday it has arrived. It's a beauty! I was a bit lucky as there was an hour maybe just to have a quick test before the fog arrived. Unfortunately the seeing was not my friend and I had to hurry so I was just jumping from target to target. Extra aperture clearly brought slightly brighter M42 compared to 80/600 just as expected. Venus was more disk-like than in the smaller scope. No annoying color fringing, at least for my taste. I found finding the perfect focus was a bit harder, but it may have caused by poor seeing conditions as mentioned earlier.

About the OTA: it is a really nice scope, mechanical design is flawless! Sliding dewcap fits perfectly and easy to move, the matte white finish is so elegant. Serial number on the lens strenthens the feeling that it must have passed a proper QA. So bad that I was not able to make a proper test with tight double stars. Defocusing bright stars brought nice concentric rings both in and out so collimation is perfect, I did not expect anythis else on this. The focuser is a dream! I have never used a good rack and pinion style focuser, only the cheap ones plus Crayford-style on my previous ED tube and the special one on Maksutovs. It's a different thing. No accidental sliding with heavy eyepieces or camera attached, just smooth operation. It was a new thing for me that both 2" and 1.25" connection is a ring, not screws. 1.25" holds the diagonal perfectly, but using that I have to take it out from the wider one in order to properly pinc the ring. I felt pinching the 2" ring is a bit loose, at least I felt it's still can slip out even on tightest position - does anyone have the same feeling? It's still okay, but it would be good to tighten it a bit more.

Here are some pictures. Nothing new, I know, but it's such a beauty :)

 

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07F9B790-C239-45D9-803B-CACD20E81536.jpeg

Edited by nakiazaki
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On 12/01/2020 at 21:35, Paz said:

With the dewshield retracted I make it 61cm long as it is shown in the photo above. It is 74.5cm with the dew shield extended.

I note that the Altair Astro site says it is 68cm with the dew shield retracted but I've measured it myself and all I know is my tape measure says it is 61cm.

The only thing I can think of is if you have the tube rings placed a long way up the tube you won't be able to retract the dew shield all the way hence maybe the difference as I have the tube rings as far back as they will go?

Paz, just a question. The self-centering twist locks are really good, the 1.25 one is holding the small diagonal and eyepieces tightly, but the one for 2" accessories is a bit loosy. As I rotate the capstan wheel it is loosening or tightening itself, but even on the most tight position, I can still pull out the inserted accessory. What do you think, is there an easy way to make it more tight? I have a feeling that if I would use some heavier camera or eyepiece it might fall off accidentally. A bit thicker inner plastic ring would be better for stronger support of the 2" diagonal. What's your experience, is it the same for you maybe?

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3 hours ago, nakiazaki said:

Paz, just a question. The self-centering twist locks are really good, the 1.25 one is holding the small diagonal and eyepieces tightly, but the one for 2" accessories is a bit loosy. As I rotate the capstan wheel it is loosening or tightening itself, but even on the most tight position, I can still pull out the inserted accessory. What do you think, is there an easy way to make it more tight? I have a feeling that if I would use some heavier camera or eyepiece it might fall off accidentally. A bit thicker inner plastic ring would be better for stronger support of the 2" diagonal. What's your experience, is it the same for you maybe?

On mine I have to really twist it to get it to clamp hard. Once its fully twisted it's solid. The downside of this is it usually unscrews the adapter from the drawtube when you try to undo it.

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My twist locks both work fine but I have realised I don't really like the twist lock design.

I have found that it is quite fiddly getting my fingers on the 1.25" twist lock to lock it. Out in the field in the cold and dark everything needs to be easy to do.

I therefore bought a Baader click lock. This is slightly easier to access but still not straightforward, and this I didn't like because you put big twisting forces on the draw tube when you tighten it which I am not confident the draw tube is really designed to take.

So I have gone back to basics and I'm using a traditional compression ring adapter. I have put a long screw on it so it is easy to tighten and this works well.

 

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Thank you for the answers, both of you. Yes, I'm still evaluating how I will like the twist lock design. My concern is almost the same than yours, Paz, that I have to twist it quite hard to reach proper solidity and I can accidentally turn my scope away which is not too good if you are using a goto mount. Normally I have to do it once at the beginning when I put my camera or diagonal into it, so it's not a big issue. But yes, maybe I'll end up with the standard compression ring method eventually, I do not know yet.

By the way, Yesterday I fixed the bigger twist lock with a 1x1 cm insulation tape on the plastic inlay ring. That narrowed down the barrel to the level where I can tighten the lock securely. So, everything is okay now :)

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Hi Paz, that's a stunning refractor, mine is also on a Porta II mount, very stable I think!

027a.thumb.jpg.7def0457105c714273472e234f5a8105.jpg

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Great scope, Paz!

F7 Is a nice focal ratio for refractors as colour is well controlled and wide field views are possible. I know you said that you don't plan to use 2" EPs, but a 30mm like the APM UFF weighs about 550g and can offer you slightly more than 3 deg of sky, which is great for scanning the milky way. Just a comment of course.

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6 hours ago, rwilkey said:

Hi Paz, that's a stunning refractor, mine is also on a Porta II mount, very stable I think!

027a.thumb.jpg.7def0457105c714273472e234f5a8105.jpg

That's a nice set up you have there. The Porta 2 is good, I use it a lot.

I agree the Altair is a good looking scope, which is useful in this country where due to the weather  you get a lot more time to look at your scope that you get looking through it!

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5 hours ago, Piero said:

Great scope, Paz!

F7 Is a nice focal ratio for refractors as colour is well controlled and wide field views are possible. I know you said that you don't plan to use 2" EPs, but a 30mm like the APM UFF weighs about 550g and can offer you slightly more than 3 deg of sky, which is great for scanning the milky way. Just a comment of course.

That is good advice as it would get even more benefit out of the scope.

I have to date only used 2" eyepieces with my dobsonian. I have 31mm and 22mm Naglers which are a bit chunky.

I am supposed to get through 2020 with no astro purchases 😮 but secretly I have been fantasising about getting a 2" diagonal as it would not cost much in the scheme of things and it would connect a good scope with some good eyepieces! Who knows if I will be able to stick to my principles!

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38 minutes ago, Paz said:

That is good advice as it would get even more benefit out of the scope.

I have to date only used 2" eyepieces with my dobsonian. I have 31mm and 22mm Naglers which are a bit chunky.

I am supposed to get through 2020 with no astro purchases 😮 but secretly I have been fantasising about getting a 2" diagonal as it would not cost much in the scheme of things and it would connect a good scope with some good eyepieces! Who knows if I will be able to stick to my principles!

A 2" diagonal would be a great upgrade Paz. I love widefield observing with my Tak or Genesis,  get yourself a decent OIII filter too and have a ball with the NAN and Veil!

Lovely looking scope by the way 👍

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2 hours ago, Stu said:

A 2" diagonal would be a great upgrade Paz. I love widefield observing with my Tak or Genesis,  get yourself a decent OIII filter too and have a ball with the NAN and Veil!

Lovely looking scope by the way 👍

Thanks - the chances of me sticking to no purchases this year is not looking good!

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Here's some notes from a couple of sessions. I was hoping to accumulate more notes from observing in good conditions so as to be as fair as possible but I've realized that poor conditions (light pollution and wobbly seeing) and unfavourable circumstances (short sessions, don't always have cooldown time, don't always have time to dark adapt) defines most of my observing so my comparisons need to be considered in that context.

Session 1

I had a session on the moon. The conditions were thin cloud coming and going - most of the time the Moon was observed through thin cloud with the odd black out and the odd spell of clarity. I did half of the sesion with the 102ED-R and half of the session with my ST120. I used a dielectric mirror diagonal with a Baader Mk4 Zoom plus 2.25x barlow and also 10mm and 4mm SLV's so going up to 179x with teh 102 ED-R and 150x with the ST120.

My first conclusion was how hard it is to actually compare scopes - which I've never tried to do pro-actively before. Getting 2 scopes ready and swapping them around takes a lot more time and effort! Also as I had to look through one after the other I could not compare side by side. This meant some differences may have been missed.

Colour Fidelity

The moon looked black/grey/white with the 102ED-R, my notes say "I think some CA but you have to look for it". In comparison the ST120 shows a purple tinge to the lunar surface and a yellow halo off the limb that you don't have to look for, however I don't find it a problem.

Field Curvature

I think the 102ED-R showed less field curvature, I notice field curvature particularly when observing the moon.

Resolution

Neither scope obviously showed more detail but this was very hard to judge with the conditions. However the 102ED-R felt like it spent more time in accurate focus. I was wondering which would show more detail - the 102ED-R has better quality glass and a slower f ratio on its side but the ST120 has aperture on its side.

Scatter

I noticed that the 102ED-R controlled super-bright and high contrast features well. In this session the toughest targets on the moon were the inner lips of crater walls just as they were getting lit up  - they bleach out more in the ST120.

Handling

The 102ED-R is easier to handle - lighter and an easier shape to carry.

Session 2

A session looking at double stars and comparing with the MC127 Maksutov. This time I had both scopes out at the same time on different mounts so I could compare quickly. However I had a Baader prism diagonal in the Maksutov and a Altair dielectric mirror diagonal in the 102ED-R most of the time. I used Polaris to test ability to see a fainter secondary, and Castor to test ability to control bright targets. It was again cloudy with thin cloud coming and going.

Light Gathering

The MC127 clearly showed the secondary of Polaris as being brighter. It also showed dimmer field stars around Castor. I think this is just a case of brute force/aperture.

Cooldown

The 102ED-R was much less affected by tube currents from the start although the Maksutov caught up over time. Brighter targets were noisy in the Maksutov while it was cooling.

Focusing

The focuser of the 102ED-R was much better than the Maksutov system. I really noticed the mirror flop and lack of a fine tuning facility in the Maksutov by having the scopes out together to test back to back. I had never particularly noticed it much before.

Controlling Bright Stars

The Maksutov showed a nice but more noisy image of Castor. The 102ED-R showed cleaner images of Castor with the stars looking like smaller points. with more clear space between.

Colour Fidelity

Castor looked whiter in the Maksutov and slightly warmer in the 102ED-R. Star testing showed fairly colour free rings but not 100% so.

Summary

The Maksutov suffered from not being cooled down but the Maksutov can go deeper and is better on faint stars.

Spherical Abberation

Star testing showed lots of thin concentric and equidistant bands  then a broader black ring then a broader outer ring. Refreshing my memory reading Harold Suiter's star testing book this is a sign of spherical abberation however I recall the same thing more so on my ST80 and ST120.

Overall

I think if the Mak was cooled down, dare I say it would stretch out in front of the 102ED-R in terms of image quality. I predict that on very faint targets the ST120 will also do well in comparison to th 102ED-R. The 102ED-R has not blown the other scopes away but it has the disadvantage of smaller aperture. However having said that it is very easy to handle and to use and I have realized through recent experience that the quality of view matters but so dose practicality. The things that have impressed me more so far are it's light weight, accurate focuser, having 2 finder mounts, and that it is not that bothered by cooldown problems. It is also a better general purpose scope - it can do DSO's or lunar caters and everything in between. All these things facilitate more observing time.

If you factor in the cost of the scopes the MC127 and ST120 are I think better value for money but the 102 ED-R  is better all rounder.

It will be interesting to see which scopes get picked after a while when the novelty has worn off. I ever get good conditions I may be able to do some better comparisons.

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19 hours ago, Piero said:

Great scope, Paz!

F7 Is a nice focal ratio for refractors as colour is well controlled and wide field views are possible. I know you said that you don't plan to use 2" EPs, but a 30mm like the APM UFF weighs about 550g and can offer you slightly more than 3 deg of sky, which is great for scanning the milky way. Just a comment of course.

Hi Paz, great advice there from Piero, I have the 31NT5 and the ExSc 30mm 80 degree series, and both give stunning views of the night sky, even at f/9; at f/7 it should knock your socks off!  Clear skies!

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Paz,

Nice eval. Thanks for taking the time to do so.

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