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Sky-Watcher SkyMax-127; true Aperture, and Diagonal size...

Maksutov cassegrain catadioptric eyepieces
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#1 Nordic_man

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Posted 19 April 2019 - 07:22 AM

Greetings !

 

I am planning to buy a small telescope to my country house, to complement a S-W ST-80 with an AZ-3 that I have there. I also have a sturdy Photo Tripod (6 kg payload for the head/mount, and 12 kg payload for the tripod) to use for mounting.

 

Due to a rather limited budget (nowadays I am retired) my choice is a S-W SkyMax-127 Mak, for which I also have an Intes Micro 0.6x Telecompressor (which I think is 2" though, so maybe it cannot be used here).
Yes, I do have a lot of Astro gear at home, at my permanent, every day place, but I would rather not (for certain reasons) like to split the "kit" I have here (and transporting, back and forth, is out of the question).

 

Thus, my choise is the SkyMax-127 Mak, and a few Eye Pieces, and a Tele Vue 2x Barlow. Yes, a better Diagonal, and a good Amici Prism too...
And yes, a SkyMax-150 (also including a bigger mount) would (at this point) be beyond my budget, and it would have been a better choice, but I hope to be able in the future to (possibly) get a third scope to my country house.
(Maybe I can one day finalize this with an 8" SCT or Dob...)

 

 

There seems to be a possibility though that the SkyMax-127 comes with a 2" Diagonal, which it, for some reason, does not (or did not) allways do.

 

Sky-Watcher at their Global site, http://www.skywatche...bk-mak127-otaw/, and Sky-Watcher USA, http://www.skywatche...cher-skymax-127, DO advertise a 2" Diagonal and connection.
In Sweden though, and in Europe, I do not know where to go, or to look, to find anything else but a 1,25" connection here.

 

Is this because retailers would like to "sell out" their old versions first, before offering the new one ?
Strangely enough though you could find the OTA with the new green dovetail, but still with a 1,25" Diagonal...

 

Does anybody know, if there is a recent (permanent) change here to the bigger Diagonal, and what about the (true optical) Aperture that (according to some) used to be less than 127 mm ?

 

I have read that that limited Aperture has been upgraded, is that so ?
If so, what should I look for, in order to know if I am buying an upgraded version ?

 

What do you say ?

 

 

Thank you very much !

 

Clear Skies to you,
Erik

 

 

Edited to specify links.


Edited by Nordic_man, 19 April 2019 - 07:39 AM.


#2 KerryR

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Posted 19 April 2019 - 09:11 AM

Given the baffle diameter on the 127, would there be any advantage to using a 2" diagonal?

I don't know if the undersized primary problem (127) has been addressed. There hasn't been any mention of it in recent threads where the issue was pointed out. That makes me think the problem still exists. I wonder if you could talk to someone at Skywatcher to find out?


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#3 Eric63

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Posted 19 April 2019 - 11:13 AM

I have a skywatcher 127mak and as far as I know skywatcher has not yet addressed the undersized primary issue. I also have the 2" diagonal version with mine and that changes the focal length to 1750mm. Now having said this, I still find that this instrument provides amazing views for its size, especially on lunar and planetary. And I also love the view with a 2" 32mm 70 degree EP. I find I get that feeling of immersion and any vignetting is not really noticeable. If you can find a 2" version I would recommend it, but if not I have to say that using a 1.25" 24mm panoptic in that instrument is quite impressive. This instrument is no slouch and I take it out more often because of it's size and ease of use.

Eric
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#4 Nordic_man

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Posted 19 April 2019 - 11:14 AM

Kerry,

 

the question is then why S-W would manufacture, or at least sell, the SkyMax-127 with a 2" Diagonal to begin with.

 

Have they changed the baffle size too ?

 

Erik



#5 Conaxian

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Posted 19 April 2019 - 11:54 AM

The only thing I don't like about my SW127 is the paint job. It gave me goosebumps observing the moon with a GSO 2" dialectric and a Q70 38mm eyepiece. Then in went the Olivon 15mm 2", and it got even better. There were subtle colorations of olive green and pale orange I've never noticed before in any scope. The 15mm is an 82 degree field and is a good performer that was almost parfocal with the Q70 (nice!) It is my favorite EP with this tube. Got it used right here on CN for a song.

After those I tried the 12mm dual ED and the 8mm.  All of them were great- I was roaming the valleys and rilles just like I used to do with my (old, sold) Intes 6" mak.

I tried a 6mm Edge eyepiece- no image. Just a thousand eye floaters, so that exit pupil is unusable for my old eyes. Can't win them all. For me, it tops out at about 220 power.

 

It is a great little telescope and a great value at its price.  Removing the meniscus and modifying the secondary baffle is a snap. Like opening a jar of pickles.

For sharp, long focal length views in a short package, it works! I consider it the equal of a 120mm ED, but the ED would need shorter eyepieces to keep up.



#6 KerryR

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Posted 19 April 2019 - 12:23 PM

Kerry,

 

the question is then why S-W would manufacture, or at least sell, the SkyMax-127 with a 2" Diagonal to begin with.

 

Have they changed the baffle size too ?

 

Erik

Well, I think it'd be tough to make the baffle larger without also increasing the already large secondary size, which would go a long ways towards degrading the Mak's claimed "refractor like" performance. I'm doubtful they did this, but I don't know for certain.

If they do indeed supply the scope with a 2" diagonal, and they haven't also done a significant overhaul to the design, then my guess would be that Skywatcher's reasoning would be two-fold: 1) Many users don't know about field stop (or baffle, in this case) vs. FOV, and 2) It simply allows users to use their existing 2" ep's if they want to, even though FOV will be determined by the baffle and not the field stop of the ep.



#7 Eric63

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Posted 19 April 2019 - 12:30 PM

From my experience the 2" diagonal did not make a big difference with respect to the field of view but it did make one with respect to the viewing experience at the lower powers.

#8 skyward_eyes

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Posted 19 April 2019 - 12:36 PM

The primary of the 127 is not undersized, the actual primary diameter measures 132mm. 


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#9 Nordic_man

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Posted 19 April 2019 - 12:50 PM

I have a skywatcher 127mak and as far as I know skywatcher has not yet addressed the undersized primary issue. I also have the 2" diagonal version with mine and that changes the focal length to 1750mm. Now having said this, I still find that this instrument provides amazing views for its size, especially on lunar and planetary. And I also love the view with a 2" 32mm 70 degree EP. I find I get that feeling of immersion and any vignetting is not really noticeable. If you can find a 2" version I would recommend it, but if not I have to say that using a 1.25" 24mm panoptic in that instrument is quite impressive. This instrument is no slouch and I take it out more often because of it's size and ease of use.

Eric

 

Eric,

 

thank you for your reply. One thing I can not grasp is how a bigger Diagonal changes the focal length of a scope. It is just a mirror (or prism) in there, how could that disperse the rays, so that the focal point moves ?

Good to hear that 2" Eye pieces work fairly well. How about DSO observing ?  Do you get enough light input to get a good view of some of them ?

 

Erik

 

 

The only thing I don't like about my SW127 is the paint job. It gave me goosebumps observing the moon with a GSO 2" dialectric and a Q70 38mm eyepiece. Then in went the Olivon 15mm 2", and it got even better. There were subtle colorations of olive green and pale orange I've never noticed before in any scope. The 15mm is an 82 degree field and is a good performer that was almost parfocal with the Q70 (nice!) It is my favorite EP with this tube. Got it used right here on CN for a song.

After those I tried the 12mm dual ED and the 8mm.  All of them were great- I was roaming the valleys and rilles just like I used to do with my (old, sold) Intes 6" mak.

I tried a 6mm Edge eyepiece- no image. Just a thousand eye floaters, so that exit pupil is unusable for my old eyes. Can't win them all. For me, it tops out at about 220 power.

 

It is a great little telescope and a great value at its price.  Removing the meniscus and modifying the secondary baffle is a snap. Like opening a jar of pickles.

For sharp, long focal length views in a short package, it works! I consider it the equal of a 120mm ED, but the ED would need shorter eyepieces to keep up.

 

Conaxian,

 

I myself find the paint job, if you mean the "black Diamond" thing, to be rather nice. Maybe not the "institutional look", like a white refractor, but not really bad.

Thank you for your input. I am planning to use a 38 mm Q70 with this Mak, so that is good to hear.

 

I don't know how far I will be able to go here, as to magnification, but I use to be able to push my scopes quite a bit. I once used around 390x with my M500 Dlx, on the moon, and that was no problem...

 

Hmm, I am not really the type of person who is comfortable with modifying my Telescopes, but maybe I will come to that too... 

 

Erik


Edited by Nordic_man, 19 April 2019 - 01:35 PM.

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#10 KerryR

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Posted 19 April 2019 - 12:58 PM

The primary of the 127 is not undersized, the actual primary diameter measures 132mm. 

Does that effectively fix the significant sub-aperture issue?

 



#11 Conaxian

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Posted 19 April 2019 - 01:05 PM

Nordic Man- For Heaven's sake don't feel you need to mess about with your telescope. I am a tinkerer by nature that modifies virtually every new toy I get.

The primo views of the moon were gotten before I trimmed the secondary baffle. 

As far as the paint, I like the ivory white but somehow the metalflake paint on the tube doesn't do it for me. I have it wrapped in Reflectix so I can't see it anyway. :)

The 38mm gives a low power 'space walk' with its enormous top glass and luxurious eye relief.  Since then I have gotten the Q70 26mm to use with this scope, too.

Hopefully parfocal, they'll make a fine set for it. 

I had very good results with Agena Dual EDs at only $52 apiece on sale.  The 12 and the 8 are both very useful.

 

I think the scope (through younger eyes) can probably work well at higher mags than I can use. My eyes are not what they once were.



#12 Eric63

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Posted 19 April 2019 - 01:14 PM

Does that effectively fix the significant sub-aperture issue?


My 2012 127mak does have such a primary but Unfortunately the flashlight test still shows the actual aperture being in the 120mm range. Regardless, it's the experience at the EP that counts and this is still a great little scope.

Eric
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#13 Eric63

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Posted 19 April 2019 - 01:17 PM

Erik

The advertised 1540mm focal length is without a diagonal. The 1.25" diagonal increases the light path and thus the focal length and the 2" diagonal even more. I have only measured the focal length with a 2" diagonal.

Eric

#14 Nordic_man

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Posted 19 April 2019 - 01:31 PM

The primary of the 127 is not undersized, the actual primary diameter measures 132mm. 

 

Thank you very much for your information, skyward_eyes.

 

That is good to hear, as there has been a lot of talk about it earlier.

 

How about the 2" Diagonal then ?

Some vendors sell the 1,25" version, and some the 2" version. How is that ?

As I said, even with the new, green dovetail, I mostly find the 1,25" version in Europe.

 

Yes, it seems to me a bit unprobale that a 2" eye piece would not vignette in this small aperture Mak.

What about that - why is it (sometimes) sold with a 2" Diagonal ?

Is the connection then a true 2" connection, for a 2" eye piece, or is it more that 2" eye pieces can be used ?

 

Erik



#15 Eric63

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Posted 19 April 2019 - 02:03 PM

Erik.

 

Don't let the aperture issue discourage you from getting this scope.  Whether it is 120mm or 127mm, this is still a nice instrument.  I was concerned about this back when I first got it until someone here on Cloudy Nights told me to just enjoy the view, and in the end that's what I did. I have provided my knowledge of the scope parameters simply as fact and not to discourage anyone.  I have often compared my 127Mak to my 150F5 reflector with a high quality refigured mirror. Appart from the brighter image of the 6", everything I could see in the 6" I could still see in the 127Mak. The difference on lunar and planetary was very subtle and unless you are someone with many years of viewing experience, I doubt you would notice it.  Good seeing conditions make such a huge difference compared to the difference between 120mm vs 127mm.   Even the larger secondary on these Maks has little noticeable impact in my opinion (my reflector has 33% CO while the 127 mak is closer to 40% due to the baffle and the reduced aperture and the lunar and planetary views are very similar).

 

Here in Canada it is sold with the 2" diagonal but I am not sure about Europe.

 

What I enjoy the most about this scope is it's compact size and how portable it is. This makes a difference on those nights that you don't feel like setup up something complicated.

 

Eric 

 

P.S.  even if it comes with a 1.25: diagonal, you can still change it to a 2" Visual back in the future if you wish.  I use 1.25" EP with this scope 90% of the time.


Edited by Eric63, 19 April 2019 - 02:04 PM.


#16 Conaxian

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Posted 19 April 2019 - 02:08 PM

Thank you very much for your information, skyward_eyes.

 

That is good to hear, as there has been a lot of talk about it earlier.

 

How about the 2" Diagonal then ?

Some vendors sell the 1,25" version, and some the 2" version. How is that ?

As I said, even with the new, green dovetail, I mostly find the 1,25" version in Europe.

 

Yes, it seems to me a bit unprobale that a 2" eye piece would not vignette in this small aperture Mak.

What about that - why is it (sometimes) sold with a 2" Diagonal ?

Is the connection then a true 2" connection, for a 2" eye piece, or is it more that 2" eye pieces can be used ?

 

Erik

I retrieved my original visual back from storage (I have an SCT focuser on it now) and measured the clear aperture (field stop?) of it.

It measures only 34mm.  I believe the long light cone formed by the optical tube is pretty narrow at that point anyway.

My opinion is that the 2" accessories are not actually necessary, but still provide an increase in the fun quotient.  I appreciate their long eye relief.

edit: And I use 2" eyepieces most of the time... lolz


Edited by Conaxian, 19 April 2019 - 02:15 PM.


#17 Conaxian

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Posted 19 April 2019 - 02:22 PM

Erik

The advertised 1540mm focal length is without a diagonal. The 1.25" diagonal increases the light path and thus the focal length and the 2" diagonal even more. I have only measured the focal length with a 2" diagonal.

Eric

I am curious how you measured the F/L.  Since the scopes are always used with a diagonal, I would have hoped they included one in their published F/L specs, but maybe not, eh?

Also, I think 1750mm sounds a little long.  That would be 210mm longer than advertised.  8 1/4" increase from a 2" diagonal just seems like a stretch.

Regards!



#18 Eric63

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Posted 19 April 2019 - 02:27 PM

I am curious how you measured the F/L.  Since the scopes are always used with a diagonal, I would have hoped they included one in their published F/L specs, but maybe not, eh?

Also, I think 1750mm sounds a little long.  That would be 210mm longer than advertised.  8 1/4" increase from a 2" diagonal just seems like a stretch.

Regards!

This is how I did it. The moon method in the post worked best.

 

https://www.cloudyni...k-focal-length/



#19 Conaxian

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Posted 19 April 2019 - 02:45 PM

This is how I did it. The moon method in the post worked best.

 

https://www.cloudyni...k-focal-length/

Thanks! That was an interesting read.  SkyWatcher should be more accurate with the specs on these things.  I suspect I'm operating at about F/14.5.

No big deal, it makes those long eyepieces even better for my use.



#20 Simon B

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Posted 19 April 2019 - 03:18 PM

This used to be a problem with the 150mm and 180mm Synta maks, but not anymore - they were fixed a few years ago. Why hasn't it been fixed with the 127 I wonder. And if it has, that news should be spread ASAP, I would have thought

 

If and when it is confirmed to be fixed, I'll probably sell my JOC and get the Synta. Otherwise, I'm keeping my extra 7mm of aperture


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#21 Nordic_man

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Posted 19 April 2019 - 03:27 PM

Erik

The advertised 1540mm focal length is without a diagonal. The 1.25" diagonal increases the light path and thus the focal length and the 2" diagonal even more. I have only measured the focal length with a 2" diagonal.

Eric

 

This is the thing I really don't understand. The light cone is shaped, finally, by the secondary mirror, isn't it ?

How can a Diagonal with just a flat mirror change the angle of this cone, and move the Focal Point ?

I thought that you had to rack the focuser in or out to adjust the Diagonal to the Focal Point...

 

 

Erik.

 

Don't let the aperture issue discourage you from getting this scope.  Whether it is 120mm or 127mm, this is still a nice instrument.  I was concerned about this back when I first got it until someone here on Cloudy Nights told me to just enjoy the view, and in the end that's what I did. I have provided my knowledge of the scope parameters simply as fact and not to discourage anyone.  I have often compared my 127Mak to my 150F5 reflector with a high quality refigured mirror. Appart from the brighter image of the 6", everything I could see in the 6" I could still see in the 127Mak. The difference on lunar and planetary was very subtle and unless you are someone with many years of viewing experience, I doubt you would notice it.  Good seeing conditions make such a huge difference compared to the difference between 120mm vs 127mm.   Even the larger secondary on these Maks has little noticeable impact in my opinion (my reflector has 33% CO while the 127 mak is closer to 40% due to the baffle and the reduced aperture and the lunar and planetary views are very similar).

 

Here in Canada it is sold with the 2" diagonal but I am not sure about Europe.

 

What I enjoy the most about this scope is it's compact size and how portable it is. This makes a difference on those nights that you don't feel like setup up something complicated.

 

Eric 

 

P.S.  even if it comes with a 1.25: diagonal, you can still change it to a 2" Visual back in the future if you wish.  I use 1.25" EP with this scope 90% of the time.

 

I am not that concerned about the Aperture, but it is nice to hear from skyward_eyes that the mirror (nowadays ?) is 132 mm.

 

The real problem is the 2" Diagonal. If the scope comes with one or not, and how 2" eye pieces will work with a 127 mm Mak.

 

Is the connection/visual back really big enough with a 1,25" Diagonal included to change to a 2" one ?

 

Erik


Edited by Nordic_man, 19 April 2019 - 03:29 PM.


#22 Eric63

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Posted 19 April 2019 - 03:35 PM

This is the thing I really don't understand. The light cone is shaped, finally, by the secondary mirror, isn't it ?
How can a Diagonal with just a flat mirror change the angle of this cone, and move the Focal Point ?
I thought that you had to rack the focuser in or out to adjust the Diagonal to the Focal Point...



I am not that concerned about the Aperture, but it is nice to hear from skyward_eyes that the mirror (nowadays ?) is 132 mm.

The real problem is the 2" Diagonal. If the scope comes with one or not, and how 2" eye pieces will work with a 127 mm Mak.

Is the connection/visual back really big enough with a 1,25" Diagonal included to change to a 2" one ?

Erik


It's the total distance to the EP created by a combination of the diagonal length and the mirror position for that diagonal.

As for the visual back, many here on CN have upgraded their Synta mak 1.25" VB to a 2" VB using a SCT accessory.

Eric

#23 Nordic_man

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Posted 19 April 2019 - 03:38 PM

I retrieved my original visual back from storage (I have an SCT focuser on it now) and measured the clear aperture (field stop?) of it.

It measures only 34mm.  I believe the long light cone formed by the optical tube is pretty narrow at that point anyway.

My opinion is that the 2" accessories are not actually necessary, but still provide an increase in the fun quotient.  I appreciate their long eye relief.

edit: And I use 2" eyepieces most of the time... lolz

 

Yes, I too believe that the light cone is pretty narrow at the visual back point, so to speak, but I am not sure if that is enough, if the scope is not made for 2" eye pieces…

I definitely like 2" eye pieces myself, when appropriate, especially for low power, wide field views.

 

Erik



#24 Eric63

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Posted 19 April 2019 - 03:50 PM

I remember when I had my scope alligment checked at the store when I bought it. The store technician removed the diagonal and then inserted an extension tube in the back before placing the EP. This was done so that he would not have to move the mirror significantly. So the diagonal impacts the mirror position, which changes the focal length.
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#25 Nordic_man

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Posted 19 April 2019 - 03:52 PM

It's the total distance to the EP created by a combination of the diagonal length and the mirror position for that diagonal.

 

I think that I would need a ray diagram to really get this thing, but never mind, I can try to read up a bit more on this subject.

My (obviously wrong) idea is that the Focal Length is determined by the angle of the Light Cone - not how many times the light is reflected or criss-crossed through the light path… Or, how far the light travels, after being reflected or criss-crossed.

 

Thank you anyway !

 

Erik




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