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14" skywatcher

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#1 Nunyur

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Posted 11 October 2019 - 09:26 AM

The wife and I are looking to get a 14" skywatcher synscan, we are interested  in visual only.We have a nexstar 127 slt now and really enjoy it but want more aperture. My hesitation is with the coma, will we need to add a corrector as well and higher quality eyepieces? That's not something I want to do due to the money.  We have also been considering a 12" lx90 sct and adding a heavy duty tripod to that.Can a 2" visual back be added to it as well?She is adamant about getting the faster scope, size and weight aren't an issue . This is a big purchase for us so we (I) want to make it the right one. Thank you for your time.  Greg and Kathee 



#2 skyward_eyes

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Posted 11 October 2019 - 10:04 AM

Coma isn't a huge problem at f/4.6 which the 14" model is. It is really a personal choice at that speed. I have friends who say yes you need a coma corrector at that speed. I personally dont feel the need for coma corrector until approaching closer to f/4.


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#3 Lukes1040

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Posted 11 October 2019 - 10:07 AM

Coma seems to be a personal preference issue. Some people can't stand it, and others don't really notice it. That being said, if you do feel the need for a coma corrector, high end eyepieces aren't required to work with it. Sometimes people get away with using higher end eyepieces in place of a coma corrector. My dob is f4.9, and I do not use a corrector. 


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#4 Taosmath

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Posted 11 October 2019 - 10:10 AM

I don't have this model, but I have an F4.5 Dob.  I have a coma corrector for it, but I rarely use it.  I personally don't find it worth the hassle.

 

However that's the issue - personally.  Everyone's tolerance for imperfections is different. You may not be bothered by coma either, or you may find it very distracting - is there any way you could look through a decent F4.5 Dob (wouldn't have to be a 14") and see for yourself?  Maybe you could visit a local club and see if one of the members has one you could look through?

 

If your 127 SLT is properly collimated, you are likely to get sharper images through that than the dob.  This is due both to the design of the SLT (a Mak which has corrections in the front meniscus and it's a F12) and the fact that its aperture is smaller.  When you look through a large Dob you are averaging the image over a column of air 14" across (as opposed to 5" for the Mak) .  This means you are more susceptible to atmospheric turbulence which most nights will be sufficient to smear the image more in the Dob than in the smaller Mak.

 

However, the images of DSO's in the Dob will be far more detailed than in the Mak. You will clearly see features in the Dob that you cannot even get hints of in the Mak.  Most of us with large Dobs have smaller scopes (Maks,  SCT's or refractors) which we use to look at brighter objects (planets, moon, double stars) and use the Dobs for what they are good at - exploring the DSO's - 'the Faint Fuzzies'.

 

You are likely to want to get at least some different eyepieces for the Dob.  The focal length of the Dob (1600mm) will be very similar to your Mak (1520mm) so you can use the same eyepieces in both to give similar magnifications for higher powers.  However the Dob will have a 2" focuser and so you may want to buy a 2" wide field eyepiece or two for the Dob, say a 30mm and a18-23 mm to take advantage of the wider field of view.  Whether you need to buy higher quality Ep's for the Dob to minimize coma etc. depends pretty much upon the answer to you first question - are you personally sensitive to optical aberrations ?  I am not.  I am quite happy with some basic to mid range eyepieces in any scope I've used so far.

 

Two weeks ago I compared a Nagler 31mm to my 31mm Axiom and couldn't really see any great difference between the two in my 18" F4.5 Dob - certainly not enough to warrant the 3x cost increase of the Nagler over my Axiom.  But maybe that just shows my lack of observational skills.  If you are similarly blessed, you too could 'observe on the cheap'.  However if you are blessed with great visual acuity and discrimination, you may be able to see more details than I can - but at a price - you really need to check it out for yourself.

 

Good luck, have fun and enjoy your new scope!


Edited by Taosmath, 11 October 2019 - 10:16 AM.

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#5 25585

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Posted 11 October 2019 - 12:33 PM

Not necessary, but once used with a coma corrector you may not want to go without again! Keep to 70° max AFOV, and coma won't be too extreme. 



#6 Nunyur

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Posted 11 October 2019 - 01:23 PM

Sounds like a future purchase haha



#7 Nunyur

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Posted 11 October 2019 - 05:36 PM

I don't have this model, but I have an F4.5 Dob.  I have a coma corrector for it, but I rarely use it.  I personally don't find it worth the hassle.

 

However that's the issue - personally.  Everyone's tolerance for imperfections is different. You may not be bothered by coma either, or you may find it very distracting - is there any way you could look through a decent F4.5 Dob (wouldn't have to be a 14") and see for yourself?  Maybe you could visit a local club and see if one of the members has one you could look through?

 

If your 127 SLT is properly collimated, you are likely to get sharper images through that than the dob.  This is due both to the design of the SLT (a Mak which has corrections in the front meniscus and it's a F12) and the fact that its aperture is smaller.  When you look through a large Dob you are averaging the image over a column of air 14" across (as opposed to 5" for the Mak) .  This means you are more susceptible to atmospheric turbulence which most nights will be sufficient to smear the image more in the Dob than in the smaller Mak.

 

However, the images of DSO's in the Dob will be far more detailed than in the Mak. You will clearly see features in the Dob that you cannot even get hints of in the Mak.  Most of us with large Dobs have smaller scopes (Maks,  SCT's or refractors) which we use to look at brighter objects (planets, moon, double stars) and use the Dobs for what they are good at - exploring the DSO's - 'the Faint Fuzzies'.

 

You are likely to want to get at least some different eyepieces for the Dob.  The focal length of the Dob (1600mm) will be very similar to your Mak (1520mm) so you can use the same eyepieces in both to give similar magnifications for higher powers.  However the Dob will have a 2" focuser and so you may want to buy a 2" wide field eyepiece or two for the Dob, say a 30mm and a18-23 mm to take advantage of the wider field of view.  Whether you need to buy higher quality Ep's for the Dob to minimize coma etc. depends pretty much upon the answer to you first question - are you personally sensitive to optical aberrations ?  I am not.  I am quite happy with some basic to mid range eyepieces in any scope I've used so far.

 

Two weeks ago I compared a Nagler 31mm to my 31mm Axiom and couldn't really see any great difference between the two in my 18" F4.5 Dob - certainly not enough to warrant the 3x cost increase of the Nagler over my Axiom.  But maybe that just shows my lack of observational skills.  If you are similarly blessed, you too could 'observe on the cheap'.  However if you are blessed with great visual acuity and discrimination, you may be able to see more details than I can - but at a price - you really need to check it out for yourself.

 

Good luck, have fun and enjoy your new scope!

Thank you so much for all of the information you have helped my head from spinning 



#8 Nunyur

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Posted 11 October 2019 - 05:38 PM

Coma seems to be a personal preference issue. Some people can't stand it, and others don't really notice it. That being said, if you do feel the need for a coma corrector, high end eyepieces aren't required to work with it. Sometimes people get away with using higher end eyepieces in place of a coma corrector. My dob is f4.9, and I do not use a corrector. 

Thank you for the useful information!


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#9 Nunyur

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Posted 11 October 2019 - 05:39 PM

Coma isn't a huge problem at f/4.6 which the 14" model is. It is really a personal choice at that speed. I have friends who say yes you need a coma corrector at that speed. I personally dont feel the need for coma corrector until approaching closer to f/4.

Thank you!



#10 leoyasu

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Posted 11 October 2019 - 05:40 PM

Hi! I'm a proud owner of a 14" SW and I really can't complain, except for having to load it down some stairs to use it. The comma is not something that bothers me and I use eyepieces (up to 24mm) like the ES 82º, some Delites or even some cheap Plossls when I seek to improve light transmission. Visually I have had great views of Mars, Jupiter or from Saturn at x500-x600 or deep space objects up to magnitude 16 or so. When I bought it, I didn't expect to have Zambuto mirrors like views but I'm quite satisfied with this mass produced mirror.

 

Some photos taken with a ZWO 120MC of this year's Jupiter opposition:

 

1.jpg

 

And an interferogram:

 

200020.png

 

It's the first time I used the WinRoddier (after reading this page: http://interferometr...n-qualitat.html) and I know that I can improve it but apparently the optics are acceptable. The capture (green channel extracted from color stack) was taken on a horrible night to be honest with a seeing of 3-4 arcsec, with 2 of the 3 mirror fans running and with a collimation not quite 100% accurate and that's why I say it can be improved.

 

I hope it helps you, cheers!


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#11 Nunyur

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Posted 11 October 2019 - 06:18 PM

Hi! I'm a proud owner of a 14" SW and I really can't complain, except for having to load it down some stairs to use it. The comma is not something that bothers me and I use eyepieces (up to 24mm) like the ES 82º, some Delites or even some cheap Plossls when I seek to improve light transmission. Visually I have had great views of Mars, Jupiter or from Saturn at x500-x600 or deep space objects up to magnitude 16 or so. When I bought it, I didn't expect to have Zambuto mirrors like views but I'm quite satisfied with this mass produced mirror.

 

Some photos taken with a ZWO 120MC of this year's Jupiter opposition:

 

attachicon.gif 1.jpg

 

And an interferogram:

 

attachicon.gif 200020.png

 

It's the first time I used the WinRoddier (after reading this page: http://interferometr...n-qualitat.html) and I know that I can improve it but apparently the optics are acceptable. The capture (green channel extracted from color stack) was taken on a horrible night to be honest with a seeing of 3-4 arcsec, with 2 of the 3 mirror fans running and with a collimation not quite 100% accurate and that's why I say it can be improved.

 

I hope it helps you, cheers!

Well I must say how very nice it is to hear from an actual user of the SW 14. Thank you for sharing your knowledge and experience you have helped to ease my nerves.  Thank you for the amazing photos. Unfortunately I don't understand the interferogram images. If you have a photo or two of DSO'S I'd love to see them. Thank you so very much.


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#12 stargazer193857

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Posted 11 October 2019 - 09:57 PM

Whether you notice coma depends on the patent field of view of your eyepiece and whether you like to look at detail in the outer half of your field of view or mostly use it for finding and framing.

If you use a Plossl, you won't see much coma.

If you like planets at high power and don't mind slewing a bit more often, you should be fine. If you like to let globular clusters drift across view or look at the double cluster, then the non pinpoint stars will be noticed. Well, with 68+ deg eyepieces.

Edited by stargazer193857, 11 October 2019 - 10:01 PM.

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#13 stargazer193857

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Posted 11 October 2019 - 10:03 PM

The sharper your eyes are, the more you will want a sharper view. My eyes are not perfect even in the center. So I tolerate the aberrated edges.

#14 leoyasu

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Posted 12 October 2019 - 04:22 PM

Well I must say how very nice it is to hear from an actual user of the SW 14. Thank you for sharing your knowledge and experience you have helped to ease my nerves.  Thank you for the amazing photos. Unfortunately I don't understand the interferogram images. If you have a photo or two of DSO'S I'd love to see them. Thank you so very much.

 

No problem, happy to help! I still haven't done deep space astrophotography (at least seriously) due to the field rotation that arises from having a Alt.Az mount. I also have a very small field with the ZWO 120 and it's difficult to get alignment stars for stacking. For now I only did some tests with the live stacking feature of SharpCap but I'm still limited by the type of mount. 

 

For the record, I leave you a link from someone who is taking pictures with SW 14": https://www.facebook...rizio.mollinari


Edited by leoyasu, 12 October 2019 - 04:23 PM.



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