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Question about 8" Dobsonian and higher magnification

beginner dob eyepieces
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#26 brimacx

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Posted 21 July 2019 - 11:13 AM

It's a good advice what you have received here. I had a 8'' dobsonian and that eyepiece. It's comfortable, the lunar and planetary views were very good and the apparent field of view (60º) it's enough to keep the planet in place for some time. 

 

Just in case it is for any help, these are the eyepieces I used:

  • GSO Erfle 30 mm. Then I changed it by a Explore 24 mm 82º. BIG galaxies, open clusters and nebulaes.
  • Hyperion 13 mm 68º. An ES 14 mm came afterwards. Galaxies, open clusters and nebulaes.
  • Celestron X-Cel LX 9 mm. Globular clusters such as M13. Lunar and planetary. An 8 mm would be also great.
  • Meade HD 6,5 mm. Lunar and planetary. 

You could consider also an economic 5 mm planetary eyepiece. Manual tracking becomes harder and seeing will not tolerate very often that magnification (depending on your observación place, of course). I had one, but the truth is that it stayed in the suitcase almost every nights. No Barlow in my case, I find them useful under different conditions than observing with a dob.

Thanks for your advice!  After lots of reading I am thinking the ES 100 14mm might be my next eyepiece unless I can get a better TeleVue used. Although I am still thinking the 9mm ES100 might be an option too. Any thoughts on the 9mm vs 14mm ES100? My primary goal now is to see at least some twinkling stars in M13 - right now it's just a small gray cloud. 



#27 brimacx

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Posted 21 July 2019 - 11:16 AM

I have a similar telescope and I use the 8mm LVW, 7mm Nagler and 5.5mm Meade on planets.

See my signature...I keep these ep's because they work.

I've been looking at the Meade 6.5...



#28 Chesterguy1

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Posted 21 July 2019 - 08:27 PM

Even with good collimation and mirrors acclimated, my seeing seldom allows satisfying viewsabove 150x with my 8”. There are exceptions. I managed to Barlow my 4.7mm EP to split Zeta Herculis at 393x several weeks back (highly, highly unusual).

Chesterguy

#29 Pelayo

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Posted 23 July 2019 - 10:12 AM

Thanks for your advice! After lots of reading I am thinking the ES 100 14mm might be my next eyepiece unless I can get a better TeleVue used. Although I am still thinking the 9mm ES100 might be an option too. Any thoughts on the 9mm vs 14mm ES100? My primary goal now is to see at least some twinkling stars in M13 - right now it's just a small gray cloud.


Globular clusters are visible in light polluted skies, but if you want to resolve them (see individual stars) you need a dark sky and a proper eye adaption. In any case, don't expect to see something like astrophotographies. It's in fact a grey cloud with stars over it. Very impressive though.

As I said 8-9 mm works very well for that purpose in your scope, but if you are thinking on purchasing a ES 100°, go for the 14 mm. You will use it for nebulae, galaxies and open clusters, that's were you will take the most of that huge field of view.

Don't misunderstand me, a 9 mm with 100 degrees would be very nice too, but even more on a 14 mm.

You could look for a 8 or 9 mm with 60°. That's enough for globular clusters and planets / moon.
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#30 brimacx

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Posted 24 July 2019 - 12:48 AM

Globular clusters are visible in light polluted skies, but if you want to resolve them (see individual stars) you need a dark sky and a proper eye adaption. In any case, don't expect to see something like astrophotographies. It's in fact a grey cloud with stars over it. Very impressive though.

As I said 8-9 mm works very well for that purpose in your scope, but if you are thinking on purchasing a ES 100°, go for the 14 mm. You will use it for nebulae, galaxies and open clusters, that's were you will take the most of that huge field of view.

Don't misunderstand me, a 9 mm with 100 degrees would be very nice too, but even more on a 14 mm.

You could look for a 8 or 9 mm with 60°. That's enough for globular clusters and planets / moon.

Thanks for the insight! My dob came with a 9mm but probably a narrow FOV...



#31 Pelayo

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Posted 24 July 2019 - 11:38 AM

Thanks for the insight! My dob came with a 9mm but probably a narrow FOV...

If it is a plössl then it's a good eyepiece. Not very confortable, not a wide FOV, but the image quality should be good. 

 

Use it alone, without the barlow. If your sky is not highly polluted you should be able to resolve it and identify individual stars, and not only a grey cloud. Take into account that you will need time observing it so that your eye gets used to what you are looking at. Spend time, be patient and use adverted vision too. 



#32 brimacx

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Posted 30 July 2019 - 12:31 AM

If it is a plössl then it's a good eyepiece. Not very confortable, not a wide FOV, but the image quality should be good. 

 

Use it alone, without the barlow. If your sky is not highly polluted you should be able to resolve it and identify individual stars, and not only a grey cloud. Take into account that you will need time observing it so that your eye gets used to what you are looking at. Spend time, be patient and use adverted vision too. 

Yes, you were right. I used the 9mm by itself and could see a handful of individual stars fleetingly with direct vision but more so with averted vision. 


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#33 Volvonium

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Posted 01 August 2019 - 04:23 PM

Another good target that is similar to M13 is M11.  It's to the right and slightly up from the tail end of the constellation, Aquila.    

 

I've got the ES100 9mm and ES100 5.5mm.   I mostly use the ES100 5.5 in my 8" dob, but solely for planetary work.  Have you considered the 82 degree line?  The ES82 8.8mm should be a nice sweet spot for your telescope, providing a nice 1.5mm exit pupil;  I find 1.5mm to 2.00mm very comfortable for DSO viewing.  


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#34 OtherBrotherDarryl

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Posted 01 August 2019 - 05:16 PM

I second Volvonium's suggestion of the 82° line. Either ES or Meade. You can pick up a 5.5, 8.8 and 14mm for the cost of one 100° piece. There will be a world of difference in fov with the 8.8 compared to the 9mm plossl, about 50% wider. The 14mm gets mixed reviews in both versions. I recently picked up a Meade 14mm and really enjoy it. Use it 50% of the time viewing DSOs through my 10" dob. I'm in class 5 skies in the NW Chicago burbs.

Edited by OtherBrotherDarryl, 01 August 2019 - 05:20 PM.

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#35 brimacx

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Posted 01 August 2019 - 07:57 PM

Another good target that is similar to M13 is M11.  It's to the right and slightly up from the tail end of the constellation, Aquila.    

 

I've got the ES100 9mm and ES100 5.5mm.   I mostly use the ES100 5.5 in my 8" dob, but solely for planetary work.  Have you considered the 82 degree line?  The ES82 8.8mm should be a nice sweet spot for your telescope, providing a nice 1.5mm exit pupil;  I find 1.5mm to 2.00mm very comfortable for DSO viewing.  

Thanks! I'll check out the 8.8 82 - so this would be good for DSO's right?  



#36 Volvonium

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Posted 01 August 2019 - 09:06 PM

Thanks! I'll check out the 8.8 82 - so this would be good for DSO's right?  

It should be good for brighter DSOs like globular clusters, where under a light polluted sky, its magnification will reduce the exit pupil down enough to darken the background sky and increase contrast, yet not overdo it so that you can still detect the pinpoint light sources of those faraway stars; it also considers having a wide enough field of view to frame the object nicely.  

 

I think i saw a used es82 8.8 available on astromart for 110, which is the going rate for a lot of the 1.25" es82 eps

 

Each DSO is a little different, depending on its magnitude and how spread out its light is.  M13 under heavy light pollution is at the threshold of being able to resolve individual stars with an 8".  Dimmer globular clusters will need longer observation and averted vision.  Some small bright Planetary nebula are easily detectable on the other hand.


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#37 brimacx

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Posted 02 August 2019 - 04:05 PM

It should be good for brighter DSOs like globular clusters, where under a light polluted sky, its magnification will reduce the exit pupil down enough to darken the background sky and increase contrast, yet not overdo it so that you can still detect the pinpoint light sources of those faraway stars; it also considers having a wide enough field of view to frame the object nicely.  

 

I think i saw a used es82 8.8 available on astromart for 110, which is the going rate for a lot of the 1.25" es82 eps

 

Each DSO is a little different, depending on its magnitude and how spread out its light is.  M13 under heavy light pollution is at the threshold of being able to resolve individual stars with an 8".  Dimmer globular clusters will need longer observation and averted vision.  Some small bright Planetary nebula are easily detectable on the other hand.

Thanks for the info! Just picked one up new on BH for 149...  




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