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Help me choose EPs for my 12" F5 dob

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#1 phsampaio

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Posted 06 August 2020 - 05:39 PM

Hello, this is my first post here! I'm a beginner astronomer and my main interest is viewing DSOs (nebula, clusters, etc.) and plantets. Astrophotography is not my thing. My observation site is on a Green to Blue zone, usually with clear skies but regular seeing conditions due to high atmospheric turbulance and dust.

 

I recently purchased an Orion XT12 intelliscope Dobsonian. 12" aperture, F4.9. It came with 2 regular Plossl EPs: 10mm and 25mm, that gives me 150x and 60x magnification respectively. Those are good enough, however as with any stock EPs, I quickly grew past them.

 

I'm planning on improving my EPs to match my telescope and at the same time increase my range of magnifications, so I wanted some recommendations from the awesome community here.

 

I have one important consideration: budget. Since I live in Brazil, everything I buy is massively more costly, so expensive EPs (say, more than $200) are out of question. I'm planning on expending no more than $600 (which would translate to more than 3000 BRL, 6000 with taxes). So I need to optimize my EPs. Another important consideration is that I have a fast telescope (f4.9) and from what I've read, those types of telescope can be quite sensitive to EP aberrations. That said, since I'm limiting my budget, I think I won't buy a coma corrector, since those are usually very expensive (the good ones, at least). In short, I need good midrange EPs that fare well in a fast telescope.

 

After much researching, my idea now is to buy two ES 68° EPs: 24mm and 16mm, and a 2x FE/barlow from ES. I've read great things about those EPs and the FE, and it seems to me that they fare relatively well in fast telescopes, even without a coma corrector. I would also get a good range of maginification: 62x, 93x, 125x and 187x. I would also have 150x and 300x if I include my 10mm Plossl.

 

What do you think? Is this a good idea? I'm also open to other suggestions, of course!

 

Cheers!



#2 areyoukiddingme

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Posted 06 August 2020 - 05:53 PM

Welcome to CN. . . 

 

Keeping with a tight budget, if you can find used eyepieces, that's the way I would go. You can expect to get about 30% off regular retail.

 

One strategy that may fit your budget would be to do a Baader zoom, barlow, and 1 lower power/widefield. 

 

A used MkIII go for around $160/$170. Add a 2x barlow for around $50 and you have ~4mm to 24, which will be to  62x to 375x, though 20mm is probably the lowest usable power for many because the apparent field is getting pretty narrow by then.

 

And for lowest power, the APM ultra flat is $230 new. They are still relatively new, so they may be somewhat difficult to find on the used market.

 

With those two, you'd have money left for a GSO coma corrector.

 

Lot of other options, of course, if you prefer not to zoom. Use Baader morpheus for around $175 would be good to have. Get the spacing right and a barlow, and again you can get a good range of magnifications.

 

There's nothing wrong with the ES eyepieces you mention. Only thing I can think of is that the 24 does not barlow well in my experience--the edges get vignetted.


Edited by areyoukiddingme, 06 August 2020 - 05:54 PM.

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#3 Magellanico

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Posted 06 August 2020 - 06:08 PM

Welcome to CN!

 

I would suggest:

 

24mm 68º for low power (wide deep skies)

 

8.8mm 82º - for high power (planetary viewing)

 

Good lucky!


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#4 scngc7317

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Posted 06 August 2020 - 06:08 PM

Strangely enough for a newbie your right on the money.

 

most important question is your scope hand driven ? I **** sume it is.

In that case you don't want to go too high on power as moving the scope and waiting for Mars to zip by gets old fast.

 

Can you buy used from people here and beat the taxes ?  Good luck waytogo.gif

 

3520

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#5 Starman1

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Posted 06 August 2020 - 07:32 PM

12" f/5 with 1500-1524mm focal length?

24-26mm low power

12-13mm medium power--most used

8-9mm high medium power

6-7mm high power

5mm high power.

that's about all you'll need unless you start doing close double stars or tiny planetary nebulae.


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#6 SeattleScott

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Posted 06 August 2020 - 09:17 PM

I would go 30mm APM UFF, 17mm Olivon, 9mm Celestron Xcel LX and 7mm (6.5mm) Xcel LX. This would cover the bases up to 230x magnification. It wouldn’t exceed $600 in the US. None are overly wide AFOV so they would work without a coma corrector.

Scott
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#7 phsampaio

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Posted 06 August 2020 - 10:54 PM

Thank you all for the quick responses!

 

Although a newbie, I certainly did my research before posting. I've been lurking in here and other forums for quite some time...

 

In regards to used EPs, here in Brazil we have a very limited (i.e. virtually non-existant) second hand market, unfortunately. So, that limits my buying choices to imported and new EPs. Having no used market also limits my selling perspectives in the future. I cannot garantee that I will sell an EP that I didn't like. That's why I'm aiming for the long run. For me, good quality EPs that I will most likely use for a long time (maybe even forever) are more desirable than a middle level one that would normaly be replaced in a few years. Still, bugdet is a concern, so no TeleVue and Pentax etc. 

 

I'll take a look at all those suggestions. Thanks for the feedback.

 

One thing I wanted to know. Does anyone have experience with using ES FE 2x and ES68 24mm together? I've read some reports that there should be no vignette (since it's a FE not a barlow) but I could not find any confirmation online. This is important because a virtual 12mm (125x) EP is probably one I would use the most, if I decided to go with my original plan of 2x FE + 24mm ES 68 + 16mm ES68.


Edited by phsampaio, 06 August 2020 - 10:56 PM.


#8 rkelley8493

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Posted 06 August 2020 - 11:16 PM

You shouldn't have any problems with vignette from a 1.25" eyepiece in a 2" focal extender. You could probably get away with a 20mm 100º + 2x focal extender and not see any vignette. You'd have more problems with the weight than with the views. Monster eyepieces + 2" focal extender = Elephant Trunk.

 

EdIt:  I'll also add that the 24mm 68º is an excellent eyepiece and will give you some great views. I don't have any experience with the 16mm 68º though.. However, the 82º Series has some good ones. I really liked the 8.8mm 82º as well as the 24mm & 30mm. I know the last two are a little over budget, but they'd be worth saving money for. 


Edited by rkelley8493, 06 August 2020 - 11:26 PM.


#9 Brent Campbell

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Posted 06 August 2020 - 11:57 PM

Welcome to CN!

 

I would suggest:

 

24mm 68º for low power (wide deep skies)

 

8.8mm 82º - for high power (planetary viewing)

 

Good lucky!

Add a 2 x barlow like the Astro tech 2 inch 2X barlow and that set would get you started well.



#10 areyoukiddingme

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Posted 07 August 2020 - 12:11 AM

Thank you all for the quick responses!

 

Although a newbie, I certainly did my research before posting. I've been lurking in here and other forums for quite some time...

 

In regards to used EPs, here in Brazil we have a very limited (i.e. virtually non-existant) second hand market, unfortunately. So, that limits my buying choices to imported and new EPs. Having no used market also limits my selling perspectives in the future. I cannot garantee that I will sell an EP that I didn't like. That's why I'm aiming for the long run. For me, good quality EPs that I will most likely use for a long time (maybe even forever) are more desirable than a middle level one that would normaly be replaced in a few years. Still, bugdet is a concern, so no TeleVue and Pentax etc. 

 

I'll take a look at all those suggestions. Thanks for the feedback.

 

One thing I wanted to know. Does anyone have experience with using ES FE 2x and ES68 24mm together? I've read some reports that there should be no vignette (since it's a FE not a barlow) but I could not find any confirmation online. This is important because a virtual 12mm (125x) EP is probably one I would use the most, if I decided to go with my original plan of 2x FE + 24mm ES 68 + 16mm ES68.

I did a quick check of my ES 24/68, in Nikon 1.6" barlow, A-P 2x barlow, and 2.5x Powermate.

 

I can confirm a little vignetting at the edge in both of the barlows. It goes from a crisp field stop to a somewhat fuzzy field stop. It's quite tolerable.

 

However, the 2.5 Powermate was crisp all the way across. Hopefully someone will chime in with the ES telecentric.

 

As for buying used, you may find some difficulty finding a seller ok with shipping from U.S. to Brazil, but it should be doable if you are patient.



#11 Starman1

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Posted 07 August 2020 - 12:33 AM

Thank you all for the quick responses!

 

Although a newbie, I certainly did my research before posting. I've been lurking in here and other forums for quite some time...

 

In regards to used EPs, here in Brazil we have a very limited (i.e. virtually non-existant) second hand market, unfortunately. So, that limits my buying choices to imported and new EPs. Having no used market also limits my selling perspectives in the future. I cannot garantee that I will sell an EP that I didn't like. That's why I'm aiming for the long run. For me, good quality EPs that I will most likely use for a long time (maybe even forever) are more desirable than a middle level one that would normaly be replaced in a few years. Still, bugdet is a concern, so no TeleVue and Pentax etc. 

 

I'll take a look at all those suggestions. Thanks for the feedback.

 

One thing I wanted to know. Does anyone have experience with using ES FE 2x and ES68 24mm together? I've read some reports that there should be no vignette (since it's a FE not a barlow) but I could not find any confirmation online. This is important because a virtual 12mm (125x) EP is probably one I would use the most, if I decided to go with my original plan of 2x FE + 24mm ES 68 + 16mm ES68.

In my opinion, the 16 is the best in the series, optically, but the eye relief is very tight--about 10mm.  If that's OK, go for it.



#12 JoshUrban

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Posted 07 August 2020 - 08:28 AM

Hey there, and welcome!

 

  How does buying used internationally work?  If you CAN, the classifieds here are excellent.  I've bought a few eyepieces for my 12.5" dob on here, and have gotten some great deals.  

 

  For my f/5 dob, I really enjoy a 32mm, 20mm, 12mm, and 7mm.  


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#13 25585

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Posted 07 August 2020 - 08:48 AM

Hey there, and welcome!

 

  How does buying used internationally work?  If you CAN, the classifieds here are excellent.  I've bought a few eyepieces for my 12.5" dob on here, and have gotten some great deals.  

 

  For my f/5 dob, I really enjoy a 32mm, 20mm, 12mm, and 7mm.  

Fab four first focal lengths waytogo.gif . Add a 2x Barlow to double to eight.


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#14 cimar

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Posted 07 August 2020 - 09:43 AM

Hi,

on a 12" f/5 I would prefer a red dot finder in combination with a 30..32mm wide field eyepiece.

Then I would decide on a series of eyepieces and would pick 3 or 4 of them. I would recommend 17mm, 10mm 6mm focal length and 3.5mm as far is your mirror is really good.

I like eyepieces of 70..80 degree of AFOV and have bought some used.



#15 epee

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Posted 07 August 2020 - 04:12 PM

I would generally agree with Starman1 regarding the focal lengths except I would add an extra-low power, wide angle slot. I fill that slot with an ES 82° 30mm. Viewing M31 from a dark site with this eyepiece/telescope combination alone could fill an evening.



#16 Starman1

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Posted 07 August 2020 - 04:21 PM

I would generally agree with Starman1 regarding the focal lengths except I would add an extra-low power, wide angle slot. I fill that slot with an ES 82° 30mm. Viewing M31 from a dark site with this eyepiece/telescope combination alone could fill an evening.

If you start with a 30mm, I'd revise the next focal lengths to 20-21mm, 14mm, 10mm, 7mm, 5mm.  Hmm, what eyepiece comes in those focal lengths?lol.gif


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#17 phsampaio

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Posted 07 August 2020 - 11:17 PM

Thanks for all the responses! I've been very busy working on different combinations of EPs in Excel... Choice paralysis is really a thing, who could've thought!

 

In any case, I'm still trying to limit my budget to around $600 (ok, maybe a little more). As for zoom EPs, for the moment, I'm shying away from them. I may be wrong, but from what I read that they wouldn't mesh well with my fast Dob and they also have limited FOV (something that I value a lot as my main interest is DSOs). I considered a mix of Baader Hyperions for some time, mostly due to their inherent value in extended range of focal lengths with extension rings, but again I read several unfavorable reviews of their poor performance in fast telescopes. 

 

The more I think about it, the more I like the idea of buying 2-3 EPs with a good barlow/FE. Doubling my range of magnification really saves me a lot of money. I'm starting to really like ES EPs. They seem to go well with fast telescopes at the price range I'm aiming at.

 

My current idea is the following. ES68 28mm 2"; ES68 16mm; ES82 11mm, ES FE 2x 1.25". This will cost me around $650 if I buy them all new. I though of this range because:

 

- ES68 28mm 2" - gives me 53x magnification, 1.28 degrees TFOV and 5.7mm exit pupil

- ES68 16mm - gives me 94x magnification, 0.73 degress TFOV and 3.3mm e.p.
- ES82 11mm - gives me 136x magnification, 0.60 degrees TFOV and 2mm e.p.
- ES68 16mm w/ FE 2x - gives me 188x magnification, 0.36 degrees TFOV and 1.6mm e.p.
- ES82 11mm w/ FE 2x - gives me 272x magnification, 0.30 degrees TFOV and 1mm e.p.

 

In the future, I could invest in a 14mm Baader Morpheus or 13mm TV, and maybe a good coma corrector. 

 

What do you think? 

 

Cheers!


Edited by phsampaio, 07 August 2020 - 11:20 PM.


#18 SeattleScott

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Posted 07 August 2020 - 11:42 PM

That looks like a good lineup.

#19 phsampaio

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Posted 11 August 2020 - 10:28 PM

I'm reconsidering my options (as usual, choices, choices, choices!) but for a few reasons. Maybe it would be more practical to buy 4 EPs with a good range of magnifications, than 3 EPs and a barlow that could only be used with 2 of them. Besides, I'm going to split the costs with 2 other people, both of which use glasses and have some degree of astigmatism. So a modest to good ER becomes necessary. The upside is that dividing the costs could help me increase the budget (or maintain a low budget and spend a lot less...). BTW, I'm buying in Euros because I have relatives from Spain that will come to Brazil in november. I'll have time to choose a set of EPs until then.

 

So, my ideia now is to choose between 3 sets:

 

Most expensive, 820 Euros

-ES68 28mm -  x54, TFOV 1.28o and 5.7mm exit pupil
-Morpheus 12.5mm - x120, TFOV 0.63o and 2.6mm e.p.

-Morpheus 9mm - x167,  TFOV 0.46o and 1.8mm e.p.
-Morpheus 6.5mm - x233, TFOV 0.33o and 1.3mm e.p.

 

Medium expensive, 626 Euros

-ES68 28mm -  x54, TFOV 1.28o and 5.7mm exit pupil
-ES82 11mm - x136, TFOV 0.6o and 2.2mm e.p.

-ES82 8.8mm - x170,  TFOV 0.48o and 1.8mm e.p.
-ES82 6.7mm - x224, TFOV 0.37o 1.4mm e.p.

 

Least expensive, 408 Euros

-ES68 28mm -  x54, TFOV 1.28o and 5.7mm exit pupil
-X-Cel LX 12mm - x125, TFOV 0.48o and 2.4mm e.p.

-X-Cel LX 9mm - x167, TFOV 0.36o and 1.8mm e.p.

-X-Cel LX 7mm (6.5mm?) - x214 (x233?), TFOV 0.28o and 1.4mm e.p.

 

The Morpheus set is more expensive than I initially wanted, but seems to have the best range of magnification, besides good ER and probably the best optic system of the 3. 



#20 SeattleScott

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Posted 11 August 2020 - 11:26 PM

The ES 82s are out if some of you wear glasses. So that leaves Morpheus versus Xcel.

The Morpheus have a bit more ER, but most eyeglass wearers do ok with Xcel. The Morpheus are wider and maybe a bit sharper, at least at 12mm. But the wider field will show more coma.
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#21 phsampaio

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Posted 25 August 2020 - 08:35 AM

Hello, again!

 

I'm pretty set on buying the Morpheus EPs, mainly because of the good ER they have. 

 

I do think I could refine my EP selection, however. With 28mm, 12,5mm, 9mm and 6.5mm, I have 54x, 120x, 167x and 233x magnification.

 

I could go with the Morpheus 14mm instead of the 12.5mm. That would give me 54x, 107x, 167x and 233x magnification.

 

Which one would you suggest? Are the 12.5mm and 14mm Morpheus EPs the same quality level? Which would be most suited to viewing DSOs?



#22 Starman1

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Posted 25 August 2020 - 09:22 AM

14mm.  jump 53x, then 60x, only 7x difference.  14mm is closer to the half-way point.

 

With 12.5mm, the jumps are 66x, then 47x, a difference of 19x.


Edited by Starman1, 25 August 2020 - 04:31 PM.


#23 phsampaio

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Posted 25 August 2020 - 03:46 PM

Thank you Don, for the quick response!

 

That's whats I've been thinking. 14mm then.



#24 SeattleScott

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Posted 25 August 2020 - 05:05 PM

I have heard the 14 is the worst in the series.

Either way you will have a sizable gap. Ultimately you will probably want the 17.5 and 12.5. Pick which one you want first.

Scott

#25 Starman1

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Posted 25 August 2020 - 06:20 PM

A gap of 50x or 60x between eyepieces for a 12" scope is not much.  That's not a "sizable gap".

It might be on a 4" refractor, but not on a 12".

His 4 eyepieces would be increases from low power of:  53x, 60x, 66x.

If there is a gap, it's in eyepiece focal lengths shorter than 6.5mm.  A 12" should be able to regularly use magnifications to 400x or so, and often higher.

A 5mm would be a fine addition to the range.

 

Whatever you may have heard about the 14mm, I have used it extensively in my 12.5", and it delivers tiny little pinpoint images across the field.

I noted no field curvature or any other issue with the eyepiece.  The eye relief is comfortable with glasses.  It's 130x in my scope, so barely 10x/inch of aperture.

It also has no noticeable edge of field brightening unless using it in a misty atmosphere.

Even my wife, who is not an experienced observer, commented she thought the star images were really sharp.

The 14mm is closer to the in-between magnification than the 12.5mm, and having 120x magnification in addition to 107x would be close to being redundant.

Likewise, the 17.5mm would yield 86x, too close to the 107x of the 14mm.


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