What for eyepiece needed?

[Marcel]

Hi, 

We have a question regarding the use of televue eyepiece in the Delos range. We own a skywatcher eq6 r pro with a skywatcher newtonian 200mm/1000mm. We just ordered an paracorr but our main question is:  What eyepiece suits te best with our telescope?

We want to order the delos 3.5 and the 10 or 12. Is the delos 3.5 too much? We want both planetary and clusters. Can anyone help us out? Thankxx

[wookie1965]

I am not familiar with the Televue Delos range but 3.5mm eyepiece would give you a magnification of x285 you would need exceptionally good skies to use that, you would be better with a 8mm and 12mm I have a 5mm BST starguider which rarely gets used in my 200p I have used it a couple of times in my Tal 100rs to split a couple of tight doubles. The 8mm gives me fantastic views of M13, M92 and M57 to name just a few.

8mm will give x125 and the 12mm x83.

[rwilkey]

Hi Marcel, welcome to the forum.  Wookie is quite right, you will find the 3.5mm too much magnification for most nights, best up to 200x in light-polluted skies.  You will find the 10 or 12mm much more useful and satisfying to look through.

[Timebandit]

 

Hi , and welcome to SGL

I have a VX8 (200mm), which I believe is slightly different in fL . I would not suggest the 3.5 delos for you , as the lack of use you would get from it . 

In my 200mm the most used eyepiece I would say for your suggested targets are a Pentax 5XW and 10XW. I do have a 3.5XW but it is hardly used in the reflector, more in my frac.

If I was you I would go for something in the 10mm to 12mm range and possibly something in the 5mm to 7mm range . You will get much more use out of these than a 3.5mm eyepiece.

Magnification is not everything. You are much better off using a lower power , and having sharp crisp image. Than using to much power and getting a blur or soft image.

I hope this helps

 

 

 

[Louis D]

I have the 3.5mm Pentax XW and rarely use it in my Dob.  It's just too much magnification and too small of an exit pupil.  I have to constantly flick my eyes to try see around the floaters in my eye.

I would second the recommendation for a 12mm or even 14mm Delos.  Just be aware that the 14mm requires 1/2" more in focus than the 12mm and shorter Deloses and might not come to focus in all focusers.

I have the 10mm Delos, but find it to be a bit too much power for many targets for proper framing.  It is an incredibly sharp eyepiece from edge to edge with no field curvature.

My favorite glob buster is my venerable 5.2mm Pentax XL.  It's just about the right power for resolving the closer GCs and PNs without creating too small of an exit pupil.  The 5mm Pentax XW or 6mm Delos would be good choices at this magnification range.  The coatings on both are a little bit better than the coatings on the XL.

[Marcel]

9 hours ago, rwilkey said:

Hi Marcel, welcome to the forum.  Wookie is quite right, you will find the 3.5mm too much magnification for most nights, best up to 200x in light-polluted skies.  You will find the 10 or 12mm much more useful and satisfying to look through.

Thankxxx , i am really glad to hear that 3.5 is less usefull. Yes we are new. Today we have rain and a thunderstorm so we stay inside. We buy a 10 mm or 12 mm Delos. We are looking forward to use it. Can you advise us about a televue Barlow an can we use it together with the paracor? Kind regards, Marcel

[Marcel]

6 hours ago, Timebandit said:

 

Hi , and welcome to SGL

I have a VX8 (200mm), which I believe is slightly different in fL . I would not suggest the 3.5 delos for you , as the lack of use you would get from it . 

In my 200mm the most used eyepiece I would say for your suggested targets are a Pentax 5XW and 10XW. I do have a 3.5XW but it is hardly used in the reflector, more in my frac.

If I was you I would go for something in the 10mm to 12mm range and possibly something in the 5mm to 7mm range . You will get much more use out of these than a 3.5mm eyepiece.

Magnification is not everything. You are much better off using a lower power , and having sharp crisp image. Than using to much power and getting a blur or soft image.

I hope this helps

 

 

 

Hi, yes it will help us out. Thankxxxx

[Marcel]

21 hours ago, wookie1965 said:

I am not familiar with the Televue Delos range but 3.5mm eyepiece would give you a magnification of x285 you would need exceptionally good skies to use that, you would be better with a 8mm and 12mm I have a 5mm BST starguider which rarely gets used in my 200p I have used it a couple of times in my Tal 100rs to split a couple of tight doubles. The 8mm gives me fantastic views of M13, M92 and M57 to name just a few.

8mm will give x125 and the 12mm x83.

Hi, thankxxx!!

[Louis D]

7 hours ago, Marcel said:

Thankxxx , i am really glad to hear that 3.5 is less usefull. Yes we are new. Today we have rain and a thunderstorm so we stay inside. We buy a 10 mm or 12 mm Delos. We are looking forward to use it. Can you advise us about a televue Barlow an can we use it together with the paracor? Kind regards, Marcel

You can't, for the most part.  Barlows and coma correctors don't generally get along because unless they're extremely short, they'll hit the CC optics when fully inserted, or you only insert it part way and now you can't rack your focuser far enough inward to reach focus.

I generally remove my CC when using a barlow because the increased focal ratio more or less negates the need for a CC.  I've also compared the edge correction at f6 with and without a CC using my 10mm Delos, and I can't detect a difference.  Coma is much more obvious in simple wide field designs that don't use a powerful Smyth lens ahead of the positive lens group like the Delos.  For example, a 40mm Maxvision 68 degree eyepiece would massively benefit from a CC while a 3.5mm XW would not.

[Stu]

Some great advice from Louis already. One thing just to point out is that the Paracorr has a small barlow effect itself of x1.15, so the effective focal length of your scope will be 1150mm when using it, not 1000mm. This obviously changes the magnification and field of view calculations so is worth considering.

Is there a specific reason why you want to buy a barlow, rather than say two dedicated eyepieces? You will easily be able to achieve max mag without a barlow so it may not be needed, just have a think about what you are trying to achieve.

As Louis says, a Paracorr is much less important at higher powers than at lower powers with a widefield eyepiece. I would not necessarily use one when observing planets for instance where you are observing on - axis, particularly as you have a mount which will keep the target centred.

Again, have a think about the types of clusters, globular or open, and bear in mind that open clusters vary in size a lot. It may be worth playing around with some of the field of view calculators around to see how your kit will frame particular objects.

[Louis D]

8 hours ago, Stu said:

As Louis says, a Paracorr is much less important at higher powers than at lower powers with a widefield eyepiece. I would not necessarily use one when observing planets for instance where you are observing on - axis, particularly as you have a mount which will keep the target centred.

You're right Stu, and I forgot to mention that some CCs can add spherical aberration on axis which only becomes noticeable at high powers.  Thus, try viewing both with and without the CC at high powers to see which view is better.

[Marcel]

10 hours ago, Stu said:

Some great advice from Louis already. One thing just to point out is that the Paracorr has a small barlow effect itself of x1.15, so the effective focal length of your scope will be 1150mm when using it, not 1000mm. This obviously changes the magnification and field of view calculations so is worth considering.

Is there a specific reason why you want to buy a barlow, rather than say two dedicated eyepieces? You will easily be able to achieve max mag without a barlow so it may not be needed, just have a think about what you are trying to achieve.

As Louis says, a Paracorr is much less important at higher powers than at lower powers with a widefield eyepiece. I would not necessarily use one when observing planets for instance where you are observing on - axis, particularly as you have a mount which will keep the target centred.

Again, have a think about the types of clusters, globular or open, and bear in mind that open clusters vary in size a lot. It may be worth playing around with some of the field of view calculators around to see how your kit will frame particular objects.

Hi Stu, the specific reason that i thought that a Barlow and a paracor together gives us the benefit of both. am i right that, because we ordered a paracorr already, that a widefield eyepiece is an better choice? Would it be delos or ethos? And because of the 1150 mm the minimum is 8 mm and above? Thankxx for your reply and we are going to play around with some foc calculators.

[Stu]

14 hours ago, Marcel said:

Hi Stu, the specific reason that i thought that a Barlow and a paracor together gives us the benefit of both. am i right that, because we ordered a paracorr already, that a widefield eyepiece is an better choice? Would it be delos or ethos? And because of the 1150 mm the minimum is 8 mm and above? Thankxx for your reply and we are going to play around with some foc calculators.

I would say that a barlow is of benefit for a number of reasons. Firstly if your scope has a very short focal length it can help you achieve high mags with eyepieces more within normal ranges eg a 500mm f/l scope would need a 2.5mm eyepiece to reach x200. Barlowing a 5mm May be more comfortable in terms of eyerelief.

Expanding this point, a barlow tends to extend the eye relief of eyepieces so it can make the use of plossls and orthos more comfortable at the short focal length end when eye reliefs is shorter, again, barlowing a 12.5mm ortho will be more comfortable than using a 6mm. At the longer end Barlow’s can extend eye relief too much (plossl and ortho eye relief is directly related to their focal length) and this can make maintain eye position difficult.

A barlow with a carefully chosen set of eyepieces can double your number of effective magnifications. Finally, because it acts to double (etc) the focal length of the scope, it can reduce the effect of  abberations seen in fast focal ratio scopes, CA, SA etc.

Summing these all up, I really think it is only the benefit of adding more magnifications that applies to you, so with the choice between two eyepieces and one eyeoiece and a barlow I would go with dedicated eyepieces.

A good wide afov, long focal length eyepiece will maximise your field of view and show th benefits of the Paracorr in terms of sharp stars to the edge, providing there is no astigmatism elsewhere in the system.