2" eyepieces and a Celestron explorer 130az?

[Giles_B]

I am new to astronomy, getting my first scope, aCelestron Starsense Explorer 130az (f5, 130mm Newtonian) about 3 months ago. This is my first post, apologies if it is a bit long or misinformed.

I've upgraded the eyepieces to Baader 6 / 10mm orthoscopics / 32mm plossi, plus a Celestron 2x Barlow, all at 1.25". I've had satisfying views of Saturn, good views of Jupiter, plus some great views of the moon. I live in the very light polluted part of a city, but have managed over the holidays to get to some darker skies, however even in dark skies I've been disappointed with the views of brighter DSOs like Andromeda and Bode, which appear as cloudy puffs of dim light, with no resolvable detail.

I understand I'm not going to get good views of DSOs on an f5 aperture, so eventually a new scope will be needed, but I'd like to get more out of this scope if I can. I'm thinking of upgrading the eyepieces further. With a view to greater eye relief (I find the high magnification orthoscopics uncomfortable) and use in a future scope that is suited to DSOs I'm considering getting some 2" eyepieces. Ideally I would like to use them for high magnification if possible. I've been looking at eyepieces from Explore Scientific 82° range, or the Celestron Luminos range. For magnification I'm wondering if it is worth splashing out on the Televue 4x powermate.

My concerns are firstly, whether a 2" plus a Barlow will be too much weight for the Celestron explorer - the televue plus a luminos would be about 900g - I'd be interested to hear your thoughts and experience.

Secondly, I'd be interested to hear your views on a move to 2" eyepieces more generally. Is it a sensible upgrade path or should I be looking for better 1.25" eyepieces instead? and will any brand enhance my views significantly over the Baaders, or is the f5 ultimately the restriction here?

[Cosmic Geoff]

Visually, galaxies appear as cloudy puffs of dim light with little resolvable detail. That's just how it is.   Also, there is nothing wrong with using a f5 scope as such.

38 minutes ago, Giles_B said:

I'm considering getting some 2" eyepieces. Ideally I would like to use them for high magnification if possible.

I think you may be misunderstanding the purpose of 2" eyepieces.  They are used when a 1.25" eyepiece format cannot accommodate the size of glass needed for low magnification/wide field in a particular scope.   Typically, the lowest power eyepiece you can get in 1.25" format is a 32mm Plossl.  For higher powers, the cheaper, lighter and more widely available 1.25" format eyepieces are almost universally used.  The scopes with 2" focusers can accomodate a 2" to 1.25" adapter.

The only way to see galaxies as shown in photographs is to image them.  Or at least try EEVA (q.v.)

 

[Louis D]

2" eyepieces will allow you to view wider true fields of view than are possible in a 1.25" eyepiece.  They don't really enable high power viewing.

Try observing open star clusters.  They are very rewarding in their twinkling diamond dust on black velvet appearance under dark skies.

[Giles_B]

Thanks for these replies, and the tip on open star clusters - I'll try these next time I get some clear skies.

 

I don't think I explained myself well enough about magnification and switching to 2" eyepieces. I think I understand that 2" will offer low magnification and a wider field of view and perhaps better eye relief. I'm interested in the wider field of view of 2", but would also like to be able to use 2" eyepieces at high magnification (when viewing the moon and the planets). The most economic way of doing this could be by combining a 4x Barlow with a medium focal length eyepiece (20mm or less), but I'm concerned the weight may be prohibitive.

 

However, as moving to 2" would also in part be with upgrading to a larger scope in mind, I'm interested to hear that I'd be unable to visualise galaxies clearly without delving into astrophotography. Would this still be the case even if visualising through a high aperture like an f12? Sorry if this is a silly question, just wanting to make sure I get this right.

 

 

[Louis D]

10 minutes ago, Giles_B said:

The most economic way of doing this could be by combining a 4x Barlow with a medium focal length eyepiece (20mm or less), but I'm concerned the weight may be prohibitive.

To avoid vignetting (both gradual and abrupt) and exit pupil issues (by pushing the exit pupil outward, SAEP can be introduced), a telecentric magnifier like a TV Powermate or ES Focal Extender is required.  This results in a long and heavy moment arm on the focuser.  Your scope's focuser is no where near high capacity enough to smoothly handle such a load.  You are far better off going with compact positive/negative design eyepieces like the BST Starguiders to get to high powers, wider fields of view, and longer eye relief.  They already have a Barlow-like Smyth lens section built in.

15 minutes ago, Giles_B said:

However, as moving to 2" would also in part be with upgrading to a larger scope in mind, I'm interested to hear that I'd be unable to visualise galaxies clearly without delving into astrophotography. Would this still be the case even if visualising through a high aperture like an f12? Sorry if this is a silly question, just wanting to make sure I get this right.

If you move up to a 12" aperture and observe from a dark site, you will begin to see more extent of galaxies.  However, they still will not resemble deep photographic exposures.  You will be able to easily resolve many globular clusters, though.  Nebula will also show more detail and extent.  You'll be able to go deeper into open star clusters, seeing fainter stars.  Planets and planetary nebula will show much more detail.  However, you will have a heavy penalty to pay when move the scope from storage to observing area.

If you really meant f/12, no.  That merely refers to the f-ratio and not to the actual aperture.  An f/12 would be a slow scope and be very forgiving on eyepieces, but it would have a very long tube unless it's a catadioptric design like an SCT or Mak.

If you have thousands of dollars/pounds to spare, EEVA (think night vision or similar) can really improve the visibility of nebula and galaxies, especially big, nearby ones with smaller scopes.

[John]

I think you are mixing up aperture (diameter of the primary mirror or lens) and focal ratio which is usually expressed as F/5, F/12 etc.

That aside your primary issue which will hamper good views of deep sky objects such as galaxies is light pollution. Larger format eyepieces will not make any difference in this. A larger aperture scope will help to some extent but the views will still be hampered by the light pollution levels.

A small scope might actually be a better bet because it can be taken to observing sites much more easily than a larger scope. And that is what will get you better views of these fainter deep sky objects.

 

 

Edited August 3, 2021 by John

[Don Pensack]

55 minutes ago, Giles_B said:

Thanks for these replies, and the tip on open star clusters - I'll try these next time I get some clear skies.

 

I don't think I explained myself well enough about magnification and switching to 2" eyepieces. I think I understand that 2" will offer low magnification and a wider field of view and perhaps better eye relief. I'm interested in the wider field of view of 2", but would also like to be able to use 2" eyepieces at high magnification (when viewing the moon and the planets). The most economic way of doing this could be by combining a 4x Barlow with a medium focal length eyepiece (20mm or less), but I'm concerned the weight may be prohibitive.

 

However, as moving to 2" would also in part be with upgrading to a larger scope in mind, I'm interested to hear that I'd be unable to visualise galaxies clearly without delving into astrophotography. Would this still be the case even if visualising through a high aperture like an f12? Sorry if this is a silly question, just wanting to make sure I get this right.

 

 

 

So add 1.25" to 2" adapters to 1.25" eyepieces to convert them to 2".  Because there is no reason for an eyepiece shorter than 14-17mm to be 2" when the field fits in a 1.25" barrel.

I like the convenience of 2" eyepieces too but do it by adding adapters to my eyepieces shorter than ~14mm.

[Giles_B]

Thanks for talking me through this - it is really helpful and deepening my understanding. It is a bit embarrassing to be making mistakes like confusion the focal ratio with the aperture (thanks for pointing it out), but it's a fast way to learn.

So far my best results have come from appreciating the strengths and weaknesses of my current set up and it is easy to overlook the part the portability of a small scope plays in getting good views, well away from my neighbours security lights!

Unfortunately my budget won't run to EEVA, but I'm certainly interested in the BST eyepieces and can see from this forum they are well respected, so I'll check these out for the high magnifications. I'll stick with the Plossi for DSOs for now.

[John]

Bristol Astronomical Society have an rurally located observatory to the west of the city which provides reasonably dark skies. When we can meet up again I'm sure open public observing sessions will begin again

https://bristolastrosoc.org.uk/observing/

[Tiny Clanger]

You may already have seen this thread, but just in case you haven't :

 

 

[Giles_B]

13 minutes ago, John said:

Bristol Astronomical Society have an rurally located observatory to the west of the city which provides reasonably dark skies. When we can meet up again I'm sure open public observing sessions will begin again

https://bristolastrosoc.org.uk/observing/

Thanks John, I'll be looking out for these sessions!

Tiny Clanger - you may be right, my experience of DSOs may be a repeat of my initial "isn't Saturn small" experience... I'll check out the guide

[rwilkey]

On 03/08/2021 at 14:41, Giles_B said:

Ideally I would like to use them for high magnification if possible. I've been looking at eyepieces from Explore Scientific 82° range, or the Celestron Luminos range. For magnification I'm wondering if it is worth splashing out on the Televue 4x powermate.

My concerns are firstly, whether a 2" plus a Barlow will be too much weight for the Celestron explorer - the televue plus a luminos would be about 900g - I'd be interested to hear your thoughts and experience.

Hi Giles, I started using 2" for high magnification but found myself going back to 1.25" each time, in my opinion you don't need wide field for planets or Moon, if the 1.25" does the job well enough why bother with the extra expense (along with filters, of course, which are double). 

I have never found using a 2" Barlow very satisfactory and sold mine, as you say, weight considerations is another factor and overkill on a 130mm reflector.  Do not think of 2" as an upgrade, I found that this was a mistake, buy for what your target is, don't generalise too much if you can afford it. 

[Louis D]

As I've said before on other threads vis-a-vis 2" Barlows, the only time I use them is just to change things up for an entire night of observing.  It's too much of a PITA to swap it in and out of the focuser due to the massive change in focus position it causes.  They're fine if you just leave them in the whole night, though.  It's kind of fun to see how my 2" eyepieces react to the Barlow's presence.  That, and the presentation is different as compared to similar focal length 1.25" eyepieces.

Edited August 8, 2021 by Louis D