Best, affordable, 2" EPs

[Relpet]

Good morning from a storm-swept south-west France.  Lightning shows last night?  Magnifique!  But to the point.

With my 8" Dob came a single 2" EP whuch, frankly, I have not yet used.  Until now, as a beginner,  I have been concentrating on the planets but as night begins to fall earlier I want to start going into deeper space.  Working on the principle that the EP that came with the 'scope will not be the best (Revelation 30mm possibly made by GSO) what would experienced users suggest.  I plan on trying out the Revelation tonight if skies are clear, as forecast, and feel I should make the most of the 'scope's capabilities.  All suggestions welcome but I am on retirement income!

[damnut]

Hi There,

I would try your original eyepiece before condemning it. The real benefit of 2" eps come with longer focal lengths = low power. The increase in field of view is appreciable. The Explore Scientific 82 deg range are excellent ep's. For lower focal length EP's there is no appreciable benefit over  1.25" if you compare like for like due to the field stop. So a 2"  10mm 82deg ep will show the same as a 1.25" 10mm 82 deg one.

Don't forget to check the  classifieds, there are some Televue plossl ep's for sale very reasonably priced. You also need to check the focal ratio of your telescope larger focal ratio telescopes  say F10 are more forgiving than low focal ratio ones say F4.

[John]

Your GSO 30mm 2" will work quite nicely across about 70%-80% of it's field. Beyond that the stars will start to look rather "seagull" shaped with the extent of the distortion increasing towards the edges of the field of view. This is called astigmatism and is common when you use low cost, wide field eyepieces in faster scopes than around F/8-F/10.

If you are happy with the views then stick with it. If you don't like the astigmatism then eyepieces such as the Explore Scientific 68, 82 and 100 degrees will show either none or much, much less of it in your scope. They cost quite a bit more than the Revelations though because the optical design and engineering needed to achieve this improved performance in fast scopes is tricky to achieve.

[Charic]

For my 8" Skyliner, I have only ever used one 2" eyepiece, the Sky-Watcher Panaview 32mm with 70° afov.

I'm not sure if your 32mm would be any worse, so give it another go before you start spending. Even the supplied 25mm with my Skyliner isn't so bad, just doesn't have the afov that the Panaview affords.

I have nothing else  to compare  with, but  the Panaview is a brilliant EP for my eyes, and great value as I bought mine second hand!.

[Relpet]

Hi There,

I would try your original eyepiece before condemning it. The real benefit of 2" eps come with longer focal lengths = low power. The increase in field of view is appreciable. The Explore Scientific 82 deg range are excellent ep's. For lower focal length EP's there is no appreciable benefit over  1.25" if you compare like for like due to the field stop. So a 2"  10mm 82deg ep will show the same as a 1.25" 10mm 82 deg one.

Don't forget to check the  classifieds, there are some Televue plossl ep's for sale very reasonably priced. You also need to check the focal ratio of your telescope larger focal ratio telescopes  say F10 are more forgiving than low focal ratio ones say F4.

Thanks, Damian.  My Dob is F6 so somewhere in between but I will check out your reommended brand.

Looks like clear skies tonight.  Hope the same for you.

Peter

[Relpet]

Your GSO 30mm 2" will work quite nicely across about 70%-80% of it's field. Beyond that the stars will start to look rather "seagull" shaped with the extent of the distortion increasing towards the edges of the field of view. This is called astigmatism and is common when you use low cost, wide field eyepieces in faster scopes than around F/8-F/10.

If you are happy with the views then stick with it. If you don't like the astigmatism then eyepieces such as the Explore Scientific 68, 82 and 100 degrees will show either none or much, much less of it in your scope. They cost quite a bit more than the Revelations though because the optical design and engineering needed to achieve this improved performance in fast scopes is tricky to achieve.

Thanks, John.  I'm hoping to try for M13 tonight if the forecast for clear skies is correct.  I have a 32mm 1.25 GSO Plossl as well so will give them both a go.

Always seems to be good advice from north Somerset!

Peter

[Relpet]

For my 8" Skyliner, I have only ever used one 2" eyepiece, the Sky-Watcher Panaview 32mm with 70° afov.

I'm not sure if your 32mm would be any worse, so give it another go before you start spending. Even the supplied 25mm with my Skyliner isn't so bad, just doesn't have the afov that the Panaview affords.

I have nothing else  to compare  with, but  the Panaview is a brilliant EP for my eyes, and great value as I bought mine second hand!.

Thanks, Charic.  Any advice not to spend money is always welcome but I will check out the Panaview you mention.

So, ho-hey for the Milky Way tonight - with any luck

[John]

Thanks, John.  I'm hoping to try for M13 tonight if the forecast for clear skies is correct.  I have a 32mm 1.25 GSO Plossl as well so will give them both a go.

Always seems to be good advice from north Somerset!

Peter

M13 should be very straightforward with your scope. M92 is another very nice globular cluster nearby, also in Hercules. Once you have found them with low power eyepieces it's worth adding some magnification to see them really well. Globular clusters are great with some aperture at 80x - 120x or even 150x

[Relpet]

M13 should be very straightforward with your scope. M92 is another very nice globular cluster nearby, also in Hercules. Once you have found them with low power eyepieces it's worth adding some magnification to see them really well. Globular clusters are great with some aperture at 80x - 120x or even 150x

Thanks, John.  As a beginner I sometimes feel like someone who has been given a French-English dictionary and told to translate Les Miserables without a single lesson in the language.  Need to read the sky better.  I did try out both eyepieces though by continually traversing a starfield overhead.  The 1.25 32mm GSO gave me pin-sharp image but poor eye-relief.  The 2" 30mm Revelation gave me excellent eye-relief but properly seated would not focus.  A starfield full of bright bananas was the best I could get.  Using the supplied extension tube did not effect a cure.  Only by raising the eyepiece slightly clear of the proper seating could I get anywhere near focus but not satisfactory.  So it looks as if I'm in the market.  Cloudy skies for the next four or five nights so time to ponder - and get to grips with my star charts,

Thanks again.

Peter

[ronin]

The 1.25 32mm GSO gave me pin-sharp image but poor eye-relief.

That sounds a bit odd, I assume a 32mm GSO plossl which should deliver about 20-24mm eye relief.

That is a lot and if that is "poor" there is something amiss as even if you got a good TV they deliver I think 20mm and no more. The often mentioned BST's and X-Cels both deliver around 15-17mm eye relief.

What is the "eye relief" problem?
Wondering if it is the GSO means you have to actually hold your head/eye so far away that you are not in contact and so the head sort of "drfits" around a bit. If you are in contact with the eye piece and there is (I think) kidney beaning and sort of black outs then I think that means there is too much eye relief and you re too close.

[Relpet]

That sounds a bit odd, I assume a 32mm GSO plossl which should deliver about 20-24mm eye relief.

That is a lot and if that is "poor" there is something amiss as even if you got a good TV they deliver I think 20mm and no more. The often mentioned BST's and X-Cels both deliver around 15-17mm eye relief.

What is the "eye relief" problem?

Wondering if it is the GSO means you have to actually hold your head/eye so far away that you are not in contact and so the head sort of "drfits" around a bit. If you are in contact with the eye piece and there is (I think) kidney beaning and sort of black outs then I think that means there is too much eye relief and you re too close.

This, sadly, is where my status as a complete novice begins to tell as I have no way of measuring a meaningful comparison.  The eyepiece in question, the SuperView, is unusual insofar as the piece you ordinarily put your eye to unscrews to reveal a thread which will screw into a T-Mount.  I bought it second-hand.  It also has a sliding nose piece which seems to change the focal length.  It was the only EP I had with which to compare the 2" Revelation, which led me to raise the topic.  I was in touch today with Telescope House  who sold me the package.  They suggested that perhaps I had not seated the 2" properly as it was my first use.  I followed their recommendation and tried in daylight on a target 5 kms away and it seems they were right about the focussing.  It was fine.  Cloudy tonight so can't star field test.

With the various EPs I have invested in I remove my glasses and position my eye at about the same distance for each.  After cataract operations in both eyes the natural lenses have been replaced by smaller fixed focus lenses - which may have a bearing.  With the 32mm GSO SuperView I found if I just moved my head in the slightest at the normal distance I would lose the image, which is not usually the case.  I had to get almost to touching to keep the image. I hope that is some kind of explanation for what may be an unintended slur on the GSO EP.

[damnut]

Hi Peter,

Do your legwork as above and you will not go far wrong. And no clear skies here, would love the warmth and azure blue skies of sw france. ...