New eyepiece help - 25mm

[C7tsj]

I am on the hunt for a new 25mm to upgrade from the stock EP that came with the scope. I will mostly be using the new EP for DSOs.

My scope is an f4.4. Whilst I have heard good things about BST, can anyone give advice as to whether this will work well in my scope? This is more a longer term investment given the price and I am unlikely to buy another EP anytime soon.

This is the EP from sky's the limit - £49 delivered.

http://www.ebay.co.uk/itm/1-25-25mm-BST-Explorer-Dual-ED-eyepiece-Branded-Starguider-/161144826675?pt=UK_Telescope_Eyepieces&hash=item2584faeb33

Thanks in advance.

Mark

[michael.h.f.wilkinson]

I would take a long, hard look at the 24mm 68 deg MaxVision. Wider FOV, very good value for money.

[bingevader]

I would take a long, hard look at the 24mm 68 deg MaxVision. Wider FOV, very good value for money.

Definitely.

[denis0007dl]

I would take a long, hard look at the 24mm 68 deg MaxVision. Wider FOV, very good value for money.

I agree, same as ES 24mm.

[ronin]

At f/4.4 I would be tempted to look at the TV plossl either 25mm or 32mm.

They are supposed to be good to f/4. Just no idea of anything else at "reasonable" cost that should work on your scope.

The BST's might, someone said a day or two back they were OK at f/4.6, but they will start to fail somewhere.

[C7tsj]

Definitely.

Hmmm? Might be pushing it as looks as though £100 once converted to GBP. My max budget is probably around £50.

Thanks for the option though.

[michael.h.f.wilkinson]

Hmmm? Might be pushing it as looks as though £100 once converted to GBP. My max budget is probably around £50.

Thanks for the option though.

I think you are looking at the 82 deg. The 68 degree is 79 euro, or about £66 (plus postage)

http://www.explorescientific.co.uk/en/Maxvision-68-Okular-24mm.html

[C7tsj]

I think you are looking at the 82 deg. The 68 degree is 79 euro, or about £66 (plus postage)

http://www.explorescientific.co.uk/en/Maxvision-68-Okular-24mm.html

Yeah my mistake, was looking at the 34mm. Thanks for the link.

[Phil Creed]

Yes, go for the 24ES-68 if you can fork over the dough.  Excellent bang-for-the-buck.

I owned a 24mm Meade 5000 SWA, which I think is a clone of the 24ES-68 / 24mm Maxvision-68.  At the time, I owned a 16" f/4.5 that didn't have coma correction.  It was sharp out to about 90%, when the off-axis astigmatism combined with the fast mirror's coma started to soften things up.  But the edges weren't the horrific, "seagulls" you'd get from a cheap widefield, as most of the edge distortions were from the mirror's coma itself, not the eyepiece's off-axis astigmatism.

By contrast, I did try a cheap 30mm widefield in this scope, by far the most brutal "test chamber" I've ever subjected eyepieces to.  Saying that it failed was like saying Lake Erie is moist.  The central third was OK; the middle 1/3 was seagulls.  The outer 1/3 resembled horrific, insanity-inducing...I dunno...THINGS you'd read about in an H.P. Lovecraft story.

Clear Skies,

Phil

[Charic]

C7tsj.........Hi, Coma is an off-axis aberration, Stars in the centre of the field are not affected by coma. This would be significant for wide field viewing, so how wide an eye piece can you tolerate on this telescope?

All Newtonian telescopes are inherent with coma, and is usually present at the edge of your field of view.

Off-axis distance and f/ratio effects coma. A faster f/ratio has more coma. My 8" f/6 will be easier to correct than on an 8" f/4 telescope.

You can fit a coma corrector then an eyepiece to help correct the issue, or buy an EP that is specially constructed to try and reduce the coma.

In answer to your original question, you could buy the 25mm BST and try it out. If it doesn't work for you, you can send it back without quibble (you'll pay p&p) but you'll get your £49 back. Its a perfect try before you keep scenario. Just speak with Alan first, his contact details are normally on the web site. 

Many will say that BST's may not be suitable!  Their prices are very attractive, but just might not work in your "faster" telescope. However, You wont know unless you try. Your probably less than £2 for return p&p depending on your method should it not work?) You may be surprised by the results.

[C7tsj]

Thanks Charic, seems like a reasonable approach and I get to test BST quality as I may want to try other sizes later.

Thanks for everyone's suggestions.

Mark

[luminova11]

Another vote for the MaxVision from me.

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