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PostPosted: Fri Feb 10, 2012 8:22 pm 
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Joined: Fri Feb 03, 2012 3:31 pm
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Location: Long Ditton, Surrey, UK
David, Looks like the 6mm Vixen NLV is a great start then, I hope to get a good price tommorow - I believe the Opticron stand is selling the complete Vixen range.

I will be sure to give an update tommorow - your advice was completely invaluable, I can now buy confident and informed!

Regards, Umar


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PostPosted: Mon Feb 13, 2012 12:59 pm 
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Joined: Sat Jun 21, 2008 11:32 am
Posts: 54
Location: se london
Sorry for my delay in replying.
I find the 8mm Wide Angle Vixen more user friendly than the 13mm Nagler + 2x Barlow due to its greater eye relief, even though I don't wear glasses. Unless I almost press my eye against the Nagler I am not really aware of the extra field of view (80 vs 65 from memory). As I previously mentioned the only possible drawback that I have found with the Vixen is its weight.
I have also used an 11mm Teleview Plossel with the 2x Barlow on Planets, the definition is excellent, but the smaller field of view requires almost constant tube nudgeing. My advice for anyone with an undriven Dobsonian is to invest in wide angle eyepieces, Monocentrics may offer the ultimate detail, but you won't enjoy using them.

Regards

Barry B


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PostPosted: Mon Feb 13, 2012 1:07 pm 
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Joined: Sat Jun 21, 2008 11:32 am
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Location: se london
Sorry for my delay in replying.
I find the 8mm Wide Angle Vixen more user friendly than the 13mm Nagler + 2x Barlow due to its greater eye relief, even though I don't wear glasses. Unless I almost press my eye against the Nagler I am not really aware of the extra field of view (80 vs 65 from memory). As I previously mentioned the only possible drawback that I have found with the Vixen is its weight.
I have also used an 11mm Teleview Plossel with the 2x Barlow on Planets, the definition is excellent, but the smaller field of view requires almost constant tube nudgeing. My advice for anyone with an undriven Dobsonian is to invest in wide angle eyepieces, Monocentrics may offer the ultimate detail, but you won't enjoy using them.

Regards

Barry B


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PostPosted: Mon Feb 13, 2012 2:42 pm 
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Joined: Mon Jan 18, 2010 9:25 am
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Thanks Barry,
I agree that with undriven scopes even non Dobsonian, wide angle eyepieces are better especially for high magnification use. And preferably they should have good edge performance.
The original 4.7mm Nagler I used had so little eye relief that I could not really see the whole field at one time.
The 7mm was much better.

I have used an uncoated Monocentric possibly made by Horace Dall.
I think the field was about 20 degrees.

Also possibly a Tolles, I will have to check.

With a driven scope, then the situation is quite different as you can use narrower field eyepieces that cost less but still have good central performance.

The ideal is to have a variety of eyepieces to suit the observing conditions and object being studied and the observers preference.

Regards, David


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PostPosted: Mon Feb 13, 2012 3:04 pm 
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Yes, I think I have used a Tolles uncoated eyepiece.
Also possibly a Hastings, but I have never owned, used or ever seen Ball eyepieces.
These gave very high magnifications indeed.

I possibly have a Hastings magnifier?

For high magnifications I used a 4mm Swift eyepiece that unfortunately contained thorium right next to the eye and a very good 3mm Clave.
Also a modern 2 or 2.5mm I think Long eye relief eyepiece.

These high magnifications are fun to play with or to test optics but normally are not needed.

Regards, David


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PostPosted: Sat Feb 18, 2012 4:36 pm 
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Joined: Fri Feb 03, 2012 3:31 pm
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Location: Long Ditton, Surrey, UK
Sorry for the delay in writing.

At Astrofest, I decided to buy the 6mm NLV for £119. The LVW range was on display, and will probably be my next purchace.

I have not been able to test it out yet, there has not been a single clear night since Astrofest.

Hopefuly I will get as much use out of it at Mars' opposition in March, and Saturn in April.

I would like to say thank you to everyone, especialy David and Barry for the much needed advice.

Much appreciated, Umar


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 Post subject: Re: Magnification
PostPosted: Sun Jan 22, 2017 10:09 pm 
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Joined: Fri Feb 03, 2012 3:31 pm
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Location: Long Ditton, Surrey, UK
Dear Users,

Hello again after a long time!

I last posted on this topic in February 2012, however, a change in circumstances since then has led me to reopen this.

As a quick summary, I had a 300mm (12 inch) GOTO dobsonian (Focal length: 1,500mm, Focal ratio: f/4.9) and wanted some advice as to why experienced amateur astronomers avoid using the highest magnifications possible for planetary viewing. David, Barry and others very kindly replied and the following discussion led me to look for 2 long eye relief eyepieces, the first providing 180-200x, and the second, 250x.

Unfortunately, in the ensuing 5 years, my 12 inch dob became too much to handle as I developed a long term illness shortly after my last post. Recently, I have managed to get back into astronomy by selling my old scope and buying a GOTO Celestron CPC 800 (Focal Length: 2,032mm, Focal Ratio: f/10). It is far more manageable and with the supplied eyepieces I have managed to get somewhat pleasing views of Venus, Mars and Uranus over the last couple of weeks. The old eyepieces I have lying around are:

1. 40mm Plossl (50.8x)
2. 20mm Plossl (101.6x)
3. 6mm Vixen NLV (338.6x) – This was bought for my old 300mm Dob, as described previously.

However, the 40mm (50x) and 20mm (100x) eyepieces gave too small a view and the 6mm Vixen, bought for the old telescope, seems to be too overpowered for my new scope.

I am now hoping to get some eyepieces better suited to planetary viewing (and what little deep sky I can under heavy light pollution) through my new 8 inch SCT.

To summarise:

1. Reviewing the above, I seem to think that getting an 8mm (254x) and 13mm (156x) Vixen LVW would be a good place to pick up where I left off?

2. Has the eyepiece market changed since 2012 e.g have new options/ranges come out, are zoom eyepieces now a good option etc?

3. How would the advice for planetary viewing through an 8 inch SCT differ from my old 12 inch Dob? Long eye relief eyepieces would be preferred.

Kind Regards,

Umar


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 Post subject: Re: Magnification
PostPosted: Mon Jan 23, 2017 4:00 pm 
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Hi Umar,
The focal length of an SCT ,with main mirror position changes, alters with focus, so it is quite sufficient to round magnifications to 150x 340x etc. Also the eyepiece marked focal lengths are not accurate.

There is a vast array of eyepieces, so any good quality eyepieces should be O.K.
Others may advise on their favourites.

On the best nights 340x or so should be quite usable on Mars, etc. when the telescope has stabilised with the temperature.

Regards,
David


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 Post subject: Re: Magnification
PostPosted: Wed Jan 25, 2017 3:28 pm 
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Joined: Fri Feb 03, 2012 3:31 pm
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Location: Long Ditton, Surrey, UK
Dear David,

Thank you for your reply.

I think I will keep my 6mm Vixen for Mars then.

I've also asked on Stargazer's Lounge and the general consensus is that the Vixen LVW and SLV ranges are still a good option, with 8, 10 and around 14mm being a good choice of focal lengths.

Regards,

Umar


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 Post subject: Re: Magnification
PostPosted: Thu Jan 26, 2017 4:58 pm 
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Location: Lancashire
Panoptics have also been recommended in the past by our Forum moderator Joe.

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 Post subject: Re: Magnification
PostPosted: Thu Jan 26, 2017 5:52 pm 
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An f/10 SCT is a lot more forgiving for eyepieces than an f/5 Dobsonian.

Regards,
David


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 Post subject: Re: Magnification
PostPosted: Fri Jan 27, 2017 1:55 pm 
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Location: Lancashire
A point sometimes forgotten. Thanks David. I purchased a £2 secondhand MEADE 9mm Plossl, and it performs better than the highly-rated BAADER GSO 9mm on the CELESTRON 104mm/ f.5 achro refractor.

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 Post subject: Re: Magnification
PostPosted: Thu Feb 02, 2017 12:25 am 
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Joined: Fri Feb 03, 2012 3:31 pm
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Location: Long Ditton, Surrey, UK
Dear David and Brian,

I decided to go ahead with buying an 8mm Vixen LVW and 10mm SLV.

I had also looked at the Tele Vue Panoptic and Pentax XW ranges, though these were out of my budget.

After you pointed out that a slow scope like mine would be more forgiving with eyepiece quality, I decided to research this point further and came across the Baader Hyperion range. This range was cheaper than the others and it became evident that their inferior edge of field performance would be mitigated by my f/10 scope. Ultimately I still went for the Vixens due to their better control of light scatter when observing brighter objects.

There hasn't been a cloudless night yet, but I can already notice that their build quality is far superior than the Plossl that came with the scope. One potential issue I do have is that the LVW is rather heavy. I hope it won't imbalance the scope or put any strain on the motors.

Thanks again,

Umar


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 Post subject: Re: Magnification
PostPosted: Thu Feb 02, 2017 10:42 am 
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Location: Lancashire
I have a 9mm Vixen Umar. It's a great eyepiece and with long eye-relief. :D

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