# Thread: Fast Newtonian eyepiece query

1. ## Re: Fast Newtonian eyepiece query

Frosty,

I have a Meade LX 70 eight inch f/5 reflector (1000mm focal length like yours). The smaller diameter of my scope matches up similarly to my eye pupil as your scope probably does for you. I happen to be a Meade guy and my 82 degree eyepieces are the Meade 5000 series. I have the whole series, but what works well for me in my scope is the 24, 14, 8.8, and 5.5 mm eyepieces. I find that I rarely use the 30mm and the 20mm. I also have an Explore Scientific 18mm that goes unused as well.

When people get into the realm of eyepieces that you are talking about, most will end up using a string of eyepieces that will start with one that will give them close to the maximum field they can comfortably get into their eye, to help with finding things in the eyepiece. They will then moved down, as needed for the object, in steps of 50 to 65% of the field diameter of the sky they are seeing, (true field of view or TFOV) With eyepieces of the same apparent field of view (the field width as it looks in the eyepiece, such as 82 degrees), just using the focal length for comparison is appropriate.

Other limits for you include some limit for the size of your scope as a general rule of thumb. At the elevation where I live, 700 ft, two times the diameter of the scope in mm, seems to work for smaller scopes. However, that tends to give out as the scope gets to the size of my eight inch as it will for your scope. The f-ratio also comes into play as well, with the upper magnification limit decreasing some for the more radical focal ratio. I have also been told that it takes really pristine skies to go higher than 400X, unless at high elevations, like several thousand feet. If you live at sea level, the magnification limit for your scope may be as low as 300X under good conditions.

A long time astronomer, who has completed most of the Astronomy League programs, all that she sees that has any relevance to her, told me that she rarely ever has a need to go above 300X, even though her 13.5 inch, premium reflector is quite capable of higher magnifications. Personally, unless I am viewing something specific on the Moon or attempting to split really difficult/tight double stars, I generally do not go above 200X. Your scope, with something like my 5.5 mm eyepiece will give a magnification of about 180X. With a good 2X Barlow, that makes 360X, which would most likely be as much or more magnification than needed.

Hope this helps.

2. ## Re: Fast Newtonian eyepiece query

The wording around the 50 to 65% is not worded quite right. What I was meaning is that the next eyepiece down in focal length will normally give you a field that is about half to two-thirds the diameter of the previous one. It just depends on how big of a step you care to take. For most of my time with astronomy, I have stayed around the 60 to 65% range simply from a fear of taking too big of a step and loosing the object. If I get into something at a really high magnification, I will drop to as small of a step as I can, simply because it is easier to loose an object at that high of a magnification.

3. ## Re: Fast Newtonian eyepiece query

You're not letting the team down by staying within your budget. Plus, going with 1.25" is actually a good choice. Bigger isn't necessarily better. Other than a wide field, there's no real benefit to a 2" optic. 1.25" optics aren't inferior in quality just because they're 1.25". Often a 1.25" is easier to make well, lighter, and costs less. The only real reason to go to a 2" eyepiece is because you want a wider view than you can get with a 1.25". You could make a convenience case for a having them all be 2" eyepieces if you're willing to pay that much to not have to swap in an adapter. I have all 2" eyepieces: 5.5mm 100°, 9mm 100°, 18mm 82° and 24mm 82°. I like the wide view. But a 1.25" 4.7mm Explore Scientific 82° is a really good eyepiece as well and costs about 1/3 the cost of the ES 5.5mm 100° and is still a huge view. Same with the 1.25" 8.8mm ES 82° vs the 9mm 100°. So, why do I have them? I found an open box NEAP deal on the 9mm 100° that was a demo unit and it tempted me (\$150 off). If I ever wanted to get my money back, it would easily sell for what I paid, maybe more. My wife bought me the 5.5mm 100° for Christmas. Otherwise, I would be equally happy with 1.25" ES 82° eyepieces (it's still pretty wide). Also, I'd rather have a quality 1.25" eyepiece than a cheap 2" wide field eyepiece. You'll find that's true especially at f/4.

Also, try not to sweat the cost of the eyepieces. It'll take you a little longer to build up a good set but they will probably be with you for life. Plus, they hold their value pretty well if you take care of them.
Last edited by Robrj; 12-01-2016 at 10:56 PM.

4. ## Re: Fast Newtonian eyepiece query

Now I know why everyone looks at me funny when I say I have a HEQ5.. it's a NEQ6.. just shows you how long it's been since I've used my scope and mount frequently... wish I knew how to edit posts.. or travel back in time..

5. ## Re: Fast Newtonian eyepiece query

When I use my 8" f4 a good coma corrector is essential. My 12" f5 can do without. I find I use the TV Paracorr most conveniently. Advice to try a bunch of alternatives with different AFOVs should help a lot. It turns out I really don't like the 82 AFOV format. The AFOV isn't wide enough to make up for the pincushion distortion but I enjoy 100 degree AFOVs just fine. I wish I had sorted that out before buying my Naglers and selling them off.

Anyway my main set for the f4 is Paracorr, Panoptics and Delos. The Delos is crisper to my eye than Delite. When I want to go crazy with wide field wonderment I use the ES 100 series.

6. ## The Following User Says Thank You to not_Fritz_Argelander For This Useful Post:

j.gardavsky (12-02-2016)

7. ## Re: Fast Newtonian eyepiece query

Originally Posted by Frosty-vegi
Now I know why everyone looks at me funny when I say I have a HEQ5.. it's a NEQ6.. just shows you how long it's been since I've used my scope and mount frequently... wish I knew how to edit posts.. or travel back in time..
Editing on the forum times out at about 15 minutes. After that time, a post can't be edited by us mere mortals.

Another option is to buy used. Since people like to upgrade, you can get many of the higher quality eyepieces for much cheaper than buying new (abotu 60% to 70% of the new price) and they're usually well taken care of. Plus, with a used eyepiece, you can usually sell it for close to what you paid if you later upgrade. CloudyNights.com has a big classified section. Astromart is a good place as well but it costs to join (\$15/year). There are classifieds on here as well but the selection is more limited and they tend to go fast. The downside is it takes patience and repeatedly checking to see what's new. Plus, it helps to know what you want ahead of time.

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