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Looking for a good barlow lens and a filter... can yall help me out?

Celestron eyepieces filters
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#26 Waynosworld


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Posted 24 November 2020 - 06:13 PM

That Celestron 20mm erecting eyepiece is good for looking at the trees and tops of power poles a few blocks away, it is basically worthless for looking at the sky in my opinion.

I have been looking at Mars a lot lately using my huge Starsplitter 14.5" F4.5 dob, it is usually alright to look at Mars with my Meade 6.7mm UWA eyepiece, even using my big dob the planet is so small it is hard for me to see much of anything except that it is Mars, when I put that 2X removable barlow lens on to my 6.7mm eyepiece it turns that eyepiece into a 5mm eyepiece, when seeing is exceptionally good I can see detail on Mars, and I have to sit there for hours to see that detail as most the time it is blurry/dancing and it looks like a mini sun, but every once in a while it gets steady for a few seconds, this scope is a light gathering bucket and I rarely am able to use the equivalent of a 5mm eyepiece.

Now last night I used my Meade 14mm UWA eyepiece to look at something else because a cloud bank came in and Mars disappeared, I had heard that the Orion Nebula was in this certain area in the sky at a certain angle away from these 3 stars, I found it pretty quick, while Mars was a dancing this Nebula was crystal clear in my eyepiece, looking at planets is hard for me where I live, there are houses/businesses/roads for a mile in every direction from my house, this time of year we heat our houses which creates lots of turbulence if your trying to look over houses at planets, and it beats me how an image that has traveled 1344 light years can be clearer that the image of Mars that took 12 minutes to get to my telescope. confused1.gif

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#27 Emirhan_05


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Posted 25 November 2020 - 08:13 AM

Always use the focal-length of the telescope to determine which eyepieces and accessories to complement, in this case a barlow.  The focal-length of your telescope is 650mm.  The planets, and other objects, require higher powers, 150x for instance...


650mm ÷ 150x = a 4.3mm eyepiece


You can get a 4mm eyepiece with a larger eye-lens and greater eye-relief...


https://www.astrosho...ab_bar_2_select (163x)


Per the 50x-per-inch maxim, your 5"(130mm) telescope can reach up to 250x, but the atmosphere and the collimation of the telescope can limit a power that high.  Almost 200x would be possible regularly, if the atmosphere allows, and if the telescope is collimated well.  The higher the power, the more precise the collimation will need to be.  The quality of the eyepieces and accessories also plays a part in that success, but that doesn't mean that you have to spend a lot of money for each eyepiece, or barlow.


Plossls are comfortable eyepieces in the longer focal-lengths, 9mm and longer...


https://www.astrosho...yepiece/p,12445 (54x)


A 12mm Plossl can be combined with a 3x barlow, and for a simulated 4mm(163x), yet still with the larger eye-lens and greater eye-relief of the 12mm. 


A 9mm Plossl can be combined with a 2x-barlow, and for an effective 4.5mm(144x).




That 2x-barlow also offers a 1.5x division, and for even more possibilities.  With two eyepieces and a barlow, the equivalent of four eyepieces, magnifications, are at your disposal.


There are these barlows as well.  The use of a Newtonian benefits from short barlows...




Welcome to the world of the Newtonian reflector.  In that one was chosen, for the larger aperture, there are certain responsibilities that come with one; namely, collimation...





A telescope has to work harder as you go up in power, therefore the alignment of the two mirrors inside the telescope, in tandem with the focusser, must all have their centers lined up together just right, and for sharp, pleasing images.

Heyo it's been a while.

After doing a bit of research, I found this(https://www.amazon.c...customerReviews)

It's a zoom eyepiece that goes from 8-24mm and comes with a 2x barlow and costs 150.

I've read the reviews and it looks really good so far. Should i buy this or the individual eyepieces that you listed? The 8mm zoom paired with 2x barlow should give the magnification of a 2x barlow, right?

#28 Emirhan_05


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Posted 25 November 2020 - 08:18 AM

I also have the EQ-130. I bought the Celestron Lens & Filter Kit for it because at local star parties, I saw other people with Dobsonian "light buckets" using the same kit. I now have other telescopes, but I still use the kit. It comes with a 2x Barlow and an array of oculars ("eyepieces") that will let you get a lot out of the EQ-130. Also, the filters can be helpful. First and foremost the Moon filter makes it possible to actually view the Moon without a beam of light being lasered through your skull. I also use the Moon filter to view Venus, for example. (Other filters will help cut Earth's atmosphere. It's not a big thing for me, but I do use the others on occasion.)


The kit costs $165 or so, but you are going to pay $100 or so for a 3x Barlow that will do you ZERO GOOD with the 20mm and 10mm oculars that came with the 130.  For myself, to get the power of the 20mm (just say), I would use the 32mm with the 2x Barlow for the same equivalent magnification as a 16 mm BUT -- and here's the ticket -- with a much wider field of view.  


Power is not everything. Often, it is over-rated, like the bald middle-aged guy in a Mustang convertible. There is nothing wrong with the magnification of the EQ-130, except that it is TOO MUCH magnification. You are looking through a soda straw. You want to get a wider view for the increase. You want to get the most of that very nice 5-inch (130 mm) objective mirror.


The laws of optics are against using that 20mm ocular with a 3X Barlow. You will be watching the floaters in your own eyes. 

Also read here on Cloudy Nights about "floaters":https://www.cloudyni...f-and-floaters/

Hey uh it's been a while.

After doing a bit of research I found this[(https://www.amazon.c...customerReviews)]. It's a zoom eyepiece that goes from 8-24mm and comes with a 2x barlow. I've read the reviews and it looks quite good i'd say. Is this good or should i buy individual eyepieces?

#29 dmgriff



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Posted 25 November 2020 - 11:17 AM

imo, zooms have a narrow field of view compared to individual eps.


for your scope at f=650mm a couple of wide field eps (say 20mm, 12mm) and a 3x barlow would cover a range of magnifications. 32x, 54x, 96x, 162x.


Moderate priced eps and barlow should suffice.


Good viewing,



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#30 Second Time Around

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Posted 25 November 2020 - 01:05 PM

Whilst you could buy a 3x Barlow to take your 10mm eyepiece up to 195x, I agree with others that a 2x would be much more useful. See below for the reasoning.

I've just bought a similar 130mm f/5 scope for a friend's daughter at Xmas and immediately upgraded the eyepieces. Both the 10 and 20mm starter eyepieces supplied are Modified Kellners, that don't work that well at f/5. Your 20mm erecting eyepiece is likely to be even worse at night, although handy for daytime terrestrial use.

These were the ones I chose for her:

32mm Plossl. In this case an Antares one, but most at this price are very similar. This gives the widest field of view possible (about 2.5 degrees) with your 1.25 inch focuser, and much wider than your 20mm eyepiece. Approx £30.

7-21mm Svbony zoom. Surprisingly good performance and highly regarded by many of us here on Cloudy Nights. Much lighter in weight than other new Svbony zooms. I always recommend a zoom for the inexperienced as it shows what's best for your eyes, your scope and your observing site. You may/may not add further fixed focal length eyepieces later. I've done so, but I still use my zooms a lot more often. Approx £40.

1.5x/2x clone of the GSO Barlow. Most of these clones will have "Made in Taiwan" printed on them. The advantage of these is the dual 1.5x/2x amplification. To get 1.5x amplification you unscrew the black lens cell and screw it into the filter thread at the bottom of the eyepiece. Approx £30.

These will give magnifications from 20x to 186x. The latter is about the maximum you'd be able to use here in the UK (and Belgium) under the jetstream. Even then 186x wouldn't be able to be used every night. Any higher magnification could be used only on nights with a really steady atmosphere.

Importantly, your lightweight mount would probably be too wobbly to use at a higher magnification in any event.

I've also bought her a long Cheshire eyepiece (about £15). This is not for observing but for collimating the scope so that the optics line up. If the scope isn't collimated even the best eyepiece won't give a good image.

For finding deep sky objects and seeing what they look like in a 130mm scope I added the excellent book "Turn Left at Orion". About £14 for the online version, £22 for a spiral bound book.

I'll also recommend she download the planetarium app Sky Safari. The free version would do to be begin with, but there are 2 very low cost upgrades. The upgrade to the Plus version will be coming from a family member.

Finally, I've added a headtorch with a dimmable red light. A red light won't ruin her night vision so much as white, but it needs to be as dim as possible to see faint objects - most are way too bright. Three of the Black Diamond range, the Spotlite 150, the now discontinued Cosmo 225, and its replacement the Cosmo 250 (all plus or minus £20) can be set to turn on only at the dimmest red light setting whatever button you push - so no accidents. Avoid other more expensive models with the Powertap feature as these have a very bright blue battery check light when first turned on.

One further accessory I'd recommend is an adjustable observing chair. You'll see a lot more when seated than standing, especially difficult objects. My friend's son is going to make her a chair for her birthday.

Good luck with whatever you choose, and be sure to tell us how you get on.

Edited by Second Time Around, 25 November 2020 - 09:31 PM.

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