Stargazing Planning to buy a first telescope? - Comments

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OK, some updates

The two eyepieces I have DO filter light for solar viewing. (I got daring, and held up just the eyepieces, and could barely make out the clouds covering the sun.) I am estimating that they are similar to shade 14 welders hood lens, an apparent standard for watching eclipses.

@jim hardy
Thanks for clearing that up. I think I can visualize the lens mounting concept you were sharing, now.

@DennisN
Thanks for verifying the size standard - should help my online shopping experience, a lot.

I bought some filter paper on Amazon for my binoculars. I assume this would also work on the telescope, assuming I can also find a clear eyepiece for the other end? However, since I have a 6mm, and 20mm eyepiece, I probably won't need to use the filter paper, unless I should buy a lens size for moon/planets that is substantially different than the 6mm or 20mm that I have for the eclipse? What would be the best size to use for viewing the moon and nearby planets?

I am loathe to spend money for adapters and such, in light of the fact that this is a cheap (toy) telescope, and should I actually get real enthusiastic, I would no doubt buy something much different/better, that the adapters might not fit. However, I WILL investigate the links you provided, to see if I can buy just a lens, for moon and planet gazing, while I explore the depths of my potential enthusiasm.

Thanks!
 

jim hardy

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I am loathe to spend money for adapters and such, i
look into pinhole camera and projection ideas.

For a mid 80's partial in Florida our clever secretary at work taped her makeup mirror to a windowsill and reflected an image onto back wall of the office.
 
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For a mid 80's partial in Florida our clever secretary at work taped her makeup mirror to a windowsill and reflected an image onto back wall of the office.
Clever, indeed!
 

Drakkith

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I have a question about my Celestron 130EQ reflector. Previously I had a 70mm refractor and I remember being astounded at the sharpness and contrast of edge on views of the ridges on the moon that it gave. The 130 pulls in a lot more light; it is uncomfortably bright when looking at a full moon with the scope unrestricted but it's images don't seem to be nearly as well focused as the 70mm was at what I think is about the same magnification.

Makes me wonder what the process for making the 5 inch mirror is, but thus far I haven't really checked close enough to actually tell. Everything about the 130 is well made and works good, but I am a bit disappointed about the blurriness of the view.

DC
Do you know the f-number of both scopes? Reflectors tend to have lower f-numbers than refractors (except the really expensive apochromatic ones) if I recall, which can exacerbate any aberrations inherent in the mirror shape.
 

russ_watters

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I have a question about my Celestron 130EQ reflector. Previously I had a 70mm refractor and I remember being astounded at the sharpness and contrast of edge on views of the ridges on the moon that it gave. The 130 pulls in a lot more light; it is uncomfortably bright when looking at a full moon with the scope unrestricted but it's images don't seem to be nearly as well focused as the 70mm was at what I think is about the same magnification.
A lunar filter is a must for just about any telescope. I have an adjustible (two opposing polarized filters) and a stand alone that I think is 10% transmittance.

Otherwise, for a reflector on a wide field view of the moon, it really should be sharp. I'd check the collimation.
 

russ_watters

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@jim hardy

By "Blacked out", I guess I mean they look like the lenses used in welding goggles. The glass is very dark, nearly black.
How "nearly black"? Can you see anything through them? A solar filter is so dark you literally can't see anything but the sun or a bare filament on a clear light bulb. Anything more and it isn't safe for solar viewing.

Also, the filters are almost always placed over the objective, where they intercept all of the light spread out instead of focused.
 

jim hardy

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Also, the filters are almost always placed over the objective, where they intercept all of the light spread out instead of focused.
good point, i tend to forget details.
Think about the energy collected by the objective lens. Ever burn paper with a magnifying glass? Galileo wrecked his eyes.

You don't want all the light gathered by the objective to get absorbed as heat in your little eyepiece, it'll likely crack.

I've seen metal covers with just a little hole in the center to go over an objective lens , blocking probably more than 99% of the light.
 

sophiecentaur

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It is pretty important to have the filter over the objective of a large diameter reflector (an expensive solution, unfortunately) If you try to get way with a high density filter at the eyepiece end, the power from the sun on the secondary reflector can overheat it. There are cheapish solar filter mylar films ( less than £20 for 200mm diameter) which are easy to mount on a cardboard support. You could do what I did and used a cheap round baking tin with the bottom cut out which fits over the end of the tube of an 8" Newtonian.
But solar observations can be a big disappointment unless you use extremely expensive narrow band etalon filters. The are what you have to use if you want to see those very impressive pictures of solar features that people publish. But sunspots are quite impressive and well worth looking at on a big sharp image of the Sun.

I have to give the statutory warning against ever ever trying to look directly at the Sun through a telescope. 10W of light, focussed on your retina will totally fry the nerves. So any filter must be fixed well and the observations have to be well supervised by a competent adult!!!
 

sophiecentaur

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I've seen metal covers with just a little hole in the center to go over an objective lens , blocking probably more than 99% of the light.
The resolution is poor then - back to the pinhole camera problem. The objective cover on Newtonians often has a 40mm (approx) hole for lunar viewing but I think the resolution could suffer a bit.
 
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How "nearly black"? Can you see anything through them? A solar filter is so dark you literally can't see anything but the sun or a bare filament on a clear light bulb. Anything more and it isn't safe for solar viewing.

Also, the filters are almost always placed over the objective, where they intercept all of the light spread out instead of focused.
So dark, that the only way I can see anything is to point it at the sun. I did it on a cloudy day. The only thing I could see was a circle of clouds, barely larger than the sun, moving past the circle. Once a cloud passed the bright sun, it was no longer visible. Looking at a light across the room did not allow me to see the light, but then, we use low wattage bulbs here. I did not try getting close to a lightbulb to test it.

The whole idea of the eyepiece heating up makes complete sense to me. However, this is a small telescope, having a lens just about 2-1/2 inches in diameter. Still, you have me concerned, so next clear night when I am awake, and the moon is out, I will point it sky-ward, and see if this wasn't intended to be filtered for moonlight, rather than solar. Can I assume that if these eyepieces are lunar filtered that I will be able to see the moon well, and if they are not lunar filtered, that the moon will not be easy to view? I really don't know a better way to test them.

Thank you for helping me care for my eyes - It would kinda suck to damage my (or anyone else's) vision, just because we wanted to check out the eclipse, up closer.
 

sophiecentaur

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However, this is a small telescope, having a lens just about 2-1/2 inches in diameter.
Standard practice for smallish solar scopes is to use what they call a Solar Wedge. It consists of a mirror at 45degrees with a dichroic reflecting surface which just reflects visible wavelengths into the eyepiece. The rest passes through and heats up a large heat sink, avoiding any localised high temperatures. A filter upstream of the eyepiece would be in a position where a fairly small diffuse image of the Sun would heat up a small area of it. It's only at the objective end that the power is easy to deal with.
You can set fire to paper with 70mm lens!
 
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Standard practice for smallish solar scopes is to use what they call a Solar Wedge. It consists of a mirror at 45degrees with a dichroic reflecting surface which just reflects visible wavelengths into the eyepiece. The rest passes through and heats up a large heat sink, avoiding any localised high temperatures. A filter upstream of the eyepiece would be in a position where a fairly small diffuse image of the Sun would heat up a small area of it. It's only at the objective end that the power is easy to deal with.
You can set fire to paper with 70mm lens!
So if I understand you correctly....

You think that the dark lenses I have, and that came with this (cheap, probably bought at K-Mart 20 or more years ago) telescope are most likely made for viewing the sun... or did I misunderstand?

Some further description:

My eyepieces fit into a palm-sized piece that makes a right angle between the scope and the viewer. (...Which fits into a barrel marked "2X", which then fits into the telescope...) The mirror inside looks like it bisects that angle, making two 135 degree angles where the edges of the tiny mirror are attached to the inside of the body of the angled piece. I can not see anything else remarkable about the piece, other than 2 tiny screws on the outside, on what looks like a removable panel, presumably designed for allowing access to service the mirror... I have not attempted to open it, yet, but I may have to, in order to get the mirror clean, as it has collected a lot of large dust particles.

(Did I describe that well enough?...)

~ Thanks
 

sophiecentaur

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most likely made for viewing the sun
As you cannot see anything else through them, I guess they must be, lol.
It would be interesting to see if the filter gets warm. It may not matter for an inexpensive scope but thermal effects can really spoil the high image quality in a high quality scope. People say you should leave a telescope for some while when you take it outside on a cold night so that it can equalise the temperature all over and get back to good collimation. Heating it up from the Sun could spoil the picture - try experimenting and see if it gets worse after ten minutes or so.
Your right angle viewer is useful, particularly for looking high in the sky. If you are not very careful with the mirror, you can easily scratch the weak reflecting surface and leave it worse than it is now. A bit of dust will only decrease the contrast but a scratch can leave every star with identifiable lines going across it (like windscreen wiper tracks and street lamps). Many people say you should stay well away from such tinkering. But, of course, care and skill are all you need to do any of those jobs. Google "Cleaning Telescope Mirrors" and there are several interesting videos.
That 2X barrel sound like a Barlow lens, which doubles the magnification of your scope. Try with and without. I have a cheap one and I'm not sure that the bigger image actually improves matters - for a start, the image is dimmer. It all depends
 
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I am looking to buy a telescope, what is cheapest telescope I can buy with highest magnification possible?

I dont have solid background about astronomy, but I have general interest in it since I was a child, long time ago I had small telescope with max 40x magnification but I was not satisfied by it, mainly because it was very unstable where the least wind causes shaking and everything I see through it was very blurry including nearby planets like Mars and Venus.
 

Drakkith

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I am looking to buy a telescope, what is cheapest telescope I can buy with highest magnification possible?
Except in the case of very small telescopes, your magnification* is often limited more by turbulence in the upper atmosphere than by the telescope itself. Not only that, you don't actually want maximum magnification for about 95% of targets. High magnification causes the image to dim and makes it harder to keep the image stable and to find targets in the first place. I often get a 'better' view of the planets with a relatively low power eyepiece instead of one that gives me the highest possible magnification I can get. My high-mag eyepieces often just make the image a dim, blurry mess. And this is with an $1500 8-inch reflector on a mount that costs just as much.

As for price, I would set a minimum price at around $100 USD (or even $200). Anything less than this and you will almost certainly be buying a very poor quality telescope. Even if the optics of this scope are average, or even good, the quality of the mount, the tube assembly, and the accessories will likely be poor and make the telescope frustrating to use.

Trust me when I say that saving up a little extra to buy a more expensive telescope is well worth the delay.

*Note that a telescope doesn't have a single magnification. Instead the magnification depends on the focal length of the primary optics (the big piece of glass at the front or the big mirror inside) combined with the focal length of the eyepiece you are using. Buying a couple of eyepieces of different focal lengths gives you a good range of magnifications to suit your needs. Many telescopes come with at least 2, one for low-mag and one for high-mag, if I remember correctly.

I had small telescope with max 40x magnification but I was not satisfied by it, mainly because it was very unstable where the least wind causes shaking and everything I see through it was very blurry including nearby planets like Mars and Venus.
This is most likely because you had a cheap telescope with a light, flimsy mount. I had one as a kid that broke the first night I had it thanks to flimsy plastic threads between the tube assembly and the focuser.

In regards to a specific telescope you should buy, I'm afraid I can't recommend a specific one. There's a saying in amateur astronomy: "The best telescope is the one that you will use." I stand buy that statement. If your nearest viewing location is four flights of stairs down and three blocks away on foot, then you probably don't want a 8-inch dobsonian that you'd need to make two trips for. If you are in a situation similar to this, a good pair of 5-7 inch binoculars might suit you best.

Try looking through this thread for more information: https://www.physicsforums.com/threads/planning-to-buy-a-first-telescope.391086/
 
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I am looking to buy a telescope, what is cheapest telescope I can buy with highest magnification possible?
This topic was discussed many times on this forum, so I recommend to search a little bit, I am sure you will find a lot of helpful inputs. In my opinion, one of the best hints is to begin with decent binoculars and a good sky atlas. It is the best investment you can do at the beginning, because both of them you will find helpful even in the case you already have a bigger telescope. Once you are sure this hobby is the right one, you can buy the telescope. Moreover at the time, you will probably know what kind of objects are the most interesting to you so you will know what kind of scope to buy (+ depending on the observational conditions in your area of course).

I had small telescope with max 40x magnification but I was not satisfied by it, mainly because it was very unstable where the least wind causes shaking and everything I see through it was very blurry
Surely, the problem was with a cheap unstable mount, not the optics I believe.
 

russ_watters

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I am looking to buy a telescope, what is cheapest telescope I can buy with highest magnification possible?

I dont have solid background about astronomy, but I have general interest in it since I was a child, long time ago I had small telescope with max 40x magnification but I was not satisfied by it, mainly because it was very unstable where the least wind causes shaking and everything I see through it was very blurry including nearby planets like Mars and Venus.
A quick note on magnification itself, since others have done a good job addressing it; I have a fairly large and good quality telescope for an amateur, and my sweet spot for planetary viewing is about 180x magnification. I sometimes go higher, but "seeing" needs to be exceptional for it to be useful.

I want to try to head off a potential expectations gap though. Right now there are 4 good viewable planets, which is a rariaty, but because it is summer all are very low in the sky. That means the "seeing" is very poor and even with my equipment, the atmospheric distortion is noticable at 180x.

Also, I've only looked at Venus a few times, but since it is basically a flat white cloud, there isn't much to see. Mars, Jupiter and Saturn are the ones to be most interested in.
 
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I want to try to head off a potential expectations gap though. Right now there are 4 good viewable planets, which is a rariaty, but because it is summer all are very low in the sky. That means the "seeing" is very poor and even with my equipment, the atmospheric distortion is noticable at 180x.

Also, I've only looked at Venus a few times, but since it is basically a flat white cloud, there isn't much to see. Mars, Jupiter and Saturn are the ones to be most interested in.
I totally agree. And for majority of amateur astronomers, I believe, the Jupiter is the top (including the four Gallilean moons) among the planets.
 

russ_watters

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And for majority of amateur astronomers, I believe, the Jupiter is the top (including the four Gallilean moons) among the planets.
Yes, Jupiter is so big and bright that a moderately skilled amateur with reasonable equipment can take near magazine-worthy photos. :wink:
 

George Jones

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As an example of Russ's comments about "seeing', I tell my non-astro friends that, because of movement of the Earth's atmosphere, under too high a magnification, the Moon's surface looks like it is "boiling"; see 1:05 to 1:11 in the following video.


And for majority of amateur astronomers, I believe, the Jupiter is the top (including the four Gallilean moons) among the planets.
Before I got my scope (an 8-inch SCT) in 2009, I knew I wanted to look at Jupiter, but I didn't realise how endlessly fascinating I would find observing Jupiter: cloud belts; Great Red Spot; shadow transits; moons disappearing into Jupiter's shadow; moons reappearing from Jupiter's shadow.

One early evening a few of months ago, I took the scope out early to look at the Moon, which easily took high magnification. Since the seeing was excellent, I checked a magazine, saw that Jupiter's Great Red Spot was going to be near the meridian in a few hours, and decided to leave the scope out until it got dark. (At 54 north, total darkness hardly happens in spring/summer.) When I took a look, not only was the GRS clearly visible, so too was a very small dark spot on Jupiter. A shadow transit (the shadow of a moon is visible on the "surface" of Jupiter) was in progress, which was a nice surprise, as I had not looked into this before observing.

The cool thing about observing Venus with a scope is that, like the Moon, Venus goes through phases. Right now, Venus is almost first-quarter, but I have lost it behind a large hill that is just to the west of me.
 

Drakkith

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Chronos

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Aperture is a word frequently mentioned by telescope reviewers. In a nutshell you want the most aperture available at your price point A 6 inch anything is going to offer way more ROI than a 3 inch anything else. The finest optics and accessories cannot compensate for the light gathering power of larger aperture. This is why you see tons of 12 inch reflectors and hardly ever see even a 6 inch refractor. Unarguably, a refractor is optically superior to a reflector . Unfortunately it is also many times more expensive and comparatively enormous at the same aperture. Portability is also a vital consideration. Unless you have an observatory, a beastly scope is simply impractical The awe of the view is rapidly outweighed by the labor and nuisance of setting up a viewing session. I would suggest a compromise and settle for the biggest aperture you can afford and still physically manage. To that end I would suggest a short F reflector. They are readily available, affordable and easy to set up and use. Cat'[hybrid reflector/refractor] scopes are also popular, but, most people are much better off getting some experience with a simple reflector before taking the Cat plunge. I own a fancy 8" Cat with all the bells and whistles, but, still prefer the view offered by my venerable [and much cheaper] 10" f4 newtonian when seeing is good.
 

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