Insights Planning to buy a first telescope? - Comments

[jim hardy]

Dad built an equatorial mount from plumbing fittings. A 2 inch Side Outlet Tee makes for sturdy leg mounts.

will post a photo if i can find one.

 

[Vanadium 50]

but what can I expect for $35?

The instructions are a hoot! "After find out the big goal, then debug with different eyepieces." And "if the window is big, the natural light is good, and the view is clear" sounds like a password between secret agents.

I think I agree with you - your next purchase should be a good mount. No matter what you look at, a good mount will help, while the optics will depend on what exactly you want to be looking at.

 

[DennisN]

The instructions are a hoot!

I've bought quite a lot of items from China and had many good laughs reading "Chinese English" instructions... some have been almost impossible to decode. And this is a fun picture I remembered from an article about a small video camera (which I did not buy, though).

 

[MaryMcN]

Hi everyone! I have one question:) I got interested in astronomy and cosmology so that my husband wants to buy a present for me and I'm not sure which telescope to choose...

 

[jim hardy]

I'd ask him for a subscription to "Sky and Telescope " magazine.
http://www.skyandtelescope.com/
They have weekly updates on what's in the sky
http://www.skyandtelescope.com/observing/this-weeks-sky-at-a-glance-june-9-17/

After a few months you'll be able to make an informed choice.

It's a lot of fun to build one.

 

[Blank_Stare]

I've never spent much time with a telescope, so my knowledge is pretty limited. I've spent a few hours over my lifetime, looking at the heavens through the lens of someone else's equipment, but that really doesn't count for much, when it comes to actually learning about the equipment.

A few years ago, I acquired this (old?) telescope and wooden tripod in a bundle of other things at auction. I'm preparing for the Solar Eclipse in August, and I'd love to use this telescope to watch it. When I went to use it, I quickly realized that there were no clear eye lenses - only "blacked-out" lenses. The problem is, since I know my knowledge of telescopes is almost non-existent, I am not certain if the lenses are OK for solar-gazing. I mean, I can not imagine any other purpose for black-out lenses, but what would I know?, you know? They say "SUN Japan" on them, but I think that's a brand name? There do not appear to be any model numbers on them, although there are some measurements listed on one end of each lens - 6mm, and 20mm. The diameter of the eye piece, where it fits into the angled telescope piece, appears to be about 25mm - but I am having a hard time measuring it with the tools on hand, so I might be off a few mm. (Is that a standard for sizing eye-pieces? If so, I am in trouble, because I don't see anything on Amazon that's even close...)

The telescope appears to be of the brand "Focal", made in Japan. It also says: "Astronomical Telescope F=700mm D=60mm", and also "code no. 20-20-66".

It looks similar to this telescope: https://www.ebth.com/items/6190881-scope-telescope-with-tripod mine is orange, however. I think this may have been a K-Mart purchase for the original owner, as I am seeing several (outside) forum posts that would indicate it. It's clear to me that this is not a high quality optical instrument, but rather, more of a toy. Still, it will do for a starter telescope, and if I get excited about the sport, I will consider upgrading in the future.

I have images of my telescope I would like to add, but apparently I lack the intuition to understand the interface in order to do so. Perhaps adding pictures is only allowed for paying members of the forums?

I am just starting to research this telescope, and, among other things, will be looking for clear lenses, so I can watch planets this winter, when skies are crystal clear at night. Please forgive me if I have left out any pertinent information. I'll be more than happy to provide anything that I can find, if you tell me what to look for.

Any assistance you can offer to help me get this scope "Eclipse Ready" in the next few weeks will be most appreciated, and if anyone has a favorite source for buying eye pieces that will fit this telescope, I would love to hear about it. In the meantime, I will be blindly searching eBay, Amazon, and Google, while I try to figure out what I have, and what lenses I am looking for to fit it...

Thanks

 

[jim hardy]

Is that a standard for sizing eye-pieces?

I think one inch is standard , 25.4 mm. OOPS TIL it's 0.965 inch, as Dennis pointed out below.

I've never seen "blacked out" eyepieces.

if anyone has a favorite source for buying eye pieces that will fit this telescope,

Are you handy with small hand tools?
Old film cameras are literally a buck or two in thrift shops. I take them apart for the lens which i can put in a PVC pipe fitting or old sewing thread spool and sand down to 1 inch..
Standard focal length is about 35 to 50 mm, wide angle is shorter. I have a zoom lens out of a fancy little Canon that should be fun but have yet to mount it"Focal" was an inexpensive department store brand. It'll do the job of getting you started.
Its objective lens(the big one) is 60mm diameter, its focal length is 700 mm, .
magnification is (focal length of objective) / (focal length of eyepiece)
so your 6 mm eyepiece gives 700/6 = 117 X which is completely unusable on a cheap tripod because you can't keep it still let alone aim it.. But power sells.
Your 20mm gives 700/20 = 35 X way more useable and great for moon and Jupiter, it'll show Saturn's rings.
A 35 from a thrown away camera will give 20X great for the moon.

Eclipse ?
I'd say use your telescope to project an image of the sun onto another surface, as in this article

http://www.skyandtelescope.com/astronomy-news/how-to-look-at-the-sun/

 

[Blank_Stare]

@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.

That article is interesting, but my eyepiece is at a 90 degree angle (perpendicular) to the barrel of the telescope. I suppose I could try to set up a screen off to one side, but I don't see me traveling 8 hours to Makanda, Ill, and then having the patience to set something like that up when I get there. I'll have to think about it - maybe I can come up with something small and simple, that will travel well. I still have 7 weeks to get creative.

Please explain how the PVC pipe, or sewing thread spool helps you grind down the lenses? It sounds like you may know a useful trick that I'd like to learn more about.

THANKS!

 

[jim hardy]

Please explain how the PVC pipe, or sewing thread spool helps you grind down the lenses? It sounds like you may know a useful trick that I'd like to learn more about.

No, no you use the lens as is.
the lens out of those "point & shoot" cameras (thrift shops are full of them)

is about 3/8 inch diameter . Cheap ones are plastic better ones glass.
I put it in something that i can sand to fit into the telescope eyepiece holder.

Sorry for the confusion.

old jim

 

[DarioC]

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

 

[jim hardy]

i have an ancient Celestron "Comet Catcher", not quite so nice a scope as yours i think.

Once in a while you have to align them

http://www.skyandtelescope.com/astronomy-resources/how-to-align-your-Newtonian-reflector-telescope/

old jim

 

[DennisN]

Hi, Blank_Stare, I'm a telescope beginner, but I have learned more about it recently...

There do not appear to be any model numbers on them, although there are some measurements listed on one end of each lens - 6mm, and 20mm. The diameter of the eye piece, where it fits into the angled telescope piece, appears to be about 25mm - but I am having a hard time measuring it with the tools on hand, so I might be off a few mm. (Is that a standard for sizing eye-pieces? If so, I am in trouble, because I don't see anything on Amazon that's even close...)

6mm, and 20mm

These seem to be the focal lengths of the eyepieces as jim hardy explained above, see also http://en.wikipedia.org/wiki/Eyepiece#Focal_length.

The diameter of the eye piece, where it fits into the angled telescope piece, appears to be about 25mm

There are different diameter standards, and yours seems to be 0.965 inches (24.5 mm), see http://en.wikipedia.org/wiki/Eyepiece#Barrel_diameter.

I recently bought a cheap entry level scope with the same eyepiece diameter as yours, and since I have planned to try to photograph the Sun, I have bought some accessories for this, I list some of them here as examples:

Adapter which enables use of 1.25 inch (31.7mm) eyepieces and filters for telescopes built for 0.965 inch (24.5mm) eyepieces:

• Metal 0.965" to 1.25" Telescope Eyepiece Adapter 24.5mm to 31.7mm Adapter

Solar filters that can be placed in front of the telescope (note: three diameters, check product description):

• Solar Filter

Various filters:

• 1.25 inch Filters
• 0.965 inch Filters

Camera mount:

• Datyson Universal Digital Camera/Cell Phone Mount

But please note:

1. Watching the Sun without proper eye protection is dangerous and can damage your eyes, as explained in http://www.skyandtelescope.com/astronomy-news/how-to-look-at-the-sun/.
2. I can't vouch for the filters I listed above, since I have not tried them yet
3. The item links from me above are from AliExpress which have delivery times of ca 30-60 days

but my eyepiece is at a 90 degree angle (perpendicular) to the barrel of the telescope

I guess you mean there is a star diagonal mounted between the telescope tube and the eyepiece, see http://en.wikipedia.org/wiki/Star_diagonal. Check your telescope if you can unmount that piece if you for some reason would like to, and mount an eyepiece directly to the telescope tube.

 

[jim hardy]

an introduction for guys like us just starting

https://starizona.com/acb/basics/equip_eyepieces_understanding.aspx

old jim

 

[DarioC]

Jim, I thought just recently that I might try a simple check on the adjustment. Just turn one of the three main mirror screws 1/4 turn and then check if a ground image is clearer. Then return that adjustment back and do the same to the next adjusting screw. Any improvement would tell me I should realign the main mirror. As for the second mirror up front, I have read the manual and will have to work on that a bit to devise something or get the correct tool.

 

[jim hardy]

I thought just recently that I might try a simple check on the adjustment. Just turn one of the three main mirror screws 1/4 turn and then check if a ground image is clearer.

Go in loosen direction first? So as to not squeeze mirror.?
I think you'll do best at night looking at a star. When mine is out instead of a point they look like a teardrop.

I'm still very much a novice at alignment. I find diagonal mirror way more difficult.
Hopefully an 'old hand' will chime in.

 

[Blank_Stare]

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]

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.

 

[Blank_Stare]

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]

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]

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]

@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]

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]

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]

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.

 

[Blank_Stare]

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]

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!

 

[Blank_Stare]

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]

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

 

[Blank_Stare]

@sophiecentaur
That post was chock full of good, useful information.


Thanks!

 

[Deepblu]

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

I don't 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.