Universal contrast filter

[aad_Dira]

i need to buy an astronomical filter for a small telescope. while i searching on the internet, i have found this one:

http://www.teleskop-express.de/shop/...ter-1-25-.html

i think that it is good for me, because i am not interested on the sun, and i can`t observe the deep sky because i live in a city. so, it is apposite for all of objects that i may observe. but i need to ask here about it before buying it, how much it is apposite for a beginner? is it really good for solar system objects? and any other information...

[mental4astro (Alexander)]

Hi aad Dira,

I had a bit of a think overnight before replying. What I see with your question raises others with me-

what do you want to achieve with the filter?

You say you "need to buy a filter"- why?

How big is you scope to say you can't see DSOs from the big smoke?

Filters are tricky things. They can "help", but they don't solve all your problem. Remember, filters will reduce the amount of precious light that your telescope is gathering for you.

The advertisment doesn't convince me that it is nothing more than a glorified colour filter, around the one known as #80A Blue. Maybe with a little added violet. It really will only help you with some Lunar and planetary observations. It can't help you with deep sky objects as it is actually reducing the very spectrum at which nebulae glow at, other than a little blue- but our eyes are not very sensitive to this part of the spectrum, especially at low light levels, so it is of no real help. The ad does mention that this filter cannot take the place of a dedicated nebula filter, but it doesn't mention that you won't see more with it either.

You say that you can't see deep sky objects from where you are. If you describe where you are city wise and site wise, we might be able to give you some tips on how to improve your situation (other than knocking out the power grid, ).

If you are after a filter, have a look at this really good filter link. It will explain how they work, both nebula & colour filters:

http://www.lumicon.com/astronomy-accessories.php?cid=1

I have four five filters myself, two nebula (a general 'light pollution' one & an oxygen III), two colour (#80A & #8), and a polarising set (two polarising filters that you can then use to vary reduce the glare of the moon or planets). I don't use them very much. I mainly use the nebula filters at home, but they are no good for all other objects. And I don't look at the Moon much at all, and very little at the planets, so the other filters don't breathe the night air very much.

What I'm getting at is I mainly just use my own eyes to do the majority of my observing. I'll give you an example. On one occassion at a star party here in Sydney, with poor seeing conditions, we tried some galaxy hunting using my 17.5" scope. My 40 year old eyes could see a really faint smudge of a galaxy where a 17 year old couldn't. That was only due to experience- not filters. See what I mean?

Mental.

[Suzy]

Alexander you covered everything just beautifully. Thank you. When I saw that link on the Universal Filter, it got my attention too and I was curious about it.

[Steffen]

Originally Posted by mental4astro

I had a bit of a think overnight before replying.

Hey, that's not how Internet discussions work! You're supposed to shoot from the hip, filling in blanks with speculation and hyperbole. If everybody slept over their responses before posting we'd end up with a whole heap of well-reasoned and comprehensive posts like yours! Where would that lead…?


Cheers
Steffen.

[bmitchell82 (Brendan)]

dyam. then we wouldn't have arm chair experts.... sandess i say

[mental4astro (Alexander)]

OK, OK!! I've got the picture! Won't happen again, I promise, .

[bmitchell82 (Brendan)]

Your a legend Alex its good to have quality responses not just drivel that normally pops up! Long live the expert!

[sasup (Stacey)]

I agree lets make Alex our go to guy. Since he never gos fishing I guess he could set up a scope tech hot-line. LOL hope to see ya at lostock

[aad_Dira]

thank you very much for replying.

Originally Posted by mental4astro

what do you want to achieve with the filter?

You say you "need to buy a filter"- why?

i need the filter to clear the details of the planets and moon. i observed before some planets with a small telescope and they appeared just as a white/brown disks.

How big is you scope to say you can't see DSOs from the big smoke?

this may seems strange, but i don`t have a telescope yet. i was joining an astronomical competition, and i hoped to get a telescope in it. so i started to search for the telescope accessories (because i need to buy a telescope soon even if i will not get it in the competition). anyway, the most likely is that i will not buy a telescope more than 3 or 4 inches, so i don`t expect that i would observe DSOs with it and i live in the city.

Filters are tricky things. They can "help", but they don't solve all your problem. Remember, filters will reduce the amount of precious light that your telescope is gathering for you.

i know, but the planets and moon is a bright object, and lossing a bit of brightness would not make a big different. on the other hand, the brightness will not be useful if the details is unclear.

The advertisment doesn't convince me that it is nothing more than a glorified colour filter, around the one known as #80A Blue. Maybe with a little added violet. It really will only help you with some Lunar and planetary observations. It can't help you with deep sky objects as it is actually reducing the very spectrum at which nebulae glow at, other than a little blue- but our eyes are not very sensitive to this part of the spectrum, especially at low light levels, so it is of no real help. The ad does mention that this filter cannot take the place of a dedicated nebula filter, but it doesn't mention that you won't see more with it either.

how much it will be useful with the planets? i don`t know actually, it is not likely that i will observe a DSOs, at least not very much, and i think that a good filter for them will be much expensive.

You say that you can't see deep sky objects from where you are. If you describe where you are city wise and site wise, we might be able to give you some tips on how to improve your situation (other than knocking out the power grid, ).

"tips"? like what? i live in the middle of Jeddah city.

If you are after a filter, have a look at this really good filter link. It will explain how they work, both nebula & colour filters:

http://www.lumicon.com/astronomy-accessories.php?cid=1

thank you for the link. but i can`t buy any good filter, i can`t pay a big price, so i need to know how much is that filter useful than other cheap filters? if you know a better filter under 40$ i will buy it.

What I'm getting at is I mainly just use my own eyes to do the majority of my observing. I'll give you an example. On one occassion at a star party here in Sydney, with poor seeing conditions, we tried some galaxy hunting using my 17.5" scope. My 40 year old eyes could see a really faint smudge of a galaxy where a 17 year old couldn't. That was only due to experience- not filters. See what I mean?

it is not my problem if you have a sharp eyesight and i don`t .

[mental4astro (Alexander)]

Hi there,

Good number of questions! Nice and meaty to get my teeth into! Ok, here we go...

That the planets appeared as white/brown disks in a small scope to me says that the scope is either poor quality, or too much magnification was being used. Leaving the quality of the telescope aside, there are three things that govern the image quality:

1) quality of the eyepieces;

2) the maximum magnification that a telescope can provide- there is a rule of 50X per inch of apeture, for all telescopes, beyond which the resolving capability of the optics degrades. So if your scope is only 2", its max. practical power is 100X, if it is 10", then 500X is its practical max. limit.

3) the atmosphere- here it doesn't matter how big your scope is, the conditions of the atmosphere is the single biggest limiting factor, and it doesn't matter how big your telescope is. Normal conditions limit the magnification to between 100X & 150X. Rarely is more possible without the image quickly degrading, say like 300X. Anything more requires very careful observing site selection- ever thought why professional scopes sit on top of tall mountians? As an example, I've only been able to get a good image at 330X with my big 17.5" scope three times in the last year, not excellent, only good.

The other thing that governs the comfort of viewing the moon and planets is that they can be really bright, especially the moon. If you only get one filter, I would suggest a polarising filter set. These are two polarising filters that you then use to vary the amount of light getting through. When I do view the moon, this is what I use.

There is an astro retailer here in Sydney that sells these polarising filters for $19 each. Purchasing two will make this polarising filter set. Look in the heading of "Guan Sheng" towards the end of the page is the filter selection:

http://andrewscom.com.au/site-section-10.htm

Under the "General Accessories" is a selection of inexpensive colour filters. The link to the Lumicon filters is not intended as an advertisement for them, but to show you what the various filters are designed to do and what they will help show.

A scope of the size you are looking at, 3 or 4", is still good for DSO's in the city. I live in Sydney, so my sky too is very light polluted. I started with only a 2" scope, and learnt how to make the most of things with it. I often observe with my 5" scope from home, not just with the17.5" as the 5" is really quick to set up. Open clusters, globular clusters, and bright nebulae are still observable, even from Jeddah City, . There is even a number of galaxies too that are within the range of scope you are looking at, from a city observing site.

The main thing is to try to shield the site you are observing from, from strong direct lighting, like street lights and the neighbours flood lights. This alone will improve things imensely. This will reduce stray light affecting the optics and help to preserve you night vision as much as possible. A good stable mount is another to dampen quickly vibrations.

The other thing that helps is training your eyes to use what is called 'averted vision'. The most light sensitive part of our eyes is located around our central vision. By looking just to one side of the object in question, you will notice with a little practice, that fainter and more detail will be visible, and when you look directly back at the object, these details will 'disappear'! This method of viewing works in both the city and at a dark sight.

The only filters that will help with DSO's are those designed for nebulae. But because they are very selective in the spectrum they let through, they are not useful for anything else, like galaxies or clusters, as they glow across the entire range of the light spectrum. In the city, these filters do help a great deal with viewing nebulae. They can actually make a real difference in see them or not, and even identifying things like planetary nebulae from the background glow. And yes they can be expensive, but it is something then you can save money for.

You say that your eyesight might not be the best, that is not a problem. That is why I mentioned this example. My 40 year old eyes are not as good as a 17 year old's, but as I said, it is experience, .

There is one other thing I can suggest, that is using a pair of binoculars when you are using your scope. These will allow you to see stars that light pollution rubs out when you are trying to find your way around the sky with star charts. The best thing is that it should not be hard to get your hands on a cheap second hand pair. I use mine every time in Sydney, and from a dark site, they make for beautiful wide field telescopes. The 'classic' astronomical size is 7X50mm.

Is there an astronomy club near you? They might hold regular viewing gatherings where new comers would be welcome to look through the various instruments. This will help give you an idea of what different scope sizes offer, and what good quality accessories can do. You might even be able to find a scope that someone might be selling. The folks there will be able to help answer the many questions you will have too.

[DavidU (Dave)]

I would not trust a filter that does not show a bandpass & transmission report.Looks suss

[aad_Dira]

thank you really very much again!

Originally Posted by mental4astro

The other thing that governs the comfort of viewing the moon and planets is that they can be really bright, especially the moon. If you only get one filter, I would suggest a polarising filter set. These are two polarising filters that you then use to vary the amount of light getting through. When I do view the moon, this is what I use.

There is an astro retailer here in Sydney that sells these polarising filters for $19 each. Purchasing two will make this polarising filter set. Look in the heading of "Guan Sheng" towards the end of the page is the filter selection:

http://andrewscom.com.au/site-section-10.htm

Under the "General Accessories" is a selection of inexpensive colour filters. The link to the Lumicon filters is not intended as an advertisement for them, but to show you what the various filters are designed to do and what they will help show.

so, do you mean that the variable polraizing filters is the best for a beginner? and what is the good amount of light reducing for me? is 1 to 40% good? most of the filters i have found have this amount light reducing.

A scope of the size you are looking at, 3 or 4", is still good for DSO's in the city. I live in Sydney, so my sky too is very light polluted. I started with only a 2" scope, and learnt how to make the most of things with it. I often observe with my 5" scope from home, not just with the17.5" as the 5" is really quick to set up. Open clusters, globular clusters, and bright nebulae are still observable, even from Jeddah City, . There is even a number of galaxies too that are within the range of scope you are looking at, from a city observing site.

you are really "refreshing" me. but there is another point, that is you are observing in Sydney from a southern sky, but i am here observing from a northern one. i don`t know how much it is different, but here i think that the brightest nebula is Orion nebula, so, other than it and Andromeda and its staellites, i don`t think that there is a nebulae or galaxies less than 8+ mag in our sky, at least very few.

The main thing is to try to shield the site you are observing from, from strong direct lighting, like street lights and the neighbours flood lights. This alone will improve things imensely. This will reduce stray light affecting the optics and help to preserve you night vision as much as possible. A good stable mount is another to dampen quickly vibrations.

thank you for this information. i can note how much this is useful because usually when i look to the sky and the is a direct light next to me, i can`t see anything before i shield it by my hand (and when i do that i can see many stars). but i has not thought before about doing this with the telescope..

The only filters that will help with DSO's are those designed for nebulae. But because they are very selective in the spectrum they let through, they are not useful for anything else, like galaxies or clusters, as they glow across the entire range of the light spectrum. In the city, these filters do help a great deal with viewing nebulae. They can actually make a real difference in see them or not, and even identifying things like planetary nebulae from the background glow. And yes they can be expensive, but it is something then you can save money for.

but, the nebulae is a faint object, and the filter will reduces more of its valuable light, why it is still good for the city observations? and even your saying that "They can actually make a real difference in see them or not".

You say that your eyesight might not be the best, that is not a problem. That is why I mentioned this example. My 40 year old eyes are not as good as a 17 year old's, but as I said, it is experience, .

that was just a joke! .

There is one other thing I can suggest, that is using a pair of binoculars when you are using your scope. These will allow you to see stars that light pollution rubs out when you are trying to find your way around the sky with star charts. The best thing is that it should not be hard to get your hands on a cheap second hand pair. I use mine every time in Sydney, and from a dark site, they make for beautiful wide field telescopes. The 'classic' astronomical size is 7X50mm.

i already have a binocular, but it is not useful with nebulae, just for stars.

Is there an astronomy club near you? They might hold regular viewing gatherings where new comers would be welcome to look through the various instruments. This will help give you an idea of what different scope sizes offer, and what good quality accessories can do. You might even be able to find a scope that someone might be selling. The folks there will be able to help answer the many questions you will have too.

[/QUOTE]

there is just a near unactive astronomical society in my city, so this is not very possible.

[mental4astro (Alexander)]

Originally Posted by aad_Dira

so, do you mean that the variable polraizing filters is the best for a beginner? and what is the good amount of light reducing for me? is 1 to 40% good? most of the filters i have found have this amount light reducing.

With a polarising filter set, you vary the amount of light getting through according to what you need by rotating the filters against each other. If it is near full moon, then probably as much as you can. If Jupiter, maybe just a single filter is needed. Light reduction is roughly 50% with a single filter, and nearly 100% with both in the correct orientation.

Originally Posted by aad_Dira

you are really "refreshing" me. but there is another point, that is you are observing in Sydney from a southern sky, but i am here observing from a northern one. i don`t know how much it is different, but here i think that the brightest nebula is Orion nebula, so, other than it and Andromeda and its staellites, i don`t think that there is a nebulae or galaxies less than 8+ mag in our sky, at least very few.

You want to know what is observable, you can start with the entire Messier catalogue. You should be able to observe just about them all, even from a city site. M1 probably the only one not visible in small scopes as it has dimmed since it was first seen by Messier.

Originally Posted by aad_Dira

but, the nebulae is a faint object, and the filter will reduces more of its valuable light, why it is still good for the city observations? and even your saying that "They can actually make a real difference in see them or not".

Nebulas glow at very specific wavelengths of light. Have you noticed how in pictures they are only red, blue or both. These nebula filters absorb all wavelength of light and only transmit those at which nebulae glow at. In a light polluted sky, these filters aid in reducing the background sky glow, so showing nebulae as their light is still transmitted.

Originally Posted by aad_Dira

i already have a binocular, but it is not useful with nebulae, just for stars.

You think you can't see nebulae with them, use them to view the Scorpio/Sagittarius region of the sky.

If there is no active astronomical club or society, it might be an opportunity to start a group, even if only as a social get-together. I'm not a member of an astro club, other than here on IIS, but I organise a monthly get-together during the new Moon weekend to a location two hours drive from my home to a dark site. People have also come without a telescope, but with bucket loads of enthusiasm.

Mate, the joke was noted too, !

[En1gma (Robert)]

+1 To what alex has said,

seriously, there should be a sub forum "alex's corner"

Rob

[aad_Dira]

thank you, i have now "the complete picture" (a local term). i think the best for me is buying 2 filters; one for the lunar and planetary observations, and another for the nebulae.

the most things i care for in planets is Mars` maria & polar caps, and Jupiter`s belts & red spot. so, i started to search for the apposite type of filters for me in the very useful link that you has gave to me. intially, i have found two good types of filters; #15 deep yellow and #29 deep red. but here i have a new question, can the polarizing filter makes the same work of the color filter in clearing these details? anyway, i will not buy a filter for the planets before i see how they seems in my telescope after i buy it (which would happen soon ). and for nebula, i will see what is the apposite for me.

[mental4astro (Alexander)]

Sounds good to me getting your scope before the filters.

Good luck with the telescope purchase!

[aad_Dira]

sorry, i will trouble you again with my questions . i will buy UHC filter (it shows most of nebulae i would observe - planetary and emission) with the telescope for saving the transportation cost, do you think that this is generally a good filter? at least for a beginner?

http://www.teleskop-express.de/shop/...TS-Optics.html

[mental4astro (Alexander)]

I would say a good started nebula filter is a general "deep sky" or "light pollution" filter. Their transmission bands are a little wider, making them easier to use in urban areas. I don't think you'll gain too much with a narrow band filter like an UHC. These would normally be used in an already dark site where its use is very specific.

I have an O III and a Lumicon "deep sky" filter. I use the "deep sky" one almost exclusively from home. I actually see more with it.

More narrow band transmission filters home in on more specific wavelengths, like those for just emission nebula, or reflection, and planetary, but you then loose the ability to see the other nebulae these filters block.

[Terry B]

All of these filters are useless. All I need is a "cloud filter".
Any idea where I can purchase one?

[mental4astro (Alexander)]

Originally Posted by Terry B

All of these filters are useless. All I need is a "cloud filter".
Any idea where I can purchase one?

Mate, easy, Radio Astronomy!

Best of all, even the full Moon ain't a problem either! 24hr astronomy!!!!!!

With the way the CSIRO is being treated, I'm sure you'll be able to get the Australian Array Scope with the small change in your pocket.