Lunar observing with a newt - filter needed?

[Altair40]

Not sure if this is a daft question but I'll ask anyway!

I've only looked at the moon once in the week I've had this SkyWatcher 130 newt due to cloud. I was on 20x and wow that was bright. I only looked for a couple of seconds and don't think I've done any damage but was wondering if people use a filter of some sort?

I didn't know at that point that I could take the small cap out of the cover and view like that with a bit less light coming in...

At 20x the moon filled the eye peice, pretty much and I was impressed that I could see shadows on the craters. Not bad at all

[Doc]

I like and use the Neodydium filter, it works really well.

[part timer]

Don't worry,

no matter how bright it is, moonlight won't damage your eyes.

Most people end up using higher magnifications on the moon which makes the image darker anyway.

If your really do want a filter then there are lots of special ones (called Neutral density filters) or you can use a variable polariser which can be set to dim the moon to whatever you feel comfortable with.

TBH, personally I wouldn't bother as you will almost certainly use higher powers or just get used to the brihgtness. If you do buy a filter then do not get any cheap green coloured 'moon filters, the're cheap for a reason!

[oldfruit]

I think most people use a lunar filter as the moon is so bright it is uncomfortable to look at for any length of time.

[Altair40]

Thanks a lot, Doc. I notice FLO sells them - bought the scope from them (plug, plug, plug).

That and a better 20x eye peice might be next. I'd sort of disregarded the moon as - oh, it's the moon. Itching to have another look now!

I'm aware I can't use this instrument to project the sun.

[johninderby]

The Baader Neodymium Moon & Skyglow filter is great on the moon. Gives the moon a nice neutral grey colour and does improve contrast on the surface as well. I don't bother with a neutral density filter as if I'm using a higher magnification that reduces the brightness anyway.

John

[Altair40]

Thanks for the other replys, oldfruit and part timer. Interesting

I did myself find my 20x lunar image very bright indeed - certainly detroyed my night vision. But I had the endcap totally off.

I may get a Neodymium filter anyway - to help with light pollution if nothing else. Filters are new to me so I need to do some reading.

Thanks all

[Doc]

Easiest thing to do is observe the moon when it's out and when it's not observe dso's, that way your night vision is intact.

[Bigwings]

Ive got some in the for Sale section Bits & Pieces.

Make me an offer..

[Astrokev]

Hi Altair40

Agree with everything others have said.

For lunar observing, don't use the cover with the small cap removed. This will reduce brightness for sure, but will also reduce the resolution of the image a tad.

You also mention observing the sun. This can be done safely by using a special solar filter over the end of the scope tube, or over the smaller aperture in the scope end cap (I would recommend Baader solar film which comes with full instructions for use - a lot of astro suppliers would stock this).

However - NEVER use any filter at the eyepiece end of the OTA only, without proper filtration at the main aperture end. The heat collected by an unfiltered main mirror will permanently damage your eyes, let alone the scope.

[Altair40]

Thanks for that, Astrokev.

Thanks because I didn't know it was possible to use this scope to observe the sun given the correct filters. Filters plural!

I've only ever projected through a 60mm refractor onto card and could actually see sunspots. This was in about 1985- 1990. Ish.

That last partial eclipse we had, I was at work and made a pin hole camera to project with. Tiny, but I could see what was happening.

Having observed the moon briefly through this small reflector, I can imagine the sheer energy involved if it were pointed toward the sun.

!

I'll need to read a lot more, then check again here to make sure I have the correct set up.

Thanks

[Altair40]

I've only been lurking on this forum for a week. Registered a day or so ago and wow, I've learned so much in a very short space of time and opportunites for observational targets have been pointed out that I had rejected out of hand.

Thanks

[Altair40]

One last post for tonight:

Bigwings, I don't think I can access the 'for sale' section here until I have 50 posts. I'm trying!

If you have no others interested, please pm me the item details in the sale section (if that's allowed by the moderators or I'll try to ask some semi intelligent questions around the forum for my 50 posts - don't want to uselessly take up bandwidth) and I'll ask the lady wife if it's ok...

Something tells me I'm going to be the taxi service and floor mopper around here for a while

But that's ok

[yeti monster]

Worry not about the bandwidth, join in as many threads as you can and gibber away like a true tinternet forumeer.........

[Moonshane]

hi there

I don't observe the sun (I'm scared!) but do observe the moon unfiltered with my 12" and 6" dobs. the initial shock wears off quickly and as your pupil contracts to a pinprick you get more comfortable. as others have said, the higher magnifications you will eventually use on the moon dim it a little without the need for filters. I firmly believe that you see more detail with a smaller pupil than a larger pupil. my theory is based on my knowledge of photography and also holidays. in photography a larger f number (smaller diaphragm hole) means more depth of field and vice versa. also on holiday in bright sun, I don't need my glasses as my pupil is smaller and I get more depth of field. I believe this also works on the moon and using a darkening filter reduces depth of field and also potentially counteracts the expensive eyepieces you use! just a theory but it seems to make sense to me.

[Astrokev]

That's logical.

[Altair40]

Hmm - that's all very useful. Thankyou.

I think I will be in the market for filters though. If I trust the materials, engineering and physics aspects; maybe Solar filters at some point.

I'll try the scope as it is, maybe going to my other 'supplied with scope' (!) 10mm ep for lunar obs and see how it goes.

The moon is waining now which brings darker targets into mind. But next month...

I drove my wife to an OU tutorial today and while I waited the staff suggested I might like to sit in the library with most of the course books for anything.

Guess which section I was rummaging through?! There was an awful lot about the sun that I didn't know. Spent two hours reading and coud have spent all day, easily :-)

The other thing is I can now measure, very roughly, angles between stars using just my arm, a tape measure and a placcy ruler. Sort of Arc tan etc - but I know where to look...

You are looking through the photosphere when observing the sun? Didn't realise that one!

[Altair40]

I've not forgotten Doc's and BigWings's suggestions for a Neodynium filter. I'll go for one of those as soon as I can...

What is all of this about filters (apart from the obvious Solar ones)? I understand they can be of some use in deep sky or removing false colour, but???

It's ok, I'll read!

After reading: Try it and see is my motto.

Or is that try and see if you can see arond here? Argh!

[Moonshane]

you don't need to worry about false colour with a newt as there is none. chromatic aberration is present in almost all refractors and better controlled in some than others. generally the cheaper and shorter you go the worse it gets on bright targets.

you can get lots of filters but don't go mad. filters do what they say on the tin, they filter out some of the 'white light' and reduce the light bands meeting your eye and therefore increase contrast. in other words they don't add anything they remove things which detract from the view.

colour filters - some like some don't; I don't. said to bring out certain features of eg planets, different colours useful for different things.

skyglow/light pollution filters - useful if you have light pollution or the moon in the sky, the increase contrast and darken the sky to make targets stand out more. the baader one is this one and some people use on the moon and jupiter.

UHC - probably the best all round filter for revealing more contrast on DSOs such as nebulae and planetary nebulae etc. some targets are almost impossible with this and or the Oiii, others just improved with them.

Oiii - lets less bands through than the UHC and better for some targets than the UHC but worse on others.

these are the main ones. you can also get comet filters and although there is one that proposes to increase the contrast and features of galaxies, the general consensus is that you only achieve better galaxy images with more aperture and darker skies.

hope this helps.