filters

[veejo]

A newbie, but learning quickly.

When looking at the moon, it's too bright, so I need sunglasses, or a filter.
And I may need filters for other things.

Any advice on good quality entry level (brand) , eg multicoated, and not too much aluminium and and more glass ???

I'II need a neutral for the moon ..... but I pressume the better way to start is with a set , short term spend for long term savings ?

do I also need a polarizing filter ?

Don't have many eye pieces yet, just the one that came with the scope (celestron 25mm plossl) and a saxon 21mm 68 Super wide angle.

[astro744]

Have a look at http://www.lumicon.com/telescope-acc...ensity+Filters for some information.

Also http://www.bintel.com.au/Filters.html which are available locally.

The ND96 (13%) transmission filter is all you will need in either 1.25" or 2" depending on which eyepiece you will use it with most. The 25% filter is fine for crescent phases of the Moon.

My experience with polarizing filters is that that they have a detrimental effect on resolution (small craters simply vanish!).

Colour filters are for highlighting planetary details of various colours. eg. a red feature will appear darker with a blue filter.

[Liz]

Hi Veejo ..... Many scope sets come with a Moon filter, but if not, they are pretty cheap to buy, at astronomy shop or even eBay.

http://www.ozscopes.com.au/moon-filter-saxon.html

http://www.aoe.com.au/filters.html

https://www.bintelshop.com.au/welcome.htm

http://stores.ebay.com.au/Telescope-Warehouse

[veejo]

thanks for the advice,

Have gone for a set of Meade filters (5 inc a grey) and a Meade moon filter (grey and green).

One of the reposnes listed a supplier who did a deal too good to pass ona set.


Should keep me busy for a while ..... now to get some LVW eye pieces :-)

or Baader so I can use them with my camera ????

[NorthernLight (Max)]

Hi Veejo,

try a deep redfilter on the moon. I found the celestron no.25 the most useful. it changes coulor as opposed to the neutral moon filter but red wavelengths are less affected by atmospheric distortion and the filter blocks more light - good for observing a bright moon under clear skies.

photography through an eyepiece? depends on your camera. If you got an slr you´ll need an adoptor that allows for an eyepiece to be placed inside. with a compact - just hold it at the eypiece (<-- should have a longer eye relief). you can even do great shots of the moon with a mobile phone camera.

[veejo]

Max,
yes have an SLR (pentax 10Mpixel), so I can focus once it's on the scope. Just need to get the adapter.

the red in the meade set (waiting to arrive) will give it a go, though doesn't look very red in their catalogue. Yes, it will be used for bright moons, I have a 3 1/2 year old son, so the moon is an easy one to keep him interested (phases, craters, etc), thats' how the money pit got started :-)

[NorthernLight (Max)]

Hi Veejo,

before you go for the eyepiece adaptor consider a barlow lens. The thing with this adaptor is that you need a lot of back focus and also the image quality get´s down, depending on the eyepiece of course, but in general the standard eypieces aren´t free of field curvature and all other sorts of distortions.
What sort of scope are you actaully using? If it is a newton with a standard rack and pinion focuser 1/4" be carefull, the eyepiece projection adaptor+T ring+SLR puts a heavy weight on the side of the tube - balancing the tube can be hard.
A barlow doesn´t make it much better but the imagequality improves as the minus element in the barlow corrects some field curvature of the prime mirror and does not introduce chromatic abberation (purple fringes around contrast rich edges). A good choice would be the televue powermate series as they allow to unscrew the eyepiece holder and attach an adaptor that connetcs straight to the t-ring. Imagewise they are pretty much top of the class.
If you are just after some decent crater images on the moon - don´t use the slr. go for a modded webcam instead. the atmosphere is always turbulent and blurs yours images but the webcam takes around 30 images per second and a few of a 100 shots are always crystal clear. stack them afterwards and make a mosaic out of a few different locations on the moon. The last issue of Australian Sky and Telescope presented a new freeware tool to do that and the results look pretty much like taken from orbit. The tool is here available: http://www.avistack.de/
The other advantages of the webcam are: bigger craters in the first place due to a smaller sensor (acts a little like zoom but is a total different concept); weight is usually not an issue; and you see what you do as the movie you take shows on your notebook screen. Downside is: you need a notebook at the scope. You can modify a webcam of your choice (there are few articles in this forum on how to) but I wouldn´t do it again. The reason is I did it with a Microsoft VX3000 that I had 2 of anyways by removing the optics painting over anoying led´s and making an eyepiece like adaptor to fit in the focuser from a black film container (where photo film is packed in). Later I asked a colleague to make me a proper adaptor with a thread to use filters from scap aluminium. it works but these days you can pick up a ready made device with a better sensor and variable exposure time (like Celestron NexImgage - which is a Phillips ToUcam modded) for under 200AUD. This can later be used for guiding if you want to go for deepspace photography - where the slr excells.
Let me know how you go.
Clear skies!