Which density of filter should I buy?

[dobserver]

Hi,

I am looking to buy a Neutral Density Filter for my 12" Lightbridge for observing the moon and planets. I am unsure as to which density to buy - I have seen four different ones. The blurb said the bigger the scope the denser the filter, but which is right for my set up? I am using a 2" 26mm QX wide angle eyepiece if that makes any difference?

Cheers,

Steph:confused:

[Doc]

I don't personally use one but I have tried the Baader ND filter. It was a 2" one and I think it was the strongest one they do. IIRC number 3.

It did what it said it would do, cut down the glare of the moon, but to be honest I don't find it that bright once you get used to it.

But then it does wreck your dark adaption so if I'm observing the moon I normally don't do deep space in the same night.

[dobserver]

Thanks for the input Doc.

Two more things then....

I am thinking of making a light shroud out of 2 mm Neoprene, attaching self-adhesive velcro up the vertical seam and then using bungees to fix it top and bottom. Does this sound like a good plan? At £18 for a sheet big enough it sure would be cheaper than buying a ready made one, but do you think it would work?

And Carl has come up with a cunning plan for making a degree scale on the tube pivot point until we can get a Wixey. We thought if we print off and laminate a scale of 0 to 90 degrees and stick this on the base unit under the pivot. Then put a mark on the metal pivot at 90 degrees we would have a rudimentary idea of where we were looking.

Do we get a Blue Peter badge?

Steph

[Doc]

You are not the first to have that altitude idea, just look through cloudynights and The Yahoo group, there's loads of these so to answer your question Yes it's a great idea but the wixey will be more accurate but give it a go.

Shrouds can be expensive around the £50 mark so your idea sounds great. Once again give it ago, you have nout to loose except £18.

The good thing about dobs is that they are so customisable.

[ashenlight]

gah, this is making me want a dob more!!

good luck with the plans, Steph

[dobserver]

Cheers - our brains are ticking on overtime here. lol

And what I love is that we can go out and buy a plant pot stand for a dust cover (as Doc suggested in another thread) for a couple of quid.

So it may have been expensive in the first place (I had always wanted an eternity ring, but I'm way happy with me dob!) but we can hopefully personalize it for not too much money.

It may not be too pretty when we've done, but it won't be anything irreversable! lol

[brianb]

I am unsure as to which density to buy - I have seen four different ones.

Simple answer - you may need more than one.

ND 0.6 (x4) is good for reducing glare on Jupiter & Mars but is inadequate for the Moon.

Some people recommend crossed polarizers for the Moon, at least this way you can adjust the transmission to suit yourself. But the Moon is essentially colourless, I make use of this by using a deep red filter (Wratten 29) rather than a neutral density; it takes the pain out of the brightness, preserves dark adaptation better than a denser ND or polarizing type and gives a steadier image - there is almost always less boiling in long wavelengths.

[dobserver]

OK so I did some shopping today - well it is a traditional passtime for a BH Monday in this day and age.....

I ordered the neoprene sheeting and some repair tape for if we need to make any holes in it. We are maybe going to cut slits where the knobs for the struts sit, to fix it top and bottom....we'll see if it works. Failing that a bungee cord will do it I'm sure....just need to get some sticky velcro and that is not expensive.

£28.00 + velcro instead of £50 or £60 for a ready made one.

Next I ordered a 1.8 Neutral Density Filter. I'm hoping this will be enough for the moon without making it too dark....fingers crossed! That was quite expensive enough, thank you!

Carl is trying to encourage me to buy another eyepiece, but he has set me some homework to do. I have to make a chart of the focal length and work out the magnification with and without the Barlow apparently! I will do it this evening as it doesn't look like we'll be doing much observing tonight! Grrr....I'm salivating here! I want to use it more before making any further purchases. I didn't realize when he bought me the wonderful thing that it would end up costing me money already!

Also we have made and applied the altitude gauge - need to calibrate and test it now. Just the azimuth gauge to to suss out...

Steph

[Doc]

Carl is trying to encourage me to buy another eyepiece, but he has set me some homework to do. I have to make a chart of the focal length and work out the magnification with and without the Barlow apparently!

This made me chuckle I have visions of Carl in his headmasters uniform and you in your school girls.

What fun it must be living in your house

[dobserver]

It has its moments, Mick

[dark knight]

Well for once it's not me putting my hand in my pocket,,,,,,,,,,,,,,,,,,,,,hmmmmmmmm but then again a good eye piece would be beneficial,,then there's that ccd from Imaging Source,,then there's,,,,no,,no,,no stop it,,ahhhhhhhh

[dobserver]

Yes, stop it this instant!!!! lol

[Doc]

This is the problem Carl, when does it finish.

I'm now in the process of adding dew prevention, going to try to do alot of it myself to save some money.

But after that it's better eyepieces, followed by a Mpcc, followed by some more filters, then a finder, then better collimation aids.

It never stops.

[dark knight]

but it's my turn to be headmaster.....

[dark knight]

Mick, have a word with Paul - I'm sure he could help you with dew prevention. He's top when it comes to electronics....or you could do what you did at Salisbury and just drink another bottle of wine lol.....

[Doc]

Mick, have a word with Paul - I'm sure he could help you with dew prevention. He's top when it comes to electronics....or you could do what you did at Salisbury and just drink another bottle of wine lol.....

As long as it's red wine so it doesn't affect my night vision

[PeterW]

As long as you turn the magnification up on the moon you can get away with no filters on a 16", pretty darn bright though, like staring into a car headlight, but you get pretty good contrast!

PEterW

[Doc]

As long as you turn the magnification up on the moon you can get away with no filters on a 16", pretty darn bright though, like staring into a car headlight, but you get pretty good contrast!

PEterW

I agree.

Never use moon filters. It's bright but still viewable.

[brianb]

Never use moon filters. It's bright but still viewable.

If you don't mind not being able to see anything else for a couple of hours afterwards....

[Doc]

But then when the moons up you don't observe dso's.

[FLO]

It is certainly possible to view the Moon without a Moon filter but I wouldn't want to do it. I wouldn't go to a beach without sunglasses either

[dobserver]

Me too, which is why I've ordered one!