Filters

I have a WO Megrez 110mm ED telescope. My primary planned uses - after I get a alt-az mount and tripod which I am advertising for in AM - are visual and planetary/lunar with some casual DSO viewing.

What kind of filters would work best for a 110mm refractor given my intended uses? I am thinking first a moon or neutral density filter. I have seen them advertised at 13%, 18% and 25% in terms of light they let through. What are the pros and cons of more or less light let in (in terms of a 110mm refractor)?

I am thinking I would like a filter that blocks out some light pollution - like the Baader Moon & Skyglow filter.

I have a Baader fringe killer but I am not sure it will be of much use.

Any thought or suggestions? I will probably pick up a modest set of planetary filters down the road but I do not want to spend a lot for a special Mars or Venus filter. Thanks.

I'm no filter expert, but I'll make a couple of suggestions.

In general, you should note that filters, while cutting down on the admitted light, will not lessen resolution, but usually enhance it by increasing contrast. However, it's easy in a small scope to filter out more light than you want to, resulting in a dim image, particularly at high power.

Your scope will show some color on the moon and planets, so your fringe killer filter, by suppressing the unfocused violet on the moon, might well boost your resolution on that target. I personally don't see the need for a moon filter per se at that aperture (probably others will disagree)--my reasoning is that one generally likes to take the power up as far as possible on the moon, and in a 4.3" refractor, the resulting small exit pupil will be plenty dim without further filtering it.

For Mars, you might consider a #21 Orange filter--very inexpensive. It lets in plenty of light (the red and light red filters might be too dark at that aperture) but will really enhance albedo features. For Saturn you might also try a #82A light blue, if anything. The light blue is also good on Martian clouds/ice.

I'll let someone else speak to the light pollution issue.

For more on filters check this link--there's also some good articles at CN.
http://sciastro.net/portia/advice/filters.htm

--George

I like neutral density filters for looking at the moon at low power. The one I use most is the 2" Orion Variable Polarizing filter. The 2" model can be put on your diagonal so you don't need to replace it on different eyepieces as you change them and the variable feature lets you adjust the amount of light for your comfort level. I usually remove it at higher magnifications over 100x or so.

If you see an objectionable amount violet fringing at high magnification on the moon and other bright objects you can try the 2" WO VR-1. It introduces less yellow tint than others I have used.

Your best bet is to borrow a friend's before you buy. If you do have to go the trial and error route good deals can be had used here on Amart.

Skip lunar filters.

Modest sets of planetary filters are common in most folks ep cases, but seldom used.

If going for planetary filters, then keep to the lighter colored ones recommended for the specific planet to be observed.

UHC is generally considered to be the best all around DSO filter for modest aperture: as in works well on the most number of objects.

I've no experience with the either Baader. Looking foward to that oppurtunity some day.

Jackie,
get a Violet filter 47 , for Venus. You want be sorry, and they are rather cheap. Looks cool for the Moon also. This is from personal exspirence using a C-102HD Celestron Refractor. I see the cloud structures on venus.
Happy Hunting ,

Bill

George, Michael, John & Bill,

Thanks for taking the time to provide advice. I appreciate it.

Jackie