Basic Filter set advice

[NorfolkGazer]

What would people say would be a good 'basic' set of filters for starting out. (apologies if this has been asked before, I did try searching)

I'm probably going to be trying a little bit of everything, Lunar, Planetary and Nebula so was thinking a ND0.6 for lunar and either a UHC or OIII for nebula stuff. Are there any other 'essentials' that you would recommend?

[johninderby]

The Baader Neodymium filter is my most used filter for lunar / planetary and general all round observing. Rather than an ND filter get a variable polarising filter which can be. used on the moon if you find it too bright although many find no need for one. Very much depends on your sensitivity to light. The variable polarising filter is also usefull on Venus.

A UHC or OIII are indeed usefull for nebulas etc. 

[NorfolkGazer]

I've just had a look at the Baader on FLO following your recommendation and it certainly gets some very good write up's. Cheers for that, I've added it to the list.

 

[Zermelo]

I presume you mention an ND 0.6 because that fits with your scope's aperture?  As @johninderby says, the variable polarizing filter is more flexible. If you get a second scope, 0.6 may not be optimal, and yes, they can also be useful on bright planets.

For emission nebulae, either a UHC or OIII, opinion seems to be evenly split on which to get first, if you buy them separately. There is also H-beta, but that only comes into its own for a few targets. There is this guide that aims to rate each type against a range of nebulae. With nebula filters (perhaps more so than with lunar filters) consensus seems to be that you get noticeably better performance for increased outlay. I bought the Astronomic UHC, which is often recommended but cost more than any of my eyepieces. Telescope aperture and eye performance can also be factors here. These filters work by cutting out a lot of the incident light, preferentially passing bands that are emitted by nebulae, and so improving contrast - but with overall reduced brightness; on a small scope the images of some targets may be just too dim (especially for OIII and H-beta).

Were you considering light pollution filters in this question? The older types that cut out specific sodium and mercury emission lines are much less useful now that LED lighting is so prevalent. The IDAS filters do aim to reduce LED pollution, but are expensive (by my standards, anyway).

And then there are the coloured filters, mostly for improving detail on solar system objects, again by enhancing contrast. FLO have a help page with a nice summary table matching colours to targets. There is a wide range of prices. You could possibly start with just one or two, if you are into planets; advice is usually to avoid the cheaper sets of coloured filters that are widely sold. And there is also the neodymium variety mentioned above.

Other info:

https://britastro.org/node/17423

https://www.prairieastronomyclub.org/useful-filters-for-viewing-deep-sky-objects/

[jonathan]

Zermelo summed things up pretty nicely.  OIII for typical nebulae is a pretty good bet, but keep in mind that OIII is Oxygen (blue/green), which won't help for red / infra red (Hydrogen?) nebulae; something to keep in mind is that our human eyes cannot perceive things like IR or UV, the typical grey misty nebula cloud we see visually is usually the green part of the spectrum as that's what our eyes have adapted to see in the dark. 

I have been told that an orange / red filter is good for increasing contrast on Mars, and perhaps green can help with Jupiter, though I have yet to try this myself.  I have a Neodynium filter but have yet to try it on planets.

I would recommend buying one filter at a time, buy good quality and spend a bit of money on each one, plus a lunar filter (ND) if you feel it's necessary for your eyes and scope (they're relatively cheap).  Remember that usually you can 'stop-down' the aperture if your scope objective cap includes a smaller cap that you can remove (or make your own out of cardboard), useful for bright objects such as moon and planets.  I use an ND filter typically when the moon is more than 1/3 lit as I find it too dazzling, also used one on Venus to see the phase which was obscured by the dazzle otherwise.

One tip I heard the other day is to just place the filter between the eyepiece and your eye, it should work just the same for a quick preview and enable you to quickly see the difference it makes.  I have yet to try this but will be just as soon as I can get outside under clear skies (might be tonight, fingers crossed!)  Credit goes to Jurgen Schmoll for that one (it's where I heard it from anyway), he gives a great talk on filters so if you get a chance to join one (currently on Zoom or whatever) it's well worth it.

Another tip I would bring is to wear sunglasses if using binoculars on bright objects such as Moon or Venus, works a treat, but NEVER AT THE SUN.  Just needed to emphasise that last part.

Edited February 22, 2021 by jonathan

[Zermelo]

21 minutes ago, jonathan said:

place the filter between the eyepiece and your eye

good point, especially for deciding which of the 'stars' in your low-power field is actually a planetary nebula incognito. Just be careful if you're attempting it with numb fingers.

[Tiny Clanger]

I endorse the 'try the filter on top ' method, if your eyepiece has a fold up cup,  just place the filter in it for a quick look before faffing around screwing it on the bottom of the EP.

Also the twin polarizing filters which give a range of ND possibilities rather than a single ND . These are easier to use in a 'scope with a diagonal, where you can separate the two parts,  screw one into the diagonal, the other in the EP in the usual way, and just turn the EP to adjust the light transmission. Less good in a Newtonian where both go on the EP, so you need to remove the EP to rotate the filter. I really have not found I need to filter the Moon for comfortable viewing in my 127mm aperture mak, but definitely need it in my 150 dob.

When the Mars/Jupiter/Saturn feast was there to view a few months ago, I decided to see for myself what use coloured filters might be on planets, opinions are divided , 'scopes of different apertures will behave differently, so I wanted the evidence of my own eyes. 

The only way that was possible in lockdown was to buy some, and the prices of 'good' sets being a bit high for an experiment which might prove the things were useless for me. So I bought one of the sets of cheap ones , about half a dozen, under £20 all the way from China . I'm well aware that cheap filters are a bad buy for (non astro) photography, but reckoned they would be acceptable for simple visual use on planets whose image is already distorted by the Earth's atmosphere !

The outcome was I found the green filter showed me the South Polar Cap on Mars (despite it being shrunk in size at the time from the usual diameter) , the orange let me see various markings more clearly , to the point where one night I came in after two hours on Mars ( 🙂 ) slightly puzzled, as what I'd seen did not quite conform to what the Mars map suggested was showing at the time, only to log in here and find more experienced observers with bigger 'scopes reporting ... a dust storm ! The unmapped division I'd seen (with an orange filter and a basic 17mm skywatcher plossl in a £200 'scope) was a dust storm . On Mars.

I don't recall offhand what the entire range of colours was, but some were too dark to be of use in my 150 dob,  and the one labelled 'MOON/LIGHT POLLUTION transmitted too much moonlight , but on the other hand, darkened my light polluted sky too much ! All these investigations were made with my 150 heritage dob, I have not had the chance of long periods of good seeing and planets high enough in the sky to give them a proper outing in my 127 mak yet.

So, to my mind, I certainly got my money's worth , £20 for a Martian dust storm ! Since then I have kept my eyes open for some second hand , better quality filters , a trio of which I snapped up last week, because I am confident that they will be of use to me when those planets swim back into view.

Nebular filters? I've read plenty, but will wait until one day (ah, one day  .... ) I may be able to look through someone else's expensive purchase and see if it would be worthwhile for me .

Heather

[NorfolkGazer]

I can hear my credit card groaning already 😆 

Thank you so much to you all for your kind replies. I've only been on this site a couple of weeks and I'm constantly amazed by the time everyone takes to reply, and often in great detail so again, thank you. Apologies for the delay in replying, its been a busy few days at work.
Taking on board what you have all said, I'm dropping the ND0.6 idea and definitely going to opt for the polarizing filter instead, especially the twin filter option as you said Heather, as my current set-up uses a diagonal, and I like the sound of rotating the EP to adjust, so thank you for that.

Once. have that, I'll start building up others, starting with the nebula options, then coloured filters from there. I'm firmly in the school of 'buy cheap buy twice', so they will be a quality purchase. 

I'm off to read all the links you posted, thank you again for all the advice.

 

[SiriusB]

Some light bedtime reading for you.😄

[Louis D]

On 22/02/2021 at 07:23, Tiny Clanger said:

Less good in a Newtonian where both go on the EP, so you need to remove the EP to rotate the filter.

Not if you get a 2" and a 1.25" linear polarizing filter.  Screw the 2" into the front of the 2" to 1.25" adapter, insert the adapter into the focuser, screw the 1.25" into the bottom of the 1.25" eyepiece, insert the 1.25" eyepiece into the 2" to 1.25" adapter, and there you go!  Just rotate the eyepiece to vary the dimming.  It works great for me for solar observing in particular (with a full aperture solar filter, of course).

[Tiny Clanger]

30 minutes ago, Louis D said:

Not if you get a 2" and a 1.25" linear polarizing filter.  Screw the 2" into the front of the 2" to 1.25" adapter, insert the adapter into the focuser, screw the 1.25" into the bottom of the 1.25" eyepiece, insert the 1.25" eyepiece into the 2" to 1.25" adapter, and there you go!  Just rotate the eyepiece to vary the dimming.  It works great for me for solar observing in particular (with a full aperture solar filter, of course).

Not if your newtonian does not have a 2" tube.

My newtonian does not have a 2" tube.

[Louis D]

1 minute ago, Tiny Clanger said:

Not if your newtonian does not have a 2" tube.

My newtonian does not have a 2" tube.

Then you can try using a short 1.25" extension tube inserted into the focuser with one 1.25" polarizer screwed into the bottom of it and the 1.25" eyepiece with the other filter inserted into it.  Of course, this assumes you have enough in-focus to accommodate the extension tube's additional optical path length.

[Tiny Clanger]

I don't.

I would need to collapse the heritage dob extending section each time I went from polarizer filter use to none. So I'll take the EP out, rotate the filter, and replace it.