Can you stack filters?

[Daz69]

Probably a stupid question, but I've just bought an LP filter from the classifieds, and was wondering if filters were stackable, or is this non beneficial? I.e. can you use an LP and a UHC together, and if so, is the order important? This LP will be my first filter, but will be getting a UHC at the end of the month hopefully. 

Many thanks

Daz

[Ricochet]

You can stack filters but you have to bear in mind what the filters do to the spectrum. For instance if you have a strong violet filter that only lets through the violet end of the spectrum there is no point pairing it with a strong red that only lets red light through as there is no overlap in the light that is passed to your eye. In the case of the light pollution and uhc filters I would say there is probably no point in stacking them. The uhc aggressively cuts out most of the spectrum that you don't want for the sort of targets you wil use it on and so all the LP filter can probably do is dim the part of the spectrum you do want. Given how dim a uhc filtered view is anyway further dimming is probably the last thing you want. 

[Charic]

You can, and its not a stupid question.
I don't use filters myself

[Charic]

When filter questions arise, I often refer to this guide. 

http://agenaastro.com/choosing-a-color-planetary-filter.html

I used filters many years ago to enhance my 35mm photography, but only have an un-used Moon filter in my case at present.
Re-reading this link, reminded me that I wanted to purchase a blue filter to enhance Jupiter to see if my old eyes could leech any more detail from the Planets surface. The only thing that prevents me from buying a filter now would be the colour cast, it would be so un-natural?  I want to see Jupiter as it is with more detail, not with a blue tint! which  could mean a bigger scope, but that's an old subject for me for now, unless luck and fortune or both turn up one day!

 

[Daz69]

Thanks peeps. The reason I ask this is because I see an internal as well as an external thread on the filter https://www.firstlightoptics.com/light-pollution-reduction/skywatcher-light-pollution-filter.html 

I live about 1 mile away due East from the Atomic Weapons Est at Aldermaston, and the glow is horrendous. No, not a green glow lol but loads of sodium glow. I will have a look at the link posted. Thank you.

Edit: Just had a quick look at the filter link, now bookmarked for future reference, thank you!

[Knighty2112]

Yes, most filters are stackable, although I've just bought an H-beta filter which isn't stackable, at least the Explore Scientific 2" version isn't anyway. 

[Charic]

Give the text a good read too, there are some examples with regards  to telescope sizing?

Below certain apertures it would appear that some filters may be of no use!  Why does  everything have to be so complicated with astronomy?

[Stu]

6 hours ago, Charic said:

Give the text a good read too, there are some examples with regards  to telescope sizing?

Below certain apertures it would appear that some filters may be of no use!  Why does  everything have to be so complicated with astronomy?

That may be a reference to a bit of a myth that OIII filters are no good below 8" aperture, something I've found not to be true. I use them with good success in smaller scopes, down to around 80mm in the past and provided you are well dark adapted they are very effective.

Aleays remember a filter can only ever make the image darker as it removed certain frequencies of light. What it does is increase the contrast between the light that you want to see and the sky background, or planetary background. So, good dark adaptation helps, as does a blanket over the head!

The only genuine use for stacking filters that I can think of is in imaging. Some filters leak IR light, which obviously doesn't matter for visual, but does if the camera is sensitive to it. An instance I read about was using both an IR cut and a green filter when imaging the sun. Without the IR filter the image was softer due to unfocused IT light, with it the image was noticeably sharper.

Alteratively, you might want to use a focal reducer with a filter, in which case you also need the thread on the filter to screw the reducer into. It's always handy to have the flexibilty.

[John]

I have tried stacking filters (UHC and O-III) but it was a bit pointless (for visual use) when you look at the band pass width of the two. I did it as an experiment but the results didn't encourage a repeat. One thing that I did notice was that the 2 layers of glass caused some additional reflections / light scatter in the view.

I agree with Stu that O-III filters are well worth using with smaller aperture scopes. People even use them with binoculars.

[Daz69]

Thanks guys for the advice, nice one.

[LukeSkywatcher]

"I agree with Stu that O-III filters are well worth using with smaller aperture scopes. People even use them with binoculars".

I also agree with this.

Why?

Because ive done it and it works. Most of the sales pitches you read online about OIII (and even UHC or coloured filters) tell you that such filters will work best with 8" aperture or above.

I suppose these companies who say they "work best with" are not breaking any trade description act.........because obviously the more aperture the more light gathered and the more detail the filters provide. It doesnt mean they CANT be used with scopes of smaller aperture.

Its a bit off-putting though and could discourage people with scopes less than 8" from purchasing such filters. I myself never owned an OIII or UHC filter until i bought an 8" scope. I felt discouraged in buying them because of what i read online about them working in scopes of less than 8".

 

 

[Dave In Vermont]

I never bought into the "8" Rule" for narrowband-filters, etc. Of course they'll dim the view - regardless of the aperture of the telescope. Whoever invented it may have surmised this to be true, but why exactly remains unknown.

And this myth has effectively robbed many people of the chance to try these and see for themselves.

Your mileage may vary,

Dave - Who always questions authority.

 

 

[LukeSkywatcher]

25 minutes ago, Dave In Vermont said:

I never bought into the "8" Rule" for narrowband-filters, etc. Of course they'll dim the view - regardless of the aperture of the telescope. Whoever invented it may have surmised this to be true, but why exactly remains unknown.

And this myth has effectively robbed many people of the chance to try these and see for themselves.

Your mileage may vary,

Dave - Who always questions authority.

 

 

I just cant find one of those singularity filters for love nor money. Everywhere is sold out all the time.

[ecuador]

On 1/22/2017 at 00:09, Charic said:

When filter questions arise, I often refer to this guide. 

http://agenaastro.com/choosing-a-color-planetary-filter.html

I used filters many years ago to enhance my 35mm photography, but only have an un-used Moon filter in my case at present.
Re-reading this link, reminded me that I wanted to purchase a blue filter to enhance Jupiter to see if my old eyes could leech any more detail from the Planets surface. The only thing that prevents me from buying a filter now would be the colour cast, it would be so un-natural?  I want to see Jupiter as it is with more detail, not with a blue tint! which  could mean a bigger scope, but that's an old subject for me for now, unless luck and fortune or both turn up one day!

 

I consider color wratten filters the least useful astronomical purchase. I have a full set from the 90's, since I was reading how it each could "enhance contrast" on this and that planet, and it was the only accessory I could afford. I soon found out that, if I for example I use #38A blue on Jupiter and remind myself that I paid for the thing, I can sort of see a slightly higher contrast great spot... only it is no longer "red" and in fact the whole planet is an ugly and distracting blue! No filters for me on planets...

As for the original question, sometimes combining filters makes sense, especially in imaging. For example, if you have an Ha filter, that is not the special "CCD" version, apart from the Ha line it will let IR come through, so if you have a mono camera without a UV/IR filter embedded, you have to add the filter. In your example though, it does not make much sense to combine a UHC (what kind of UHC? there are various kinds) with another LP filter.

[Dave In Vermont]

I, too, find the colour-filters are seldom used. But if you buy just one colour-filter, I'd suggest the #80A Blue-Filter. This as these can be used on the most objects out there. The other type I'd suggest - also using the "If you only buy one" rule, it would be the Baader Moon & Skyglow Neodymium-Filter. You find these often simply called 'The Neodymium-Filter.' And these are very good and widely employed filters on the market. They are not a colour-filter, though. They belong in a class of filters called Wideband-Filters.

Dave - The Filter-Nut