Which size of filter to go for: 1.25 or 2 inch?

[skir]

After some breath taking views of the moon last night I also managed to half blind myself looking at it!

So I think I need to buy a moon filter of some sort. But as I have a 2 inch focuser what would be best? 1.25 or 2 inch? There is obviously quite a difference in price so what is the advantage of having the 2 inch?

I've also a couple of ideas for a moon filter.

There is a skywatcher variable polarising filter but also I could just get a uhc instead? Which might also cover me for nebulas as well? If I have that right?

[NGC 1502]

If you have a 2" focuser, then I think it's a good idea to get 2" filters.

But first check that if using a diagonal (refractor, sct, mak) that the nosepiece has a filter thread, and if it's a Newt, that the 2" to 1.25" adaptor also has a filter thread.

This means that you can fit the filter to the 2" diagonal or adaptor, and change eyepieces without the fiddle of swapping the filter each time.

One other point to check however, if using the filter attached to a 2" to 1.25" adaptor, is will the EP nosepiece hit the filter ? Some EPs have a long nosepiece that could contact the filter.

Of course 1.25" filters are cheaper, if you are ok with swapping them around.

Regards, Ed.

[rwilkey]

Hi Skir, I have a preference for using 2" filters as they can be used with 1.25" eyepieces as well, as Ed says above, as long as the nosepiece of the 1.25" ep does not come into contact with the filter. I often use the 14mm Baader FTR to offset this problem. I also more often use a twist-lock centering adaptor (Orion) when I am using 2" filters, it works very well.

[skir]

Well for eps currently I have 2 televue plossls and a radian, so unsure if they would have problems contacting the filter?

So the main advantage of the 2 inch is not having to swap it over every time you change eps, yes?

Also would a uhc do the same job as a polarising filter or should I be getting one of each?

[skir]

I have this extension http://www.rothervalleyoptics.co.uk/revelation-self-center-35mm-extension-tube-2-quot_d5577.html having looked at it in the lower half it is threaded, so would this enable it to screw a filter into it?

[Moonshane]

generally I'd screw the 2" filter onto the 2-1.25" adapter not the 2" extension as it's better to keep the filter as close to the optics (eyepiece) as possible. I tend also to buy 2" filters. my preference for the moon is a Baader Neodymium filter when 50% or more illuminated. I don't use a filter at less than 50% even with my 16" dob. after a few seconds the brightness dies down as your pupil contracts.

[skir]

Thanks, yes looking at the base of the 1.25/2 adapter I can see it has a threaded section, checking out my eps the plossls are fine, but the radian has a longer nose piece so I guess I'd need to screw the filter into the bottom of the 35mm extension?

[Moonshane]

or do this as suggested above

[skir]

Ok thanks. That is a useful option.

So would the baader neodymium do the job of a polarising moon filter and a uhc filter on its own?

[Moonshane]

it's not a UHC filter but it does a good job on the moon and the planets mentioned. I don't use it as a LP filter myself.

[skir]

How is it on dso's?

[skir]

Also the baader fine tuning rings come in 14mm and 28mm lengths. The 14mm looks to provide enough clearance for my radian. But I guess adding in the fine tuning ring will change the focal length of the ep, is that correct?

[Joseki]

If you reduce the effective aperture you'd reduce the brightness of the moon - for free (cardboard taped to the front of the scope with a hole cut in it - positioned off centre and avoiding spider legs). Of course the Baader ND filter is useful to have anyway, check out the FLO writeup:

http://www.firstlightoptics.com/light-pollution-reduction/baader-neodymium-filter.html

[rwilkey]

Also the baader fine tuning rings come in 14mm and 28mm lengths. The 14mm looks to provide enough clearance for my radian. But I guess adding in the fine tuning ring will change the focal length of the ep, is that correct?

Using the FTR will not increase the focal length of the ep, just puts the focus point further back or forwards, whichever!

[Moonshane]

or possibly not at all if it fits within the drawtube - some have a stop and some not.

[skir]

Ah, ok, I was reading something about the baader fine tuning rings in use with baader eps so I guess that does not apply to other eps.

[rwilkey]

Hi Skir, no it doesn't apply to other ep's because on the Baader Hyperions they have a negative group of elements in the nosepiece, so you actually fit the FTR between the negative group and the main group housed in the body of the ep. FTR's don't work with the 24mm Hyperion because it doesn't have a negative grouping in the nosepiece.

[rwilkey]

Just to be extra clear, FTR's have no glass lenses in them at all, and that's why they work fine as extension rings in the way suggested above, the good thing is they are threaded for 2" filters and in my experience are some of the most useful accessories in my ep case.

[skir]

I've also seen on here people comparing the baader nd to the skywatcher lpr filter. Is there much between these two other than price?

[Moonshane]

in reality probably not much difference. I suspect just better coatings and finer polish which makes small differences generally.

[skir]

I'd appreciate it if anyone who has a skywatcher lpr filter could add their comments here as I'm convinced the baader is a good piece of kit, but need to know if the skywatcher matches it or is at least close in performance.

[Anweniel]

Its hard to make a comparison unless you use both and its probably more likely you have one or the other. I use the SW LPR filter in fact I had the 1.25" then upgraded to the 2" when I change scope (and hence focuser)

It does cast a slight colour when imaging but nothing drastic and nothing really noticeable during observing sessions. Primarily I use mine to reduce the effect of nearby sodium lighting and although not perfect it does reduce some of the harshness and allows for slightly longer exposures when imaging closer to the problem light than without it.

Personally I would choose the Baader ND over the SW LPR but the price difference is a bit of a clincher when you are on a budget! The SW is good value for money and I use it almost every session be it for imaging or observing.

[skir]

Its hard to make a comparison unless you use both and its probably more likely you have one or the other. I use the SW LPR filter in fact I had the 1.25" then upgraded to the 2" when I change scope (and hence focuser)

It does cast a slight colour when imaging but nothing drastic and nothing really noticeable during observing sessions. Primarily I use mine to reduce the effect of nearby sodium lighting and although not perfect it does reduce some of the harshness and allows for slightly longer exposures when imaging closer to the problem light than without it.

Personally I would choose the Baader ND over the SW LPR but the price difference is a bit of a clincher when you are on a budget! The SW is good value for money and I use it almost every session be it for imaging or observing.

I think the 'budget' element is the key thing here really as in is the baader really worth that much more than the SW?

[Anweniel]

There is a comparison here: http://stargazerslounge.com/topic/33706-skywatcher-lpr-filter-vs-baader-neodymium-filter/

To me I think if you are talking value for money the SW wins out... Its usually a question of taste though isn't it. I don't see a LOT in it but some may see the value in the subtleties if that makes any sense?

[skir]

There is a comparison here: http://stargazerslou...odymium-filter/

To me I think if you are talking value for money the SW wins out... Its usually a question of taste though isn't it. I don't see a LOT in it but some may see the value in the subtleties if that makes any sense?

yes I'd read that thread but was hoping to hear a bit more from anyone else with experience of both.

I think if money was no object I'd just buy the baader nd........and I might still do anyway!