V - Filter

[Gary70]

I use a modest sized Refractor at 6" & f8 there is a "little" ca, it really isn't too obtrusive (for me) but I think I am ready to get filtering.

My question isn't wich one, (I know how rare to have decided on a piece of equipment wihtout 100 threads telling you which is the best) I am eyeing up the Baader Semi APO filter, it comes in 1.25 and 2" , my scope has a 1.25 diagonal and a 2" focuser with an adapter to 1.25, Should I replace the stock diagonal with a higher quality 2" and then buy a 2 " filter?

Then can I leave it in there even if if I use a 1.25 ep?

My thinkimg is that if I get the 2" and also a new 2 " diagonal I can in the future if needed plug a high mag 1.25 or a wider fov 2" ep in without having to mess around?

I think that makes sense

Thanks guys

[Gary70]

Darn posted instead of previewans I cant edit.....

Or is it not necessary and I can just get the 1.25 and still use a 2" ep if needed? but maybe upgrade the Diagonal anyway..but only 1.25.

[ronin]

Do you really need one ?

Only ask as I worked with apodisation filters years ago, they were designed to go over the front of the objective and so alter incoming profile before the light got to the objective. The idea of putting one in the eyepiece seems incorrect.

The light intensity was changed according to a profile across the objective diameter, could be simply linear, parabolic or any other weird and wonderful profile you could produce.

If the filter is simply one that is in effect a blocking filter for say reducing the red and blue that are transmitted then I personally cannot see the point.

Ultimately no filter will make your achro and apo. If they could TV, TMB, AP, WO and all the others wouldn't make triplet apos, they would turn out an achro and sell you a filter.

[Gary70]

A pretty good point ronin, I dont know that i need one, in fact i know very little about filters except what i read on here and elsewhere, more just trying to improve my nights out in any way I can, losing a bit of blue fringe might help? I am not sure, as I said I can live with the fringing i get. hopefully the concensus will follow yours and i can spend my money on something else I think I need

I only do visual and the odd sketch, mostly planets/ moons and doubles, so i dont need an apo, but i thought if it went in the diagonal i could pretty much leave it there?

[John]

If you don't find the CA intrusive I'd not bother filtering it, or some of it, out. I used a William Optics VR-1 for a short while on a Skywatcher 150mm F/8 and it does reduce the CA fringing by around 30% or so but it also gave a yellowish tint to the image which I did not like.

Of course the CA is present across the whole of the image and not just the edges of bright objects, you just notice it there more.

There are magical devices called Chromacors but they are really rare. They actually correct the CA and other aberrations in these achromat refractors and you can get close to ED doublet performance from the scope which really makes a big difference.

[jimmyjamjoejoe]

My limited experience with a "fringe killer" didnt impress me much if i'm honest. Really didnt change much except to give the image a warmer, yellow tint.

[Gary70]

If you don't find the CA intrusive I'd not bother filtering it, or some of it, out. I used a William Optics VR-1 for a short while on a Skywatcher 150mm F/8 and it does reduce the CA fringing by around 30% or so but it also gave a yellowish tint to the image which I did not like.

Of course the CA is present across the whole of the image and not just the edges of bright objects, you just notice it there more.

There are magical devices called Chromacors but they are really rare. They actually correct the CA and other aberrations in these achromat refractors and you can get close to ED doublet performance from the scope which really makes a big difference.

I remember you mentioning those before, been looking ever since imposible to find seems around 2007 the market dropped right out for them, Aries were making them but I haveno idea how such a popular device ceased manufacture??? cost maybe,, they were not cheap from what I can tell.

Thanks guys £80 or so saved

[John]

I remember you mentioning those before, been looking ever since imposible to find seems around 2007 the market dropped right out for them, Aries were making them but I haveno idea how such a popular device ceased manufacture??? cost maybe,, they were not cheap from what I can tell.

Thanks guys £80 or so saved

I think the influx of affordable ED doublet refractors killed the market for the Chromacor off largely. Aries were talking about a Mk 3 version built into a special diagonal but I've not heard any more for quite a while. The Mk 1 and 2 Chromacors (I've owned both) were pretty fussy devices to use in practice and placed high demands on focuser precision, optical matching and positioning within the optical path. The do work really well when set up properly though.

Istar Optical were working on something similar called a Raycorr but, again, it's gone a bit quiet on that front lately too.

I eventually found a Skywatcher ED120 at a good price and that plus my Vixen ED102 currently satisfies my refractor urges very nicely. Very little in the way of CA visible in those scopes even on bright objects

[Gary70]

That's a lovely pair you got there (coudn't resist sorry )

What seperates the SW Equinox Pro from the Pro ED? apart form a couple hundred pounds the optics appear on paper to be identical..

[John]

....What seperates the SW Equinox Pro from the Pro ED? apart form a couple hundred pounds the optics appear on paper to be identical...

The optics are the same. The body work and focuser on the Equinox are better quality and glossier. My ED120 has a Moonlite focuser fitted though.

[Gary70]

Moonlite, i looked at those, then saw the price and looked away.. they do like nice though,

Is the view through the ED vastly superior to the standard SW evostar 120? from a visual perspective that is.

[John]

Is the view through the ED vastly superior to the standard SW evostar 120? from a visual perspective that is.....

On deep sky objects it's pretty much the same. On brighter objects there is virtually no false colour visible with the ED120 and it seems to take higher power than the Evostar 120 - I find 225x and 257x usable quite often whereas the Evostar I had a while back seemed to max out at around 200x.

[Gary70]

On deep sky objects it's pretty much the same. On brighter objects there is virtually no false colour visible with the ED120 and it seems to take higher power than the Evostar 120 - I find 225x and 257x usable quite often whereas the Evostar I had a while back seemed to max out at around 200x.

Thanks John i've never looked through an apo, I appreciate you taking time, odd how I knew you would have owned both

[John]

Thanks John i've never looked through an apo, I appreciate you taking time, odd how I knew you would have owned both

I've owned rather too many scopes over the years - I've settled down a bit more lately though

[Ohmless]

Are you having issues with deep sky IRT CA? I don't really have a problem in that regard with my scope. After looking at photographic differences through the different filters that reduce CA, I was most impressed with the fringe killer. It appeared to me to cut out more of the violet and some blue. Personally, I use a yellow #8 as that cuts out violet also, though less than a FK of course, but I am cheap.

[Gary70]

Mine was planets,but not a big deal just aesthetics i guess, not too much DSO for me unless I travel, and I dont do photography being rather new to this game, time spent taking photos is time lost just watching the comos at work .