Have I made a mistake with the Olll

[Mike73]

To be very honest Alan I don't fully understand the curves either   but I was surprised to see just how similar the cheaper TS OIII curves were to the expensive Astromomik UHC. I originally went from a Skywatcher OIII to the Lumicon expecting the views to be very similar with obvious improvements in sharpness maybe but the actual difference in views between the two OIII's was not just subtle but huge!

Yep the Sumerian is still going strong and I really enjoy using it every time its out, funnily enough though I'm saving hard to eventually get a 180 Mak for use at home.

[Naemeth]

To be very honest Alan I don't fully understand the curves either   but I was surprised to see just how similar the cheaper TS OIII curves were to the expensive Astromomik UHC. I originally went from a Skywatcher OIII to the Lumicon expecting the views to be very similar with obvious improvements in sharpness maybe but the actual difference in views between the two OIII's was not just subtle but huge!

Yep the Sumerian is still going strong and I really enjoy using it every time its out, funnily enough though I'm saving hard to eventually get a 180 Mak for use at home.

What all the graphs show is that the filters have high levels of relative transmission between ~480nm and 520nm, where the human eye has a sensitivity for light between about 390nm and 700nm.

[John]

From those charts, the TS O-III seems to have a max transmission in the O-III line of a bit below 90% wheras the Lumicon seems close to 100%. The flat topped curve with a sharp drop off either side of the Lumicon O-III would indicate that it's likely to be more effective to me.

I'm not sure that the gradually tapering "spike" of the TS O-III is the best profile really.

To be honest though, these charts are quite difficult to interpret and I've seen varying scales used which does not help clarity of data.

[John]

I've come across this web report on deep sky filter performance. It includes data for many filter brands and types and, importantly, tries to plot their transmission data consistently on the same graph and to the same scale so that you can more easily compare them directly. There is probably more info here than many would want but for those inclined it's interesting stuff:

http://www.karmalimbo.com/aro/filters/filters-findD.htm

[alan potts]

Someone there has done a lot of work on filters and though I think it may be clearer to me on a second or even third read well worth keeping, I have bookmarked it. Many thanks.

I don't know a lot about these things but I don't think there is much between the Lumicon and the Astronomik we have, lets face it for the cost compared to the TS they should be better.

Alan.

[scarp15]

This is because of exit pupils. Line filters block more light, therefore work best with bigger exit pupils. If we "over power" our line filter (use too higher power) the view will quickly dim. Most objects we can't see are big low surface brightness objects (the veil, rosette, NA neb etc), we use low power here and the O-III rocks.

Objects we can see, we ramp power up to frame them nicely. O-III doesn't like higher power and shows us as much with very dim views.

Keep your exit pupils big and your O-III will give you happy observing

Interesting, combining the lumicon O-III filter, with my former 35mm panoptic, provided unforgettable views of the Veil and did very well on other subjects such as the Owl Nebula (with 12" and subsequently 14" dobs). At f4.5, very low power and a hugh exit pupil.

I hope for similar with my 26mm nagler, when I finally get an opportunity to use it.

[John]

I don't know a lot about these things but I don't think there is much between the Lumicon and the Astronomik we have, lets face it for the cost compared to the TS they should be better.

Alan.

In terms of overall quality I think the two brands are very close. They may have chosen different transmission ranges for their respective O-III, UHC, etc filters though and that will affect the views they deliver. 

I've currently got two H-Beta filters, a Lumicon (which I've recently bought) and a 1000 Oaks (kindly loaned by Mark at Beaufort). Both are in the same sector of the market price and quality wise and their transmission charts look rather similar too. When I hold them up to the light the Lumicon shows a much stronger pink tint than the 1000 Oaks but I've no idea how that will translate into actual use.

[Naemeth]

In terms of overall quality I think the two brands are very close. They may have chosen different transmission ranges for their respective O-III, UHC, etc filters though and that will affect the views they deliver. 

I've currently got two H-Beta filters, a Lumicon (which I've recently bought) and a 1000 Oaks (kindly loaned by Mark at Beaufort). Both are in the same sector of the market price and quality wise and their transmission charts look rather similar too. When I hold them up to the light the Lumicon shows a much stronger pink tint than the 1000 Oaks but I've no idea how that will translate into actual use.

Perhaps, John, the stronger tint is just due to the strength of the filter for emphasizing (perhaps it is more correct to say that it eliminates more of the blue end of the spectrum) the redder part of the spectrum (which is what you want with a H-Beta filter!)

[RikM]

I thought H-beta emits in blue at 486nm ?

The main difference visually between an OIII and a UHC is that the UHC includes the blue H-beta line as well as the two Oxygen lines.

[Naemeth]

I thought H-beta emits in blue at 486nm ?

The main difference visually between an OIII and a UHC is that the UHC includes the blue H-beta line as well as the two Oxygen lines.

To be honest with you Rik I'm not entirely sure. I just assumed that H-Beta, being a Hydrogen filter would cut everything but the hydrogen part of the spectrum (the red end).

[alan potts]

H-Beta was a filter that I wanted to try but I just have not seen a secondhand one and both the Lumicon and Astronomik are rather costly new. I am sure there are others but these two I could buy without problems some of the others at this price range are difficult to lay hands on.

One thing is for sure they make photographic filter, even the best look cheap.

Alan

[alan potts]

Just to let you all know I bagged the veil nebula last night in between a rest from the 3mm and 3.5mm research I also managed to see NGC 6960, not sure if this one has a name, I something around there is know as the witch broom.

It was not the best of conditions when I decided to try it, it was starting to dew, a little after this the fog formed which it does at this time of the year. I could also see it a little without the filter, once I knew where it was hiding. In the 190mm M/N it was not fantasically clear and I would would not go so far as to say it jumped out at you and grabbed you around the neck but it was without doubt a nebula to sit and take in, a rewarding target that would get better with time spent on it.

I do think these two targets and the other bits and pieces in the same area cry out for at least 10 inches of aperture though and I should think that a 16 inch would really bring it to life.

I was wondering, I tried my 35mm Panoptic in the 1 meter scope, is there an optimum magnification, exit pupil that helps this object.

Alan

[RikM]

Here is quite a nice sketch http://stargazerslounge.com/topic/157032-veil-nebula/?hl=%2Bveil#entry1614374 and very similar to what I get with my 10".

With good skies it doesn't need huge aperture. It is really quite a large object (or group of objects) so a shorter focal length can give you a wider perspective. However, aperture does make bits of it sing. Heres a comparison between 20" and 4". Both good. http://stargazerslounge.com/topic/19005-sketch-study-of-the-veil/?hl=%2Bveil#entry1178291

[alan potts]

Thanks for the links Rik.

Pickerings wisp looks a bit like a birds head with eyes and beak, I didn't see that part, at least I don'r think I did. Sadly I don't think my 12 inch has a wide enough FOV to nail it all but I will give it a go tonight, it's looking clear again.

Alan

[Mark at Beaufort]

Pickerings wisp looks a bit like a birds head with eyes and beak

Alan

I just looked at that sketch (thanks Rik for the link) and I agree Alan it does look like a birds head, eyes and beak. I don't think I have tried the Veil using my 4" APO and the 21mm Ethos which gives me 3 degrees. Perhaps if it remains clear I might have a go tonight using the UHC and Olll filter.

[alan potts]

I have just put the LX out so I will give it a go with that tonight, might see half of it or I can always try the reducer to see if that helps at all. Time to get the big eyepieces out.

I will try it with my APO, John says you can see it with a 4 inch so it will down to local conditions as usual.

Alan

[RikM]

I have had quite respectable views of the veil with an 80mm refractor on a good night from the outskirts of Cheltenham, so you should be fine with your 115mm and a proper dark sky.

[allen g]

For the Veil - I use my 4" TV refractor - 31 nagler(which together give me 4.46*)and Lumicon OIII (or Astronomik UHC) and see all of it perfectly with no moon. With the moon out no dice!

[Stu]

I've seen it very nicely with a 106mm and 31t5, 3.68 degree fov with an OIII under dark skies. Needs good dark adaptation in my experience, I can't see it in this scope from home though so dark sky really helps.

I'm planning on upgrading to an Astronomik OIII which may be better?

Stu

[Mark at Beaufort]

I had a go tonight with my Astro Tech 4" APO, 21mm Ethos and a TS Olll filter. I could see both the western and eastern segments  but could not pick up Pickering's Triangular Wisp. I also tried the Skywatcher UHC but this was not as clear as the Oxygen 3 filter.

Still clear so will now try with the 6" Newt to see if things improve.

[Stu]

I had a go tonight with my Astro Tech 4" APO, 21mm Ethos and a TS Olll filter. I could see both the western and eastern segments but could not pick up Pickering's Triangular Wisp. I also tried the Skywatcher UHC but this was not as clear as the Oxygen 3 filter.

Still clear so will now try with the 6" Newt to see if things improve.

Nice one Mark. I've only managed Pickerings in my 4" from very dark skies in Dorset. Good luck with the 6"

Stu

[alan potts]

Well I had the LX on it last night and it was a big let down. It was not a very good night, clear as a bell but very unsteady seeing. I was looking at Venus as it was getting dark and even X76 was a battle, when it did get dark the milky way was visible right across the sky, who ever said this hobby was easy.

Anyway I spent 40 mins looking at the viel, or where I thought it should be, and there was nothing. I even rechecked the goto and tested it on other targets and there was nothing wrong there, so it looks like the SC with it's 3 meters of focal length and a 41mm Panoptic is not the best scope and eyepiece on Earth to choose for this nebula.

The seeing did not get a great deal better so it was a early night, nice when you can be choosy.

I will try it with the APO and look at it again with the Mac/Newt, that gave a very pleasing result.

Alan.

[swamp thing]

Hmm! If my calcs are correct that should give you around 73x Alan?

The veil should be still do-able in a 12" scope at a dark sky with this combo. I often used my 20mm T5 in my old 16" scope to observe finer detail in it. This combo gave me just over 90x.

Are you sure you were in the right place?

[Mark at Beaufort]

That is interesting Alan about your 12" SCT. I decided to experiment with the 10mm Delos and the TS Olll filter which gives a mag of 71x and a FOV of 54 minutes. I could still see the Veil although not as good as the view with the 21mm Ethos.

I took out the 6" Newt but the quality of the sky had deteriorated and the clouds came over so was not able to check.

[alan potts]

Steve,

In all honesty I would not lay my life on it but I try going in every direction away from where the scope stopped and I could not see a thing. I think also I sort of remembered the line of stars the veil follows, but there are so many I could just be talking rubbish.

I will try another night, with conditions being something of a pain my heart was not fully in it. There is no doubt the 12 inch is big enough, I was just a little worried the magnification was making it too difficult to see. If that is the case and I would think not in view or your report of X90, albeit with a larger scope, I could always try the reducer and a 24mm UWA which would give a larger FOV with a lower power.

Alan