Filter Diameters

[AndyWB]

I have a Baader UHC-s filter that I got for my Heritage 130p, and it works pretty well - it's not too aggressive for the small scope. However, I'd like to get an OIII filter, and the 250px could handle a 2" one.

I've only one 2" eyepiece, though, and the 1.25" adaptor tube for the 250px isn't threaded 

Would I be daft to get a 1.25" filter, such that it could be used with the 130p too, and with most of my eyepieces, or should I get a 2" one that can only be used with the Maxvision 28mm? Or a 2" one and try and track down a different 1.25" adapter (and where would I begin?)

Actually, said like that, the 1.25" sounds much more sensible, but I was wondering what others think?

[steppenwolf]

Personally, I'd go for the filter size that will be used in the EP that you use the most - I'm guessing that that would be 1.25"?

[Stu]

I suspect you would use it far more in the 250px so I would be tempted to get whichever one makes most sense for that.

I would also consider which targets you are hoping to view with it. For instance, I think I'm right in saying the MV gives a 1.6 degree fov in the 250? This would nicely fit the Eastern Veil in it. There are a number of other larger targets out there which benefit from OIII so just consider how important the wider field of view of the MV is for these.

Stu

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[faulksy]

quite sure that at the moment theres a lumicon oiii in 1.25 on abs

[faulksy]

I have a Baader UHC-s filter that I got for my Heritage 130p, and it works pretty well - it's not too aggressive for the small scope. However, I'd like to get an OIII filter, and the 250px could handle a 2" one.

I've only one 2" eyepiece, though, and the 1.25" adaptor tube for the 250px isn't threaded 

Would I be daft to get a 1.25" filter, such that it could be used with the 130p too, and with most of my eyepieces, or should I get a 2" one that can only be used with the Maxvision 28mm? Or a 2" one and try and track down a different 1.25" adapter (and where would I begin?)

Actually, said like that, the 1.25" sounds much more sensible, but I was wondering what others think?

it was astranomic, equally as good

http://www.astrobuysell.com/uk/propview.php?view=83903

[Stu]

I'm sure they are both very good. The Lumicon seems to have a slightly narrower band pass around the two OIII lines

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[jetstream]

The Luimicon does seem to have an orange,red leak starting about 620nm where Astronomik has none.I am curious about something, though maybe its better off in a new thread(?).

I can use my 10mm EP / Astronomik OIII with great success on the Veil,from very dark skies.This is @ 2mm exit pupil,which is outside the published ranges for the OIII's.

I am wondering if any Lumicon OIII owners have tried this small exit pupil and with what result?

[Stu]

The Luimicon does seem to have an orange,red leak starting about 620nm where Astronomik has none.I am curious about something, though maybe its better off in a new thread(?).

I can use my 10mm EP / Astronomik OIII with great success on the Veil,from very dark skies.This is @ 2mm exit pupil,which is outside the published ranges for the OIII's.

I am wondering if any Lumicon OIII owners have tried this small exit pupil and with what result?

Is that something you've seen visually Gerry, or have just picked up on the bandpass graphs?

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[John]

The Astronomik does seem a little more "generous" than most other O-III's. Personally I like this about it as it makes it useful with even my smaller aperture scopes and you see a good amount of background stars to set the dso in context. So, for me, it meets all my dso filtering needs with the exception of H-Beta for which I have the Lumicon H-B. 

Others might prefer a more severe O-III filter though as I guess it's contrast enhancement of nebulae might be a little greater especially in larger aperture scopes. They might also wish to have a complimentary UHC when a wider band pass is desired.

[jetstream]

Is that something you've seen visually Gerry, or have just picked up on the bandpass graphs?

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Just from the Pensack provided graph in the other thread.Not sure what effect if any it would have. http://www.karmalimbo.com/aro/pics/filters/o3a.jpg.I am curious how the Luimicon OIII works at the 2mm exit pupil range though,and at what aperture this is tried with.I can easily see the Veil from my house in bright skies- < 19 mag-with my 90mmfrac @ 2.3mm exit pupil with the Astronomik.The 16mm Nagler is great for this.

Sorry about the 620nm -it starts just after 650nm-too many graph lines!

[Stu]

Just from the Pensack provided graph in the other thread.Not sure what effect if any it would have. http://www.karmalimbo.com/aro/pics/filters/o3a.jpg.I am curious how the Luimicon OIII works at the 2mm exit pupil range though,and at what aperture this is tried with.I can easily see the Veil from my house in bright skies- < 19 mag-with my 90mmfrac @ 2.3mm exit pupil with the Astronomik.The 16mm Nagler is great for this.

I have the Lumicon so when the skies get a little darker I will give it a go. Can try in the 85 or 106. I've not seen the veil easily from my skies though, probably need to get somewhere a little darker which I plan to do once the nights draw in a little. I'm not wishing the summer away, but...... :-)

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[AlexB67]

You could get an adapter for your 2 inch extension tube so it can accept 1.25 inch eyepieces as well, that way you can use both the 2 inch filter with 2 inch and 1.25 inch eyepieces.

I think all the eyepieces you have will not have the risk of sinking deep into the tube and risk touching the filter. 

Something like this would do I think.

http://www.harrisontelescopes.co.uk/acatalog/Revelation_Self_Centering_2__to_1.25__Eyepiece_Adaptor.html

so attach filter to extension tube, insert the adapter into the 2 inch extension tube, and pop in 1.25 inch eyepiece.

[AndyWB]

You know what, Alex, that's what I'm going to sort first - the right system of extension tubes/adapters. I've been putting it off, I guess.

My guess is that the 1.25" eyepieces would be used the most - but there are some big targets out there that I gather benefit from the wider field of view, as Stu says. And yes, the Maxvision 28mm gives about 1.6 degrees.

Then I'll think about filters, sizes, and makes.

[jetstream]

Most objects that the OIII shows are big in the eyepiece,I exclusively(almost) use 2" EP's with the OIII.Your 28mm should work well.