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JOC

Low Magnification, what is useful?

33 posts in this topic

I've read a fair bit about things like the veil nebula and other large sky objects.  I don't know if I will ever get to see many FGW's (Faint grey wispies), but if I go searching for larger things like the Veil in the summer is the 32mm that I have for my F6 1200mm going to give too much magnification?

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Generally speaking, the lowest power to use is one that just provides an exit pupil equal to that of your eye pupil. A lower power with larger exit pupil will  result in loss of effective aperture. The 32mm eyepiece that you have will probably give you the widest field with your telescope for the magnification unless you spend more than the telescope might have cost on one of the exotic premium eyepieces.   :icon_biggrin:

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I have used my 31mm EP in both an 80mm F/6 and my C8 (F/10), and the Veil showed well in both. At F/6 you have about 5mm exit pupil which works well under dark skies. The 80mm shows the whole complex easily in my 82 deg EP (5.3 deg actual FOV), but in the C8 I get just part of the complex, in much more detail, due to the 1.33 deg FOV I get. Your 32mm Plossl will give essentially the same field of view, but at a larger exit pupil. Only using 2" EPs can you get any more of the Veil to fit

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I use the Wonderfull Skywatcher  32mm Panaview, its a 2" fitting, so I need  swap out the adaptor when going back to a BST,  the adaptor and EP come out as one!

For a Newtonian,  as a guide, multiply your dilated pupil by the focal ratio ( this should  provide the lowest power and the best result )  but there is a limit to how low you can go on a Newt, otherwise you'll see the secondary mirror, and other issues, no limit on a refractor.

32mm is just a little over my limit, but works well,  and the Panaview came highly recommended, plus I can't get a 29mm EP?

Personal choice, trial and error, but I like my Panaview, its a total keeper for this scope and my eyes.

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A few images to illustrate what has already been said.

The smallest circle is your 32mm Plossl in the 200 f6, the next largest is a 30mm 82 degree ES 2" eyepiece in the same scope, whilst the largest one is the 2" eyepiece in my frac (740mm focal length). With a shorter focal length you get even wider.

The points about optimum exit pupil are important here too, going too large can give a washed out view and at extremes you do risk seeing the secondary shadow.

But, even with your 32mm eyepiece, get yourself an OIII filter and under some dark skies and you will still be able to see the Eastern and Western Veil section clearly one at a time.

IMG_0920.PNG

IMG_0921.PNG

IMG_0923.PNG

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I use a 2" Lumicon OIII on a 27mm Panoptic to get a good view of the Veil.  Without the filter, I can't make out anything at all.  With it, it's plain as day and loaded with detail.

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I've seen the Veil with scopes down to 80mm in aperture but a good UHC or O-III filter is really needed to see anything of it. My favourite views have come with either my 4" F/6.5 refractor and the 31mm Nagler eyepiece which shows a 3.9 degree true field and both the E & W segments of the Veil in the same FoV or with my 12" dob which gives a 1.6 degree true field with the same eyepiece - enough to get either the whole of the E or W segments in, but not both at the same time !

The smallest aperture instrument which has shown me the Veil is my 11x70 binoculars. On a really dark night a couple of years back I was able to see the E segment of the Veil (the brightest portion) without a filter with these binoculars. Not often repeated from my back yard !

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1 minute ago, John said:

I've seen the Veil with scopes down to 80mm in aperture but a good UHC or O-III filter is really needed to see anything of it. My favourite views have come with either my 4" F/6.5 refractor and the 31mm Nagler eyepiece which shows a 3.9 degree true field and both the E & W segments of the Veil in the same FoV or with my 12" dob which gives a 1.6 degree true field with the same eyepiece - enough to get either the whole of the E or W segments in, but not both at the same time !

The smallest aperture instrument which has shown me the Veil is my 11x70 binoculars. On a really dark night a couple of years back I was able to see the E segment of the Veil (the brightest portion) without a filter with these binoculars. Not often repeated from my back yard !

waiting for the veil to try to see it with a 24mm es 68 in borg 71 and OIII. 24mm gives 4,2mm exit pupil and around 4 degrees, 17x, enough for both sides of the veil...if it can be seen, that is. :) i probably need some pretty dark skies.

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2 minutes ago, BGazing said:

waiting for the veil to try to see it with a 24mm es 68 in borg 71 and OIII. 24mm gives 4,2mm exit pupil and around 4 degrees, 17x, enough for both sides of the veil...if it can be seen, that is. :) i probably need some pretty dark skies.

You should have more than enough FoV - My 21mm Ethos will also show the whole thing (3.17 degrees) but the 31 Nagler gives that little bit of "elbow room" to the object, which makes for a nicer framed view, IMHO.

 

 

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Many thanks all.  It sounds like my 32mm Plossl is well worth trying - in fact in the circles above it looks like it should fit each section at a time quite nicely.  Through the classifieds I have picked up two Skywatcher filters the O-III and the UHC - I know these probably aren't in the same class as those costing £50+ each, but I've read reviews on SGL that suggest they aren't useless either so when the veil comes around maybe I can try both of those and see if I can find it.  If the nebula is going to be as big in the EP as the pictures above suggest then maybe I will have a good chance of finding it.  Esp. with the Goto which I think I've now read enough about to set up better than I have been (although I've got to identify two 'summer' stars to calibrate it on - I'll have to get Stellarium up and running one night, but I'm sure with that identifying two new stars is solvable).  I've put the filters into a holder and left a blank space so without removing the EP I can experiment with both the UHC and the O-III as well as an unfiltered view within moments.  If the difference is as startling as Louis D suggests and my cheap skywatcher is good enough to show it that should be an easy way to reveal it.

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1 hour ago, JOC said:

Many thanks all.  It sounds like my 32mm Plossl is well worth trying - in fact in the circles above it looks like it should fit each section at a time quite nicely.  Through the classifieds I have picked up two Skywatcher filters the O-III and the UHC - I know these probably aren't in the same class as those costing £50+ each, but I've read reviews on SGL that suggest they aren't useless either so when the veil comes around maybe I can try both of those and see if I can find it.  If the nebula is going to be as big in the EP as the pictures above suggest then maybe I will have a good chance of finding it.  Esp. with the Goto which I think I've now read enough about to set up better than I have been (although I've got to identify two 'summer' stars to calibrate it on - I'll have to get Stellarium up and running one night, but I'm sure with that identifying two new stars is solvable).  I've put the filters into a holder and left a blank space so without removing the EP I can experiment with both the UHC and the O-III as well as an unfiltered view within moments.  If the difference is as startling as Louis D suggests and my cheap skywatcher is good enough to show it that should be an easy way to reveal it.

Good plan. Get yourself under a decent sky and you will have a good chance of seeing it. Plonk the Finder on 52 Cygni and the Western Veil (the Witch's broom) runs right through it. Good dark adaptation helps too.

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I've just picked up an ES68 24mm and an Astronomik UHC filter which I'm hoping will give some good views of the Veil over the summer :)

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10 hours ago, Littleguy80 said:

I've just picked up an ES68 24mm and an Astronomik UHC filter which I'm hoping will give some good views of the Veil over the summer :)

UHC might help you detect it, but it is the OIII which will reveal the glory.

Overall, however, UHC is a more versatile filter.

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1 hour ago, BGazing said:

Overall, however, UHC is a more versatile filter.

This is why I went for the UHC first. An OIII filter is definitely on the list though. Will the UHC really be that limited on the Veil? 

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28 minutes ago, Littleguy80 said:

This is why I went for the UHC first. An OIII filter is definitely on the list though. Will the UHC really be that limited on the Veil? 

Here is some further detail for observing the Veil  http://observing.skyhound.com/archives/aug1/NGC_6960.html

Initially a UHC would be fine and then if you were able to obtain an OIII in time that would become an advantage.  A Low power, larger exit pupil is compensated when applied with an OIII, H-beta or UHC filter when fully dark adapted and under a good dark sky.  

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2 hours ago, Littleguy80 said:

This is why I went for the UHC first. An OIII filter is definitely on the list though. Will the UHC really be that limited on the Veil? 

I have observed Veil under 21.4 skies this summer...several times, on two different locations. 

DGM NPB made it stand out. OIII (I had TS one at the time) made it...magical. My SCT8 does not allow for a field wider than approx 1.2, but I still vividly remember how cool it was, especially Witch's Broom. Magic, even at only approx 3.5mm exit pupil. Can't wait to try Astronomik OIII on it this summer. Too bad I was always bad at drawing...

Don't know which UHC you have, DGM is pretty tight. If you have one of the UHCs with a wider passband...the difference will be even more pronounced, I guess.

IMHO, OIII filter is worth it for a look at the Veil alone...

Edited by BGazing
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Is there any advantage to putting two filters together such as the O-III and the UHC or is the object sufficiently 'pale' in the sky that too much light would be blocked?

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2 minutes ago, JOC said:

Is there any advantage to putting two filters together such as the O-III and the UHC or is the object sufficiently 'pale' in the sky that too much light would be blocked?

A UHC filter is basically an OIII and H-Beta filter combined, or at least that's my understanding! So there's no advantage to combining them

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12 minutes ago, JOC said:

Is there any advantage to putting two filters together such as the O-III and the UHC or is the object sufficiently 'pale' in the sky that too much light would be blocked?

no, there is no advantage. if you stack them together all you would get out is OIII lines.

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3 minutes ago, Littleguy80 said:

A UHC filter is basically an OIII and H-Beta filter combined, or at least that's my understanding! So there's no advantage to combining them

Can't argue with the apparent logic of that statement, thanks too BGazing, it had to be worth asking the question though :-D

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On 4/22/2017 at 12:25, BGazing said:

IMHO, OIII filter is worth it for a look at the Veil alone...

Just picked up a bargain second hand Astronomik OIII. Here's hoping for lots of clear skies this summer :D

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16 minutes ago, Littleguy80 said:

bargain second hand Astronomik OIII

Was that the one in the SGL classifieds?  I think I saw that, but having already got the Skywatcher UHC and the Skywatcher O-III from the SGL classifieds a few weeks ago and not really knowing yet how I will get on with nebulas and the like I thought I would try with those Skywatcher ones first.  I'm sure you've probably purchased the better item though.  I hope you get good views through it.  Assuming the clouds ever decide to clear again!

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21 minutes ago, Littleguy80 said:

Just picked up a bargain second hand Astronomik OIII. Here's hoping for lots of clear skies this summer :D

For a couple of years an Astronomik O-III (2") was my only deep sky filter. It was really excellent !

Edited by John
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6 minutes ago, JOC said:

Was that the one in the SGL classifieds?  I think I saw that, but having already got the Skywatcher UHC and the Skywatcher O-III from the SGL classifieds a few weeks ago and not really knowing yet how I will get on with nebulas and the like I thought I would try with those Skywatcher ones first.  I'm sure you've probably purchased the better item though.  I hope you get good views through it.  Assuming the clouds ever decide to clear again!

Got it off AstroBuySell. I'd been planning on getting the SkyWatcher Filters too but got lucky and found the Astronomiks second hand for not too much more than what the SkyWatchers cost new. I'm sure they'll keep me happy for some time. I've nearly assembled the basic set of kit I wanted, after that no more purchases this year! I'll just be putting what I have through it's paces :) 

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Congratulations on your purchase? How old is that filter? I ask because Astronomik tightened recent production of OIII to 12nm... (I have the new version but am yet to try it on anything but Orion).

Edited by BGazing
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