Astronomik UHC or Lumicon UHC ?

[Dave In Vermont]

The entire Cygnus-region is what I love about Summer-times. Whether driving my 80mm F5 refractor, or my 12" F10 SCT - it's got some amazing things available for all.

Dave

[Piero]

+ Lumicon OIII, and if you have a 2" focuser, I'd suggest the 2" model too.

[N3ptune]

Dave, beautiful place, a lot of stars. (; Next trip out I will enjoy the Cygnus region, it's the good time to do it.

Piero

Hemm well I have one 2 inches piece, the LET 28mm. I like it but way less then my Celestron X-Cel LX 25mm. So all my eyepieces are basically 1.25. The problem with the LET 2" it's the distortion in the FOV. It's comfortable but not enough for me to be enthusiastic about buying a large filter for it.

I usually watch the nebulas with my 25mm (40x), 18mm (55x) and even 25mm + barlow 2x (80x)  to inspect specific parts.

 

[John]

The whole Veil Nebula complex is really large - it's a bit over 3 degrees in total extent which is 6x the diameter of the full moon. 52 Cygni is a good starting point because the Western segment of the nebula runs right past it - it's also known as the "Witches Broom" for reasons which will become obvious when you see it. The brighter segment is the Eastern one which is sometimes known as the "Bridal Veil"

Here is a location map:

 

[N3ptune]

Very large indeed.

It's the first thing I am going to look at on my next trip. I will look all around the large Veil region and search for nebulosity. (With a new filter hopefully)

A UHC or a OIII I want them both honestly, still am not sure about which one to start with --> It's a "flip a coin" situation almost, both are a good choice,  undoubtely!

Thanks for the veil map and the graphics that were published here earlier, it was instructive for me.

[jetstream]

1 hour ago, N3ptune said:

John,

I made a mistake here, last week I pointed the telescope toward the Veil Nebula (with no filter), but I didn't see a thing except for star 52 and other stars.(I didn't know it was invisible without the OIII) It looks quite faint, magnitude of 7 and no information on the surface magnitude in my NGC catalogue.

If you can see it with a 4" refractor, I should be able to see something. Has map bellow I was at my spot #2, it could be a pollution matter for me.

Cygnus is beautiful and inside the milky way.. what a nice place to watch your are lucky to see the Veil John.

Whats the scale of your map? You might be very close to really dark skies, the SQM-L is a valuable tool to find the exact edges of dark skies.

Which filter first?

OIII, Lumicon 2". Your going to want a large TFOV for the nebs out there in general...

[N3ptune]

There is no scale there but between I and III it's around 80 kms (52kms straight line)

--> I might get a OIII and not a UHC but unlikely in 2 inches this time. it's way too expensive right now..

I just feel my LET 28mm is not satisfying enough to buy 2 inches filters.

======================

I wonder, why is it better on 2 inches?

- 2 inches LET 28mm (Afov55d) 37x + 2 inches OIII filter

or

-1.25 inches XL-LX 25mm (Afov60d 40x + 1.25 inches OIII filter.

The best bet would be on the 2 inches ? or the best bet would be a 2 inches filter on another 2 inches eyepiece against the XL-LX ?

[jetstream]

I use Televues recommended true field of view formula = field stop diameter / focal length of scope x 57.3

So the 2" LET 28mm with a 31mm fs dia will be 31/1000x57.3=1.77 deg TFOV

The 1.25" 25mm excel lx has a (guess) fs dia of about 26mm- for a 1.48 deg TFOV

You can use a 2" filter with 1.25" eyepieces but not the other way around, I bought a 1.25" Hb for the HH and then bought a 2" Hb later... Your scope will be a great wide field viewer and down the road can give you between 2 deg and 2.5 deg TFOV depending on your low mag (exit pupil) tolerance.

A quality 1.25" filter would give good views in your scope but it is a must to get to dark skies with it. Have you taken your OIII to the dark site to try on the Veil? I would do this first, find 52 Cygni and point the scope at it- the Veil will appear. Any idea of the NELM of your dark site(s)?

 

[Dave In Vermont]

A 200mm F/5 Newt is a good instrument to haul in wide swathes of sky with. I have a 200mm F/4. If your 'Light-Bucket' has a 28mm basically Kellner eyepiece (I've got one of those also), you may want to get another 2" EP or two to get the widest FOV possible for the Cygnus-region and such denizens as the Veil Nebula. And, perhaps, test the waters without breaking-the-bank. I'll drop a link to a source that can help.

I got the 32mm & 38mm 70° EP's from here to test-pilot, and am quite pleased with them in both an F/5 and an F/12 instrument:

http://www.universityoptics.com/2inch.html#WS70

UO ships international and carry honest-to-goodness good stuff at prices that won't put you in the soup-lines.

Best wishes & happy Cygnus -

Dave - your neighbor.

[Louis D]

11 hours ago, jetstream said:

You can use a 2" filter with 1.25" eyepieces but not the other way around

Technically, this is true; but I have successfully used 1.25" filters above the eye lens on 2" eyepieces with lots of eye relief to "blink" for objects by moving it in and out of the field of view.  You just have to be careful not to scratch the eye lens while doing this.  You can certainly get a good idea if it is worth investing in a 2" version of a particular filter this way as well.

[Louis D]

16 hours ago, John said:

It's the best Summer DSO in my opinion. It's large and has several sections but is located in Cygnus so nicely placed during the coming months. I was viewing it last night with my 4" refractor and the Lumicon O-III filter as it happens. Glorious sight with the filter, practically invisible without it

I had my best view of the Veil nebula using my 15" dob, 27mm Panoptic, and 2" Lumicon OIII filter from my suburban backyard of all places.  As you say, practically invisible without the filter, incredibly detailed like a photo with it.  One of my favorite views ever.

[N3ptune]

JetStream

I don't have a clue about the NELM of my dark site, the only tip I have is the map bellow my spots are on orange and yellow zones.

At my zone III I can see the owl nebula which is really faint, maybe 3 to 5 times the contrast from my spot which is close to Montreal, the large white zone.

I can see the whirlpool galaxy and the Crab nebula (A little bit) at zone III, i can't see them at all at zone I.

Dave

I will check the website, can't do it now.

 

 

[Stu]

6 minutes ago, N3ptune said:

JetStream

I don't have a clue about the NELM of my dark site, the only tip I have is the map bellow my spots are on orange and yellow zones.

At my zone III I can see the owl nebula which is really faint, maybe 3 to 5 times the contrast from my spot which is close to Montreal, the large white zone.

I can see the whirlpool galaxy and the Crab nebula (A little bit) at zone III, i can't see them at all at zone I.

Dave

I will check the website, can't do it now.

 

 

Best thing is to actually check it yourself. If you look at Ursa Minor and can see the seven main stars then you NELM is at least magnitude 5. To see faint stuff you need to be at 5.5 or 6 really. Being able to see the Milky Way clearly is a good indication of a dark sky.

[N3ptune]

8 hours ago, Dave In Vermont said:

UO ships international and carry honest-to-goodness good stuff at prices that won't put you in the soup-lines.

 

The price is impressive for these 2 inches oculars, for a 80 degrees 139.95 US (if the eye cleareance is good, how is it?)

It's around 250 ~ 260 CAD. (I had in mind more like 500$ just for 1 EP, the filter i2" is around CAD, it's a 550$ project (instead of a 800$ project)

STU

I can see stars with my eyes up to 5 magnitude, definitly not more then that, I can't see magnitudes 6 at spot I (My only benchmark right now) The milky way can also be seen at spot I - II and III without the moon.

If the moon is there, no Milky Way.

[jetstream]

Stu's advice on the visibility of the MW is very sound- for good DSO viewing with and without filters. A great tool is the Unihedron SQM-L which measures the sky brightness. My first priority if I were you would be to find dark skies closest to you and visit them to maximize your existing equipment. This will also tell you if the travel is something you like. I think there is a phone app that measures the sky brightness, not sure how accurate it is.

As far as cheap filters go...some work really well, some don't. The more we pay the better we hope the specs are where they should be... the key word is hope lol!

The Milky Way visibility is the key indicator for nebula viewing...

[John]

16 minutes ago, N3ptune said:

The price is impressive for these 2 inches oculars, for a 80 degrees 139.95 US (if the eye cleareance is good, how is it?)

It's around 250 ~ 260 CAD. (I had in mind more like 500$ just for 1 EP, the filter i2" is around CAD, it's a 550$ project (instead of a 800$ project)

 

Those are pretty basic SWA eyepieces to be honest. OK in an F/10 scope but the edges of the FoV look pretty messy in scopes faster than F/7.

UO have had great success in the past with their Konig, Classic Ortho and HD Ortho lines but some of their more recent ranges a rather lacking in my opinion.

The 1.25" UWA's listed currently by UO are clones of the William Optics UWAN's / Skywatcher Nirvana's so are pretty decent. Their eye relief will be around 12mm I reckon.

The 80 degree 1.25" eyepieces are chinese clones of the Japanese Widescan III series. Again, decent at F/10 and slower but the edge definition falls apart in faster scopes.

 

[N3ptune]

20 minutes ago, jetstream said:

A great tool is the Unihedron SQM-L which measures the sky

If i can look at the MW? this not enough to tell about the sky quality? Because, at the begining we were at 130$ for a UHC or OIII filter, now we are at a 550$ project + a 150$ device to look at the sky quality.

I can't do miracles here.

 

[N3ptune]

John well my scope if a fast F5.

And that's exactly the problem I get with my LET 28mm, only the center is kind of flat but all around, its suffering from omnidirectional distortion and even coma on the stars.

It's not a collimation issue because my XL LX 25mm, the FOV is flat with not much coma on the edges.

[jetstream]

lol! Just go out and check some dark sites and try to find the best places, dark skies trump everything... I was looking at the Veil, North American neb with no filter last night- this is the difference dark skies make. With the filters the views were quite amazing

The SQM-L saved me a pile of money on gasoline.

As John said earlier, take your lowest power EPs out and give them a try at the darkest spot you can find.

[John]

12 minutes ago, N3ptune said:

John well my scope if a fast F5.

And that's exactly the problem I get with my LET 28mm, only the center is kind of flat but all around, its suffering from omnidirectional distortion and even coma on the stars.

It's not a collimation issue because my XL LX 25mm, the FOV is flat with not much coma on the edges.

Some of the distortion will be coma which the fast(ish) newtonian optics generate but quite a bit will be astigmatism which the eyepiece will be generating. The X-Cel LX's are quite a bit better corrected eyepieces than the LET 28mm is which shows when you use them in fast scopes.

Still, what you have is quite useable and well worth trying on the Veil and other targets as has been said.

 

[N3ptune]

Quote

Some of the distortion will be coma which the fast(ish) newtonian optics generate but quite a bit will be astigmatism which the eyepiece will be generating. The X-Cel LX's are quite a bit better corrected eyepieces than the LET 28mm is which shows when you use them in fast scopes.

It's funny they give the LET with the scope, it's not bad.. but it's not the end of the world either. Maybe I didn't used it enough to appreciate it fully.

So i understand, if i want to use a 2 inches filter on a 1.25 eyepiece, i have to hold the filter in my hand and look through it ?

On 2016-07-06 at 23:18, jetstream said:

A quality 1.25" filter would give good views in your scope but it is a must to get to dark skies with it.

Jetstream, I am having a hard time understanding that. Could I resume to this:?

My 25mm 1.25" with a 1.25" OIII filter should perform less then my 28mm 2" with a 2" OIII filter? But if the sky is really dark, then the 1.25" setup should give me similar results?

[John]

7 minutes ago, N3ptune said:

It's funny they give the LET with the scope, it's not bad.. but it's not the end of the world either. Maybe I didn't used it enough to appreciate it fully.

So i understand, if i want to use a 2 inches filter on a 1.25 eyepiece, i have to hold the filter in my hand and look through it ?

 

 

- If they supplied a well corrected 2" 28mm eyepiece, they would need to charge quite a bit more for the scope.

- Some 1.25" - 2" eyepiece adapters are threaded for 2" filters so you can put the filter on there. Before you do this though, make sure that none of the barrels of your 1.25" eyepieces will contact a filter that is fitted to the end of the adapter - don't want any accidents !

 

[N3ptune]

My choices are the following now in this order. Of what looks like the best choices.

1. Get a 2" eyepiece to get largest Tfov and get a 2" Lumicon OIII filter.

1a Get the 2" Lumicon filter to use with my 2 inches 28mm and use the same filter (manually) with my 1.25 EPs

2. Get a 1.25" OIII filter (Astronomik or Lumicon) to use with my current 1.25 EPs.

3. Get a 1.25" UHC filter (Astronomik or Lumicon) to use with my current 1.25 EPs.

=====================

At this point, I am still confused. I don't feel it's appropriate for me to spend 550$ on a 2" EP and the 2" OIII filter, it seems out of reach.. I can pay it but there is a little voice telling me not to do it.

I am very much interested in a OIII but still attracted to the UHC filter.. because of this website:

http://www.prairieastronomyclub.org/resources/by-dave-knisely/filter-performance-comparisons-for-some-common-nebulae/

 

RECOMMENDATION RANKING SUMMARY

UHC best on 41 nebulae, close second best on 47 nebulae.

TOTAL 1st and 2nd RECOMMENDATIONS for UHC: 88 objects.

 

OIII best on 34 nebulae (biased by the inclusion of some planetary nebulae),

close second best on 22 nebulae. *NOT* recommended on 6 nebulae.

TOTAL 1st and 2nd RECOMMENDATIONS for OIII: 56 objects.

 

[jetstream]

7 minutes ago, N3ptune said:

It's funny they give the LET with the scope, it's not bad.. but it's not the end of the world either. Maybe I didn't used it enough to appreciate it fully.

So i understand, if i want to use a 2 inches filter on a 1.25 eyepiece, i have to hold the filter in my hand and look through it ?

Jetstream, I am having a hard time understanding that. Could I resume to this:?

My 25mm 1.25" with a 1.25" OIII filter should perform less then my 28mm 2" with a 2" OIII filter? But if the sky is really dark, then the 1.25" setup should give me similar results?

Well, many objects you will see are very big and having a dark edge around it will help things stand out which I call contrast. It is easy to "see right through" a nebula, a great example is the North American nebula which you can easily see in your telescope. Its not a matter of the 1.25" filter performing less, it a matter of maximizing things in our control.

Contrast is everything- dark skies give you contrast, proper filters give contrast on certain objects, proper exit pupil give good contrast with and without filters, wide TFOV gives contrast by allowing the object edge to contrast the sky around it.

Because you have a reasonable TFOV already the 1.25" filter will work well but most likely won't be optimum.

No need for confusion, either get a 1.25" filter or a 2". My feeling is that from your less than dark skies the OIII would be a good first choice. The key to all this is dark skies.

[jetstream]

This image is from when Knisely and others were trying to give a good approximation of what the Veil would look like under dark skies with an OIII, you will get similar views from dark skies. He is using an exit pupil of about 5.3mm, right in the strike zone.