Astronomik UHC / OIII with TV60

[Piero]

In the last five months, I tested my Astronomik 1.25” UHC and OIII on both extended nebulae and planetary nebulae using a very small refractor (Tele Vue 60).

I did not always do a one-by-one comparison on the same night because I did not have so much time and I also wanted to enjoy my session. These tests span over several months and often targets are reported more times. 

All these sessions were in Cambridge, under good seeing and generally clear sky. To give a better indication of the transparency, the milky way is not visible and about 5 stars in Ursa Minor are generally visible. Temperature was from 3C to 18C.

Eyepieces used for testing are: 

- TV Panoptic 24 (15x, 4mm e.p.)

- TV Nagler 13 T6 (28x, 2.2mm e.p.)

- TV Nagler 7 T6 (51x, 1.2mm e.p.)

- Vixen SLV 5 (72x, 0.8mm e.p.)

- TV Nagler 3.5 T6 (103x, 0.6mm e.p.)

(where e.p. means exit pupil).

Although I tried to be as much detailed as possible, I am only a beginner in reporting astronomic equipment. Therefore, please consider this review as an indication of what these filters can offer in a small telescope, rather than a comprehensive comparison between OIII and UHC filters. For the latter, I suggest the review by David Kinsley.

My conclusions:

A small telescope like the TV-60 is not capable of detecting intricate filaments of extended nebulae or faint details in planetary nebulae. Therefore, the point is about spotting the object and perceiving the overall structure, this at least under moderately light polluted skies. In my opinion both the filters can be effective, but they have different applications. (1) I generally found that the OIII can reveal the planetary nebulae that I observed and show their global shape, whereas this the UHC often does not. (2) On large extended nebulae, the UHC is a nice tool for visualising the extension. This is something I appreciate a lot particularly when using a wide field telescope such as the TV60. On the other hand, the OIII can better reveal certain contrasted areas. (3) For targets positioned just above the horizon or if the sky is not fully dark, the UHC worked really well, whereas the OIII darkened the field too much and made the target observation not appreciable. This can be the case for the nebulae in Sagittarius visible at Northern Latitudes in June, where the daylight is long.

I cannot say much about the quality of my Astronomik filters as compared to other filter brands. All I can say is that I have not ever been disappointed with them. Stars (and the nebula) change colours when the filter is applied but this is common with nebula filters. I did not find any sort of image distortion or introduced aberration with my limited experience at least.

So, here is the report (sorted by object class, by catalogue name, by time):

Extended Nebulae

M8 - Lagoon Nebula. Sgr CL+Neb

05/07/2015. 15x +/- UHC or OIII. The OIII was too strong mainly because the sky was not dark enough and this target is just above the horizon. Instead a UHC was ideal and revealed the nebula via direct vision clearly. This is one of my favourite targets in Sagittarius.

M16 - Eagle Nebula. Ser CL+Neb

05/07/2015. 15x +/- UHC. This nebula was only visible with averted vision. Whereas I did not see much difference in the Omega Nebula between averted and direct vision, for the Eagle Nebula averted vision showed a much wider nebula extension.

M17 - Omega Nebula. Sgr CL+Neb

05/07/2015. 15x +/- UHC. The nebula was clearly visible at 15x with direct vision. It appeared as a small but quite dense cloud.

M20 - Trifid Nebula. Sgr CL+Neb

05/07/2015. 15x +/- UHC. The Southern part of this nebula benefitted from the UHC filter and showed a patch of cloud around the cluster. The Northern part of the nebula was not visible instead.

M42 - Orion Nebula. Ori CL+Neb

23/02/2015. 15x +/- UHC or OIII. UHC shows nebula extension. OIII shows more contrast.

C20 - NGC7000 - North America Nebula. Cyg Neb

05/07/2015. 15x +/- UHC. The presence of diffuse nebulosity was visible in the area, but it was not obvious to spot the presence of this nebula specifically.

C27 - NGC6888 - Crescent Nebula. Cyg Neb

05/07/2015. 15x +/- UHC or OIII. Spotting the nebula was difficult though. I suspect it requires a darker sky. With averted vision and a UHC filter, very faint small grey patches were suspected around the nearby stars. A OIII filter made these patches slightly more noticeable. However, in my opinion this seems to be a challenging target.

C49 - NGC2237 - Rosette nebula.  Mon Neb

23/02/2015. 15x +/- UHC or OIII. Detectable with OIII filter. Very soft grey patch. No structure. Invisible with UHC filter.

22/03/2015. 15x +/- OIII. Detectable with OIII filter. A grey patch 2 degree large. No structure visible.

NGC1980 Ori Neb

22/03/2015. 15x +/- OIII. At 4mm exit pupil, OIII shows a bit of nebula around the star Hatsya.

NGC6604 Ser CL+Neb

05/07/2015. 15x +/- UHC. This cluster with associated nebulosity is located at about 1.5 degrees North of the Eagle Nebula. It is a fairly spread cluster without many stars. The nebula shape was not really identifiable, but it was possible to spot the presence of diffuse nebulosity in the area.

IC1396 - Elephant’s Trunk Nebula. Cep CL+Neb

02/07/2015. 28x +/- OIII. Star hopping from Alderamin. Although the nebula was not visible with the OIII filter, it was nice to see this cluster.

Planetary Nebulae

M27 - Dumbell Nebula. Vul Pln Neb

05/07/2015. 15x +/- UHC. This planetary nebula is clearly distinguishable from the background sky and shows up like a grey ball. No detail at this magnification was visible though. Really pretty target.

07/07/2015. 28x +/- UHC or OIII. This is the largest planetary nebula I have seen so far. I am not sure the OIII helped much. Possibly the UHC works a bit better on this nebula, maintaining its extension as well as the nearby star field. I could not see real details, but the sky is not fully dark in this season.

M57 - Ring Nebula. Lyr Pln Neb

13/05/2015. 15x +/- OIII. The OIII filter largely improves the detection of this nebula at 15x. Without a filter, its detection is not easy. It emerges in the sky as a grey little ball. 20/05/2015. 28x +/- OIII, 103x +/- OIII. I tried the OIII filter with the Nagler 3.5 (103x). Although the ring shape was noticeable, it was just too much magnification and the overall image was largely degraded. At 28x + OIII. The Ring Nebula emerged from the background sky and appeared as a colourless bubble. I believe that an exit pupil of 1-1.5mm can improve the view for this target.

26/05/2015. 28x +/- UHC, 103x +/- UHC or OIII. The UHC filter increases a little bit the visibility of this target at 28x, but does not improve the contrast. The object appears as a grey blob without a shape. At 103x the ring was detectable using an UHC filter using averted vision, but this was not easy to see. The ring shape was more noticeable with an OIII filter despite the severe loss in image brightness. Without filter the nebula appeared just as a grey blob and no ring was detectable. Generally, I think an exit pupil of 0.6mm is just too small for nebula filters. It seems to me that 1.0mm is the maximum usable effectively. As this is the exit pupil typically used when observing planetary nebulae, I would say that an OIII filter is a better choice for these targets as it allows to increase contrast which is needed on these targets. Conversely, for bright extended nebulae to watch with low power eyepieces (or exit pupils larger than 3mm), a UHC filter can be beneficial for targeting and maximizing nebulae extension.

03/06/2015. 103x +/- OIII. The ring was visible with averted vision, but no other detail really. The contrast between the ring and the internal area is much more visible with an OIII filter. Still nice planetary nebula.

M97 - Owl Nebula. UMa Pln Neb

20/05/2015. 28x +/- OIII. Interesting target. Completely invisible without OIII filter. With the OIII, it emerges from the sky and the nearby stars. It is a quite large planetary nebula. No colour or shape was detectable, but it simply appeared as a grey bubble. At 15x + OIII was detectable, but was too small to see any major detail.

26/05/2015. 28x +/- UHC. Invisible at 28x with or without UHC filter. This target requires an OIII filter for being detectable with small aperture telescopes. Consistently with what said for M57, the OIII filter is a better choice for planetary nebulae (and for extended nebulae where we want to maximise nebulae contrast).

C39 - NGC2392 - Eskimo nebula. Gem Pln Neb

25/03/2015. 51x +/- OIII or UHC. Spotted it at 15x without filters, but averted vision was required. It appears like a very small patch next to the star. At 51x the nebula is visible as a grey little ball. The boundaries are obfuscated. An UHC filter helps increasing the contrast between the sky and the nebula. An OIII filter shows even more contrast, although I think an UHC filter is better at this exit pupil (1.2mm). Using these filters, the boundaries of the nebula appear much clearer although no structure is visible at this magnification. At 72x (and no filter) is still visible as a grey little ball. Boundaries are obfuscated.

C59 - NGC3242 - Ghost of Jupiter. Hya Pln Neb

06/04/2015. 51x +/- OIII or UHC. This appears as a faint tiny and diffuse light. No structure. At 51x it appears like a little full circle. An OIII seems more effective than an UHC filter here possibly because the planetary nebula is low on the horizon. The OIII filter makes it appear from the sky, whereas really few nearby stars are visible. 72x does not show more detail. UHC filter works fine but does not boost up the object at the same level as the OIII does.

Supernova Remnant

M1 - Crab Nebula. Tau SN Rem

06/04/2015. 51x +/- OIII or UHC. Invisible after trying with different magnifications and averted vision. Filters did not help either. Darker skies are required for this target. Possibly try with an eyepiece at 2.0mm exit pupil.

C33 / 34 - NGC6992 / 6960 - Veil Nebula. Cyg SN Rem

13/05/2015. 15x +/- OIII. No visible, although it is not the best time of the year to see this target.

20/05/2015. 15x +/- OIII. Again, no visible although it is too low on the horizon.

11/06/2015. 15x +/- OIII, 28x +/- OIII. No visible or detectable. I carefully searched the stars and positioned at 52 Cygni. 28x +OIII seemed to show a soft transparent cloud, but I cannot say that that was the Veil Nebula. The sky was not fully transparent and dark. This might be the reason.

05/07/2015. 15x +/- OIII. I did not spot it. After positioning at 52 Cyg, I gradually moved in the surrounding area at South, but was not able to spot any nebulosity. As for the Crescent Nebula, this is a challenging target and I believe it requires darker skies.

[John]

Fantastic report Piero

You have really been thorough with your note taking and descriptions of the effects of these filters.

I still think the Veil is possible with your 60mm scope and the O-III filter under the right conditions. The Eastern segment is the brightest and I've managed to spot that on an exceptional night with 15x70 binoculars and no filter. So worth perservering.

You are really pushing your 60mm scope with your observing. Your observing skills are really well developed and if and when you get a larger aperture scope you will be able to really exploit it to the full

[Stu]

I can only echo John's comments Piero, a really thorough and interesting report, great stuff.

Your findings between UHC and OIII match my own in my 76mm in relation to better contrast with OIII but greater extent of nebula with UHC. Not a hard and fast finding but generally the case.

Objects like the Crescent aren't trivial even with a 16" under dark skies so you are going some with 60mm

I agree with John that the Veil, at least the Eastern segment should be doable under the right conditions ie dark and transparent skies.

NAN also really benefits from transparent skies. I've seen the shape very clearly in 15x50 binos, but under less good conditions in Samos I struggled to get definition even though I could detect where it was.

Keep up the good work, great to see someone pushing a small scope to the limits!

Stu

[Paul73]

Piero

What a well structured and written report. There is a myth the O III are for big apertures only. Obviously, this is not true.

There is nothing wrong with your brand of filter. There seems to be a bit of a completions off the hears and minds of SGL between Lunicon and Astronomik as to which is best.

I've never tried any filters through a nice little refractor. I'm picking up an ED 80 tomorrow / today morning. So I will be able to compare 10" Newtonian with 3"(ish) refractor with my Lumicon UHC & OIII filters.

Paul

[jetstream]

Excellent report Piero! You are honing your observing skills greatly with your 60mm, wait until more aperture wanders your way!  I use the Crescent neb as a test of transparency from a dark site, when conditions are right it sure comes alive!

In my 90mm, the North American neb reminds me of a bright postage stamp kind of- what a strange view compared to the 10", where the immensity of object is revealed. The fracs show the Veil as is described, a wedding veil, again small, bright and compact but in perfect form.

You know, I can tell you just might be a nebula hunter like myself  .... there is so much to see and explore, my upcoming challenge is IC1318 again, but better prepared this time.(need a 2" Hb).

Looking forward to more reports. How about the Cocoon neb/ that sucker is hard for me to see for some reason...

[Paul73]

How about the Cocoon neb/ that sucker is hard for me to see for some reason...

Stick to the Cocoon Galxies. Easier and two interacting galaxies are a lovely sight (8" to 10" +).

Paul

[alan potts]

What can I say that has not been said, a great piece of work. It shows how long you have been working on it when M42 puts in a showing, I haven't seen it for ages.

Alan

[Piero]

Thank you all for your kind words. I would also like to thank Gerry for giving the important hints on the Rosette Nebula and the exit pupil generally; John for providing me with an initial list of candidate targets; and the people on Stargazers Lounge and Cloudy Nights who continuously write reports for the Astronomy community. All these previous reports were very useful for structuring this little work. 

@John. Thank you again, John. I have not given up with the Veil . I will continue observing it through this summer. In August I am going back to my country and also 3-4 nights to the house of my granparents on the Dolomites. There the Milky Way is visible throughout the sky and is one of the best sky I have seen. If the sky is clear, I will test it there with both filters and without. Really looking forward to this! Thanks for the kind words about observing skills. I consider myself just as beginner despite the 'Advanced Member' status. There are many things which to me deserve understanding and investigation and all of this is really intriguing! Another good thing of observing with a 60mm is that a person can focus on specific types of objects (e.g. galaxies and globulars are basically discarded apart from M31, M32, M81, M82, M110, M3, M5, M13, M22 under reasonably dark skies). Somehow, this helps cool down aperture fever and reduces the complexity of target selection that a beginner generally faces. 

@Stu. Thanks for your kind comment, Stu! I agree with you that the Crescent is not trivial at all. I observed that region a couple of times and stayed with my eye at the eyepiece to get as much dark adaptation as I could. Still not obvious. I did not see a shape but there was some very very faint cloud to my eye. I am just a beginner and I could have confused it, of course. This is another target that I will surely look at this August on the Dolomites.  What does NAN mean? 

@Paul. Thanks for the nice comment, Paul. I believe that that myth is due to the fact that small apertures collect less light and so less stars are generally visible. Taking this into account an OIII could 

clear the star field more heavily on smaller apertures than larger ones, I would say. Said this, if one stays with exit pupils between 5-2mm, the OIII works pretty well on small apertures too. This is not my finding, but comes from David Kinsley. I can just agree with this. The only thing I can add which to me makes a striking difference between the usability of the two is when the sky is not dark (due to daylight) and objects are low above the horizon. For those targets (and from the UK, it means those wonderful targets in the Sagittarius) my telescope+OIII was severely affected and often targets were not visible at all, whereas the UHC allowed me to spot these nebulae very easily. These nebulae were not visible without filter. The Lumicon vs Astronomik comparison is something like a Delos vs Pentax XW battle. I never looked thought a Lumicon, but I guess I with my current observing skills I would not spot differences apart from a possible decrease in sky background brightness due to the shorter passed band line. To me the Astronomik filters are excellent not because they are better than other brands (which I cannot say because I have not tested), but because to my eye no aberration is introduced, and they allow you to spot things that without one could not always get. I am exited to read your impressions with your Lumicons and 80ED!

@Gerry. Thanks again Gerry! I like your interpreation of the North America Nebula like a bright postage stamp! I cannot help but agree with you! This is another object in my list for the Dolomites. Really curious to see how it will look like from a very dark sky. I suspected you were a nebula hunter because of the exit pupil thing and the recurrent comments on these targets I have been appreciating nebulae since an amateur astro-photographer took a photo of NGC7000 and gave it to my mother many years ago. It was taken in ~1995 using a film camera. Although not at the level of Olly Penrice's images, it was still spectacular and I was really impressed with it. I might take a picture of it when back to Italy and post it here . Looking forward to reading about your report on IC1318! I love that region of sky surrounding Sadr (Cyg). It must be surely amazing with a 10" telescope, but is also amazing with a simply wide field telescope due to the background dust! Cool stuff! Cocoon nebula.. mm..! I feel intrigued now!

@Alan. Thanks very much Alan for your words. I saw M42 quite extensively with both filters but I only started reporting my sessions in the end of February and by then I moved to other targets. This is why I did not report a more comprehensive description for M42 (whereas I should). With the TV60 at 15x, M42 benefits from both UHC and OIII filters, but in different way. The OIII shows a sublime image where the border between the nebula and sky background really emerges. The same can be said about the North part (that one linked to M43). In the centre of the nebula, some 'waves' were also visible. It is a super target to my eye. The UHC shows a much larger extension for this nebula and this is amazing with a wide field telescope. Small fine details visible within the nebula with the OIII are less obvious with the UHC, but the nebula just appears as massive globally and faint details on the outside borders are accessible as pure diffuse bright areas. Surely all these things are visible and with more detail using a large aperture telescope. No doubt about this. I love wide field views though and easily framing a such large target on from 4.3 to 2 degrees is just awesome to my eyes! At the time I did not have my Nagler 13. I look forward to seeing M42 with it using these filters. That is a nice frame of 2.8 degrees of sky.

[YKSE]

Piero, nice summery!

NAN=North American Nebula?

For NAN and the Veil, I'd that a 32mm plossl will be better than 24mm Pan, the increased brightness with larger exit pupil should have greater impact.

Try the monkeyhead nebula in winter too, you'

ll find much difference between using 24mm and 13mm.

[Stu]

Piero yes, sorry, NAN is North America Nebula, was being lazy

I'm sure you will have good success up in the Dolomites! It's all about dark skies, I could see plenty of the Sagittarius Messiers naked eye in Samos, didn't really need a star map to find my way around the major ones although I did use one for those pesky globs! Too many of them

[Piero]

Piero, nice summery!

NAN=North American Nenula?

For NAN and the Veil, I'd that a 32mm plossl will be better than 24mm Pan, the increased brightness with larger exit pupil should have greater impact.

Try the monkeyhead nebula in winter too, you'

ll find much difference between using 24mm and 13mm.

Thanks Yong! not sure about the 32mm plossl though. I bet it works wonderfully but I promised myself not to buy other eyepieces for a while   .

Monkey head nebula... cool! Sure I will go for it! Thanks for letting me know! 

Piero yes, sorry, NAN is North America Nebula, was being lazy

I'm sure you will have good success up in the Dolomites! It's all about dark skies, I could see plenty of the Sagittarius Messiers naked eye in Samos, didn't really need a star map to find my way around the major ones although I did use one for those pesky globs! Too many of them

Thanks Stu! Yeah, I should have got it! Yes, it's all about dark skies AND good weather! hopefully some nights will be clear. Thankfully I do not have to book anything, but can simply go over there for 3-4 days during the two weeks I am in Italy. Sagittarius will not be accessible due to the mountains unfortunately, but there are plenty of other targets     

[glowjet]

Thank you Piero for a most enlightening and encouraging report on the use of these filters, with a quality small aperture scope.

I say encouraging, because I am somewhat of a lazy Astronomer, who has Baader UHC / O111 and Lumicron filters in his case, but never gets round to using them for viewing specific targets. If old age and health permits ( no violins please ) It has given me the incentive to have a fresh look around the skies this coming Autumn

[Moonshane]

Really impressive report Pierro. I am a die hard dob man but even I have started to appreciate the smaller refractor for observing sessions, especially quicker grab and go sessions.

I agree with your observations in full although with larger scopes you can of course scale up a little with what you can see. In not so dark skies though even a 16" scope will sometimes struggle with the Veil and or Crescent even with an Oiii.

Look forward to hearing more in due course.

Reports like this both inspire and encourage people to get out observing again and to look at familiar and unfamiliar objects even when the skies are less than perfect. It's the sort of thing that SGL is all about.

[Piero]

Thank you Piero for a most enlightening and encouraging report on the use of these filters, with a quality small aperture scope.

I say encouraging, because I am somewhat of a lazy Astronomer, who has Baader UHC / O111 and Lumicron filters in his case, but never gets round to using them for viewing specific targets. If old age and health permits ( no violins please ) It has given me the incentive to have a fresh look around the skies this coming Autumn

Really impressive report Pierro. I am a die hard dob man but even I have started to appreciate the smaller refractor for observing sessions, especially quicker grab and go sessions.

I agree with your observations in full although with larger scopes you can of course scale up a little with what you can see. In not so dark skies though even a 16" scope will sometimes struggle with the Veil and or Crescent even with an Oiii.

Look forward to hearing more in due course.

Reports like this both inspire and encourage people to get out observing again and to look at familiar and unfamiliar objects even when the skies are less than perfect. It's the sort of thing that SGL is all about.

Thanks for your nice comments John (glowjet) and Moonshane.

If you feel that this report encouraged you and people on SGL, I feel really honoured! I have been encouraged from this community as well, and as I said, without all of you people I would not have been able to write this report. 

@Moonshane. I do love Dobsons, and I will be more than happy one day when I will buy one. At the moment portability is a strong constraint though, and the tv60 fits the bill nicely. An OOVX10 or a truss 10" F5 like the one you sold to Rob (Qualia) are on my wish list!

[Piero]

Last night I had a wonderful session out and new targets were tested with the OIII filter.

The observation was done quite late and therefore the sky was generally darker. 

Full report is here:  http://stargazerslounge.com/topic/248515-an-enjoyable-night/

I decided to open a new thread as many other objects were described. 

That report offers an additional appendix reporting: 

- Veil Nebula (I finally managed to see it! wow!)

- Heart Nebula

- Soul Nebula

and other observation for the already mentioned: 

- Crescent Nebula

- North America

- Eagle Nebula

- Omega nebula

Cheers, Piero

[allen g]

very nice report and very much appreciated.  When it is said that these filters are only suitable for large aperture scopes - they are wrong.  I find they very useful in my TV 101.  They work very well more so at dark sites. thanks allen g