Abell 85 (CTB 1)

I've been trying to see this ghost for many years with absolutely no success - not a hint of nebulosity through 20 and 28 inch scopes under 21.95 SQM skies at 7400 feet altitude. I've tried OIII, UHC, h-beta and broad band filters to no effect except to become familiar with the star field and the chains of faint stars that try to mimic nebulosity. That, and I've enjoyed the nice open clusters all lined up nearby.

In short, I've given Abell 85 my best shot under great skies several times with only negative observations to show for my efforts. I'm not discouraged, and plan on continuing to observe until I do see some nebulosity here, but I've started to wonder if I'm using too large a scope. Would I have a better shot with a smaller scope and it's much wider fov than continuing to pound away with my 28 inch?

I'm sure there are a few observers here who have seen Abell 85 and I'd be interested in your observations, scope, filters and sky conditions that you used to see some nebulosity in Abell 85. Many thanks!

Howard,
I dind't try Abell 85 so far (you will see why when you view my signature :-)
The only observation I know is by Uwe Glahn (http://www.deepsky-visuell.de/Projek...orderungen.htm, scroll down), with 27" f/4,2 and OIII filter from a site that is considered one of the best sites in the Alps, at nearly 8500ft altitude. I would like to take the liberty and try to translate his observation report (because he is gone for a few days if my information is correct).

16", 110x, [OIII], NELM better than 7mag
nothing visible

27", 113x-172x, [OIII], NELM better than 7mag
Brightest [OIII] areas lie east of 9,5mag star GSC 42853095. Extremely difficult star field - high star density and many star chains. Best at 172x, nebula is very faintly identifiable with indirect vision as a faint brightness step - a dozen stars and the GSC star as S end form a 5'x3' N-S oval, which shows a distinct brightness edge in its centre, whose O is brighter than W; but the nebula isn't visible as such; a similar, but even more difficult edge is hinted 7,5' S of the GSC star; nothing visible of the other areas glowing in [OIII].

Maybe he will add something himself?

Greetings from Germany,

This is an object that I had not been told beforehand how difficult it was and I love the NPB filter and was at an amazing site on a night with great transparency. In short I have never seen it so well ever since. This was an unmistakable observation and it was studied for some time due to it's large size and difficulty. Here is that observation. Only two other times since was I even able to barely detect only the very brightest 7' or so SW segment, one of these time I had confirmation by Mark Wagner, once with Carter. In all cases I used a cloak over my head for 10-15 minutes and viewed with the skyglow shielded by this cloak which I have found is a real valuable approach for many very dim objects. This same night at Chew's Ridge I had my best views of Bubble nebula as well as Cave Nebula so something was just right this night at 5500 feet.

Here is my observation from Chews Ridge at 5500 feet and I will add that at Lassen 8000 feet a year later I was bairly able to make out it's brightest part so I feel I was very lucky on the attempt shown below with 18" f/3.7 dob absolutely use NPB filter.

ABELL 85 Cas SNR 23 58 53.5 +62 30 28 30.0x 2.0' Abell_85_Area: NPB filter offers best view. Best to find this is to move 40' N of Ngc7788 to a 6' EqTriangle of mag 9 stars, then 11' NNE to a mag 8.8 star that is 2/3 of the way west and just on the S of the brightest 1/3 arc of Abell85 [Star is HIP118148]. This is a very faint object overall. The full 1/3 of a circumference that is visible is about 2 fields [45'] in a slight curving arc like a bowl with opening to the north. The thickness varies with some wider section mostly to the western side of the arc but much of the arc is about 1/20fov [1.2'] wide. Moving just to the west along the arc from the main field star that sits just on the S boarder of the arc there we see a fairly thick part that is thicker than almost any other area I can see along the full arc. P4 APN 09/11/10 01:25 ChewMira 216 9mmNag 18SmF3.7Pc NELM 6.6 21.5 mag/arcSec

Howard,

I have never tried Abell 85 for some reason? Big Jim Chandler and Steve Gottlieb are coming in today for a observing run and the weather looks good for tonight.

We will (give it a go and let you know.) I hope you have clear skies out in the North west!

If anyone has a NPB filter from omega optical use it. O3 is almost not present. The eye is bad at Halpha but I think there is some abilty and u all have 48 inch but its low so I wish u excellent transparancy, its needed.

Hi Mark,

Excellent! I had tried this S/SW section also many times with H beta and 22", but without success. Not even a hint of nebulosity. This is probably for excellent conditions only.

There are now some narrowband images of this SNR that show that the OIII-brightest part is different from the HII-brightest part. The most prominent section in OIII is the E section. There is an excellent image by Mischa Schirmer
http://www.astro.uni-bonn.de/~mischa..._ccd/ctb1.html

But also on this E section, I had up to now no success :-(

Hey Mark, what a great observation of Abell 85! I'm completely stoked to keep at it but I'll need a dark and exceptionally transparent sky - no surprise but those are in real short supply up here. And thanks for the tip to use the NPB filter, I'll use it next time - I didn't have this filter the last time I had good enough skies to give Abell 85 a shot.

Thanks for posting those links on the OIII vs Ha differences specific to Abell 85. I have wondered if there was some sort of calibrated test that was able to detect eye sensitivity in ultra low light at H-Alpha wavelength. I have seen in my own shootouts that certain objects high in Ha show up much better in the NPB filter and yet there is supposed to very poor sensitivity (near zero) by the rods in our eyes at the Ha bandwidth of 656nm yet the NPB specs point this out as a 'feature'. My #1 filter is generally NPB and only after that do I even try OIII. There are certainly advantages to OIII for certain objects (PNs mostly) but more often than not for the emission nebula I find the NPB is one heck of a great filter. Where an emission nebula puts out Ha there is generally H-beta as well but at only a fraction of the Ha strength. From what I can tell the NPB just barely also catches the H-Beta and this may be the bulk of what offers the NPB a stronger view on certain objects. Thanks again for the link.

Quote:

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Originally Posted by Jimi Lowrey

Howard,

I have never tried Abell 85 for some reason? Big Jim Chandler and Steve Gottlieb are coming in today for a observing run and the weather looks good for tonight.

We will (give it a go and let you know.) I hope you have clear skies out in the North west!

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Good luck tonight Jimi, but Abell 85 is in Cassiopeia so you'll do better to wait for late spring or summer to give this one a shot. We have a pretty good night here so far - mostly cloudy but no rain! Clear nights are mighty rare out here this time of year but I hope you guys have a great one. Say hi to Steve for me.

Hi Howard,

I've seen it at least twice with my 22". The key is very low powers. My two observations were at 75x with the O-III filter. I saw only the brightest part at the 5 o'clock position near the mag 8.7 star.

Jimi,
Let me know if you are successful with your 48". I suspect that you should be even at your lowest power, which is probably closer to 150x.

I found the OIII kills it relative to NPB in a noticeable way. That I have revisited and confirmed. But with 22" maybe there was enough to get through the OIII.

I did not know Jimi's scope could go that low. Next year though 48" would absolutely pull it in. Here is just the comment part of a 10/2010 observation from a site at 2000 feet in mag 21.4 skies. I had not prepared with all the closed eyes and hood so much for this one. That may have also made a difference. Mark Wagner has better detection than myself and he described more that I was able to see this time.

Abell_85: NPB filter was better than OIII. Mark Wagner saw it and described well to me. I was thinking it was only just detectible. My Chews Ridge observation from the month before was far easier to detect the extent. OIII filter wipes it out for me so is not the best filter for this object.

Lastly since this is 'the abell 85 thread' here is all I got at Lassen Bumpass hell lot on 7/29/11

Abell_85: NPB filter is best. Both Carter and I saw the western most apparent segment of this very dim object. I am unable tonight of tracing the large north facing arc much more than 10' max near this point to the west of the visual arc. ... [cut out the rest which is description of the star hop to find the brightest segment]

Also of note: Carter and I were both able to see Cas-A SNR brightest segment this night but that is a thread yet written and I thank SteveG for mentioning Cas-A earlier that year.

CTB 1 is one these giants in my list so I tried it several times under rural conditions but without any success using my 20inch. Using a [OIII]-filter may cause "lots of filaments" (like the case of S 147) .

If I remember right, a buddy of mine, Frank Richardsen, told the me, that he was able to see the Nebula using 130mm TMB binoculars under excellent conditions in the Alps in Switzerland.

regards , Jens

Thanks Mark for the comment. I don't have an NPB filter, but planned to get one soon. Perhaps someone at the TSP vendor shack would carry one. I have to say, it was TOUGH! Perhaps that is why you see it a bit better than I do and you are using a slightly smaller scope.

I'll give it a go when I go out next time. Shneor has an NPB filter.

Quote:

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Originally Posted by Jens Bohle

CTB 1 is one these giants in my list so I tried it several times under rural conditions but without any success using my 20inch. Using a [OIII]-filter may cause "lots of filaments" (like the case of S 147) .

If I remember right, a buddy of mine, Frank Richardsen, told the me, that he was able to see the Nebula using 130mm TMB binoculars under excellent conditions in the Alps in Switzerland.

regards , Jens

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This is really interesting Jens - a 130mm binocular sighting of Abell 85! I've suspected a small scope might have a good chance of seeing it, but certainly a large binocular would do better. Do you know what type of filter your friend used for his observation?

Howard,

I have no idea which filter he used, but I assume that he has put some [OIII]-filters in the eyepieces.

regards, Jens