Hanny's Voorwerp

[Jerry Morris]

Last night, Jimi Lowrey and I attempted to observe Hany's Voorwerp in Leo Minor. Jimi is very familiar with this object, having viewed it before in his scope, so we were curious if this object was obtainable in my 30" scope. Jimi brought his collection of Zeiss and TMB super monocentric eye pieces and a Sloan G filter to assist in the effort, and had a printout of the object's location in the star field for reference.

We knew this would be as tough catch, so we observed various planetaries for about an hour to get completely dark adapted and to wait for good sky placement of the object. Sky conditions were generally good, with transparency about 7 (of 10) and seeing about 5 (of 10). At about 10:30 PM, we slewed the scope to the LEDA 165538 galaxy and started the effort. The scope was at about 75 degrees altitude.

Jimi, being familiar with the object's placement in the star field, positioned the scope and tried various eye pieces, and sure enough, after patiently waiting for what sky conditions would reveal, got a few "pops" of the object with averted vision. The better eye piece choice seemed to be his 10mm ZAO2 Zeiss, with a Sloan G filter, presenting better contrast and matching the sky seeing conditions. Then I took a turn, and after several minutes of waiting for sky conditions to co-operate, got three distinct "pops" with averted vision. Jimi then tried his 9mm TMB super monocentric with Sloan G filter, and got a few "pops" with it as well. I tried that eye piece combination and got one "pop". We decided that the 10mm ZAO2 seemed to match the sky conditions better, and during the hour long attempt while the scope was trained on the object's star field, Jimi was able to hold the object with averted vision to the count of 4. I got a total of 7 "pops" during the evening's effort, and told Jmi I was pleasantly surprised we could actually capture these elusive photons in my scope. We both commented that a night of excellent seeing and transparency would definitely help in observing an object like this one, which is clearly on the ragged edge of my scope's capability.

It was a definite benefit having Jimi present with his advanced observing skills and excellent eye pieces and filter, and I'm sure that made the difference for me between success or failure on an object like this.

[Jimi Lowrey]

On a night of not so good seeing The Voorwerp was not that difficult with the Sloan G filter, if we did not have the filter I do not think we would have seen the Voorwerp. With Jerry's excellence tracking with his scope all we had to do was be Patience and wait on the seeing. I think it will be direct vision on a good night with the filter. I also think it could be seen in a smaller scope under good conditions with the Sloan G filter and high power.

This is my sketch I did some years back with my 48" and no filter.

122

SDSS image

123

[Howard B]

Impressive observation Jerry and Jimi! Where do you get a Sloan G filter, and why is it a good choice for Hany's Voorwerp?

[Jim Chandler]

The SDSS used a ugriz filter set developed by Jim Gunn. If I recall correctly, it was Bill Keel of the University of Alabama who suggested that the Gunn g filter might be useful in pulling out Hanny's visually. Specifically why he suggested it, I don't know. Astrodon sells the ugriz filters.

[Jimi Lowrey]

Howard the Sloan G passes 401/550 NM which from the spectral image of Hanny's Voorwerp is right in the Middle of the OIII line that the Voorwerp is strongest in.

Bill Keel or the University of Alabama who is the lead investigator on Hanny's Voorwerp suggested to me that the Sloan G filter should enhance the Voorwerp visually from his work on the spectra and as it turns out he was right on. you can get the Sloan filters at Astrodon.

http://www.astrodon.com/products/filters/astrodon_photometrics_-_sloan/

[FaintFuzzies]

Hanny's Voorwerp is an O-III object - basically a huge galaxy sized object next to the galaxy....but it was determined (I think from Dr. Keel's paper/research) that it sits between 600-700k light years away...so the O-III lines of the object is red-shifted to about ~530nm from 501 and 496 nm...which is beyond the cutoff of traditional "nebular" filters, such as O-III, NPB, UGC, etc... The Sloan G filter passes everything from 400 to 550mn, while rejecting everything else...

When I observed it with Jimi's scope with and without the Sloan G filter - it was night and day.

I observed it for the first time without the filters back in 2009 as we tried various filters and all seemed to kill it. I don't remember if the CLS didn't completely extinguish it like the others or not. I'm at work, so I don't have my notes handy. Perhaps Jimi can comment.

[Howard B]

Thanks everyone, the Sloan G filter is on my list now! What other objects do well with this filter?

[Jimi Lowrey]

Howard, I used it on the faint outer halo of the ghost of Jupiter the other night it brought out the faint haze really well. I get some response to some PN and none in others . One thing that you will see is that how much it improves the contrast it dims down the sky brightness slightly and helps the contrast a lot.

[Uwe Glahn]

Together with Frank Richardsen we tried the Voorwerp with my tracking 27" under good transparency around NELM 6m5+. F

First thought: "no chance", second thought: "lets try"
First we tried the ideal AP, we decided to take 586x, around 1,2mm AP. We used and tried no filter. First the neighborhood:
- IC 2497, direct vision, 1:2 E-W elongated with brighter nucleus
- 2MASXJ09410675 3443565 steadily with averted vision, small, round
- 18mag star 1,9'S with averted vision
- faint 18bmag+ galaxies N not visible
Than we start to look after Hanny's Voorwerp. In a 30 minute "Voorwerp-action" I could see a very faint but clearly laminar glow next to the IC. Sometimes it seems to be connected with the IC galaxy. During the whole time it glimpsed 5-6 times. I could not hold it, but the glimpsed position was to exact to forget the action. Frank independent saw exactly the same detail.
All in all absolute hard to detect, but we think we got it. Now it would be very interesting how the neighborhood looks in Jimi's 48" and Jerry's 30" to say when the Voorwerp could be seen.

[deepskytraveler]

I am privileged to be doing an observing run this week with Jimi Lowrey on his 48" along with Dragan Nikin and John Spack. Last night, 23-24 March, sky conditions were very good (compared to central Ohio) with transparency 7 to 8 (of 10) and seeing above average to average. Around 2:30AM CDT we made our second attempt at Hanny's Voorwerp. The previous night we had tried it but with seeing below average none of the four observers were able to report a positive observation. Using a ZAOII 10mm eyepiece at 488X with a Sloan G filter, the spiral galaxy IC2497 was visible constantly with direct vision. Another faint nearby LEDA galaxy was also visible, mostly with direct vision. Hanny's Voorwerp required averted vision and moments of excellent seeing to pop into view. When it did I saw a diffuse glow about half the size of IC2497 and extending nearly to the galaxy. Over a period of five minutes or so, it popped in and out over a half dozen times and staying visible a few of those times for 15 to 20 seconds. A difficult observation, but well worth the effort to become one of less than twenty people who have observed it visually.

Mark Friedman in Ft Davis, Texas

[Hanny]

Just thought to say hi in here.. so.. hi :)

[FaintFuzzies]

Wow! Thanks for joining and welcome to DSF, Hanny!

[FaithJ]

Hello Hanny. :)

[Hanny]

Hiya and thanks for the welcome :)

[Marko]

From the details Alvin has brought out about the red-shift to about 530nm it would seem the Johnson/Cousins V filter may offer improved contrast for this object over the Sloan G given a large scope. The Sloan G is 150nm wide at that point with near 100% transmittance so it wins with transmitted light (important here of course). The Astrodon version of the V filter is by far much narrower in the 530 area and is tapering off in this range. The V is about 50nm wide but sloping off from it's peak of 94% at 520nm, 91% at 530nm, 86% at 540nm, 83% at 550nm where Sloan G drops like a rock. At 10% transmission the V is 140nm wide which approaches the Sloan G bandwidth of 50nm but is well down.

Marko

[Dave Tosteson]

Jerry and Jimi, I tried for Hanny's at the 2011 TSP with my 32"f4 with no filter at 361X, about 2345 CDT. It was only 22 degrees above the horizon, and conditions were obviously not ideal. This was a negative observation, and I would like to try for it higher in the sky. The Astrodon filter sounds like it would help quite a bit. I heard of several people at the 2012 TSP that were able to view it in Larry Mitchell's 36".

Dave Tosteson

[FaintFuzzies]

Dave,

That is correct. Jimi and I were among that group who observed it with Larry's 36". It was tough, but there. Also it was pretty high up as well in April versus June in TSP 2011.