Uranus’ moon attempt, Sycorax – failed effort despite mag 21.8 stars!

[Dennis]

Hello,

Inspired and encouraged by Jeff’s recent work in recording Sycorax, one of the (very) faint outer moons of Uranus, I decided to have a go myself after a recent success with Nereid, a (relatively) bright moon of Neptune at magnitude 18.72.

First of all, I visited the NASA JPL HORIZONS on-line solar system data and ephemeris computation service to plot the position of Sycorax over the period of 4th to 5th October 2008 at 1 hour intervals. This would give me the RA and DEC coordinates of Sycorax. The data retrieved from my request indicated Sycorax should be at 23h 24m 17s and -04° 39’ 22” (J2000 epoch), at a magnitude of 21.25, much dimmer than Nereid’s 18.75, gulp!

After setting up and converting the HORIZON J2000 coordinates to the Current Epoch coordinates, I slewed the ‘scope to the expected position of Sycorax and took a 5 minute exposure just to record the field stars to compare the FOV with The Sky Pro 6 to make sure I was in the correct region. A small move of the ‘scope was required before I began the series of 5 x 30 minute exposures. The night was quite warm so the ST7 struggled to get down to -8 °C below ambient. After 2 ½ hours had passed, I took 3 x 30 min Dark Frames and 15 Flat Fields before crawling into bed, with Orion climbing up the ecliptic.

After processing the data and producing a “normal” and a “negative” image, I was disappointed not to find a trail of some sort, potentially identifying the target, Sycorax. Hmm, did I go deep enough? My favourite technical Planetarium program, The Sky Pro 6 only went down to around magnitude 19 with the USNO-A2.0 stars (6.3Gb download with 526,280,881 stars) so it was time to check the on-line USNO-B1.0 charts (over 80Gb with 1,036,366,767 stars) and Palomar Observatory Sky Survey (POSS) Plates I and II to see if anything turned up.

After becoming familiar with the website and web-based query form, I was soon downloading USNO Star Chart, POSS I & II images and Tables of Stars listing their position and magnitude. Using this data, I was able to establish, with reasonable confidence, that I had candidate stars in the range 21.0 to 21.8 magnitude but alas, had somehow missed the elusive Sycorax. Either I had the wrong field or maybe the movement of Sycorax spread its dim light out such that it was too faint to be recorded even on 30 minute exposures.

Oh well, hereon I’ll stick to objects brighter that mag 20 and leave the fainter stuff to Jeff!

Equipment details:
C9.25, F6.3 Reducer/Corrector, ST7E CCD camera.
5 x 30 minute exposures auto guided using the dual chip (TC211) of the ST7.

Composite details:
Pane A: Original CCD image (5x30 min exposures).
Pane B: Negative image to help reveal fainter stars.
Pane C: USNO-B1.0 Chart – no labels (10x10 arcmins).
Pane D: Corresponding USNO-B1.0 DSS Plate from POSS I & II data.
Pane E: Central crop of Pane B.
Pane F: USNO-B1.0 Chart – labels (10x10 arcmins).

Cheers

Dennis

PS - This research has made use of the USNOFS Image and Catalogue Archive operated by the United States Naval Observatory, Flagstaff Station http://www.nofs.navy.mil/data/fchpix/).

[h0ughy (David)]

wow fantastic - looks like the hunt was the main fun. Simply outstanding Dennis, even though you missed it , this is awe inspiring!!!

[Kevnool (Kev)]

Its amazing the amount of work and your putting into your images......i,m impressed....cheers Kev.

[Dennis]

Thanks Dave & Kev, I appreciate your comments.

This was a fairly serious undertaking compared to my usual “point and click” space tourist approach! The whole journey turned out to be a bit of a roller coaster ride as I felt for sure that I “should” have recorded Sycorax.

After acquiring 2 x 30 minute frames I “blinked” them using the “blink comparator” in CCDSoft and lo and behold, I saw what appeared to be a body moving between the 2 frames. However, in the fullness of day and with another 3 sub frames of 30 minutes, it was evident that the “moving body” was an imaging artefact and not Sycorax.

However, I had some real fun exploring all the various web sites and tools to help with my search and the whole process certainly gave me an insight into the more serious side of astronomy. I’m glad it’s a hobby and don’t have to meet goals and objectives and get measured against key performance indicators in order to earn a salary!

I also learned a little more about CS3 along the way.

Cheers

Dennis

[deadsimple (Ash)]

Originally Posted by Dennis

I decided to have a go myself after a recent success with Nereid

Nice work though. Despite not meeting your goal, what you learned during the whole process was just as interesting and probably more informative than just having a pixel or two show up with no work/effort

Keep it up, you've inspired me to take a more serious approach to amateur astronomy .. I only got into it a couple of weeks ago and like seeing a glimpse of possible future activities I could undertake with better equipment, greater knowledge of available resources, and patience. Waving a Dob around like I do right now seems so Neanderthal in comparison

[theodog (Jeff)]

Hi Dennis.
Absolutely teriffic effort.
Sorry, I'd been away and just read your post.
Is it possible for you to e-mail me 2 original images? I know they will be big.
I'll have a look for you. I can't do it with the jpeg's.

Also don't give up. I thought my limit was 20, but kept trying. When things click it becomes easy. I'm now trying for fainter.

Again great effort and research, and congratulations.

[theodog (Jeff)]

Hi Dennis,
Just checked with Guide 8 and your field is spot-on.

From the above Minor Body site it gives a brighter mag than you have.

[Dennis]

Hi Jeff

Thanks for your offer to have a look at my images and also, a big thank you for confirming that the field was okay. I have since discovered that Starry Night Pro Plus 6 has all the faint moons of Neptune and Uranus but when I plotted Sycorax, it was outside my field.

So, it seems that the NASA JPL HORIZONS site is the best source for generating ephemerides for these faint objects.

Good luck with your “going fainter” project – I look forward to the results.

Please PM me your e-mail so I can send the files.

Thanks!

Dennis

[theodog (Jeff)]

OK Dennis.
I have looked at your images from several angles. Blinked them, Neg'd them, adjusted contrasts etc.

Fed them into astrometrica to produce the returned image.
Details gained;
Time of start 4-10-08 at 22:26 EST
Time of exp 30min
Cooling ~-12
Focal length of system -bloody close to 1339mm
Camera orientation 89.7deg ie top of frame is east.
The red cross indicates the measured centre of the frame.
**the FITS header indicates a "lunar filter"?

Now the good news,
I believe, from Guide 8, that the object in the indicated position IS Sycorax.
It has the correct position and direction of movement.
The second frame you sent was ever-so-slightly focus shifted and drifted, (I have that same problem often) so image is very difficult to see due to its extreemly low level of registration.

In short, I believe you have imaged Sycorax.
Well done and congrat's.

[Dennis]

Hi Jeff

Thanks for the analysis – I appreciate your time and effort in running my images through the various applications and analysis procedures to produce the results.

Hmm, it’s a faint sucker all right. The sky conditions were pretty awful at the time; very hazy and of course, the light pollution from being only some 7kms from the CBD. This result has certainly encouraged me to try again from a darker sky site whilst Uranus is so favourably positioned for us in the S hemisphere.

The “Lunar Filter” is CCDSoft’s designation for “No Filter”; that is, just the empty hole in the CFW8A filter wheel with no filter fitted.

Thanks again for all your help – it is much appreciated.

Cheers

Dennis

[h0ughy (David)]

Originally Posted by Dennis

Hi Jeff

Thanks for the analysis – I appreciate your time and effort in running my images through the various applications and analysis procedures to produce the results.

Hmm, it’s a faint sucker all right. The sky conditions were pretty awful at the time; very hazy and of course, the light pollution from being only some 7kms from the CBD. This result has certainly encouraged me to try again from a darker sky site whilst Uranus is so favourably positioned for us in the S hemisphere.

The “Lunar Filter” is CCDSoft’s designation for “No Filter”; that is, just the empty hole in the CFW8A filter wheel with no filter fitted.

Thanks again for all your help – it is much appreciated.

Cheers

Dennis

might be a trip out to Ron's or Pauls place Eh Dennis

[AlexN]

Dark skies may definitely help..

Great effort Dennis. 30 min subs

[Dennis]

Thanks Dave & Alex, your appreciation of the results provides me with encouragement to try again at a darker sky site.

I’d particularly like to say a big thank you to Jeff for not only blazing the trail with his incredible efforts previously, but also for mentoring me in my efforts.

Without his encouragement through the Ice In Space Forum, it is unlikely I would have even dreamed of attempting Nereid, let alone Sycorax.

Alex: Up until my attempt at Nereid, I had been really struggling to get consistently successful 3 minute subs with the EM200 at fl’s upward of 1250mm, until I took a wooden mallet to it as per the Astrophysics “how to adjust the worm” web page instructions – yes, that’s right, a wooden mallet!

Cheers

Dennis

[Matty P (Matt)]

Amazing work Dennis! The amount of work that goes into the preparation for something like this is definitely inspirational.

Congratulations for capturing it as well. Fantastic!!!

[AlexN]

holy crap! Taking a mallet to a tak mount. brave man dennis. If it works though.. I suppose its all good.