Wrinkling out Phobos and Deimos

[Bombardon (Eugene)]

Recently I unearthed a 12.5 mm Plossel to which I glued a thin slice of tinfoil at the secondary focus to form an occulting bar. Some 16 years ago I had no trouble using the bar to block out Mars and a very early Cartes du Ciel program to find these two elusive rocks circling Mars in my 16”{ F7 dob. In similar conditions at the time I was able to spot Deimos in an 8” F9 dob. Now, with Mars putting in a much less favourable show I have been watching its close approach and failing to find its companions in damp skies over the past two weeks with my F5 10” dob.
Last night everything changed. Dry westerly winds whipped the garden all day but by late evening wind had abated and the cobalt sky looked promising. I was so determined last night I wore sunglasses to watch the evening news on TV and even cleared up early after dinner to insure no kitchen light interfered with my darkened by yard. My wife was most impressed.
Outside, back steps handrail was dry and cold. First time this season and very promising.
Jupiter looked steady but not crisp. I hopped about from M 83 to Centaurus A and felt conditions looked good. At 160X Mars had some markings but still assumed the marshmallow look I was so familiar with. I waited some time to let it clear the low horizon and had a pleasant view of the Leo Triplet with various eyepieces.
My Cartes du Ciel showed the rocks both on the western side of the planet and as far removed in their orbits as possible at 9.30 pm local time. Now using a nameless 2X Barlow and the 12.5mm adapted eyepiece, I searched ahead of the drift. A field star seemed too far way and too bright to the west of the disc but was useful in making focus as sharp as possible. I lined up the bar so that the planet drifted through it correctly and I watched several passes. After some gentle pushes East, finally two sharp twinkling points of light just caught my eye quite close to the western edge. I repeated the process several times. Then I removed the eyepiece and tried a Meade HD60 9mm untampered eyepiece. The field star immediately grew dimmer and glow surrounded the planet. However, after several tries by pushing the planet out of the field east, one tiny spark could be seen just before the disc appeared. Mars still retains its marshmallow look from my backyard!
Some tips that may help: I am no expert but some eyepieces are unsuitable for the task. You must select one whose focal point is outside the field lens. My sliver of tinfoil covers about a quarter of the field in the eyepiece. By looking through the eyepiece with the slider removed and using the tip of a pen while looking through the eyepiece you can roughly find the focal point. When tinfoil is glued in place adjust it centre with a pen tip until it displays sharp edges and then leave to dry. Cartres du Ciel has come a long way and is now an excellent downloadable free program. Zoom in until Mars become a clear disc with markings and then start using hour shifts and then 5 minute shifts to find the best separation of the moons. I have only tried with both satellites lined up either east or west and close together but as far from the planet as possible. The fainter Deimos has the wider orbit but don’t expect differences in brightness. Well worth a try even in a 6” or 8” glass.

[Stonius (Markus)]

Nice recounting of the tale. You've inspired me to have a go!

[Tinderboxsky (Steve)]

I enjoyed your report Eugene. Thanks for sharing.
I have Phobos and Diemos on my list for this opposition. Am just waiting for the right seeing conditions.

Steve

[mental4astro (Alexander)]

Originally Posted by Stonius

Nice recounting of the tale. You've inspired me to have a go!

Ditto!

Ta Eugene. I'll have a go tonight. A good separation phase with both on the same side happens tonight at around 11pm AEST, so I'll start looking around 1/2 hour before hand.

I like the idea of the field mask of the eyepiece. I'll look to knock up something similar for the task too.

Alex.

[kinetic (Steve)]

Great story Eugene,

I consider nabbing Deimos with my rig, although by imaging, one of
my favourite personal achievements in this hobby.
I'd love to have a go visually, might give it a try,

cheers,

Steve

[Bombardon (Eugene)]

Thanks for the encouragement all. I have checked Cart du program and Alex is right - although I make both sats east, with Phobos about 12" and Deimos about 50" around 11.30 pm. tonight. Open to correction here as these programs are not my strong point Eugene

[Bombardon (Eugene)]

When I study your photo more closely, Steve, I realise what a scoop that was to record the glimmer within such glare. Great achievement. E

[ausastronomer (John Bambury)]

Hi Eugene,

Nice report. I haven't tried for these 2 moons in recent oppositions. The last time I hunted them down was during the 2003 opposition in my 10"/F5 dob. They were very tough targets in that aperture during a very favourable opposition, with Mars being about 24" in apparent size. I subsequently observed them both again during that opposition in Andrew Murrel's 20"/F5 dob Hector. However, that opposition was one of the best in the past 50 years and this one is not near as good. Consequently, those people searching for them in telescopes <14" or 15" aperture shouldn't get too disheartened if they don't succeed, as they will be very difficult in smaller apertures.

Good luck everyone in the hunt !!!

Cheers,
John B

[Bombardon (Eugene)]

John, I would not have tried in my 8' F9(!!) in 2003, except I had succeed in the 16" on the same night and Mars was very large then. It took me several nights with careful planning to recover them in the 10" this year. The occulting bar makes all the difference as all the glow suddenly disappears and even nearby background stars appear.
I do have happy memories of Hector as it gave me my first real view of the Homunculus, and that must have been nearly 20 years ago, when Winuna's star parties needed freezer suits! Kind regards, Eugene