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Old 28-07-2018, 12:15 PM
Insomniac
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Phobos and Deimos spotted!

Finally! I'd always hoped to see Deimos, but never quite expected to see Phobos as well, let alone at the same time. This was around 10.30 p.m local time 26 July here in a north Auckland suburb - despite the nearly full moon nearby. Both were around greatest elongation.

Equipment: 20 inch motorized Obsession, Paracorr field flattener, University Optics 12 and 9mm orthoscopic lenses. Ladder!

The hardest part was placing & keeping Mars only JUST outside the edge of the f.o.v. with the smallest of nudges and lots of overshooting mistakes.
Phobos was no more that a Mars' diameter away and within a faint diffraction spike, and Deimos much further away on the other side.

My wife saw them too. The positions of both matched up with their positions as predicted by Skysafari and Skytools and with respect to the direction of drift in the fov with the scope's motors disengaged.

For comparison, Sirius B is much easier to see in this scope, with no need to put Sirius outside the f.o.v. I suspect that having seen these now will make them much easier to spot in future as long as the seeing is quite steady.
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Old 28-07-2018, 12:20 PM
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Merlin66 (Ken)
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Well done mate!
An occulting bar would have made things a bit easier......
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Old 28-07-2018, 12:38 PM
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I guess so. I'm a bit lazy, but must try that next time!
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Old 28-07-2018, 03:20 PM
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Tinderboxsky (Steve)
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Yes, excellent catch. I am hoping to do the same over the next week or so.
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Old 28-07-2018, 03:36 PM
Tropo-Bob (Bob)
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OMG; well done.

I have given up on the idea. Too difficult!

I have enough trouble seeing Saturn's moons in the glare.

Last edited by Tropo-Bob; 31-07-2018 at 03:55 PM.
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Old 28-07-2018, 05:26 PM
Insomniac
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Seeing them was quite a coup for me, but then it's tempered by people saying that both should be well within the capabilities of much smaller apertures.

So if anyone's seen them in scopes much smaller than 20 inches, more credit to you!
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Old 29-07-2018, 04:43 PM
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Imaged the little buggers last week. LX90-10" @ f/20 with Grasshopper Express mono videocamera. 5 second exposure. No chance to see them in 10" though ... this is one for the cams.

Sky Safari screen shot at the same time for reference, and Mars at frame rate.

Regards,
Tony Barry
WSAAG
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Last edited by tonybarry; 29-07-2018 at 04:47 PM. Reason: [EDIT] added pic of Mars
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Old 29-07-2018, 04:49 PM
Insomniac
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Nice! Buggers they are, too!
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Old 29-07-2018, 11:17 PM
ausastronomer (John Bambury)
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Quote:
Originally Posted by Insomniac View Post
but then it's tempered by people saying that both should be well within the capabilities of much smaller apertures.

So if anyone's seen them in scopes much smaller than 20 inches, more credit to you!
Nice effort. They are a challenging target in any telescope under 20".

As Ken suggested an occulting bar helps enormously. With Phobos being close to Mars it is by far the toughest. With the current opposition Mars has an apparent angular size of ~24' which is similar to the August 2003 opposition and easily people's best chance to catch them since 2003. That all having been said they are still tough to get in 16" to 20" class telescopes. With an occulting bar you might get them in 12" and larger scopes under very favourable conditions. Deimos might be visible in scopes down to about 10" or so, but they aren't an easy thing and favourable conditions help enormously.

Cheers
John B
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Old 30-07-2018, 10:46 PM
Wavytone (Nick)
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Sirius pup is comfortably in reach of the Tank... I'll give these a try over the next few weeks.
I have to watch my back... there's at least one ready to kill for this scope.
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Old 01-08-2018, 11:40 AM
Insomniac
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Occulting bar on no bar, I strongly recommend the use of a non-super wide field eyepiece.

The less glass in there the better. Whilst I love my Naglers, I reach for the more limited fov of the orthoscopics when I want to squeeze every last detail out against a darker background.
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Old 01-08-2018, 03:55 PM
Wavytone (Nick)
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Ditto.

I’m even considering making a ball eyepiece just for fun, as Edmund stock some reasonable glass spheres... just trying to see if I can find a coated one.

Eye relief will be nil and useable field of view about 30 degrees, I think, sharpest in the central third.
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Old 01-08-2018, 04:04 PM
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Merlin66 (Ken)
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Hastings triplet as a monocentric??? Surplus Shed as at least one....
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Old 03-08-2018, 07:39 PM
Wavytone (Nick)
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Ken, Mental - surprise - steinheil triplets exist, though have to make a DIY barrel:

https://www.edmundoptics.com/f/Stein...-Lenses/12275/
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Old 05-08-2018, 03:02 PM
Wavytone (Nick)
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Spotted Deimos last night, fairly easily at 300X by putting Mars just outside the field in a narrow-field eyepeice. Phobos was behind mars unfortunately so no chance.
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Old 14-09-2018, 06:29 PM
Insomniac
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Finally got round to making an occulting bar - just a thin strip of electrical insulation tape across an orthoscopic. And once I'd spotted both moons again and knew where to look, I managed to see them without. That was about a month back...
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Old 19-09-2018, 07:13 PM
Insomniac
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Quote:
Originally Posted by Wavytone View Post
Spotted Deimos last night, fairly easily at 300X by putting Mars just outside the field in a narrow-field eyepeice. Phobos was behind mars unfortunately so no chance.
Attaboy!
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