My quest for Miranda – the saga continues!

[Dennis]

Hello,

Recently, I’ve been chasing Miranda, a fainter moon of Uranus with a magnitude of 16.55 according to Starry Night Pro.

Previously I had managed to record the 4 brighter moons, Titania, Oberon, Ariel and Umbriel. I can usually record these moons when they are suitably placed in terms of their apparent separation (7 or 8 arcsecs) from the glaring disc of Uranus.

Oct 23rd had Miranda some 8 arcsecs from the disc but unfortunately, I didn’t manage to record this fainter of the 5 moons, despite recording stars down to 17.8 magnitude. However, it was a fun project and good practice for the next time!

Cheers

Dennis

[Darth Wader (Wade)]

Dennis I always enjoy reading your fascinating reports. A good effort and may you have better luck next time!

Cheers
Wade

[Quark (Trevor)]

Dennis, what a top capture, you really are the demon of the outer gas giants. I am sure you will track down Miranda, its just a matter of time.

Dennis, this is probably irrelevant to your capture setup, but I wonder if the idea of using occulting bars in eyepieces could some how be applied to your ST7E, to totally block Uranus.

Regards
Trevor

[Dennis]

Thanks guys – I enjoy these types of projects. In particular, both the research to establish the optimum time for recording the moons and then the relatively simple post capture processing. Not too many hours spent image processing at the computer!

Trevor – I might just have a browse and see what I discover about occulting bars – thanks!

Cheers

Dennis

[Ric]

That's a pretty amazing image in itself Dennis.

As Trevor said "It's only a matter of time"

Cheers

[DavidU (Dave)]

I like the" Dennis does the near impossible" imaging.Awesome !

[Dennis]

Thanks Ric & Dave, I’m glad that I’m not the only one that enjoys looking at these non-descript blobs of white on a dark background!

Previously I only used SkyTools for planning when to image the 4 brighter moons and it wasn’t until I fired up Starry Night pro 6 after an effort by Steve (Kinetic) that Miranda showed up and appeared to be within the capabilities of my gear.

Running SNP forward, it seems that Miranda's greatest apparent distance from Uranus is around 9 arcsecs so it will require quite a balancing act to capture it; a long enough exposure to record it but not so long that the glow from Uranus swamps the feeble pin prick of light.

Cheers

Dennis

[DavidU (Dave)]

Dennis, exactly what type of scope do you image with?. I was toying around with working out the field spacing and width of an occulting bar made out of a coloured gel.

[Dennis]

Hi Dave

The ‘scope is a Tak Mewlon 180mm F12, a Dall-Kirkham Cassegrain design. The native focal length is 2160mm and I am experimenting with the Tak x1.6 Extender (efl of 3450mm at F19.2) and a WO x2.5 Barlow (efl of 5400mm at F30) to optimize the image scale/exposure combination.

So far, the Tak 1.6 Extender and 30 sec exposures seems the best combo, producing tighter stars whereas 30 secs at an efl of 5400mm smears the light, not unexpectedly!

The SBIG ST7 CCD camera has a 2” nose piece which sides into the x1.6 Extender or WO x2.5 Barlow. The assembly then slides into a Moonlite motorized focuser.

Cheers

Dennis

PS – Here is a link to Tak Europe for details on the M180.

[Matt Wastell (Matt)]

Nice work Dennis
I am sure given the right angular distance from Uranus you will get Miranda - I a so impressed with Ariel in your pic - great work!

[DavidU (Dave)]

Dennis, it looks like it is difficult to do a typical occulting bar as the image is only focused once at the CCD surface. Two things I would try is to cut out a half circle of blue gel( from stage lighting suppliers) and mount this on the end of the adaptor that goes into the camera.
This will give a half filtered image that should give unfiltered moons on what ever side of the image that is selected.A few tiny bits of bluetak will hold it in place.One other is to use a half circle of aluminium foil carefully blackened with flat black spray.

[Dennis]

Hi Dave

I had previously thought of using a half-circle red filter in the CFW8A filter wheel as I noticed that the (over exposed and bloated) disc of Uranus was smallest in the R frames from an RGB set I captured.

Nice image by the way! What gear was that taken with?

Cheers

Dennis

[DavidU (Dave)]

Not my image. I just looked for a pic with moons.A glass place should be able to cut a red filter for you.

Originally Posted by Dennis

Hi Dave

I had previously thought of using a half-circle red filter in the CFW8A filter wheel as I noticed that the (over exposed and bloated) disc of Uranus was smallest in the R frames from an RGB set I captured.

Nice image by the way! What gear was that taken with?

Cheers

Dennis