Dwarf Planets?

[Matty P]

Is it possible to observe or image any of the Dwarf Planets in our Solar System?

I know because they are reasonably small they won’t reflect much light making them fairly dim. Will I be able to observe or image any of the Dwarf Planets with my 8” SCT? :shrug:

Thanks in advance. :thumbsup:

[edwardsdj]

Sorry to state the obvious, but Pluto and Ceres are dwarf planets. These must be the easiest two and I've certainly never tried for Pluto in my 8" SCT, though I've read it is possible.

[Matty P]

Does anyone know the magnitude of any of the Dwarf Planets? :shrug:

I can't find any information on them. :doh:

[Dennis]

Hi Matty

Have a look here for Eris:

http://www.iceinspace.com.au/forum/showthread.php?t=13566

And Pluto:

http://www.iceinspace.com.au/forum/showthread.php?t=12756

Cheers

Dennis

[Matty P]

Thanks for the links Dennis, you have inspired me to give it a try. :)

I am not quite sure how you aquired the images though. Did you take images in intervals of a few minutes or hours?

Any suggestions on what kind of exposure settings I should use with my DMK when capturing something like Pluto? I am a bit unsure.
:help2:

[Dennis]

Hi Matty

For Pluto, the details are:

Vixen 102mm f9 refractor.
SBIG ST7E CCD camera.
5 x 5 minute exposures.

So, on 21st August I captured 5 x 5 minute exposures and stacked them together to give an equivalent single exposure of 25 minutes. I did the same thing on the next evening and then animated the two images to show the movement of Pluto against the fixed stars.

Why did I take 5 x 5 minute exposures rather than a single 25 minute exposure?

If you make a mistake with a single 25 minute exposure, you loose the lot all in 1 go.
If you make a mistake with one of the 5 x 5 minute exposures, you only loose 1 sub-frame.
To auotguide a single 25 minute exposure is much more difficult and demanding of the mount and guiding system than auto guided a 5 minute exposure.
A 25 minute exposure would have saturated the brighter field stars, causing blooming.
If an airplane or satellite passes through the field on 1 of the 5 x 5 minute exposures, you can erase the trail by doing a median combine of the 5 frames, which would reject the trail.

Eris was captured using my Celestron C9.25 with the Celestron F6.3 Reducer /Corrector. The exposure was 10 minutes and I captured between 3 and 5 sub-frames for the 4 day sequence.

To whet your appetite, here are another couple of examples of using this technique. I’m not sure of what mount/scope combo/type that you have, but I’d try for sub-frames of at least 3 minutes with the DMK and see what results you get.

Cheers

Dennis

[astroron]

Some good shots there Dennis, :thumbsup:You even managed to capture a Black Hole in the second Image, middle of the three smaller images;)
Ron

[Dennis]

Thanks Ron – trust you to find it! :P Just a bit of poor flat fielding methinks.:lol::lol:

Dennis

[Matty P]

Thanks for the detailed explanation Dennis, :)

I will try for sub-frames of around 2-3 minutes with the DMK. Hot pixels are going to be evident the longer the exposure.

Another thing, tracking with my scope is definately not the best so the less exposure time the better.

What magnitude was Eris and Pluto at when you captured them?

:thumbsup:

[Dennis]

Eris was magnitude 18.7 and Pluto, by comparison, was a whoppingly bright 14th magnitude object!

Yep – you’ll see a fair bit of noise, which dark frames can help minmise, provided the dark exposure is taken at the same temperature as the light exposure.

Also, be prepared for trailed stars, as 3 minute exposures can be quite demanding on mounts, especially at focal lengths of 1500mm and over.

Cheers

Dennis

[AJames]

Hi All,
You might like to go to my website, which has the magnitude you mention and a suitable ephemeris for 2008. The next page has for 2009 to 2015.
A general description of Eris is in the earlier pages.
http://homepage.mac.com/andjames/PageEris002.htm

The changes of imaging Eris is probable difficult without a large aperture, dark-skies and good conditions. I know 17th is tough, 18th is possible, 19th unlikely. Suggest doing the pic on the meridian, when Eris is highest in the sky, and at or very near opposition.
Be very interested if you do it. I'e only seen one, and that was made with 1-metre 'scope.

Andrew

[Dennis]

A couple of the images posted in the response above show stars at magnitude 19.11, 19.13 and 19.18 if the USNO figures are accurate.

These were taken with a C9.25 and Vixen 4" refractor from suburban skies in Brisbane. I have also managed to get down to mag 19 with my Vixen 4” refractor and the ST7 from suburban Brisbane; again, if the USNO values are correct.

Cheers

Dennis

[AJames]

Well, if true then it might be easier that stated. The magnitudes you quote, do you know what what measurements these are? I know the CCD is pretty good gaining fainter stars, but the limiting problem is likely the sky brightness.
There are some visual magnitude calibration fields that I've seen, but I'll have to think exactly where I've seen them, but the biggest problem is that UBV photometry is not common for 19th magnitude stars - probably something to do with the light absorption of the filters themselves.
Are the USNO Values you refer too are from the B2? If it is, the values here they are not exactly visual magnitude equivalents.
Another possibility to to image the field with Eris (or some other asteroid) in it, then image it again after several nights, and see if one of the stars has moved. Another would be getting a recent image of the star field with Eris in it, then compare the field stars visible with your own image. (Eris is slightly red as well, which might pose addition difficulties.)
The mags (and graph) quoted at;
http://homepage.mac.com/andjames/PageEris002.htm
Have come from NASA's HORIZON Ephemeris.
My views have been; "It may also be possible to record the body by amateur deep CCD images, though its detection likely requires at least 30cm to 40cm apertures."
If you do achieve this it would be most impressive.

Andrew

[Dennis]

It is true; have you actually browsed the images that I have posted in this thread?:shrug:



One of the images posted in this thread shows the movement of Eris over 4 nights; specifically the 19th, 20th, 21st and 22nd September.:) I also picked up another couple of asteroids identified in the field using the tight integration of the capture software, CCDSoft and my planetarium application, The Sky 6 Professional.



I have imaged Eris over three nights using a 10cm refractor, from suburban skies in Brisbane.:) So, I take it you are now suitably impressed? :whistle:

Cheers

Dennis

[DaveGee]

Hi Matty,

Pluto is usually around mag. 14 so is an easy target.

In June 2006, Pluto occulted a mag. 15 star and I (as well as many others across Australia) managed to record the event. I used a 10inch newtonian and Meade DSIpro, detecting Pluto's atmosphere in the process.

I also made an animated gif of pluto's progress across my FOV over an interval of 10 days. See...
http://users.tpg.com.au/users/daveg/pluto_060612/pluto_appulse.gif
The big jumps are 24 hours apart and the small jumps are 1 hour.

Of course at the time of the observation, Pluto had a full planet status not the dwarf planet status it now enjoys.

Of note, you don't really need to see the dwarf planet to detect it during stellar occultation, all you need to see is the target star and let the dwarf planet or asteroid do the rest.

[Rob_K]

Very impressive shots, Dennis & Dave! :thumbsup: Particularly like the Eris shots Dennis!

Matt, just because it doesn't seem to have been mentioned in this thread and at the risk of stating the obvious, it should be pointed out that at present the IAU only recognise three dwarf planets: Ceres, Pluto and Eris. However there are many other known objects that might be candidates for this classification, as well as many more bodies expected to be found in the Kuiper belt and beyond.

Good luck with your observing/imaging!

Cheers -

[[1ponders]]

As for Ceres, it is easily captured with an ED80 and a 300D. If I can dig up the images I'll post them.

[[1ponders]]

Here are a couple of links to Ceres images
http://www.iceinspace.com.au/forum/showthread.php?t=12712
http://www.iceinspace.com.au/forum/showthread.php?t=13543

[Dennis]

Hi Matty

As Dave (Gee) and Paul have suggested, I would aim for Ceres or Pluto to start with. I usually acquire the correct field of view by using a planetarium program such as The Sky or SkyTools, and then a GoTo usually places say, Ceres, more or less in the middle of the chip.

I pay a lot of attention to focusing the ‘scope. The camera control program, CCDSoft for the SBIG ST7, has a nice graphical display which shows me in real time when I have achieved best focus.

With the DMK, you can coarse focus on a mag 3 or 4 star and then try fainter stars as I have found that the fainter stars do not saturate the chip and turn blobby. Saturated stars do make it difficult to determine the sharpest focus.

I then take a 15 to 30 second image of the field that includes say, Ceres to confirm that it is the correct field by comparing the brighter stars to the FOV in say The Sky. I then make minor adjustments to compose the FOV so the object of interest is centred, or at one edge if it is moving quickly and I want to catch a trail across the whole frame.

If I take exposures longer than 60 to 90 seconds with the Vixen 4” refractor at a focal length of 918mm, I usually have to auto guide to keep the stars nice and round.

Good luck!

Dennis

[AJames]

Dennis,
More than impressed, gob-smacked in fact!
Frankly, the way the technology is these days, no wonder it is hard to underestimated what is capable.
What amazes me more is that this is seemingly better than the pro plates available - using CDS's Aladin 5.0. (See attached images of the 2MASS J plate and the DSS2 plate. The central star is GSC 04687-01873.
The USNO B1 Catalogue, seem too indicate the magnitude limit of this image of yours is about 21.8.
Certainly changed my knowledge. Will fix my webpages too.
Congrats Well done! :)
Andrew

[Matty P]

Thanks for the help guys, it is much appreciated. :)

I will start off with Pluto and Ceres to get my feet wet. My planetarium software confirms that Ceres is 8.7th magnitude and Pluto is 14th magnitude at the moment. It also shows 4 four other Minor Planets Pallas, Juno, Vesta and Astraea all much brighter than Pluto. (I might also add the software may be out of date, time for an upgrade) :doh:

I will be using a Celestron 8SE SCT at f/10 – 2000mm in Alt-Azimuth mode. I’m not sure how good tracking will be with the mount for a 3 minute exposure, so I might cut the exposure time down to 90-120 seconds (or less) and see how that goes. If possible I might go and pick a focal reducer for a larger FOV as well.

A few questions,

When imaging any of the Dwarf Planets, are you able to see them on the Laptop or computer screen? :shrug:

If I take 5 x 90 second exposures, do I stack them all to make one image. Then wait for an interval of 1/2 hour then repeat the procedure?

Thanks for the help. :thumbsup:

[Dennis]

Hi Matty

My experience with unguided long focal lengths of around 2000mm is that exposures of anything more than ¼ to ½ second will not be critically sharp due to the Earth’s rotation. Although a focal reducer will perhaps allow exposures up to maybe 1 sec without trailing, the real answer to long exposure imaging is a Polar Aligned Equatorial Mount.

Tracking in Alt-Az mode may lengthen the exposure time at the centre of the Field Of View (FOV) but other field stars will show increasing trails the further you move away from the centre.

I have an excellent German Equatorial Mount (GEM) and even when accurately polar aligned, I personally find long exposure imaging (60 secs or more) quite a challenge even when using auto guiding let alone simple tracking of the Earth’s rotation.

Anyhow, give it a go as there is nothing like practical experience to help you understand the concepts, processes and results from experimenting with what you have, before rushing out to purchase new equipment.

You should be able to see Ceres and the brighter Minor Planets on the notebook display with sub 1 second exposures. Here is an example of the effect of different length exposures using my DMK on the Trapezium. With an F12 ‘scope and an x2.5 Barlow I was working at an effective focal length of 5400mm which is around F30 for the system, albeit on a GEM whilst tracking (not guiding).

Cheers

Dennis

[Matty P]

Thanks again Dennis, :)

I will give it a go and see what I can get.

All I need now is clear skies. :lol: