Announcement J62

If the weather was any better, I'd be submitting to the MPC! I've only ever submitted astrometric data to the MPC. AAVSO accept data on variable stars, supernovae etc but they are looking for photometric data - now that's a different ball game altogether - I'd hope to do that later this year...

The MPC also accept photometric of asteroids, particularly light curves that can determine rotation periods etc. But as above, I'm a while away from that.

Do you have an imager? You'll need at least that that for astrometry/photometry. And even with the four incher you can still image the brighter asteroids and get a code. You'll certainly be limited in observations you can make, but its do-able....

Dave

Well done Eamonn!

Keith..

Thanks lads. I was really thrilled in receiving J62. It feels like a relief after a successful NCT test for your car. Now I know I have a telescope system that can perform.

Just reading the last few posts on trying for an OB. Code. When you explore the MPC site, I do understand there may be some resistance to these MPC procedures. To be honest, I also had that feeling, in particular the MPC formatting procedure.

You don’t need big elaborate instrumentation and exotic software.

This experience and knowledge that Dave and I have gained can be passed on to others. One suggestion is that Dave and I could make a short workshop type presentation at the next Whirlpool Star party for those who want to give it a try. However, in the meantime there are a lot of IFAS members out there that have small telescopes, some taking images and are using some imaging software, etc. Take your time studying the MPC. When I first saw the MPC I thought it was a jungle.

Dave’s article in Arcturus is an excellent starting base.

Below is a scenario I have put together for the minimum amount to achieve astrometric accuracy on a considerable amount of asteroids, that need positions frequently to fine-tune orbits. You never know, you could be working on the asteroid that is about to impact the earth in 20??. I hope not. This is real science for anybody to do.

Dave, you can correct me if some of this equipment is not up to it. I was trying to select items below that would be the minimum requirements to achieve the Ob. Code.

Minimun observatory set up for to achieve observatory code

1. Minimum Goto telescope size 4 inches and upwards. You could use the Lidl one from last Xmas Meade ETX 90mm dia. €260 or the StarSeeker 114 for €200.
2. Meade DSI PRO 2 for €450
3. Imaging software, there are cheap ones below €100.eg. AstroArt, and there could be freeware. There is the Orion StarShoot with Maxim DL Essentials Edition for €300.
4. Astrometrica €25.
5. Computer.

All the above is around €800 new or a lot less if seconhand.

You would reach 14/15 magnitudes with this system. There are a lot of asteroids that need astrometric positions at these mags.
Accuracy limitations of for example inexpensive Meade type mounts and the advantages of re-stacking mean you could limit exposures to a maximum of 30 seconds duration.

To provide good astrometric positions:

· Exposures need to be short so that images are as near round as possible. However, believe it or not an uncollimated telescope with awful astigmatic star images can also achieve the same result, but a lesser magnitude because Astrometrica can centroid a star image. (Not recommended best practice). Do collimate your telescope frequently.

· The total exposure needs to be as long as possible to give a good S/N ratio (the stronger the better for measurement accuracy)

· The timing of the exposure needs to be good in absolute terms so that any error in the position introduced from the timing is negligible. For fast moving objects this means timing to better than one second. Use computer clock with Tardus or Dimension 4. These are free downloads for your timing.

As the accuracy of astrometry is so dependent on the strength of the image being measured, use Astrometrica to stack multiple exposures together to increase the signal strength.

For $25 you can get results as if your telescope or CCD several times larger or more sensitive than you actually have.

Astrometrica provides functionality to:

· Stack multiple images together
· reduce astrometric positions
· provide magnitude information
· create a report file in the correct format for sending to the MPC
· Provide an overlay for any moving objects in the field of view (as long as the orbital elements have been downloaded)
· detect moving objects in a set of three or more images
· preview images prior to stacking to discard any that may have defects

You’ll also need to download USNO A2.0 Catalogue by way of CDs. This acts as a comparison catalogue of stars so that Astrometrica can measure from. This is free.
As Dave said earlier, do give it lash.
Eamonn A

Eamonn - I found the obs code was also a vindication that I'd got something right! And I was really afraid of getting a brush-off response to my first set of measurements...

Your write-up is spot on. I'd marginally change some of the items - you can over ahundred on the imager - the DSI-C (the first imager is grand) that's what I use. There's a good few seccond hand for next to nothing and they have no moving parts to go iffy.

You could probably forgo the processing software - MPC recommend no post processing other than calibration (darks, flats, bias). The DSI and most imagers come with software that'll do all this anyhow.

Astrometric is a 100 day evaluation - so it'll cost you nothing to find out if astrometry is for you. Catalogues are free but need broadband (8 gigs for the USNO A2.0) but I have a copy - for the price of the cd's I can pass it on.

My only concern would be the mount. It needs to be motorised and have reasonable tracking ability. If your mount can handle a 15 second exposure with no trailing, you should be OK at least for the brighter objects (14 to 15 as Eamonn says). Certainly the OTA's mentioned are fine.

You'll need access to a GPS receiver to get your co-ordinates - I was very kindly loaned on.

The MPC site is a minefield indeed and is quite intimidating. The description of how to get a code is quite intimidating too. But the MPC bark is worse than its bite. But with J62 and J65 on the map, myself and Eamonn can make that part of the task painless. It really is quite simple - so don't be put off.

I think Eamonn's idea is a good one. I'd be more than happy to put material together with Eamonn and do a workshop if there was enough interest. Any takers?

Cheers

Dave

I think Eamonn's idea is a good one. I'd be more than happy to put material together with Eamonn and do a workshop if there was enough interest. Any takers?

If you guys could knock up a workshop I'd say you'd be booked out for the next few years at Astronomical societies throughout the country and probably abroad too. I for one would certainly like to learn more.

We'd* be delighted! Does anyone know if the Whirlpool organising committee would be prepared to accept a small workshop? Sounds like Birr would be an ideal place to do something....

Cheers

Dave

* I'm assuming your fully in on this Eamonn - it was your suggestion