A feast of ISS passes

We’ve recently been treated to some bright passes of the International Space Station and it looks as though there are more to come (weather permitting) over the next week or so.  The following table (edited from http://www.heavens-above.com ) shows the times of the brightest passes.  Times/directions will vary depending on where you are but should be fairly accurate for anyone in the Midlands:

Date	Mag	Starts			Max. altitude			Ends
		Time	Alt.	Az.	Time	Alt.	Az.	Time	Alt.	Az.
17 Jun	-3.6	23:16:59	10	W	23:20:11	76	SSE	23:23:17	10	E
18 Jun	-3.4	22:15:23	10	WSW	22:18:29	60	SSE	22:21:36	10	E
18 Jun	-3.6	23:51:06	10	W	23:54:15	78	S	23:57:25	10	E
19 Jun	-3.5	22:49:28	10	W	22:52:36	80	S	22:55:45	10	E
20 Jun	-3.4	21:47:51	10	WSW	21:50:59	70	SSE	21:54:07	10	E
20 Jun	-3.5	23:23:37	10	W	23:26:45	71	S	23:29:54	10	ESE
21 Jun	-3.5	22:22:01	10	W	22:25:09	80	S	22:28:18	10	E
21 Jun	-3	23:57:51	10	W	00:00:52	43	SSW	00:02:27	23	SE
22 Jun	-3.4	22:56:14	10	W	22:59:20	62	SSW	23:02:28	10	ESE
23 Jun	-3.4	21:54:39	10	W	21:57:47	77	S	22:00:56	10	E
23 Jun	-2.6	23:30:32	10	W	23:33:26	34	SSW	23:35:05	20	SSE
24 Jun	-3.2	22:28:54	10	W	22:31:59	52	SSW	22:35:03	10	ESE
25 Jun	-2.2	23:03:20	10	W	23:06:03	27	SSW	23:08:01	15	SSE
26 Jun	-2.8	22:01:41	10	W	22:04:41	42	SSW	22:07:41	10	SE

It’s nearly 54 years since Man’s first artificial satellite was put into orbit and 50 years since Yuri Gagarin first ventured into the unknown.  The first decade and a half of space exploration saw a flurry of activity on both sides of what was then known as the “Iron Curtain”, with the U.S.A. and U.S.S.R going head-to-head, each trying to out-do the other in demonstrating their technical prowess, culminating at 20:17:40 UTC on 20th July 1969 when Apollo 11 touched down on the surface of the Moon.  In the 42 years since that momentous occasion we have seen numerous robotic missions to the planets and, for the last 30 years, regular forays into near Earth orbit of the NASA Space Shuttles which have delivered and maintained the great telescopes and, for the last decade or so, have contributed to the construction of the ISS. Along the way there have been many triumphs, but we should never forget the human cost:

Apollo 1, Soyuz 1, Soyuz 11,  Challenger, Columbia – all pioneers who paid the ultimate sacrifice.

As someone who was born less than a year since Garagin took that flight, I’ve long had an interest in space – be it spaceflight or astronomy and remember the heady days of the Apollo programme and the wonder of knowing that a quarter of a million miles away (give or take) on the Moon there were humans walking about.  In those days, of course, there were far fewer satellites in orbit and you needed the finances of a small country to afford the sort of telescope that’s commonly available nowadays.  If you were lucky and happened to be looking in the right place at the right time you’d see a dot moving across the sky and maybe realise that was a satellite. That was how it was for me until one evening last summer when I happened to look up and see a swiftly moving dot followed by a much brighter object.  I was somewhat mystified at the time as I didn’t for one moment think it was what it turned out to be: a Progress supply vessel followed by the International Space Station!

Since then, I’ve tried to keep track of when the ISS is due over and have been fortunate to capture it in passing.  Sadly, as the Shuttle era draws to a close I’ve not been able to grab an image of ISS and Shuttle either docked or before/after docking.  Maybe when Atlantis takes its last flight I’ll get a chance. Why all the fuss about the ISS? Well, I think it’s to do with the fact it’s crewed and it’s easily seen. I’m not sure whether, in their time, SkyLab, Salyut or Mir were ever visible from the UK or whether anyone was able to image them, but the ISS is unmistakable and, with suitable equipment it’s possible totake a picture showing its progress across the sky.  The ultimate challenge, though, is to capture an image of the ISS not as a streak across the sky but a snapshot, so that is my next project.  Hopefully I’ll be able to post the results soon!

Accurately setting the “Home” or “Park” position on a Skywatcher EQ5 Pro Mount

Update 18 Jun 2011:

Since I originally prepared this article I’ve found that the steps set out in the Starting from a known position section aren’t necessary.  When the mount is powered on, regardless of whether you choose to start from parked position or not, and irrespective of what position the axes are in,  the positions of AX1 and AX2 shown in UTILITY → SHOW POSITION will be the same.  I’ve therefore removed the steps that are no longer required

It’s been quite a while since my last posting.  In the intervening period I finally got round to acquiring a decent mount, the SkyWatcher EQ5 Pro. The only trouble is the weather’s not been too good andit’s way past 10pm before it gets dark enough for observing!

One element of setting up an equatorial mount is the establishment of the “Home” position. This is where the mount is “parked” at the end of a session. It is sometimes described as “weights down, scope up” and is often the position displayed in adverts. There’s an excellent video tutorial on YouTube accessible via http://www.astronomyshed.co.uk/ (“Complete Setup From A to Z Part 1”) which shows how to establish this position using an HEQ6 mount.

In essence, the procedure uses a spirit level to “level” an axis then rotate the axis by 90^o so that it is then perpendicular. When both the RA and DEC axes have been set this way, the mount is in the correct Home position.

As owners of Skywatcher EQ5 mounts have long accepted, the setting circles leave a lot to be desired, and while it’s possible to use the technique in the tutorial on an EQ5, the inaccuracy of the setting circles means it’s a bit of a hit and miss affair.

The following procedure builds on the technique, using the Show Postition function of the SynScan controller to accurately determine when an axis has rotated through 90^o. Though described for an EQ5 mount, this procedure can be used with any equatorial mount with SynScan, whether factory-fitted or upgraded.

On the EQ5 tripod, one leg is marked N. This is the leg which is pointed North. For the purpose of this procedure this will be regarded as the front of the mount.

It is assumed that the user is familiar with the operation of the SynScan controller and its menus. Navigation to a sub-menu will be described thus:

UTILITY → SHOW POSITION

( Starting from a known position section removed)

Setting the RA axis

1. Stand behind the mount, release the RA clutch and rotate the RA axis until the weight bar is horizontal and to the left. Use a spirit level to check then lock the RA clutch.
2. Switch ON
3. Step through the setup procedure. Note: Setting date/time/location correctly is not required at this, or any other stage of the process, nor is 1,2 or 3-star alignment.
4. Show the position of the axes.     UTILITY → SHOW POSITION
5. Use the scroll keys to change the display so that the axis positions are shown in degrees, minutes, seconds:

AX1=+090^o 00′ 00”

AX2=+000^o 00′ 00”

(AX1 is the DEC axis, AX2 is the RA axis)

6. Set a fairly high slew rate (RATE 8 for example) then use the RA directional key to slew the mount until AX2 is close to reading 90^o. Select a slower rate and carefully slew until the display reads

AX1=+090^o 00′ 00”

AX2=+090^o 00′ 00”

7. Using a fine marker and straight edge, make a mark to enable you to manually return the RA axis to its parked position.

Setting the DEC Axis

1. If you have one, fit a dovetail bar to the puck. This will provide a straight edge to rest the spirit level on.
2. Release the DEC clutch and rotate the DEC axis until the dovetail is horizontal, using the spirit level to check.
3. Again, start off with a high slew rate and rotate the DEC axis until the display indicates the AX1 axis is 90 degrees different to what it was. If your preference is to have the DEC motor to the left, then the display should read

AX1=+180^o 00′ 00”

AX2=+090^o 00′ 00”

If, however, you prefer to have the DEC motor on the right, the display will read

AX1=+000^o 00′ 00”

AX2=+090^o 00′ 00”

8. Using the marker and straight edge make a mark so the DEC axis can be returned to this position manually
9. Switch OFF
10. Switch back on again and step through setup.
11. Choose UTILITY → PARK SCOPE then switch off when prompted

The mount now has its axes accurately positioned and parked.