ISS – Brisbane 18th Nov 2016. Mewlon 210 and Canon 5D Mk III.
I received an automated e-mail from a NASA Subscription Service, informing me that the International Space Station (ISS) was due to make an appearance at my location in Brisbane.
"Time: Fri Nov 18 6:47 PM, Visible: 5 min, Max Height: 71°, Appears: 30° above SSW, Disappears: 10° above NE."
After plotting the celestial path of the ISS in my planetarium program, The Sky X Pro, I realised that at 6:48:22 PM the ISS would be passing very close to a Magnitude: 4.11 star, (Object Name: HIP 113638) in the Constellation of Grus, at an altitude of +64° 47' 22".
With sunset at 6:19 PM it wouldn’t give me much time to set up the telescope, align the mount, find a bright star and focus the camera before the ISS appeared. As luck would have it, the bright star Fomalhaut was almost overhead so I was able to align the mount at the Zenith using a spirit level and then slew to Fomalhaut to sync the mount on the mag 1.17 star. I then used my Bahtinov Mask to manually focus the Canon 5D Mk III on Fomalhaut before slewing to HIP 113638, just as the ISS appeared in the SSW.
I watched the scene through the finder scope and when the ISS approached the cross hairs, I squeezed the remote release and fired the shutter at the maximum drive rate of 6 frames per second. I was relieved to find that when I played the images back on the rear LCD of the camera, I had 6 frames with the ISS traversing diagonally from top right to bottom left.
Of these 6 frames, 3 were good, with one of these standing out as being the sharpest. And I almost didn’t set up due to the bright twilight! A lucky shot indeed!
I had approx. 45 mins to set up and get ready, which sounds a long time but when you have to haul all the gear out set it up, boot the PC, make all the connections, align, focus, etc. the time just whizzes by.
I have 3 pads in the back garden where I place the tripod feet so these help me get ahead of the game and on the day, everything just worked 1st time round, making it a success.
If just one thing had gone wrong where I had to re do some task or procedure, I’d have enjoyed a visual over pass and missed the shot.
Can you stack any of the other two frames with the better one?
Dean
Hi Dean
I tried but I lost more than I gained.
I think that the shots where the ISS appeared towards the edges of the frame, as opposed to the good central shot, were a little soft as the Tak Mewlons only have a sweet spot at the centre of the 5D Mk III sensor.
The Dall-Kirkham design of the Mewlon is known to produce off axis coma.
Top shot Denis , Amazing detail
I just so happened to set up the Zamar but hadn't completed the 2 star alignment when I looked up to see the ISS Arcing it's way East from the Zenith . So I whipped out the 10mm kelner I use for alignment and shoved in the 12mm Nag. (212x)The problem is ladder getting in the road of a fast moving scope!! Once the ISS had fallen to standing height I managed to track it thanks to the finder and got a good look . I only saw the square nature of the Solar Panels but hey I'm not complaining as the ISS would have been relatively low at that point. Thanks Wes
Very nice Dennis, I am amazed by the detail you've got on ISS itself!
Quote:
Originally Posted by Zubenel
Top shot Denis , Amazing detail
I just so happened to set up the Zamar but hadn't completed the 2 star alignment when I looked up to see the ISS Arcing it's way East from the Zenith . So I whipped out the 10mm kelner I use for alignment and shoved in the 12mm Nag. (212x)The problem is ladder getting in the road of a fast moving scope!! Once the ISS had fallen to standing height I managed to track it thanks to the finder and got a good look . I only saw the square nature of the Solar Panels but hey I'm not complaining as the ISS would have been relatively low at that point. Thanks Wes
Thanks Derek, Colin and Wes, I appreciate your comments.
@Colin, as noted above, the off-axis images were terrible (Dall-Kirkham Cassegrain) but the couple towards the centre of the frame were nice, with one being the standout. See attached composite.
@Wes – hah, thanks for the story Wes, you DOB folks can set up much so more speedily than use GEM users.
Wow great shot! Thanks for sharing your process too. Any chance you have a tip for estimating correct exposure?
Leigh
Hi Leigh
I based the settings on my experience from a previous session (Nov 2015) where I used 1/1600, ISO800 at F6.3 and some of the brighter ISS components were blown out to pure white with no detail or texture in those parts.
For this session, I figured I would prefer a grainy but sharp image rather than a cleaner but blurred image, so I went for ISO 1600 and 1/2000 sec, part hope and part guesswork!
The ‘scope is an F11.5 instrument and although I do have a Reducer/Flattener, I didn’t use it, deciding to shoot at 2415mm FL for the larger image scale.
It's lit by sunlight and is the same distance from the sun as earth. Take a meter reading off blue sky during the day with the optical system ISO etc you want to use. Bracket a stop either side of that.
Use blue sky about 90 deg from the sun. ie if it is mid morning meter off 45 deg elevation in the west.
Alternative is to use the sunny 16 rule -
f stop........shutter speed
16................1/ISO
11................1/(2*ISO)
..8................1/(4*ISO)
..5.6.............1/(8*ISO)
..4................1/(16*ISO)
This works on paint parts but reflective metal parts reflecting the sun won't conform to this exposure rule.
Thanks Joe and Dennis for sharing all that info. I only have an asi 120mm planetary camera so I'll have to translate the iso settings over to gain settings ..i think...
I have one capture under my belt so i'll be sure to refer to those settings as a guide for future attempts. I did have the thought of using a star of similar magnitude to help set exposure but will have to wait for another opportunity to try it out.
Thanks Joe and Dennis for sharing all that info. I only have an asi 120mm planetary camera so I'll have to translate the iso settings over to gain settings ..i think...
I have one capture under my belt so i'll be sure to refer to those settings as a guide for future attempts. I did have the thought of using a star of similar magnitude to help set exposure but will have to wait for another opportunity to try it out.
Cheers
Leigh
Hi Leigh
I would use the Moon to establish a suitable starting point for the settings of your camera/scope set up, rather than a star.
A star might behave more like a specular reflection and you might have to drive the exposure way down to avoid blowing the highlights and that might be too dim for an extended object such as the ISS.
I’d try to image various regions of the Moon and see what setting produce a nice image with no blown highlights. If you can maintain some details and texture in bright craters such as Tycho and Aristarchus, then that could be useful reference point.
If I were shooting an ISS transit across the lunar disc, I would expose to get a good histogram for the moon’s surface and let the ISS look after itself, at the risk of blowing out any specular highlights and reflections from e.g. solar panels.
