Need advice on picking a lens

[BlackSheep]

Hi All,

I have a ISS transit of the supermoon coming up on the 9th across Canberra that Id like to image with my FF DSLR (Canon 6DII). I normally do wide angle milkyway, but while that isnt easily viewable at the moment I'm looking for other reasons to head out assuming the smoke and welcome rain clears.

I have access to borrow a 70-300 lens or otherwise I'd like to look to buy one for future use. Is a 300 going to give me enough zoom to be able to get a view of the ISS similar to https://www.universetoday.com/wp-content/uploads/2017/01/ISS-transit-ESA-group-B.jpg? Otherwise I was thinking going big up front and buying a 150-600, likely https://www.digidirect.com.au/lenses/slr-lenses/sigma-150-600mm-f-5-6-3-dg-os-contemporary-lens-for-canon which I'm confident I will use in other situations as well. I should at I'm very much in the newbie stage of astrophotography.

Cheers,
Karl

[Saturnine]

Hi

I'm assuming you mean the 9th of February as it seems that the ISS will also be close to transiting the moon from here at about 22:44 pm. Having captured a couple of transits in the past I would recommend a focal length of at least 600mm and with a full frame 6D, 800 to 1000mm would give you better image scale. Do you have a tracking mount or just a camera tripod, if only a tripod, good luck.
Depending on the distance of the ISS from your location at the time of the transit, it will somewhere between 0.6 sec duration and 60 arc sec. in angular size if close and 1.3 sec duration and 25 arc sec. if further away. Just checked the full details of the transit using https://transit-finder.com/results and get 9/02/20 22:54':19.46" Angular size 30.44 " and duration of 1.19 sec.
To give you some idea of the image scale here is an image of the Moon and Saturn taken with a 550D and ED80 ( 600mm F/L ) Saturn is approx. the same angular size as the ISS for your transit.

[BlackSheep]

Excellent, that's great info and thanks for the picture to help manage my expectations. I recently picked up the star adventurer and was thinking I will do a burst of images after I see it come over the horizon if I do end up getting a lens to do it.

[Saturnine]

To really capture the ISS crossing the disc of the moon you need to be in video mode, with a long focal length and pointed at and tracking the lunar disc. Even then it is just a speck and happens so quickly that it is over before you see it. Keep a close eye on the time and start videoing 15 / 20 sec. before the transit time and for a little while after just to make sure you get it.
If trying to manually track the ISS across the sky and take bursts at the same time would be a very tricky , wouldn't say impossible but damn difficult at long focal lengths. If you get a chance with an ISS pass before then, set up the gear you intend to use and try out the methods you are thinking of using.

[CalvinKlein]

Another excellent lens to consider is the Sigma 50-500mm. I used it for a long time with my Star Adventurer and got some good ISS-Moon transits. I also bought the 1.4 and 2x extenders, though I use the 1.4x far more often. The 50-500 also makes a pretty good astrophotography lens for brighter targets like Orion / Carina / LMC & SMC / Lagoon nebula etc ...

It's also a very useful general purpose lens and I carry it in the car all the time along with my old Canon 70D.