Can you record the size of Mars’s disc, in the run up to opposition and beyond?
Mars reaches an apparent diameter of 6 arcseconds on 31 May, pretty small but a viable size to record the planet as a disc. This month’s challenge is intended to extend right through into 2023 as we want to you start imaging or drawing the planet at regular intervals from now until opposition on 8 December this year, and then through into the following year.
The start of this long-term project won’t be too easy because Mars will be located in the brightening morning twilight, with it being best placed at the end of the month. The frequency of recording will need to be adjusted with the weather, but an observation a week or two apart at the start of the sequence should be sufficient.
The planet will remain tricky through June and most of July, but then the lengthening nights and a brightening planet will work in your favour as we pass the summer solstice on 21 June. It takes tenacity to remain with a planet like this, especially as the earlier results will probably look quite poor. However, sticking to your guns and grabbing results when the weather allows is a great way to connect to a distant world like Mars.
The 2022 opposition, on 8 December, will present Mars with a maximum apparent size of 17.2 arcseconds at the start of that month, which is someway short of last opposition’s 22.6 arcseconds, achieved in October 2020. However, for the UK at least, Mars reaches opposition at a higher altitude this year and this will make a big difference. If you do manage to stick with Mars all the way from now through to – and possibly past – opposition, comparing results will give you a unique insight into how this planet can change in appearance dramatically.
If you aim to image Mars, you need to make a choice of whether you want to capture it in colour, monochrome, or monochrome with filters, to generate a colour result. If you are intending to do a colour capture, consider investing in an atmospheric dispersion corrector, or ADC, to reduce atmospherically induced colour fringing at the start of the project, which is a side-effect of low altitude.
An infrared-sensitive monochrome camera fitted with an infrared pass filter will give you a colour fringe-free result and will go some way to overcoming the effects of atmospheric turbulence. This is because longer wavelengths tend to be less affected by atmospheric seeing.
The distance between Mars and Earth will reduce as we approach December and surface detail should start to become more apparent in the months ahead of this. Additionally, constant recording will reveal the effects of the Martian weather and seasonal changes in the planet’s polar caps.