Telescope for planetary imaging

[Mark Fairfax]

Looking for a second telescope + mount for planetary and lunar viewing & astrophotography.
Not looking to break the bank as it will be my secondary and I’m not interested in DSO’s with it as I already have an eVscope for these.
It will be mainly used in my back garden but I do have a large estate car for the possibility of transporting it to dark sites, star parties, etc.
I have a Canon DSLR but not averse to purchasing a ZWO planetary specific camera at a future date.
(My post-processing will be done with a Mac and not Windows)
Any advice would be greatly appreciated…

Thanks,
Mark Fairfax
(New member)

Mark Fairfax

[Callum Potter]

Mark Fairfax wrote:

Looking for a second telescope + mount for planetary and lunar viewing & astrophotography.

I’m not really a planetary imager, but it seems to me that SCT’s are probably still the most popular telescope for imaging planets.
The long focal length gives a good scale with the planetary cameras, and you’d probably looking at somewhere between 200mm to 300mm aperture.
And you also need a good mount, but you don’t need to guide so that makes things a bit simpler.

Callum

[Mark Lonsdale]

Hi Mark,

Like you I am very keen on planetary imaging. I got started with an 8SE SCT, graduated to a C11, and now own a C14Edge HD (the Edge version of a C14 is not strictly necessary for planetary, but it does have a lockable primary mirror which improves the stability of your collimation). As Callum says above, SCTs tend to be the default option for planetary, and they are excellent for the purpose. From my observations of the work of others, a 9.25″ SCT is a very good compromise between power and portability.

But during my apprenticeship as an imager, I was living part of the year in Strasbourg, imaging from my apartment kitchen window. There, I used a Celestron guided Maksutov-Cassegrain (a 127SLT). This I found to be an excellent little scope for planetary and lunar:

1. It is very transportable – I used to take it for star nights in Saverne in the Vosges mountains;
2. It is already at f15 so barely a need for a barlow if you use a camera with pixels around 2.9 microns;
3. As a Mak Cass, there is essentially no need to collimate, whereas with an SCT you need to be very careful to collimate to a very fine degree (i.e. using the Airy disc), especially after transporting the scope;
4. The alignment procedure for the Celestron 127SLT includes “solar system alignment”, which means you can just point it at the planet and align – you don’t need two or three alignment stars, whcih can be an issue in an urban setting (certainly in my apartment looking out over Strasbourg!). The tracking is then sufficiently good for planetary imaging (especially if you check that the OTA is well balanced on the mount, if necessary adding a small counterweight to balance the imaging train).

So, go with an SCT if you want to be really serious; or try a small Mak Cass just to dip your toe in the water.

BTW there are some excellent FAQs on planetary imaging here:

https://www.cloudynights.com/topic/812022-planetary-imaging-faq-ver-10-feb-2022/

Regards

Mark (also!)

[Mark Fairfax]

Thank you very much Callum & Mark L for the great advice!
I’ll do some more research & creative accountancy regarding budget but mainly get on my better half’s good-side.

Mark

• This reply was modified 2 years, 7 months ago by Mark Fairfax.

Mark Fairfax

[Dr Richard John McKim]

As to aperture, 200 mm will give you good results, but most observers seem to graduate to larger apertures. 250 mm should answer most needs, and unless you are getting excellent seeing conditions consistently (or become expert at processing) you probably will not find much advantage in going to 300 mm or more. Beyond that size, transportability will be a factor. However, for a fixed scope the focal length will be longer and longer with a larger aperture. I presume you are going for an SCT but I have had excellent reports from users of Maksutovs of around 250 mm aperture.

I would suggest that you think carefully about what focal length you will need to get a decent size of image. I use a 16 inch Dall Kirkham with a focal length of 400 inches. This enables one to get a decent size for Mars even at an aphelion opposition on the chip, without a Barlow lens, but I have actually found the image size somewhat too large for Jupiter near Opposition. I am mainly a visual observer so it does not matter too much to me. But as a Section Director I find the biggest complaint from (or obstacle for) observers is getting a large enough image. Some observers have coupled two x2 Barlow lenses together but this can lead to internal reflections and ghosting. There is a x3 Barlow on the market and that may be a better solution. If you intend to image Venus with a Barlow you should be aware that ultraviolet will be absorbed by glass and that a special Barlow will be needed, if you need a longer focal length.

Many observers have missed a discovery by taking too long to process their images, and I know several observers who always work upon them immediately after the observing run, and then send them in. So another piece of advice is not to accumulate your unprocessed images. You can always submit a better processing at your leisure, but report the result on the same day if you can. I find that some people can submit images six months late, but by that time their usefulness is much reduced.

I will leave others to give advice about manufacturers…..

[Mark Fairfax]

Thank you too Richard – all very helpful advice!

Mark

Mark Fairfax

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