How much telescope do I actually need for astrophotography?

Question

I've done the 'sparkly curtains behind landscapes' form of astrophotography for years with DSLRs, lately full frame Nikon. I know what I'm doing with the camera, and want to take the next step into incompetence with telescopes to point at stars with a camera attached, but I'm getting conflicting advice on what kit I need.

One group are saying 'basic motorised Newtonian will be fine' - e.g.

• https://www.harrisontelescopes.co.uk/acatalog/skywatcher-explorer-130m-telescope.html#SID=34,

• https://www.firstlightoptics.com/celestron-astromaster-series/celestron-astromaster-130eq-telescope.html.

Another are saying 'that's not powerful enough, you need a cadiotropic goto like

• https://www.picstop.co.uk/goto-telescopes/celestron-nexstar-evolution-6-schmidt-cassegrain-goto-telescope.html?wgu=217_60210_15449648240362_d6add8be16&wgexpiry=1547556824&source=webgains&siteid=60210.

They're obviously very different bits of kit...! And I can see both arguments TBH. Either one is trying to waste my time with inadequate kit, or another to waste my money into his pocket with overspecified kit.

Help....?

Answer 1

Electronic viewing is filling the area between traditional eyepiece viewing and Astro Photography. Electronic images may be viewed live, near live and with digital processing on the fly as the image is viewed or processed after the images have been collected.

The cameras have lower resolution but higher sensitivity than DSLR's and astro photo cameras. Short exposure time are the norm. Imaging/processing time is generally measured in seconds and minutes instead of hours. Stacking algorithms have been integrated into the viewing software. While tracking is still necessary the software is much more forgiving. People are viewing/imaging DSO's with Dobsonians.

I use Mallincams in my observatory. They are used with a 10" SCT, a 5" SCT and several Canon DSLR lenses.

One has the choice of going big and beautiful or small and good enough is good enough.

Take a look at the Mallincam io forum^* and judge for yourself. They have a photo section with thousands of images and answers to the questions those interested might have.

^{* You'll need to request membership first}

Answer 2

I would start with at least an equatorial mount sth as the HEQ5.

However, there are many factors to take into account such as what kind of targets you want, mostly, to shoot. Also, you you want to take photos with a wide of narrow field of view, just like Stephen asked in his comment. Then you also have t think about guiding the mount.

So, I wouldn't choose any of these set ups. But we need more information in order to narrow down your options within your budget's restrictions.

Cheers

Answer 3

The mount is the most important thing. Then the camera. Then the telescope.

Get the best mount you could possibly afford. I'm not saying you should start directly with a Paramount MYT (although that would be great), but I suggest you take a good long look at Losmandy and figure out what works for you. It's going to be expensive, yes.

http://www.bisque.com/sc/pages/ParamountLandingPage.aspx

http://www.losmandy.com/

The mounts need to be designed for the carrying capacity that will take all your gear - telescope, camera, filters, autoguider, etc. Always allow some headroom in terms of carrying capacity - don't max out the mount.

If those are too expensive, the bare minimum I would recommend is something like a Celestron CGEM or equivalent, but these are less worry- and fiddle-free than the higher end mounts. You could get good results with the CGEM (I have), but more work is required. Be prepared for some learning curve there.

https://www.celestron.com/products/cgem-computerized-mount

With mounts in this class, it's actually best to stay below 1/2 of their declared capacity - if the mount claims it can carry X lb or kg of gear, stay below X/2. More expensive mounts can carry closer to their stated max load. For planetary shots you could increase the load a little bit and get closer to the limits, but for DSO (galaxies, nebulae) definitely follow the guidelines I've told you. An oversized mount (designed to carry way more than your gear's weight) will always work better.

In terms of camera, some sort of cooled, large sensor camera for deep space objects (DSO), and a small sensor non-cooled camera with a fast chip (a.k.a. planetary camera) for planets. There are many good camera makers out there. I use ZWO products with good results.

https://astronomy-imaging-camera.com/

The big sensor camera will be quite similar to a DSLR (some actually use the same sensor as some popular DSLR cameras), except it's cooled and it's optimized for astronomy. Cooling helps quite a bit with the noise. You could use a DSLR instead, it's just going to be more noisy so you probably need to collect a bit more data to remove noise.

The planetary camera could be used for autoguiding when taking DSO shots with the big cooled camera.

Telescopes: you will probably end up with two instruments - a refractor for wide angle DSOs, and an SCT for zooming into smaller targets (like small DSOs and planets). These don't need to be very fancy. Even a doublet refractor will do well (like an Orion ED80 with a focal reducer). A Celestron C8 (or the better corrected EdgeHD series) would work well as an SCT, but more aperture is better (assuming your mount can carry it).

https://www.telescope.com/Orion/Orion-ED80-80mm-f75-Apochromatic-Refractor-Telescope/rc/2160/p/9895.uts

https://www.celestron.com/products/edgehd-8-optical-tube-assembly

High resolution planetary shots can be taken with a large dobsonian on an equatorial platform. This way you could get way more aperture than any SCT, and the dobsonian could do double duty as a visual instrument.

There's really no aperture limit for planetary shots. More is always better. Yay dobs!

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For DSOs, start with a short focal length instrument, like an ED80 with a focal reducer. It's a heck of a lot easier to figure out how the mount works, and autoguiding and all that, when the scope has a focal length in the range of 400 ... 600 mm. Pick easy targets first, like M31 or the Orion nebula.

Learn how that works, and then move up to bigger focal lengths, like with an SCT.

For planetary shots you could use a huge focal length from the beginning (SCT with barlow), since you don't need high precision in tracking (also, no autoguiding either).

Answer 4

1. Strong mount. EQ5. Quality bronze parts.
2. Wide angle telescope. One with high Diameter / Focus Length ratio. Such telescopes are not popular, because astronomers do not need wide angle normally. And making angle high will significantly grow the costs. Refractors are better, because you will have less trouble with probable "correctors" which could blur your image. You will pay also for good lenses without chromatic aberrations.
3. Good motors and CCD camera. CMOS cameras are not going to work, you need CCD one with possibility to cool it to eliminate dark current.