What type of telescope (reflector) for photometry?

Bundesdeutsche Arbeitsgemeinschaft fur Veranderliche Sterne e.V.(Germany) (BAV)
Sat, 05/15/2021 - 10:20


I am doing photometry with a 90/500mm refractor and a Canon 450D. I consider to buy during the next 1-2 years a new telescope and camera. I do not want to go to big telescopes, maybe something like 8" maximum. But I wonder which type, Newton, SC,..., is best to use for photometry? I am not experienced with reflectors.



American Association of Variable Star Observers (AAVSO)
I guess the reason why…

I guess the reason why nobody has answered to this question yet is that this is a close call. There are some differences between the different telescope *types* that have a specific relevance for photometry, here is an example: Newtonians typically offer a wider field of view for the same aperture diameter (typicalle the focal length is ca 5 times the aperture diameter, while SCs are more like 10 times..., and a wider field of view helps to find comparison stars sometimes (e.g. when using a camera with a smal sensor), OTOH longer focal length can be better to mitigate a bright sky background from light pollution.... so you see this can be complicated.

But there are other differences that might be unrelated to photometry but are more important for general usability, like weight. And cost, of course.

So I would recommend to follow two principles:

1) Nothing beats aperture. 8" is better than 6" , period. So when comparing SCs and Newtons, compare telescopes of identical aperture to make an apples to apples comparison.

2) That said, the best telescope is the one you use the most. Beside the financial budget, you should consider what "budget" you have in terms of weight & bulkiness of the gear, especially if you want to use it as a mobile rig that you might need to carry around a lot. SCs are lighter and thus also require lighter mounts (at the same aperture diameter)

When I was unsure which telescope to pick I visited a local astronomy club ("Volkssternwarte" in Germany) for advise, and hopefully that will soon be possible again to do in person.