Telescope for astrophotography - Forums

Topic starter

Nov 21, 2016 · Edited: Nov 21, 2016

hello, i wanted to buy a telescope to take photos, now i am using a tube from 8 inch Dobsonian F6 (very good scope for visual observations), when i started i had one problem, focus was too short, so i needed to move primary mirror about 2 mm closer to secondary (problem solved)
now i have other problems - focuser itself is moving , tube is made from about 0.5mm tick steel plate and it bends under own weight a little bit, and when temperature changes, not much, about +/-5 degrees it stretches and contracts. these are reasons why i want a new one. since i am using Newton telescope, and want to take a pictures of nebulae and galaxies i aimed at this one >
http://www.teleskop-express.de/shop/product_info.php/language/en/info/p5034_TS-UNC-254-mm-f-4-Newton-Teleskop-mit-Carbon-Tubus.html
+coma corrector. there were other choices too, but i am afraid of CS telescopes because of their long focus/aperture ratio and big secondary mirror + i have no ideas about problems i can get from them.
So maybe someone can tell me something about this telescope, maybe there is something i should know more before i buy it?
Thanks a lots, and have a clear sky!

p.s. i am using HEQ5 mount

Brent Newton

Nov 23, 2016

I have heard Newtonian scopes tend to have difficulty with cameras due to where they focus. To solve this, make sure it comes with extension tubes. Other than that, it looks like a fine scope, f/4 is excellent for imaging.

A 10" scope may be a little much, but I am unfamiliar with the EQ5 Mount - if it can handle the weight, then great, but you might consider moving to a 6" if you plan on adding a guide scope, which will increase weight even more. But if the mount can handle the weight and / or you plan on using an off-axis guider then go for it!

As a final note, from your post history you seem to have as much experience imaging as I, so you probably already know this, but for all others reading this thread in the future, never go right up to the weight limit of your mount, keep it at no more than 2/3 of its rated capacity.

Sebastian "BastiH" Hinz

Nov 25, 2016

Hello Peleks,

I have to agree with Brent, a 10" newtonian is certainly too heavy for the EQ5. I used a TS 10" f4 on the heavier EQ6 and with the additional weights of camera and finderscope it pushed the capacity of the EQ6 to its limits. The combination was very vunerable to wind and had to be balanced perfectly to work at all. I am very satisfied with my TS scope but before you buy the UNC be shure to plan/calculate the distances between coma corrector (off-axis-guider?) and your camera's sensor. It's possible that you may need a different focuser for your optical train to work or that not all types of correctors will fit.

CS

Basti

peleks

Topic starter

Nov 25, 2016

Thanks BastiH and Brent1123, for this telescope as i heard are focuser with 3 focusing points, and the scope itself weights about 12 kg, mount is Heavy EQ5 it can handle 15 kg and tube i have now also weights the same, so i am not worried about weight, bu ill check those distances between camera coma corrector and offaxis guider (i will go for that one, since dont want to add weight with guiding scope)

isac.bogdan

Dec 18, 2016

there is a diference from eq5 and heq5
EQ5 - 5-6 kg for astrophotography and 10 kg visual
HEQ5 - 8-9 kg for astrophotography and 15 kg visual

Diego Colonnello

Dec 19, 2016

Hi Pekels, i have a Saxon 200mm f5 newt that i upgraded with a carbon fiber tube from Klaus Helmerichs (germany) it has been a big improvement and it is 1 kg lighter.
I decided to stay with F5. faster telescopes are harder to collimate and are less forgiving…
Astrophotography is all about the mount. if you can move to an eq6pro and keep everything under 15 kg you will be fine.

bobzeq25

Dec 20, 2016 · Edited: Dec 20, 2016

The virtually universal recommendation of every expert who's written a "getting started in astrophotography" book is a small refractor.
Light, short focal length, and fast, aperture relatively unimportant, except that large aperture will be too heavy and too long focal length.
Here's the recommendation of Craig Stark, PhD scientist, noted astrohotographer who lectures on the subject, and the author of the
PhD2 program you're going to use for guiding. The style in which is he says it shows Craig has been to this rodeo before, and knows
how hard it is for a visual astronomer to discard the now counterproductive "aperture fever".

"As light as possible.
___________________________________

Seriously.
____________________________________

No, seriously."

Mike G.

Jan 3, 2017

+1 on refractors. No moving parts, nothing that requires periodic collimation. Tons of options…!…get a fast APO (<f/4 ) that already comes with a field flattener. You'll never regret it. Keep the dob for visual.

DavidLJ

May 2, 2017

If this is not too late for your purpose : I bought a HEQ5 mount at the same time as I bought a Vixen 8 inch f/4 Newtonian but quickly found that after adding a camera, a filter wheel, a small autoguiding 'scope/camera combination and a finder 'scope the mount really struggled to cope with the combined weight to the point where autoguiding was problematic when the OTA was aimed at certain sections of the sky. The only solution was to upgrade to an AZ-EQ6 mount. This might give you a frame of reference when marrying your intended 'scope to a suitable mount.

David Goldstein

May 4, 2017

Just to dovetail on what bobzeq25 said, a 600 to 800mm refractor will also be lighter and easier on your EQ5, plus eliminate the focusing issues and don't need collimation - they usually work right out of the box.

peleks

Topic starter

May 4, 2017 · Edited: May 4, 2017

thanks all, bought my 10 inch F5 carbon newton, perfect scope, it is heavy, i dont use guidescope, instead i use offaxis guider, so in total everything weights about 14-15kgs, heq5 handle it very nice(upgraded it with Rowan Belt Mod), the important thing is to balance everything and use some windshield if wind is higher than 2m/s
so what i think about max weight - if we are not lazy and balance everything, then mounts can handle about 80-90% of designed weight in astrophotography

if we are doing this with a precision of +/- tram station then we stay below 50%
p.s. guideline is +/- 1pix (pixel size 3.75^2mm) thats about 2 times below max resolution in my place, and i am thinking to buy a camera with pixel size of 5 to 7mm^2 so it will not be a problem

p.s.p.s. a really really really good scope (if to compare with old metal dobsonian)

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